CHEMICAL COORDINATION

“ It is the type of coordination present between the cells or different organs within the body of multicellular organisms. In this kind of coordination a group of cells releases specific chemicals, which regulates the activities of other cell of the body.”

Endocrine system

ENDOCRINE SYSTEM

DEFINITION Endocrine glands are organs in the

body that produce hormones which are released directly into the bloodstream. Together these glands make up the endocrine system, which performs essential functions like regulating metabolism, growth and reproduction.

INTRODUCTION Endocrine derives from the Greek words endo

meaning inside, within, and crinis for secrete Chemicals are released by these glands(hormones)

hormone derived from Greek word which means ‘to excite’

The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine.

In animals glands are of two types Exocrine gland: release products (enzymes) into

DUCTS› Ex) Sweat, digestive juices

Endocrine glands:– directly to bloodstream; NO DUCTS› Ex) Hormones

Features of endocrine gland: their ductless nature their vascularity, the presence of intracellular vacuoles or granules

storing their hormones.

Endocrine system vs. nervous system

Endocrine system Effects are slow to

initiate Response are

prolonged (few hrs to week)

HORMONES released in blood stream

Nervous system Effects very fast

and quick Responses are short

lived. NEUROTRANSMITTERs

travel through neurons released in synaptic cleft

CHEMICAL CLASSIFICATION OF HORMONES

1. Peptide/ Protein2. Steroid3. Amine (modified amino acids e.g. Thyroxine, Epinephrine,

Norepinephrine) PEPTIDE HORMONE

May occur as short chain of amino acids e.g., ADH, Oxytocin

Or occur as long chain amino acid e.g. Glucagon, Insulin, Prolactin

Not lipid soluble Received by receptors external to the cell membraneSTEROID HORMONE They are lipid soluble Diffuse easily through the membrane

Hormone Actions

PEPTIDE HORMONE › React with specific receptors

outside the cell› This triggers an enzyme

reaction with lead to the formation of a second messenger (cAMP).

› cAMP can produce specific intracellular functions: Activates cell enzymes Change in membrane

permeability Promote protein synthesis Change in cell metabolism Stimulation of cell secretions

Hormone Actions Steroid Hormones

› Pass through the cell membrane› Binds to specific receptors› Then enters the nucleus to bind

with the DNA which then activates certain genes (Direct gene activation).

› mRNA is synthesized in the nucleus and enters the cytoplasm and promotes protein synthesis for: Enzymes as catalysts Tissue growth and repair Regulate enzyme function

Endocrine Glands Hypothalamus Pituitary

› Anterior lobe› Posterior lobe

Thyroid gland Parathyroid

glands Adrenal Glands

› Cortex› Medulla

Islets of Langerhans

Gonads› Ovaries› Testes

Pineal gland Thymus others

Hormonal Communication

Hypothalamus Neuroendocrine organ Central part of brain

attached by numerous nerves to pituitary gland

Weight is about 4g(human) Control the pituitary gland

by producing chemicals (releasing/stimulating or inhibiting hormones)

Maintains homeostasis(heart rate, body temperature, water balance, and the secretions of the pituitary gland)

Pituitary gland(Hypophysis)

Pea size gland hang from the base of brain by stalk (infundibulum) loge in the bone of skull, weigh is about 5gm

In past considered as master gland but it itself under the control of hypothalamus

It consists of a hormone-producing glandular portion

Have two lobes1.Anterior pituitary (Adenohypophysis)2.Posterior pituitary (Neurohypophysis)

Anterior pituitary –hypothalamus

(Adenohypophysis) It Secretes six regulating

hormone (tropic hormone)

1. Thyroid stimulating hormone (TSH)

2. Adrenocorticotropic hormone (ACTH)

3. Follicle stimulating hormone (FSH)

4. Luteinizing hormone (LH)

5. Growth / somatotropin hormone (GH /STH)

6. Prolactin

7. Melanocyte stimulating hormone (MSH)

Anterior P. Homeostatic Imbalances

Growth /Somatotropin

hormone (GH) It is a non- trophic,anabolic

hormone which simulates the growth of all body tissue specially skeletal muscles ,bone and cartilage.

Control protein synthesis and general metabolism

Imbalances 1. Hyperseretion in childhood

produces gigantism2. Hyperseretion after adult-hood

produces acromegaly3. Hypo secretion in childhood

produces dwarfism

Posterior Pituitary or Neurohypophysis

Neurohypophysis It does not synthesize hormones, however, it stores and releases two hormones produced by the neurosecretory cells of the hypothalamus

• It is an extension of hypothalamus

• Antidiuretic hormone (ADH)

• Oxytocin

Pituitary—Posterior lobe Oxytocin

› Stimulates smooth muscle contraction of uterus at labour

› Stimulates mammary glands during lactation.

Antidiuretic H.› Stimulates water

reabsorption in collecting ducts.

› Decreases urine output

› Hypo secretion of ADH produces diabetes insipidus

› Excessive thirst and urination

Thyroid Gland Located at the base of neck in

front of trachea Bilobed and butterfly shaped Weigh about 25-40gm Composed of follicles which

produce 1. Thyroxine (TetraiodothyronineT4)2. Triiodothyronine (T3) 3. Calcitonin

Both T3 and T4 are important in controlling metabolism and are essential for normal physical growth and mental development.

Calcitonin causes excess blood calcium to be deposited in bones.

Homeostatic imbalances

Hypothyroidism results› Myxedema (in adults)lethargy,

weight gain, dry- skin, hair loss, cold intolerant, confused and depressed.

› Goiter—low intake of iodine in diet

› Cretinism (in children)mental retardation,dwarfism,lack of sexual maturity.

Hyperthyroidism results› Graves disease (enlargement

of overall gland along with

› Exopthalamic goiter(excess accumulation of fat and mucus in eye orbit)

Parathyroid GlandsTwo pairs of pea-sized

glands embedded on the surface of thyroidWeigh about 0.05g-0.3gParathyroid hormone (PTH)Antagonistic to CalcitoninStimulated by falling Ca2+

in blood and inhibited by rising blood Ca2+

Stimulates osteoclasts to free Ca2+ from boneStimulates Ca2+ uptake

from intestine & kidney

Pancreas Consists of two major types

of secretory tissues which reflects its dual function › Exocrine gland

secretes digestive juice

› Endocrine gland releases hormones

Patches of pancreatic cells (Islets of Langerhans) secretes› Insulin from beta cells in

response to high blood glucose level

› Glucagon from alpha cells in response to low blood glucose level

Adrenal gland/ suprarenal gland

Triangular structure located at the top of kidney

Weight of each gland is 5gm Have two parts1. Adrenal medulla 2. Adrenal cortex Adrenal cortex produces three

kinds of steroid hormones Glucocorticoid(cortisol) Mineralocorticoid (aldosterone) Small amount of sex hormone

(Androgens).

Adrenal cortex Cortex› Activity stimulated by ACTH› Controls prolonged responses by

secreting corticosteroids.1. Glucocorticoid(Cortisol)

regulate glucose metabolism and the immune system.

2. Mineralocorticoids(Aldosterone) regulate salt and water balance

3. Gonad corticoids(Androgens)development of secondary sexual

characteristics in male like growth of facial hair and deepening of voice.

It is produced in both sexes and its excessive secretion in females causes masculinization i.e,appearance of beard

Adrenal Cortex Imbalances

Hyper secretion leads to Cushing’s Disease Weight gain Hypertension Reduced sex drive Diabetes Depression/inability to think clearlyHypo secretion leads to Addison’s DiseaseFatigue, weakness, loss of appetite Weight loss Gastrointestinal problems (nausea, vomiting, etc.) Darkening of the skin Low blood pressure and low blood sugar

Adrenal Medulla Medulla

› The adrenal medulla mediates short–term responses under the influence of sympathetic nervous system.

› It secretes two emergency hormones under stress conditions to bring about fight or flight response.

Epinephrine(adrenaline) increases blood glucose, heart

beat, breathing rate and metabolic rate.

directs blood to the heart, brain, and skeletal muscles.

Norepinephrine (noreadrenaline) Works like epinephrine Sustains blood pressure

Pancreas Homeostatic ImbalancesDiabetes

TYPE I Diabetes Beta cells are destroyed by

lymphocytes as a result of autoimmune disorder.

No insulin is produced.TYPE II (Diabetes mellitus) Insulin is produced Target cells lose insulin

receptors Excess glucose excreted in

urine As a result of fat

metabolism ketone bodies accumulates in bloodBlood Level Regulation in Diabetics

Thymus gland

It is present in the upper part of chest behind the breast bone.

It consists of two lobes that join infront of trachea.

It secretes a hormone, Thymosin, which stimulates the development and differentiation of T lymphocytes after they leave the thymus.

It plays a role in regulating the immune system by stimulating other kinds of immune cells.

Pineal gland It is a tiny cone-shaped

body located in diencephalon (fore brain)

It secretes Melatonin which› Influences growth and

development of gonads› Controls Day/night cycles› Timing of sleep, body

temperature, appetite› Participates in setting the

body’s clock

Gonads Ovaries

› Estrogens› Maintains female reproductive cycle› Development of secondary sexual characters› Progesterone› Preparation and maintenance of uterus for the

development of embryo Testes

› Testosterone› Stimulates bones and muscles growth› Development of secondary sexual characters