View
2
Download
0
Category
Preview:
Citation preview
131 131
.. ..
*** Students are advised to solve the questions of exercises in the same sequence or as
directed by the faculty members.
132 132
Index : Preparing your own list of Important/Difficult Questions
Instruction to fill
(A) Write down the Question Number you are unable to solve in column A below, by Pen.
(B) After discussing the Questions written in column A with faculties, strike off them in the
manner so that you can see at the time of Revision also, to solve these questions again.
(C) Write down the Question Number you feel are important or good in the column B.
Advantages
1. It is advised to the students that they should prepare a question bank for the revision as it is
very difficult to solve all the questions at the time of revision.
2. Using above index you can prepare and maintain the questions for your revision.
ruseducation beyond boundaries
133
INTRODUCTION :
The branch of biology which deals with the study of endorcine system and its physiology is known as ''
Endocrinology''.
''Thomas Addision'' is known as father of Endocrinology.
Whereas the gland with duct is called exocrine gland which secretes enzyme etc. Endocrine glands pour
their secretion directly into blood. These glands lack ducts, so these glands are called ductless glands.
Co-ordination in the body of almost all the higher vertebrates is controlled by two systems Nervous
system and endocrine system.
Nervous system and endorcine system are called Integrative system of the body.
Nervous system carries informations in the form of impulses to the different parts of body. High speed
services are offered by this system.
Where as, the work of co-ordination by endocrine system is slowly by secretion of some chemical
substances.
Substances secreted by these glands are known as hormones. The meaning of work 'hormone' in Greek
is ''to excite'' = hormaein.
Differences between Nervous and Endocrine Coordinations
Nervous Co-ordination
Endocrine Co-ordination
(Chemical Co-ordination)
1.
2.
3.
4.
5.
Information passes as electrical
impulses along nerve fibres.
There is rapid transmission of
information.
Response is immediate.
Response is very exact.
Response is short lived.
1.
2.
3.
4.
5.
Information passes as a chemical
substance through the blood and lymph.
There is slow transmission of information.
Response is usually slow.
Response is usually widespread.
Response is long-lasting
HORMONE :
The term hormone was coined by Starling.
Hormones are also called ''Primary messengers'' or chemical messengers.''
First discovered hormone is secretin. It was discovered by Bayliss & Starling in 1902.
ruseducation beyond boundaries
Source & Chemical Nature : - Hormones are chemical messengers which are secreted by one part of
body and are poured directly into the blood stream, and they reach at their target place with the help of
blood. A small amount of hormone affects some specific cells or physiology of cells of organ according
to atmospheric conditions.
Chemical Nature of Hormone :
The animal hormones may be classfied into 6 categories.
1. Amino acid derivatives : The hormones epinephrine and norepinephrine from the adrenal medulla and
thyroxine from the thyroid gland are derived from amino acid.
2. Short peptides : The hormones oxytocin and vasopression from the posterior lobe of the pitutary gland
are short peptides of 9 amino acid. The melanocyte stimulating hormone (MSH) from the intermediate
lobe of the pituitary gland is also short peptide of 13 amino acids.
3. Long peptides : The hormones insulin from the pancrease, adrenocortico tropin (ACTH) from the
anterior lobe of the pituitary gland, calcitonin from the parathyroid gland consists of 84 amino acids.
4. Protein : The gonadotropic, thyrotropic and somatotropic hormones from the anterior lobe of pituitary
are protein with high molecular weights.
5. Steroids (Fat soluble) : The hormones like cortisol and aldosterone from adrenal cortex, testosterone
from interstitial cells of testes, estrogen and progesterone from Graaffian follicles of ovary and placenta
are the examples of steroid hormones. The hormones contain cholesterol and bile salts.
6. Fatty acid derivative : - Prostaglandin
Physical & Chemical Specialities of Hormones : -
The moleucles of most of the hormones are small, and their molecular weight is low.
Hormones are soluble in water and are easily diffusible in tissues.
The secretion of hormone is always in very small quantity because these are most reactive substances
Hormones are destroyed after use.
Hormones can not be stored in the body except Thyroxine.
Hormones are soluble in water and blood.
Liver and kidneys separate them from blood and decompose them. The waste product formed after
decomposition, hormones are excreted with urine. It can not be reutilized.
Hormones are non-antigenic & non species specific substances.
Usually, hormones do not participate in the metabolic activities of target cells but they affect and control the
activity level of these target cells. Due to the effect of hormones, not only the rate of metabolic activites is
effected but also the permeability of cell membrane is changed so the nature of reaction is also changed. so
the nature of reaction is also changed.
ruseducation beyond boundaries
135
Differences between Hormone & Enzyme
Hormones
Enzymes
1.
2.
3.
4.
5.
6.
7.
8.
They are produced at one site and are passed
by blood to another site for action.
They have low molecular weight.
Hormones may be steroids, proteins,
Peptides or amino acid derivatives.
They are used up in their action
They are effective in low concentration.
Their excess or deficiency may cause
disorders.
They may act slowly or quickly.
They may accelerate or retard the specific
recations.
Hormone controlled reactions are not
reversible.
1.
2.
3.
4.
5.
6.
7.
8.
They may act at site where they are
Produced or carried to another site for action.
They have very high molecular weight.
Enzymes are simple proteins.
They are not used up in their action.
They also act in low concentration.
However, the rate of enzyme catalyzed
reactions steadily increase with an increase in
their concentration
They act slowly.
They speed up the reactions.
Enzyme controlled reactions are reversible.
Differences between Hormone & Vitamins
Hormones
Vitamins
1.
2.
3.
4.
5.
Hormones may be steroids, proteins,
peptides or amino acid derivaties.
They are effective in low concentration.
Their excess or deficiency may cause hormonal
disorders.
They are secreted by the animal in its own
body.
Hormones influence the genes to produce
Specific enzymes required during metabolism.
They do not influence the working of those
organs which have secreted them.
1.
2.
3.
4.
5.
They are never proteins but simple organic
compounds such as amines, esters.
alcohol, aldehyde or organic acids.
They are needed in small quantity. Excess
vitamins are excreted. Their deficiency causes
malfunctioning called deficiency diseases or
avitaminosis.
They are rarely synthesized in the body.
They are moslty taken with food.
They act as co-enzymes and help emzymes to
perform their function.
They are not produced by body organs
(except vitamin D)
ruseducation beyond boundaries
MECHANISM OF HORMONAL REACTIONS
MECHANISM OF HORMONE Two types
Once hormone enter into blood stream it can reach almost to any cell in the body.
However, each hormone effects only certain kind of cell which is called as target organ.
All hormone do not act in the same way due to location of receptor.
Hormones are two types :
(i) Water solbule hormone
(ii) Lipid soluble hormone
Water soluble hormones interact with a surface receptor, normally a glycoprotein and initiate a chain
events within it where as lipid soluble hormone (Steroid hormones) readily pass through the plasma
membrane to cytoplasm of the target cell. Molecular mechanism of hormones are of following types :
(1) At Gene level
(2) At Plasmalemma level
1. AT GENE LEVEL : - In this type of mechanism steroid hormone and Thyroxine hormones are involved.
(a) Steroid hormones : In this process steroid hormones enter into target cell where they combine with
receptor protein, this Receptor protein conveys the hormone from cytoplasm to nucleus this hormone
stimulates the DNA for synthesis of protein. Now DNA synthesises the m-RNA and this m-RNA
goes into cytoplasm, where Ribosome synthesize the protein by translation. This new protein in an
enzyme, which affects the vital activity of target cell.
(b) Thyroxine hormone : The thyroid hormone thyroxine and tri-iodothyronine cause increase
transcription by certain gene in nucleus. To accomplish this, These hormones first bind directly with
receptor protein in nucleus. Receptor protein is located on chromosome. Advantage of intranuclear
receptor the thyroxin hormone can continue they express their control function for weeks :
2. PLASMALEMMA LEVEL : - Following hormones an example of this mechanism :
(a) Tyrosine kinase mechanism : A good example of this is the effect of insulin. For transport of insulin
hormone, insulin receptor is found in cell membrane, which is made up of 4 sub-unit. 2 sub-units ( -
protein) are -protein which are situated towards the outside of cell membrane this sub unit binds the
insulin hormone, 2 sub-unit ( -Protein) protrude into the cytoplasm of the cell. The intra celluar
portion of the units has tyrosine kinase activity. These receptors are usually less than 100 in most
of our body cells but may be more than 1,00,000 as in some liver cells.
Binding to the receptor Binding of insulin to the outer 2 sub units of receptor triggers tyrosine
kinase activity of the intra cellular portion of -sub units. This causes a structural change in -sub units.
to become an activated tyrosine kinase. The activated tyrosine kinase produces autophosphorylation of
the cytoplasmic receptor as well as phosphorylation of some cytoplasmic protein (Insulin receptor
subtrate, IRS).
ruseducation beyond boundaries
137
(b) C-AMP or Second messenger system : This C-AMP mechanism has been shown by following
hromones :
Adreno Corticotropin (ACTH) Secretin
Thyroid stimulating hormone (TSH) Catecholamines
Luteinizing hormone (LH) Most hypothalamic releasing hormone
Follicle stimulating hormone (FSH) Vasopressin/ADH
Parathyroid hormone (PTH) Glucagon
ruseducation beyond boundaries
In this type of mechanism when adrenaline is attached to the surface receptor protein which found on the
plasmalemma then first of all it forms a complex which is called as hormone receptor complex (HRC). A
transducer protein is found on inner surface of receptor protein which is called as G-Protein. This G-
Protein consist of , , -sub unit. GTP is also found on G-Protein.
After formation HRC than GTP change into GDP, in this process phosphate group is released which
activates the G-Protein.
After activation of G-Protein their sub units are divided into two group (i)- -subunit and (ii)- , -subunit
( , -subunit both are not separated with each other)
Activated -subunit of G-Protein activate adenylate cyclase.
Activated adenylate cyclase change ATP to C-AMP on cell membrane.
This C-AMP goes into cytoplasm where it activates the inactive protein kinase-A to active protein kinase-A.
This active protein kinase A changes inactive phosphorylase kinase into active phosphorylase kinase.
This active phosphorylase kinase changes inactive Glycogen phosphorylase in to active glycogen
phosphorylase.
This active glycogen phosphorylase changes glycogen into Glucose-1-Phosphate.
Each molecule of protein kinase-A activates about 100 molecule of enzyme phosphorylase kinase and so
on.
As a result a single molecule of adrenaline releases as many as 100 million molecules of glucose within
only 1 minutes (Amplification).
(c) IP3 & DAG Mechanism : In this type of mechanism local hormones are involved such as
prostaglandins, Acetylcholine, Somatostatin etc.
Same CAMP mechanism transducer G-protein act.
ruseducation beyond boundaries
139
G-protein activates enzyme phosphodiesterase.
Phosphodiesterase (Phospholipasec) Enzyme breaks phosphotidyl inositol biphosphate into inositol
triphosphate (IP3) and diacylglycerol (DAG).
IP3 is water soluble and diffuses into cytoplasm, IP3 specialy mobelized Ca++
ion endoplasmic reticulam and the
Ca++
ion promote smooth muscle contraction and changes in secretion by secretory cell and change in ciliary
action.
DG remain in the membrane where is activates an enzyme called protein kinase C, which in turn,
activates many other enzyme, Activated protein kinase C plays an important role in cell division and
cell proliferation.
The action of lipid soluble hormone are slower and last longer then the action of water soluble
hormone.
ruseducation beyond boundaries
SPECIFIC TERMS
Chalones The hormones which are secreted from one endocrine gland to stimulate other endocrine
gland is called as Chalones.
Autocoide The hormone which are secreted from one endocrine gland to target organ is called as
Autocoide.
Diabetogenic The hormone which mainly affects or stimulates carbohydrate metabolism is called
as diabetogenic.
Ketogenic The hormone, which mainly affect the fat metabolism.
Calorigenic The hormone, which mainly affects the basal metabolic rate (BMR) is called as
calorigenic.
PITUITARY GLAND
On the basis of development pituitary gland is completely Ectodermal.
It is situated in the sella-turcica of sphenoid bone.
This gland is atached to the hypothalamus through a stalk which is called as infundibulum.
The upper terminal end of infundibulum which is attached to the hypothalamus is called as
tubercinerium/Median eminence.
The lower terminal end of infundibulum is bulging type which is called as posterior lobe or pars nervosa.
Tubercinerium, infundibulum & pars nervosa are collectively called as Neurohypophysis.
ruseducation beyond boundaries
141
A small & fine tube is developed in the foetus which is called as gut. This gut is developed into alimentary
canal. Anterior part of gut is called as stomodaeum (developed from ectoderm).
A small projection is developed from dorsal surface of stomodaeum (the anterior part of gut) this part is
separated from stomodaeum and form Rathke's pouch.
Upper surface of Rathke's pouch is developed into mid-lobe which is also known as pars intermedia.
The upper margin of R.pouch, which surrounds the infundibulum & forms a collar like structure called
as parstuberalis.
Remaining part of R.pouch. is developed into anterior lobe which is also called as pars distalis.
Pars distails, pars tuberalis & pars intermedia are collectively called as adenohypophysis.
Neurohypopohysis + Adenohypophysis is called as hypophysis cerebri or pituitary body.
A remaining & vestigeal cavity of R.pouch is found in the anterior lobe which is called as Hypophysis recess.
Superior branch of hypophyseal artery supplies blood to the hypothalamus.
Inferior branch of hypophyseal artery supplies blood to the pituitary gland.
Hypophysal portal vein collects the blood from hypothalamus and supplies to pituitary gland.
Branches of hypophyseal artery & hypophyseal portal vein combined and form a network of blood
capillaries which is called as circle of Willis.
In human, mid lobe is ill developed or membrane like, while mid lobe is absent in elephant & Whale.
Three types of glandular cells are found in Adenohypophysis.
1. Basophils They are large cells & found in the peripheral part of gland. They are more in number.
2. Acidophil They are small in size & found in the central part of pituitary gland.
3. Neutrophils They are smallest in size and are found in scattered form. They are minimum in number.
STH & LTH are secreted by acidophils.
Remaining hormone of adenohypohysis are secreted by basophils.
All hormone of pituitary gland are protein Hormone.
HORMONS SECRETED BY ADENOHYPOPHYSIS
All these hormones are of proteinaceous nature.
1. GROWTH HORMONE OR SOMATOTROPIC OR SOMATOTROPIN HORMONE
[G.H. or S.T.H.] : -
By Somatotroph cells or -acidophil cells
Function : Major effect
On growth
On metabolism
ruseducation beyond boundaries
Effect on Growth : -
(1) On bone : It increases length of bone.
(2) On soft tissue :
(i) GH promotes mitosis & increases number of cells in many organs & tisue e.g. liver and muscles.
(ii) GH stimulates growth of muscle and cartilage due to increase synthesis of collagen, muscle grow in bulk.
Effect on metabolism :
Fat : Increases lipolysis so that free fatty acid level of plasma rises. Under the influence of growth
hormone fat is used for energy in preference to carbohydrate and protein, due to this protein deposition is
increases.
Carbohydrates : Hyperglycermia develops due to decreased uptake of glucose in the cells, so it is also
called diabetogenic hormone.
Protein : GH increases amino acid uptake by the cells of the liver & muscles & helps in protein synthesis.
In the presence of thyroxines and insulin, growth hormones become more active and stimulates the
body growth. In this way this hormone is important for the growth of body.
+
+
+
+
+
Diseases due to hyposecretion or hypersecretion of somatotropin hormone :
(a) Hyposecretion of STH : Due to deficiency of STH in chidhood dwarfism is observed.
Dwarfism due to the defect of pituitary is called Ateliosis. These dwarfs are called as midgets.
This midget is physically & mentally normal while sexual maturation is delayed.
(b) Hypersecretion of STH : - Due to hypersecretioni in childhood and adolescene, a higher quantity of
amnoacids is supplied to the body cells.
(i) Epiphyseal cartilage present on the edges of bones does not convert into bone for a long time.
Thus the bones of legs & hands become very long and height of that person increases very much.
Body becomes imbalanced. This disease is called Gigantism.
(ii) Acromegaly : - Due to hypersecretion of STH in adulthod, jaw bones of the affected person become
long, cheek bones buldge out, broad hands, legs & fingers of person becomes gorilla like. These
symptoms are observed as a result of acromegaly.
ruseducation beyond boundaries
143
2. THYOTROPHIC OR THYROID STIMULATING HORMOONE [T.T.H. OR T.S.H.] :
T.S.H. is secreted by basophil cells. (Thyrotroph cell).
It is glycorprotein in nature.
T.S.H. stimulates thyroid gland to secrete thyroxine. TSH helps in almost all step of the thyroid hormones
synthesis & it causes growth of throid gland.
Secretion of TSH is stimulated by Thyrotrophin releasing factor & inhibited by somatostatin of
hypothalamus.
3. ADRENO CORTICO TROPHIC HORMONE OR CORTICOTROPINE [ACTH] :
ACTH is secreted by basophil (corticotroph) cells.
In man, this ACTH is mainly made up of valine and tyrosine aminoacids,.
It accelerates the cortex part of adrenal gland to secretes hormones.
4. FOLLICLE STIMULATING HORMONE [FSH] :
It is also secreted by basophils. (Gonadotroph cell)
It is glycoprotein in nature.
This is secreted in male and female both.
In males, it stimulates spermatogenesis and normal functioning of seminiferous tubules.
In femables, it stimulates oogenesis and development of Graafian follicles of ovary.
FSH is also known as Gametokinetic factor.
Estrogen hormone that is secreted Graafian follicles is also affected by FSH.
5. LUTEINIZING HORMONE OR INTERSTITIAL CELL STIMULATING HORMONE
[LH OR ICSH]:
It is also secreted by basophil (Gonadotroph) cells. It is also glycoprotein in nature.
It stimulates ovulation in female as a result of this corpus luteum is formed.
Hormone progesterone which is secreted by corpus luteum is also stimulated by L.H.
In men LH is called ICSH. It affects the Leydig's cells or Interstitial cells of testes and stimulates the
secretion of male hormone "Testosterone".
L.H. is also called "gamete releasing factor".
FSH and LH both are called gonadotrophic hormone GTH.
FSH and LH act in combined form so these are called synergesic hormone.
Gonadotrophic hormones (FSH & LH) are start secreting during puberty. Their secretion is regulated by
hypothalamus.
ruseducation beyond boundaries
6. LUTEOTROPHIC OR PROLACTIN OR LACTOGENIC OR MAMMOTROPHIN HORMONE
(PRL) :
It is secreted by acidophil (Lactoroph) cells.
Function of prolactin hormone.
(1) Lactation (Galactopoiesis) : Prolactin is responsible for lactation in postpartum (after delivery)
women.
Regulation of Prolactin secretion by Hypothalamus : Hypothalamus mainly stimulate the production of
all pituitary hormone, but it mainly inhibits prolactin production because normally hypothalamus prolactin
inhibitory hormone (Dopamine) is greater than the releasing hormone.
Breast is prepared for lactation by oestrogen (duct growth) and progesterone (lobule growth) but both of
these hormone inhibit the actual secretion of milk.
Dopamine is catecholamine (Biologically active amine) and neurotransmitter in the hypothalamus. It
inhibits lactation.
During pregnancy : Prolactin hormone steadly increase until term but due to high level of oestrogen and
progesterone (secreated by placenta) lactation is inhibited.
After expulsion of the placenta at parturition, there is an abrupt decline in circulating estrogen and
progesterone.
The drop in circulating estrogen initiate lactation.
Nursing stimulates prolactin secretion.
Prolactin inhibits the action of GnRH on the pituitary and antagonize the action of GnRH on the pituitary
and antagonize the action of gonadotrophin on the ovaries. Ovulation is inhibited and the ovaries gets
inactive.
Nursing is important and effective method of birth control.
7. HORMONES SECRETED BY MIDDLE LOBE OF PITUITARY GLAND :
The part of adenohypophysis of pituitary gland, which is very close to neurohypophysis is a very thin
portion, it is called pars intermedia or middle lobe of pituitary gland.
In man it is in the form of a thin membrane only. It is inactive in men.
MELANOCYTE STIMULATING HORMONE [MSH] :
It is secreted by middle lobe. (By corticotroph cell).
MSH is also called intermedin.
In man, MSH is secreated by anterior lobe, because middle lobe is ill-developed.
It stimulates the melanochytes to synthesize melanin in mammals.
ruseducation beyond boundaries
145
This hormone is related with change in the colour of skin in Amphibian and Reptiles. This phenomenon
of colour changing is known as metachrosis.
It darkens the complexion of skin by distributing melanin pigment evenly under the skin.
Just oppsoite to it, melatonin secreted by pineal body, collects the melanin pigments at one place thus
fairing the complexion of skin.
MSH is found in all the vertebrates, but it is functional in poikilothermic animals e.g. fishes, amphibians,
reptiles etc.
The importance of MSH in man has not been evaluated.
HORMONE RELEASING FACTORS OF HYPOTHALAMUS :
Hormones secreted by adenohypophysis of pituitary gland are under the control of neuro-
secretory cells of hypothalamus. These neuro-secretory cells produce some substances in very small
amount which are called releasing factors.
(1) Grwoth hormone releasing factor : [GHRF] : It stimulates the secretion of growth hormone.
(2) Thyrotrophin relasing factor [TRF] : It stimulates the secretion of TSH.
(3)
GnRH
Follicle stimulating hormone releasing factor [FSHRF]: It stimulates the secretion
of FSH.
Luteinising hormone releasing factor [LHRF] : It stimulates the secretion of LH.
(4) growth hormone inhibitory factor [GHIF] (Somatostatin) : It stimulates the secretion of LH.
(5) Prolactin release factor [PRF] : It stimulates the secretion of Prolactin.
(6) Prolactin inhibitory factor [PIF] (Dopamine) : It inhibits the secretion of Prolactin.
(7) Melanocyte release factor [MRF] : It stimulates the secretion of MSH.
(8) Melanocyte inhibitory factor [MIF] : It inhibnits the secretion of MSH.
(9) Adrenocorticotrophic releasing hormone (ACRH) : It stimulates secretion of Adrenal cortex
hormone.
POSTERIOR LOBE OR NEUROHYPOPHYSIS :
Posterior lobe of pituitary gland is 1/4th part of total gland. It is just like nervous tissue, because in it, the
termnial ends of the axons of neurosecretory cells of hypothalamus are swollen. These swolen ends are
called "Herring bodies". Hormones are released in these bodies.
ruseducation beyond boundaries
There are same large, branched fatty neurogilal supporting cells in between axons, that are called
"Pituicytes".
1. Posterior pituitary hormones are not synthesised in the gland itself but they are synthesized in the
supraoptic nuclei and paraventricular nuclei of hypothalamus.
2. The hormone are then transported from their origin to posterior pituitary through axons of
hypothalamohypo physeal tract and sotred in association with 2 protein i.e. Neurophysin-I, and
Neurophysin-II.
(A) Vasopressin or Pitressin or Anti Diuretic Hormone [ADH] :
Main functions of ADH : Its main function is to increase the reabsorption of water in upper part of
collecting duct and in distal convoluted part of uriniferous tubules. Due to this, amount of urine is reduced.
So it is also called ADH.
The hormone increases the blood pressure by constriction of blood vessels of tissues.
Due to hposecretion of ADH or vasporessin, the amount of urine increases, this process is called
Diuresis. Patient feels thristy, Dehydratinon starts in the body. This disease is called Diabetes insipidus
(taste less urine, polyuria).
Due to hyposecretion of ADH, deficiency of water starts in Extra cellular fluid (ECF). Blood pressure
reduces, urine becomes dilute and blood becomes thick or concentrate.
Intake of coffee, tea and excess alcohol etc decrease the secretion of ADH.
Secretion of ADH is maximum in desert fauna (animals of xerophytic region) e.g. camel.
Kangaroo Rat (Dipodomys) also shows very high hypersecretion of ADH.
Kangaroo - Rat never drinks water in its life-time
Hypersecretion of ADH causes dilution of blood and increases concentration of urine and thus blood
pressure increases.
ruseducation beyond boundaries
147
Control of ADH
(B) Oxytocin or Pitocin : It is the main parturition hormone. It stimulates the fast/rapid contractions and
expansions of non-striated muscles of the uterine wall at the last moment of gestation operiod (pregnancy).
Due to this uterine constrictions, labour pains start jsut before child birth.
This hormone is secreted by pituitary glands of mother at the time of parturition.
This hormone also initiates the contractions in uterine wall muscles during copulation/coitus as a result of
that semen of man is sweeped out in the fallopian tubes of woman.
After parturition, this hormone constricts the uterine wall and thus brings back to the normal position.
Oxytocin hormone contracts the myoepithelial cells present at all the sides of alveoli of mammary glands.
Thus it helps in milk ejection so it is also called milk let down hormone.
In female, this hormone related with emotion.
Even thought, cry or sound of baby can bring about release of this homone in lactating mother.
This hormone helps during egg laying in birds.
Injection of oxytocin are initates cows and buffaloes for instant milk release.
Muller's organ and subneural glands of lower vertebrates are homologus to pituitary gland.
THYROID GLAND
It is the largest endocrine gland in the body.
This is situated at the latero-ventral side of the joint of trachea and larynx in the neck region of man. The
shape of this gland is like letter H or Butter fly. It is bilobed in birds and mammals, but it is single lobed
in reptiles. Both of its lobes are connected by non-glandular band, formed of a connective tissue. This
band is called isthmus. No hormone secreted by isthmus.
ruseducation beyond boundaries
I
It is endodermal in origin.
Endostyle of lower vertebrates like Herdmania, Amphioxus is homologous of thyroid gland.
In human, this gland weight, about 25 gm to 35 gm approximately. (This is some what larger in women as
compared to men).
Each lobe of thyroid gland is made up of connective tissue. There are present so many folicles made up of
glandular cells in connective tissue.
These follicles are scattered in loose connective tissue, the stroma. A layer of cuboidal glandular cells is
found in the wall of follicles. An iodised colloidal fluid substance Thyroglobulin is filled in the cavity of
these follicles. Thyroglobulin is glycoprotein in nature. Parafollicular cells are occasionally found in
between basement membrane of the follicle & these cells secrete thyro calcitonin.
Thyroid is the only endocrine gland in the body which stores its hormone in its inactive state.
Production of Thyroxine :
Thyroxine contains two phenyl rings linked up by an ether bridge.
Biosynthesis :
(1) Iodide trapping when KI taken up by follicular cells.
(2) Oxidation of Iodide KI I2.
The oxidation of iodine is promoted by the enzyme peroxidase.
ruseducation beyond boundaries
149
(3) Organification The binding of iodine with the thyroglobulin molecule is called organification of the
thyroglobulin
Tyrosine + I2 MIT & DIT. (Monoiodotyrosine and Di-iodotyrosine)
(4) Coupling MIT + DIT = T3 (Tri-iodothyronine)
DIT + DIT = T4 (Tetra-iodothyronine)
All of these step of thyroxine biosynthesis are stimulated by TSH hormone.
T1 = Mono iodo tyrosine
T2 = Di iodo tyrosine
T3 = Tri iodo thyronine (20 %)
T4 = Tetra iodo thyronine (80 %)
Secretion of T4 is compartively more than T3, and T3 hormone is four times more active than T4 hormone.
T4 changes into T3 on reaching in the tissues. After enter into tissue deiodination takes place in T=4=
which , change into T3.
T4 is called thyroxine in this T-chain of hormones.
Thyroxine or Tetra-Iodo-Thyronine is a derivative of aminoacid.
Each thryoglobin molecule contain an average of T3 molecule for every 14 molecule of thyroxine
(1 : 14 T3 : T4).
Thyroid hormones in the form of thyroglobulin are stored in the follicles in an amount sufficient to supply
the body with its normal requirements of thyroid hormone for 3 months.
E.C. Kendal first of all crystallised this thyroxine hormone.
Harrington and Barger studied the molecular structure of thyroxine.
Thyroid gland requires iondine "120 g" every day for the production of thyroxine.
Normal recommended minimum intake 200 gm/day, if iondine in take < 50 gm /day, then thyroid
disorder develops.
If there is deficiency of iodine in food then thyroid try to absorbs more and more iodine from blood and
increases its size it is called simple goitre.
Goitre is found more abundently in the persons those live on mountain slopes, because iodine (at that
place) flows along with water. When most of the people show the symptoms of this dissease then it is
called endemic goitre and hill station called as ''goitre zone''
Persons who take sea foods, never show the symptoms of goitre.
ruseducation beyond boundaries
1. Growth, Developemnt and Metamorphosis :
Thyroxine stimulates the metamorphosis of tadpole larva in amphibians.
Due to its deficiency, larva does not show metamorphosis to be an adult.
Some amphibian larvae e.g. Ambystoma and Necturus (Water dog) do not undergo metamorphosis to an
adult, and these larva stages start reproducing without gaining adulthood. This process is called as
Paedogenesis.
2. METABOLISM :
General :
(i) Thyroxine regulates the Basal Metabolic Rate (BMR) in the body.
BMR : The rate of calorie consumption that is necessary for survive is called basal metabolic rate of
body.
The hormone enhances the oxidative metabolism of body cells as a result of it energy production is
also increased in the form of calories.
BMR increases Body Temp. increase loses weight.
Due to over production of heat it is called as calorigenic hormone.
(ii) Increase activity of Na+ K
+ AT Pase. It increases the number of mitochondria in all the cells of body
i.e. increases metabolic rate of life. It increases the consumption of oxygen by the cells of body.
Thyroxine play the both anabolic as well as catabolic role. At optimum concentration it play
anabolic role but in oversecretion it play catabolic role.
Fat Metabolism :
Enhances enzyme activity both synthesis & predominantly catabolism of cholesterol.
Carbohydrate action
Blood sugar increase, act as a diabetogenic hormone.
Protein both catabolism & anabolism but at optimum concentration of thyroxine, anabolism is
dominant.
ruseducation beyond boundaries
151
3. ON INDIVIDUAL SYSTEM : Heart
Thyroxine increases Heart beat increases (Tachycardia) Increases Cardiac output.
Maintain the contraction of myocardium.
It regulates the heart-beat because it acts directly on SA-Node.
CNS optimum conc. of thyroxine is required for developemnt of the nerve fibre & their myelination.
GIT thyroxine increase motility of GIT causes diarrhoea. Appetite also increase.
On blood Thyroxine stimulates. The formation and maturation of R.B.Cs
The hypothalamus and anterior pituitary gland control rate of thyroid secretion.
Anterior pituitary gland secretes TSH.
The most important effect of TSH is proteolysis of thyroglobulin which causes release of thyroxine into
the blood.
Secretion of TSH is controlled by a hypothalamic hormone. Thyrotropin Releasing Hormone (TRH).
Increase thyroid hormone in the body fluid decreases the secretion of TSH by anterior pituitary.
IRREGULARITIES OF THYROID GLAND AND IT'S DISEASES :
1. Hyposecretion of thyroid or Hypothyroidism :
It may be a genetic disorder or due to deficiency of iodine in food or due to excess iondine excretion in
urine.
ruseducation beyond boundaries
In childhood, hypothyroidism causes Cretinism, these children are called cretin, they may show such
symptoms like : Thick lips, protruding tongue, pot belly, ill developed sex organs & retarded physical &
mental growth. The children remain dwarf and become ugly. Their BMR, rate of heart beat and body
temperature decreased. They are sterile.
In adults, hypothyroidism causes Myxoedema. (Gull's disease) The symptoms of this disease are falling
of hair, loose and swollen skin, deposition of adipose fat and mucous beneath the skin so body as a whole
becomes obese, BMR and blood pressure are reduced. Patient becomes sensitive to cold and shows loss of
sexual power. Mental slowing, bradycardia, weight gain occurs and lose of hair from head. Myxoedema
is also called as Sporadiac goitre.
Simple goitre/Endemic goitre : It is due to deficiency of iodine in food, and also known as Colloid
goitre. Thyroid gland enlarges due to swelling. It is not a genetic disorder. The neck also swells up and
looks like a collar. It is cured by extra intake of iodine in food or intake of sea food.
Hashimoto's disease : In this disease, there is acute deficiency of thyroxine. Then the medicines given for
the treatment of disease or even hormone thyroxine itself acts as antigen. In its reaction, body produes
antibodies, which destroy the thyroid gland itself. It is known also as suicide of thyroid or Autoimmune
thyroiditis.
2. Hypersecretion of thyroid or Hyperthyroidism :
The gland shows enlargement due to some microbial infections or genetic disorders, and this enlarged
gland secretes thyroxine in excess amount. As a reuslt of it, BMR, heart beat rate, blood pressure,
absorption of glucose in intestine and consumption of oxygen increase. Too much energy is produced in
mitochondria, that it is not stored in the form of ATP but it is released in the form of heat in the body .
Thus in place of growth unnecessary irritation, exhaustion are observed in the body of patient. Due to
excess heat/calorie/energy formation, patient feels extreme hot.
Hyperthyroidism may cause following disorders in the body :
Expohthalmic Goitre or Grave's disease or Basedow's disease or thyrotoxicosis
In this disease, deposition of mucous beneath the eyeball takes place. As a result of that eyes look enlarged
and buldging or protruding out side the eye socket, giving the patient a fearful look. In this disease whole
gland shows enlargement in the neck region.
ruseducation beyond boundaries
153
Plummer's disease : In this disease, thyroid gland does not show even growth but there become small
tumours all over the thyroid just like buds, it is also called Toxic adenoma.
Thyroid gland shows enalrgement (swelling) at the time of hypersecretion.
Parafollicular cells or C-cells :
Some large and clear cells are found in the stroma of thyroid gland & basal part of follice. These cells are
endocrine nature. They are the remains of ultimobranchial bodies made up of fifth branchial pouches of
embryo, i.e. para follicular cells are endodermal in origin.
These cells secrete thyroclacitonin (Calcitonin) hormone which lacks iodine. It is protein in nature.
Thyrocalcitonin reduces the destruction of bones and increases the rate of excretion of Ca++
in urin, thus
reduces the number of Ca++
in extra cellular fluid.
It enhances the deposition of Ca++
in bones thus making bones solid and strong.
This hormone is antagonistic to Collip hormone or parathormone.
PARATHYROID GLAND
These glands remain embedded in the dorsal surface of surface of thyroid gland. They are two pairs in
number. They remain embedded in each lobe of thyroid completely or partially.
It was discovered by Raynard and its detailed studied was given by Sandrom.
Total weight about 140 mg and its size is 6 × 3 × 2 mm.
These glands are made by epithelium of third and fourth branchial pouches or pharyngeal puches slite of
embryo i.e. these are also endodermal in origin.
These glands secrete only one hormone parathormone. It is also known as Collip's hormone or PTH. Its
was obtained by Collip in its pure form.
This hormone is proteinaceous in nature/Polypeptide hormnone.
Parathormone is essential for survival because it significantly contributes to "homeostatis" by regulating
the amount of calcium and phosphate ion in ECF.
Calcium is key element in many physiological functions like proper permeability of cell membrances,
muscular activities, nerve impulse conduction, heart beat, blood coagulation, bone formation, fertilization
of ova.
ruseducation beyond boundaries
Calcium is most abundant of all minerals found in the body and about 99 % of calcium and phosphorus are
contained in the bones.
Maintenance of proper calcium level under "homeostatis" is in fact, a combined function of
parathormone, thyrocalcitotnin and vitatmin D3 (cholecalciferol).
Parathormone promotes absorption of calcium from food in the intestine and its reabsorption from nephron
in the kidneys.
Simultaneously, its accelerates elimination of phosphate in urine (phosphaturia action). Thus, calcium
level tend to rise in the ECF due to effect of parathormone and phosphate level is decreased in ECF.
This calcium is then utilized by bone-forming cells, (Osteoblast) in bone formation under the influence of
vitamin D3.
Parathormone stimulates the osteoclast cells to feed upon bones, these cells remove unnecessary parts of
bones by melting, thus change asymmetrical bone into symmetrical one. The remoulding of bone is done
by these cells life long. As a result of this, amount of Ca+2
remains constant in blood in normal conditions.
Each 100 ml of blood contains 12 mg of Ca++
About 1 kg of calcium is found in an adult man.
Parathormone maintains the activity of muscles.
Just opposite to it, thyrocalcitonin hormone works antagonistically to oppose the parathormone and
Vitamin D. Thyroclacitonin reduces the amount of Ca++
in blood by increasing the excretion of Ca++
in
urine and by reduing destruction of bone.
1. Hyposecretion : Due to hyposecretion of parathomone or PTH, the amount of Ca++
decreases in ECF (It is
known as hypocalcaemia) and amount of PO43 is increased.
Due to the deficiency of Ca++
in blood, muscles and nerves get unnecessarily irritated and start convulsion
and cramping. Sometimes voluntary muscles remain contracted for a long time, it is known as tetany
disease.
If this tetany appears in intercostal muscles and diaphragm, then animal dies due to Asphyxia.
Removal of parathyroid gland causes quick death. It is the most fatal state/lethal condition.
2. Hypersecretion : Due to hypersecretion of PTH. osteoclast cells feed excess amount of bone
unnecessarily. As a result of this,bones become brittle and weak. This condition is called as Osteoporosis.
When quantity of Ca++
is increase in ECF and level of PO4 is reduced, this condition is known as
hypercalcaemia and hypophosphatemia respectively.
Due to excess deposition of Ca++
in kidneys and gall bladder, stones are formed.
ruseducation beyond boundaries
155
ADRENAL OR SUPRA RENAL GLANDS
Position, Origin & structure :
This gland was discovered by a scientist Eustachius.
It is found on the head (anterior most part) of both the kidneys.
Adrenal gland is ecto mesodermal in origin.
ruseducation beyond boundaries
It weights about 4 - 6 gm in man.
Whole gland is surrounded by a fibrous capsule.
Each gland has two parts :
Outer part of gland is called cortex and inner part is called medulla.
Cortical portion is 80-90% and is develop from mesoderm of embryo.
Medullar portion of this gland is mae up of neural-ectoderm of embryo. Only 10-20 % part is medullar
part of gland.
Adrenal Cortex :
Most of the cells of this part are fatty. This portion is divided into three regions from periphery to centre.
1. Outer zone or Zona glomerulosa :
Mineralocorticoid hormones are secreted by this zone.
2. Middle zone or Zona fasciculata :
This zone secretes glucorticoid hormones. In this region polyangular cells are arranged in the layers.
3. Inner zone or Zona reticularis : Cells of this region are spread in the form of a network, these are
arranged in layers. This zone secretes a small amount of sexhormones.
About 40-50 hormones are synthesized in adrenal cortex. All these hormones are of steriod nature. Their
basic constituent is chloesterol, these are also called corticoids. Out of these 40-50 hormones, only 7-8
hormones are active.
1. Mineralocorticoids :
2 main hormones fall under this category.
(1) Aldosterone (2) Deoxycorticosterone
Aldosterone -
These hormoens are related with distribution of water in tissues and balance of electrolytes in the body.
These hormones maintain the ionic balances of Cl , K+, Na
+ and water in the blood and ECF.
ruseducation beyond boundaries
157
Aldosterone hormone affects distal convoluted parts of uriniferous tubules & upper part of collecting
duct.
It basically activates the Na K pump.
It helps in reabosption of Na+ & Cl ions and controls the excretion of K
+ ions.
Aldosterone hormone is also known as salt retaining hormone it increases sodium concentration.
An increase in Na+ ion concentration (than normal) in ECF is called Hypernatremia.
In hyposecretion of aldosterone hormone, there is a tremendous loss of ions of Na+, Cl and HCO3 by
urination and K+ ions are increased in blood.
2. Glucocorticoids :
Mainly two hormons comes under this categories : - (i) Cortisol (ii) Hydrocorticosterone
(A) Cortisol : It is an important hormone secreted by zona fasciulata. It is also known as
Hydrocorticosterone. Cortisol has a small amount of mineralocorticoid activity.
Metabolic Effect :
On Carbohydrate metabolism :
Increases sugar in blood causes Hyperglycemia. It stimulates the gluconeogenesis in the liver.
Protein metabolism : Cortisol stimulates the protein break down in some organs like lymphoid tissues
(thymus, lymph node etc), muscles, bones, skin etc.
Fat metabolism :
(i) Facilitates lipolysis.
(ii) Promotes deposition of fat, in subcutaneus tissue of the body.
On nucleic acid metabolism :
Cortisol inhibits the synthesis of nucleic acid in all other tissues except liver where (i.e., in the liver) RNA
synthesis is increased.
This hormone controls the activity of collagen fibre and controls the local inflammation or oedema.
This hormone is "anti-inflammatory.
Cortisol in used in arthritis/Rheumatism
Cortisol checks the antigen antibody reaction and controls the local allergy so, it is also called as anti
allergic hormone.
This hormone increases the no. R.B.Cs and decreases the W.B.Cs in the blood so, This hormone is
Immuno-suppressive.
Now a days, contrisols are used in transplantation of organs.
3. Sex Hormones/Sex corticoids/Gonadocorticoids :
Sex hormones secreted by adrenals are called gonadocorticoids.
They are secreted in very small amount by zona reticularis.
ruseducation beyond boundaries
Male hormones are called androgens and female hormones are called oestrogens.
Both the hormones are secreted by men & women, but sex hormones are mainly secreted by gonads.
The sex hormone of oppsoite sex secreted by adrenal gland.
These hormones stimulate the muscles, external genitalia and sexual behaviour.
Male hormone secreted by adrenal gland is mainly dehydroepiandrosterone [DHEA].
Female sex hormones progesterone and estrognes are secreted in minute quantities.
Adrenal medulla :
Origin : The adrenal medulla develops from the neuroectoderm of the embryo.
Structure : The adrenal medulla consists of rounded groups of relatively large and glandular cells. These
cells are modified of sympathetic nervous system which have lost normal processes and have acquired a
glandular function. These cells are called chromaffin cells or phaeochromocytes. These cells are
connected with the preganglionic motor fibres of sympathetic nervous system, these are dicussed together
as sympatheticoadrenal system.
Hormones of Adrenal medulla :
Two hormones are secreted by this part. They are collectively called as catecholamine.
These hormones are synthesized by chromaffin cells with Tyrosine amino acid.
(A) Adrenaline or Epinephrine :
This hormone is 80 % part of the total hormones secreted by Adrenal medulla.
It was termed as Emergency hormone by Walter Cannon, because this hormone prepares the body to
face unavoidable emergency situations.
Functions of Adrenaline :
It constricts the blood vessles of skin (Vaso contriction).
The hormone enhances the flow of blood by vasodilation of blood vessels of brain, heart, liver and skeletal
muscles.
Increases the rate of heart beat, cardiac out put, so increases blood pressure.
Adrenaline enhances the heart beat and thus increases cardiac output, due to this, circulation of blood
becomes faster.
The hormone stimulates the trachea and bronchi muscles to relax, as a result of it, rate of breathing is
increased. So adrenaline hormone is used in asthma.
It dialates the pupils of eyes. Goose flesh is observed due to its effect. It constricts the erecter pilli muscle
of hair, and hair are raised.
The hormone contraction in spleen, as result of it, spleen pours its stored blood into blood stream and
controls the blood volume in body.
ruseducation beyond boundaries
159
It checks the secretion of saliva and reduces the peristaltic movements in alimentary canal.
Due to the effect of this hormone, clotting period of blood is reduced, This hormone also stimulates the
contraction of Uterus in female at the time of parturition.
Adrenaline provides the body with an emergent chemical defence mechanism in stress conditions that
threaten the physical integrity and chemical consistancy of the body e.g. accident, restlessness, fear, anger,
mental tension, pain etc. It immediately prepares the body to face the emergency by a violent stress or
alarm reaction.
The cortisol hormones of adrenal cortex serves to maintain the body in living condition and recover it
from the servere effects of stress reactions. Thus an increased output of cortisol is "life saving" in "shock
conditions". So it is also known as life-saving hormone.
The hormones of adrenal medulla prepare the animal for fear, fight or flight in emergency conditions. (by
excess secretion of these hormones) Adrenaline hormnoe is called 3F = FFF homone and adrenal gland is
called "triple F gland" (FFF gland)
Noradrenaline or Norepinephrine hormone :
It is only 20% part of total hormones secreted by adrenal medulla.
It acts as vasoconstrictor, thus increases the blood pressure. Exception It does not constrict coronary
artery of heart.
IRREGULAR SECRETION OF ADRENAL HORMONE :
(i) Hyposecretion :
Addison's disease : Hypoadrenalism
Caused due to hyposecretion of corticoid homrone of adrenal gland, following are some symptoms of
addison's disease dehydration in the body, Blood pressure, BMR and body temperature are reduced,
excretion of water and Na+ increase. The skin of hands, neck and face turns to bronze colour.
Hyposecretion of corticoids causes reduction in amount of glucose in blood, it is called hypoglycemia. In
this disease, patient may die, so hormones of adrenal gland are called life-saving hormones.
(ii) Hypersecretion :
Cushing's syndrome (disease) :
Due to hypersecretion of Gluco corticoids, body increases breadthwise or body becomes broad because
excess deposition of fat under the skin (to cause moon face, fish mouth and buffalo hump). Protein
catabolism increases in body. Irregular growth of skin and bones is observed. Hyperglycemia occurs.
Amount of Na and water increase in ECF, which is called oedema. Due to this B.P. also increases.
Conn's Disease : (Primary aldosteronism)
Due to excess of mineralocorticoids, an imbalance of Na+, K
+ is observed. This disease is called "Conn's
disease". Due to this disease there occurs irregularity in nervous system, as result of that muscles get
contracted, Muscle weakness, hypertension and hypokalemia are observed.
ruseducation beyond boundaries
Adrenogenital Syndrome/Adrenal virilism/Pseudohermaphrodite :
In this case, girls develop male characters, eg. menstrualion cycle is stopped, uterus and ovary are reduced
or constricted and clitoris becomes enlarged. Somatic hairs are develops on body, development of Beard
and moustache. Only hair symptoms are called as Hirsutism.
In a man, female sex hormone is secreted by adrenal is in excess amount. he will show feminine characters
i.e. development of mammary glands this disorder is called gynaecomastia.
If in a male, androgens are present in excess amount, it developes extra enlargement of penis. This defect
is called macrogenitosomia e.g. manis, Armedillo.
Adrenal gland is also known as 4 S gland
S Sugar metabolism
S Slat retaining actions
S Sex hormones
S Stress reactions
4 S
Control of adrenal Secretion :
Adrenocorticotropic hormone [ACTH] of anterior lobe of pituitary gland controls the hormones secreted
by adrenal cortex.
ACTH controls very little or even does not control the secretion of mineralocorticoids. These are controlled
by Renin hormone secreted by kidneys.
Pituitary gland does not control the secretion of adrenal medulla hormones, the adrenal medulla hormones
secretion is controlled by nervous system.
The amount of cortisol and ACTH in blood is maximum in the morning and minimum in early part of night.
ruseducation beyond boundaries
161
THYMUS GLAND
This is situated in the anterior part of heart called mediastinal space. It is a bilobed gland. It is originated
by third branchial pouch of embryo, i.e. it is endodermal in origin.
Thymus gland is well developed in a new born child, but it reduces continuously from adulthood to old
age. It remains in the form of a string at last.
Its structure is just like lymph gland. It is covered by connective tissue coat capsule and internally both the
lobes are redividing in to small lobules.
Each lobule has a dense, darkly staining peripheral cortex and a looser lightly staining central medulla.
The cortex consists of densely packed lymphocytes.
The medulla consists of reticular epithlial cell, a few lymphocytes and the "Corpuscles of Hasslls" thymic
corpuscles.
Thymus gland is related to immune system of body.
Hormones and functions of thymus gland :
Thymus gland secretes thymosin or thymin hormone, that is proteinaceous in nature/Polypeptide.
Main-immunity develop upto 9-10 year. If thymosine immunity power very high tymosin myasth gravis
develop.
(1) This hormone helps in immune system of the body.
(2) Hassall's corpuscles are found in thymus gland, these are also called thymic corpuscles or epithelial cell
or reticular cell, they act as phagocytes.
(3) After the birth, T-Cells or T-lymphocytes are matured in thymus gland, then these lymphocytes are
releases by thymus gland, reach to lymphatic organs like spleen, payer's patches and lymph nodes &
deposited in it.
(4) Thymosin hormone stimulates the maturation of lymphocytes to destroy the antignes produced by bacteria
or pathogen.
ruseducation beyond boundaries
(5) According to one of the theories of Ageing the decline and disappearance of Thymus gland by middle age
is the primary cause of ageing.
(6) Thymosin helps in the development of sex gland but inhibits sexual maturity in early young age.
(7) Thymus provide cell mediated immunity so thymus is also called "Throne of immunity" or "Training
school of T-lymphocytes".
Secretion of thymin decreases the neuromuscular transmission, so hypersecretion of thymine may cuase
myasthenia gravis (may be treated by corticoidesfor short time). It provides the antibody against receptor
& block the Neuromuscular junction.
PINEAL BODY
Position :
It is situated at the dorsal side of diencephalon of anterior part of brain i.e. prosencephalon. It is also
known as Epiphysis cerebri. Pineal body is a part of brain. It is ectodermal in origin.
There are found pinealocyte cells (formed by the modification of nerve cells) and supporting interstitial
cells or neutroglial cells in pineal body.
Pineal body called as third eye in frog.
Hormone & Functions :
Pineal body secretes a hormone melatonin, which is an amino acid.
Melatonin is functional in lower vertebrates only.
In amphibians and reptiles, this hormone is related with metachrosis (change in the colour of skin). It
affects the Melanophores of skin, thus acts antagonistically to the MSH of pituitary i.e. it fairs the
complexion of skin.
Central part of gland secretes antigonadial hormone.
The hormone controls the sexual behaviour in mammals. It inhibits the sexual irritation, and also inhibits
the development of genitalia and their functions.
If pineal body is removed from rat, these will attain premature adolescence.
The gland probably controls the sexual behaviour according to light differentiation, thus it acts as a
biological clock.
It is proved that the level of melatonin rises during periods of darkness and falls during periods of light.
Children blind from birth attain puberty earlier than normal.
Maximum developoment of pineal upto 7yr & then it undergoes involution & at the age of 14 yr interstitial
tissue and crystals of CaCO3 or Ca3(PO4)2 are deposited in it, these are called "Brain sand" or "Acervuli".
ruseducation beyond boundaries
163
PANCREAS
Position : Pancreas is a pink coloured mixed gland
Endodermal in origin. 99% part is exocrine Acini Digestive enzymes.
1% part in endocrine Islets of Langerhans Different hormones.
Each islet of Langerhans has 4 types of cells
(A) Alfa cells ( -cells) : These are the largest cells present in peripheral region these are approximately
25 % of the total cells. They secrete glucagon hormone.
(B) Beta cells ( -cells) : These are the small cells present in central region. These are about 60 65 % part
of total cells. They secrete Insulin hormone.
(C) Delta cells ( -cells) OR Gamma cells ( -cells) :
These cells are found in middle region. These are about 10 % part of total cells. They secrete
somatostatin hormone which regulates the activities of -cells and -cells.
(D) F-cell or PP-cells : Along with above mentioned cells, some other cells are also found in islet of
Langerhans, these are called PP-cells which secrete pancreatic polypeptide hormone.
(1) Insulin :
It was first prepared/found by Benting and Best.
Molecular structure of insulin was given by A.F. Sanger (with the help of cow's insulin)
The term insulin was also given by A.F. Sanger.
Insulin is the first protein that is artifically synthesized in lab and is crystallized.
Human insulin was synthesized by "Tsan".
Functional human insulin is made up of 51-amino acids that has 2 chains.
(i) -chain It is made up 21 aminoacids
(ii) -chain It is made up 30 amino acids. Both chains are bind together with cross bonds of disulphide
bonds.
"A.F. Sanger" was awarded by Noble Prize for it.
Functions of Insulin hormone :
(I) Actions on cell membrane permeability.
(II) Actions on metabolism of : Carbohydrate, Protein, Fat, Nucleic acid, Minearl.
ruseducation beyond boundaries
On cell membrane permeability : Exept brain cells, R.B.Cs. retina, insulin stimulates the permeability
and consumption of glucose in all somatic cells.
Actions on Metabolism :
Carbohydrate :
(1) Insulin inhibits gluconeogenesis.
(2) Promotes glycogenesis. There are two major sites of glycogenesis, Liver and the muscles.
(3) Enhances peripheral utilization (oxidation) of glucose, causing the blood glucose level to fall.
(4) Inhibits glycogenolysis.
(5) Insulin reduces the glucose level in blood so, it is also called as Hypoglycemic factor.
(6) Insulin is an abolic hormone.
Fat :
(i) Insulin promotes lipogenesis and inhibits lipolysis.
(ii) Due to deficiency of Insulin incomplete oxidation of fats takes place which, is the main cause of
ketoacidosis in blood.
Protein : Insulin promotes protein synthesis by promoting uptake of amino acid by liver and muscle cell.
Nucleic acid : Insulin promotes synthesis of DNA and RNA.
Hyposecretion of Insulin :
(1) Due to hyposecretion of insulin, permeability and consumption of glucose is decrease, Glycogenesis
decrease in the liver so, glucose level in blood is increase and this disease is called "Diabetes mellitus" or
sugar disease.
(2) World Diabetes Day 14 November.
Glucose is excreted throught urine, if amount of glucose is in excess in the blood, this is known as
"Glycosuria". In this stage, amount of glucose in blood increases upto > 180 mg./100 ml of blood plasma.
The amount of water increased (in this stage) in the urine, so intervals of urination reduced, it is called
polyuria.
Polydipsia - Due to excess loss of water and minerals through urine. The patient feels thristy.
Polyphagia - Due to deficiency of glucose and energy is somatic cell patient become excessive hunger.
Due to incomplete oxidation of fats in fatty tissues, ketone and acetone bodies are formed. This ketoacidosin
apply toxic effect on brain cells.
The combined effect of ketoacidosis, dehydration and hyperglycemia may cause diabetic comma to the
patient, patient becomes unconscious and even some time may be die.
Insulin hormone is given to the patient by injection in this disease, Insulin given orally is not effective,
because it digest in the alimentary canal like protein.
ruseducation beyond boundaries
165
Now a days, oral insulin is used in following states :
(A) IZS Insulin Zinc Suspension. (B) PZI Protamine Zinc Insulin
Hypersecretion of Insulin :
Or Hyperinsulinism :
Due to hypersecretion of insulin amount of glucose decreases in blood. It is called hypoglycemia.
In hypoglycemia state, body cells take more and more glucose from blood So need of glucose for nervous
system, retina of eye, genital epithelium is not fulfilled, as a result of that patient looses its reproductive
power and sight. Due to excess irritation in brain cells, patient feels exhausted, unconsciousness, Cramps,
and at last patient may die.
"Insulin shock" After physical exercise or fasting, if a diabetic patient takes an inlusin injection, sugar
level in blood reduces quickly up to 40 mg/100 ml of blood. It is called insulin shock. The patient may be
unconscious or even may die.
Disabetes mellitus are two type
(i) Type - I Diabetes mellitus : It is also called as juvenile diabetes or Insulin Dependent Diabetes
mellitus (IDDM). It is usually develops before age 40 and it is characterised by loss of -cells with
eventually absence of insulin in the circulation. due deficiency of insulin fatal high level of ketone
bodies. increase the blood. Insulin is the metabolic hormone which present ketonebody formation.
(ii) Type - II Diabetes mellitus : It is also known as matuarity onset diabests mellitus or Non-Insulin
Dependent diabetes mellitus. It is usually develops after age 40 year and is not associatede with total
loss of the ability of secrete insulin.
(2) Glucagon :
It is secreted by -cells.
It was discovered by "Kimball and Murlin".
Glucagon is a hyperglycemic factor.
It is made up of 29 amino acids.
It is antagonistic to insulin. It is secreted by the gland, when sugar level of blood reduces.
Glucagon hormone increase the amount of glucose in blood.
It stimulates gluconeogenesis in liver, as a result of that amount of glucose in the blood increased.
It stimulates Lipolysis of fats in fatty tissues.
The secretion of insulin and glucagon is controlled by a limit control feed back. When amount of glucose
is increased in blood, then insulin is secreted by -cells. As a result of it, when amount of glucose is
reduced in blood, then glucagon is secreted by -cells.
ruseducation beyond boundaries
(3) Somatostain :
It regulates the secretion of insulin and glucagon.
(4) Pancreatic Polypeptide (PP) :
Its functions are known yet today perhaps it controls the absorptin of digested food in intestine.
OTHER ORGANS WHICH SCRETE HORMONES
(A) Kidney : - Main function of kidney is excretion, but it secretes some hormones also. These are as follows :
1. Renin : - It converts a plasma protein is secreted by Juxtaglomerular complex of kidney. Renin
hormone acts as an enzyme. It changes the Angiotensinogen into Angiotensin I.
Angiotensinogen hormoneninRe Angiotensin I.
Renin hormone increase reabsorption of water and Na+ ions in uriniferous tubules.
It stimulates the secretion of aldosterone hormone from adrenal cortex.
2. Erythrogenin : The hormone reacts with plasmaprotein (Globulin) and forms a new hormone
erythropoietin.
Erythropoietin stimulates bone marrow to form RBCs.
3. Renomedullary prostaglandins : It is the most active renal hornone. It makes relaxation in unstriated
muscles of blood vessels of kidneys. It enhances the excretion of Na ions by urine (diuretic effect),
renal vasodilation & decreases tubular reabsorption.
(B) Skin : Due to the effect of ultraviolet rays of sunlight steroids like Argosterol and cholesterol are changed
into Argocalciferol and cholecalciferol vitamin D respectively in the skin, it reaches to its target organ by
blood stream.
Vit. D is supposed to be a hormone. It acts as a co-hormone with parathormone.
It helps in bone formation and teeth formation. It increases the absorption of calcium and phosphorus by
intestine.
'Rickets' disease is observed in children due to the deficiency of vit. 'D' as a result of which bones become
weak and thin.
In adulthood, its deficiency causes Osteomalacia. Bones become weak and brittle.
(C) Gonads : -
(i) Testes (Male gonad) :
Leydig's cells or Interstitial cells of connective tissue of seminiferous tubules of testes secrete male
hormones androgens.
Main androgens are testosterone and androsterone.
These are steroid in nature.
Testes also secrete inhibin/activin
ruseducation beyond boundaries
167
WORKS OF TESTOSTERONE
It increase the diameter of pectoral bone.
It stimulates the haemopoiesis in bones.
It increases the cholesterol level in blood.
Testosterone is the main androgen (30 to 100 ng/ml).
It changes the sexual behaviour in male eg. deveop the sexual attraction towards the female.
This Hormone stimulates the development of secondary sex organ. Such as epididymis, vas deferens,
seminal vesicle.
This hormone developes the low pitch of voice which is known as musculizatin of voice.
This Hormone stimulates the number of sebaceous gland on the face which causes the Acne & pimples.
It increases the developemnt of beard & moustache.
It develops the musculization power in muscle.
It also stimulates the growth of hair on the upper limb, lower limb, thoracic, abdominal part, armpits &
near to the external genital organ.
It stimulates the skeletal growth.
It also help in the organisation of Ca+2
in bones.
(ii) Ovary (Female gonad) :
Estrogen/Oestrogen : The hormone is is secreted by the inner layer theca interna of graafian follicles.
Estrogen includes estradiol, estrone and estriol.
Estrogen is steroid in nature.
This Hormone stimulates the development of secondary sex organ such as fallopian tube, uterus, vagina.
Promotes the development of mammary gland. It stimulates the tubular growth.
It devlops the high pitch of voice which is also called as Feminine of voice.
This Hormone removes the hair from face, upper & lower limb, thorax & abdominal part. But
stimulates growth of hair near the external genital organ & armpits.
It makes the muscle soften.
It also develops the growth of skeletal muscle & bone. It help in the organisation of Ca+2
in the bone.
It increase the diameter of pelvic bone.
It stimulates the blood formation but decreaes the cholesterol level in the blood.
It stimulates the rate of growth of hair of head.
It also changes the sexual behaviour, means attraction towards the male.
ruseducation beyond boundaries
Corpus Luteum : (Temporary endocrine gland).
After ovulation Graafian follicle changed into a yellow gland in the ovary, it is called corpus luteum.
Regulation and control of its production is done by L.H. Corpus luteum is an endocrine gland. Following
are the hormones secreted by this gland.
(1) Progesterone :
The hormone stimulates the developemntal characters of pregnancy.
Due to the effect of this hormone, uterine wall endometrium become thick and blood circulation is
increased in it. Fats and glycogen are deposited in its cells.
This stimulates the alveolar growth of mammary glands become highly developed, as a result of this
breasts become enlarged.
It helps in implantation of embryo in the uterine wall.
The hormone maintains pregnancy, so it is also called "Pregnancy hormone" Progesterone inhibits
the contractions in uterine wall muscles, so it is also called "anti abortion hormone".
(2) Relaxin :
Perhaps corpus luteum also secretes it, but it is secreted at the end of pregnancy/gestation period.
(3) Estrogen
(4) Inhibin
(D) Placenta : (Temporary endocrine gland).
Placenta connects the embryo and uterus of mother at the time of embryo development. It secretes some
hormones
(i) Chorionic gonadotropic hormone (CGH) = Human chorionic gonadotropic (HCG)
It is a protein hormone. It helps to maintain the pregnancy and controls the secretory action of corpus
luteum.
At the initial stage of pregnancy CGH or HCG is secreted in excess amount by placenta and it is
excreted by urine. At this stage pressence of CGH of HCGH in the urine is tested by urin test.
It is a positive test for pregnancy. It also called Gravidex test.
HCG or CGH is tested in urine test for pregnancy test.
(ii) Placental lactogen or human chorionic somatomammotropin :
It is also a protein hormone, and stimulates the mammary glands for milk production.
(iii) Estrogen : It is a steroid. It controls extradevelopment of breast during pregnancy.
(iv) Progesterone : It is also a steroid. It controls the slow action of slowly abolishing corpus luteum and
maintains the pregnanacy.
(v) Relaxin : It is a protein hormone. At the time of parturition, it helps to expand the pubic symphysis of
pelvic girdle to facilitate the child birth in females.
ruseducation beyond boundaries
169
Hormones which always remains in tissue fluid :
There are some hormones which never reach upto blood stream but always remains in ECF.
These are as follows :
(1) Neurohormone : These are secreted in the nodes of axons of nerve cells. Acetylcholine and Norepinephrine
are the main neurohormones.
(2) Prostaglandin : These are fatty acids. These are most active substances among all the known substances.
Prostagladin are of so many types. Kidneys, gonads, seminal vesicles, thymus, brain etc. Due to
vasodialator this hormone decreases the blood pressure.
These prostaglandins are first of all observed in semen of man. These stimulate contraction of unstriated
muscles.
These prostaglandins are secreted by seminal vesicles and reach upto vagina of female thorugh semen of
male, and then these activate the muscles of uterus of female.
(3) Kinins : These are chemicals which are secreted by any organ of body at the time of chemical change in
ECF, and reduce the B.P. by expanding blood vessels. These also reduce th time of blood clotting.
Kinins are also called as "Firstaid hormone".
(4) Pheromones or Ectohormones :
The term "Pheromone" was coined by Karlson and Butenandt.
These are secreted by exocrine glands. These are also called "Semio-chemical". They travell from one
place to other place by air.
These chemicals are secreted by animals and effect the other animal's behaviour and mode of life of the
same species.
Just like hormones, their target place is far from place of origin.
First of all, pheromone Bombykol was studied. It is pheromone of silk moth. Pheromones are volatile in
nature, and travel through air from palce to place.
Pheromones are of 3 types :
(1) Sex Pheromone :
These attract male and female animals for reproduction. Female silk moth secretes Bombycol or
Gyplure from its body which attracts male for mating.
(a) Muskone : It is secreted by Musk deers.
(b) Civetone : It is secreted by cats.
(2) Aggregation pheromone :
This pheromone is secreted by one member of social insects and pheromone sends mesages to other
members of that society. Thus helps in aggregation. e.g. : Geradiol pheromone in honey bee.
ruseducation beyond boundaries
(3) Alarm pheromones :
These pheromones are secreted by one members of the insect species and alarm the other members of
the same species. e.g. : Secretion of formic acid in ants insects etc.
SPECIAL POINT
Heterocrine gland : These are those endocrine glands which are involved in hormone secretion as
well as some other function eg. pancreas, gonads, placenta, GI mucosa and kidneys.
In females protactin induce maternalism i.e. strong emotional attachment.
In male prolactin promotes paternalism i.e. protective attitudes towards family members and intensive
food gathering for the family.
Sporadic cases of simple goitre (sporadic goitre) in a population are normally due to genetic defect.
Tropic hormone : A hormone which stimulates another endocrine gland to secrete its hormone is
called trophic hormone.
Simmond's diseases : This condition is due to atrophy of the anterior lobe of pituitary gland.
Pheaochromocytoma : It is due to hypersecretion of adrenaline causes, high blood pressure, high
level of sugar in blood and urine, high metabolic rate, nervousness and sweating.
True sexual precocity : True sexual precocity is early maturation of ovaries and testes with
production, of ova before the age of 9 years in girls, or sperm before 10 years in boys, occurs without
evident cause.
Sexual pseudoprecocity results from adrenal cortex, testes, ovary or from other sources, including
extragonadial tumours.
Eunuchoidism : Failure of testoterone secretion in male causes eunuchoidism. (A) eunuch has a
undeveloped secondary sex organs like prostrate, seminal vesicle and penis (B) lacks external sex
character such as beard, moustache and low pitch of voice and (C) does not produce sperm.
Growth hormone : Stimulate the liver to form "Somatomedins" (Insulin like growth factors"). This
somatomedins potent effect to bone growth.
In heart CGMP has antagonistic effect to CAMP, CAMP mediate muscle contractin in response to
adrenaline, while CGMP slow down muscle contractin is response to acetycholie (NCERT).
CGMP used in second messanger in atrial natriuretic peptide and Bronchodilation use as medicine
(life saving drug) vasodilation in genital organ nitric oxide.
ruseducation beyond boundaries
Recommended