THE ENDOCRINE· SYSTEM

Plasma Membrane

Receptor protein

How Steroid Hormones Work Figure 37.4

G) Steroid hormone (S) passes through plasma membrane.

® Inside target cell, steroid hormone bonds to a specific receptor protein.

® Receptor-steroid hormone complex enters the nucleus

·· ant:!, binds :to DNA, ..

Alteration of cell activity

How Peptide Hormones Work Figure 37.5

142

Peptide hormone'

S~cond Messengers F1gure 37.6

TFhe Human Neuroendocrine System 1gure 37.7

-~. / Pineal gland

· ··/~~Hypothalamus .

. J·v -~. I Antenor

~;,··.::::-,.j' Pituitary 11obe . •·;-. ./ Postenor \.· ..... ..,._11' - 1' lobe

Parathyroids --=======:::,•./o~ Thyroid

(behmd thyroid) .L''"/ Thymus

Adrenal

· cortex } Adrenal

Adrenal glands .

medulla

Ovaries------­(in females)

Testes----~

(in males)

On\'( ~'-. MV.lo<' ~awis

,.hcf'& ~('8. man'"( N\o'!"~

143

~~:~0 ~·~;\ ....

Prin~:ipal Endo~:rine· Hlanqs a n d the I r Endocrine Gland and Hormone

I. Posterior lobe of pituitary Antidiuretic hormone (ADH) Oxytocin

2. Anterior lobe of pituitary Growth hormone (GH) Thyroid-stimulating hormone (TSH) Gonadotropic hormones

Luteinizing homione (LH)

Follicle-stimulating hormone (FSH) Adrenocorticotropic hormone (ACTH) Prolactin (PRL) Melanocyte-stimulating hormone (MSH)

3. Thyroid gland Thyroid hormone (thyroxine) Calcitonin

4. Parathyroid glands Parathyroid hormone (PTH)

5- Adrenal medulla Epinephrine and norepinephrine

6. Adrenal cortex Aldosterone Cortisol

7. Pancreas (islets of Langerhans) Insulin Glucagon

8. Ovary Estrogens

Progesterone

9. Testis Testosterone

10. Pineal gland Melatonin

11. Thymus T~1ymosin

Target Tissue

Kidney tubules Uterus Mammary glands

. General Thyroid gland

Sex organs

Sex organs Adrenal cortex Mammary glands Melanin-producing c,ells

General Bone

Bone, kidneys, digestive tract

Muscle, cardiac muscle, blood vessels

Kidney tu buies General

General Liver, fat tissue

General female reproductive structures

Uterus Mammary glands

General

Male reproductive structures

Sex organs (?), pigment cells

White blood cells

.. · ..

Stimulates re~bsorptibri\;r w~ter; c;~~~~t wa.ter .. Stimulates contraction of uterus .. ; . · Stimulates milk letdown

Stimulates growi:h .. . Stimulates secretion ofthyroid hormones ·

~~ ~.

Stimulates ovulation (females); stimulates secretion of · testosterone (males) ., ...... . Stimulates ovarian follicle (females) and sperm production Stimulates secretion of adrenal cortical hormones Stimulates milk production Controls pigmentation in some animals

Stimulates metabolic rate; essential to nom1al growth and develiop>mf:nt:'~ Lowers blood calcium levels by inhibiting loss of calcium from

Increases blood calcium levels by stimulating bone breakdown;··· stimulates calcium reabsorption from ·in kidneys; activates vitamin D

Initiate stress response; increase heart rate, blood pre~sure, metabolic rate; dilate blood vessels; mobilize fat stores; raise blood sugar levels •

Maintains proper balance of sodium and potassium ions in blood Aids in adaptation to long-term stress; raises blood glucose levels;

mobilizes fat stores; stimulates carbohydrate metabolism; acts to reduce inflammation ~'{;

111 Lowers blood glucose levels; increases storage of glycogen Raises blood glucose levels; stimulates breakdown of glycogen in liver'

Stimulate development of secondary sexual characteristics and . growth of sex organs at puberty; prompt monthly preparation of uterus for pregnancy

Completes preparation of uterus for pregnancy Stimulates development

Stimulates development of secondary sexual characteristics and growth spurt at puberty

Stimulates development of sex organs; stimulates production of sperm

Function not well understood; influences pigmentation in some animals; may control biorhythms in some animals; may help control onset of puberty in humans

Stimulates maturation and production of white blood cells

(b) anterior lobe

growth hormone

(GH)

Figure 6

most cells

mammary glands

(a) posterior lobe

posterior pituitary----­(stores and releases hormones)

ADH.

kidneys

follicle-stimulating hormone (FSH) and luteinizing hormone (LH)

testes or ovaries

mammary glands, uterus

--------hypothalamus (regulates release of hormones from anterior pituatary)

f------- anterior pituitary

thyroid-stimulating hormone (TSH)

thyroid gland

ACTH

adrenal cortex

The pituitary gland is composed of two separate lobes: the posterior lobe and the anterior lobe. (a) The cells of the hypothalamus synthesize antidiuretic hormone (ADH) and oxytocin, which travel from the hypothalamus to the

pituitary along specialized nerve cells. The hormones remain in the pituitary gland and are released into the blood when they are needed. ADH acts on the kidneys and helps regulate body water. Oxytocin initiates strong uterine contractions during labour.

(b) Hormones released by nerve cells of the hypothalamus regulate hormones secreted by the anterior pituitary.

376 Chapter 8 NEL

Bone

209 The Mp-ter Gland Figure ___ 3

..... ____ _ ---.

0 ot:::'

~ '<::-0

F 0

r:§~ .f!

Peter Raven and George Johnson, U' Communications, Inc., Dubuque, low

'anding Biology, 3/e. Copyright© 1995 Wm. C. Brown .ights Reserved.

,r:

2)*~

Intermediate· Mostly glandular tissue

Melanocyte­stimulating hormone

'Present in most vertebrates (not adult humans).

MSH Pigmented cells in integument

Induces color changes in response to external stimuli; affects behavior

cortex

Figure 26.5 Functional links between the hypothalamus and the anterior lobe of the pituitary.

thyroid gonads

Figure 26.6 Secretions of the anterior lobe of the pituitary and some of their targets.

ANTIDIURETIC HORMONE

INCREASE~ Concd=~~ion of PLASMA SALT.,.,,,,,:·-'·''!!.; r··~·'·''~ .r·-:·:c,,~:: <'··· ST!i':f-!JR:V~L LACK of D1etary WATER or to --"''•:,~~- ENVIJ<ON_MENT LOSS of BODY WATER from ~- .,., .. / ·.~ {~ (e.g. p,gmful

SwEAT GLANDS (in sweat) NERVOUS · · stimu/;) LuNbS (in expired air) I(EFLEXES and GuT (In raeces) \ EMOTIONAL

orto STRESS EXCESS DIETARY SALT /

results in t

INCREASED OSMOTIC PRESSURE Stimulate of BLOOD---------- stimulates (:'~(.::---SUPRAOPTIC NUCLEUS

OSMORECEPTOI<S ."::;i:•,:'

[Dimimshed Concentration of P!ast77a Salt due to rz.g. Excess Intake of !1{;ytrzr

t [)1/ution of 13/ood Stream

t [)/mim'shed Ost77ot:/c

Pressure t

k/1 /n Act/vdy of the Osmoreceptors

t Fall in Output' of ADH

t !Jtinim'.sned Reahsorpt-ion

of Water t

Increased Out-put-of Dilute Urimz

~ !<est-ores OSMOTIC.

PRESSURE

·'\ '\

'\

' ' '\

Nerve cells transmit ,. impulses along axons of

·SUPRAOPTICO-HYPOPHYSEAL ~~- _ TRACT to

· .... POSTERIOR PITUITARY to cause discharge of

ANTIDIURETIC HORMONE(ADH) into BLOOD STREAM for DIRECT ACTION on CELLS LINING DISTAL and COLLECT­ING TUBULES of KIDNEY

NEPI-iRON ADH increases their rerme..ability to water

~ ', Augmcznts reabsorption of ', WATER from GLOMERULAR

", FILTRATE in DISTAL (2N°) CONVOLUTED TUBULE and in COLLECTING

t TUBULES

R-educes output of URINE to BALANCE and RESTORE OSMOTIC PRESSURE RELAT!ONSJ.I!PS

to normal} -------- ~ RELATIONSHIPS to normal.

~ maint-ain FLU![) EQUIL!BJ<!UM

{This hormone. also has vasoconst'r.ictor effects~ .increased 13/ood Pressure)

170

OXYTOCIN

Secretion of Hormone, OXYTOCIN. ~~;··· .. · ,_;_~. . seczms to depend on AFFERENT W// (S~nsory) nerve imp~lses -"-----to-~------- f-:jYPOTHALAM US

4 VULVA

' I from

r"-

~ Nerve cczlls of the :-__,-_-_-_-_-"""'...:.;'g-~{---S~PRA-OPTIC NUCLEUS. send

- ···.·:_,:·:· Impulses along axons of ,'~ - --NIPPLES ;11/; ,6f BREASTS

/ /. (dunn9 SUCKLING)

/ I / 1 LACTATING

SUPRAOPTICO-HYPOPHYSEAL TRACT to

POSTERIOR PITUITARY to discharge

OXYTOCIC HORMONE. into BLOOD STREAM

/ // MAMMARY /UTERUS GLANDS

Stimulates MYOEPITfiELIAL C..ELLS In ducts to contract

t Rap/d express/on of preformed MILK from secret"tn9 alveoli to R£S£.R VOIRS

(GALACTAGOGUE acbon­or 'Let--down· of rmlk)

for PRIMARY ACTION

Reinforces contractt'ons of uterine smooth muscle

dvr/n9 and aJtrzr chtldbli-th

t

The funct/on of Oxytoc/n /n the J??a!e ts unknown

and leads eventually to INVOLUTION ofthe (IT£RUS

(i.cz. rrzturn to approximately pre-pregnant size)

169

' 1

I

UNDERACTIVITY of POSTERIOR PITUITARY Damage, by INJURY or DISEASE, to

~~ ~.---I-IYPOTHALAM US

"'.' ( or to ----SUPRAOPTICO-HYPOPHYSEAL TRACT

or to X- -----POSTERIOR PITUITARY causes

I t . Absence from Blood Stream of ANTIDIURETIC HORMONE t (ADH)

DIMINISHED from ' "l REABSORPTION of WATER

.. ·~< 1 [OBLIGAIDRY REABSORPTION of

~~-~-PROXIMAte;~) CONVOLLJTED

·~ ~ TUBULE

11 ', FACULTATIVE REABSORPTION of ',, from

' DISTAL (2N°) CONVOLUTED TUBULE and COLLECTING DUCT does not occur (Ce..'l's /;/ling collecttng du-ct remain im_permea/;/e to water)

Increased ELIMINATION //of WATER

/ /

/_,.URINARY VOLUME rises

DIABETES INSIPIDUS characterized by EXCESSIVE THIRST and EXCESSIVE PRODUCTION of DILUTE URINE

Normal GLOMERULAR FILTRATE-ofovczr 100 litrczy'

Oa'f about 70 to 80 li trczs of glomerular filtrat.z wat£r anz reabsorbed outwith influence of ADH.]

about 20 to 30 litres per day

normally under ADH control.

up to20 or30 litres of PALE Dl LUTE U Rl N E excreted/day (sPECIFIC GRAVITY 100/ to /.002) instead of normal 1-1.12 litres straw coloured more concentrated fluid (s.G. !.020 - /.032)

Small a.l77ou.nts o/ ?ost"e.r.ior Pituitary extract a.bsor.bv:d /.rom u.ndtzr the t"onqu~ or qivv:n .by su.bcutaneous /n/v:ct.ion reduce v:/inunat.ion of water t-o normal.

171

OVERACTIVITY of PITU:ITARY EOSINOPHIL CELLS Functional overactivity (or tumour) chidly of the EOSINOPHIL cells of the Anterior Pituitary leads to GIANTISM in the CHILD: ACROMEGALY in the ADULT.

J ( --.-... -.._ I T I -.. I

Overproduction of GROWTH Hormone Overgrowth of all Body: Tissues j_ I ',, ' : ...... General Circulation Onsrzt-belbre Onsrzt"arterpu.6rzrty

· 1 · bony epiphyses h3ve "f closed at puberty

lncrea·ses NITROGEN retention. Influences Protein, Carbo­hydrate and Fat metaboJism of ALL CELLS of the body.

NORMAL CHILD AGE 13 AGE 13

&ones tfl/i::ke~ IZ'SpiZC/;,;./_.y or t=ACE, JAW. NOSE, llANOS andFE£T--+

tT!xzse p3bent"s frequently. show a ra/sed .Sasal Meta.6ol/c rat:rz; a lu"y>h /Jiood Su9ar level and !'he presence or Sugar in the urine. Other /eatures a/this cond/t/on

are due o/ten to pressure of tumoar on surrounolnq .6rain bssurz or somet/mes to over­product/on or othrzr Anterior Pituitary flormones.}

.Dest-ruction o.f' t.hrz overactive cissue- usua//y by RADIUM the~apy­p~vrznts proqrrzss./on of the cond.it./on.

165

UNDERACTIVITY of ANTERIOR PITUITARY Deficiency or absence of EOSINOPHIL cells . t Underproduction of GROWTH Hormone·

(Somatotrophin) · t

LORAIN DWARF

Delayed Skeletal Growth and ·, Retarded Sexua I Development" but alert, intelligent, well proportioned child.

AGE 13 NORMAL CHILD AGE 13

Extracts of human GROWTH hormone rest:ore growth a.nd develop.172ent pattern. to .n.or771a.l..

Destructive disease of part of Anterior Pituitary(usually with damage to Posterior P~tuitary. afd/or 1-lypothalamus)

Underproduction of GROWTH and other ENDOCRINE-TROPHIC Hormones

II t FROHLICH'S DWARF

AGE 13

Stunting of Growth, Obesity (Large

apprztt'trz for svgat); Arrested Sexual

Development~ Lethargic;

Somnolent;­Mentally SubnormaL

Atrophy of other

Endocrine glands

Signl of deficiency of their hormones.

A s.i'nu!ar condition occurs /n ADifLT without dwarh'nq .but' wi't.h suppression of srz:x /unct./ons and re~ression of' secondary sex charact'er.rst/cs.

· Extracts of GROWTH and GONADOTROP/-1/C hormones a1d .1~ restor.in9 patient to normal.

164

OVERACTIVITY of PITUITARY BASOPHIL CELLS

Overactivity (often due to Tumour) of the Basophil cells of the Ante~ior Pituitary

j Overproduction

especially of

ADRENOCORTICOTROPHIC HORMONE l (ACTH or Corticotrophin)

lli9h 8/ooo' Su9ar • s7~nne Overstimulation. Glucocortico;ds

Overactivity of

Hypertrophy and /

SUPRARENAL Excess ''Mineralocorbcoids'' CORTEX - Corb'co/d-;- (except Aldost-erone)

'\ Andro9ens

Weakness Obes/ty

·Hirsvt/sm

gives

· CUSHI~G's SYNDROME.

This condition is usually .indist.inqt.ushahle c/in/cally ./rom that- seen .in primary ovrz.ractz"v.ity or tu.rnour o/ t:.hrz Su_prarenal Co.rtrzx Jl-seJf. The sy.rzdrome /s here s.hown in the adult- wo.ma.n.

Overproduct/on of THYROTROPHIN--+- Overac6vity of THYROID gland

166

PANHYPOPITUITARISM Cam12.lete Atrold_hy(or insufficiency)of all secreting cells of Anterior Pituitary t . . inAdult -SIMMOND'S DISEASE-~:

FAILURE to APPEARANCE of PREMATURE SENILITY / PRODUCE Features usually / ANY HORMONES assoct"ated with /

very OLD AGE --

1 LACK of HAIR 9rey, sparse: GROWTH HORMONE. loss of .6odyhai'r.

X Grave upset: In _SKIN dry, sallow, TISSUE meta.6olism wrinkled.

LACK of

BODY emaciated (great lass of wei9ht)

BONES frail

GONADOTROPHINS ----'~SEX ORGANS atrophy. Menstrvation ceases. ~prodvcb"vrl cycle stops. Secondary Se)(

characteri'stt"cs gradl/al/y regress.

I ----

frn,:s patient is only 42 years of

a!J'Z] Al"tw- ZoNDt!K, Ois~ases 01' th~ t:nclocrinrz: Glancls.

LACK of ENDOCRINE-TROPHIC

HORMONES -ALL ENDOCRINES

atrophy and show depressed srzcre c/on of rhrz/r llarmones

l - B~sal meta~ol;sm d<pr•ss•d

f Body temperature depressed, Heart rate low.

(Mental changes supervene)

Blood prczssure low. Blood sugar low. Electrolytic upset .

.ExtrC~cts of Anter.ior Pituitary .171ay rrz!J"e-vrz the condidon .but rarely succczed /:n complrzfu/y nzstor/ng- t.hrz pat/ent to normal

167

Figw·e 37.12 The interaction of PTH and calcitonin to regulate calcium (Ca••J levels in the blood. PTH acts to remove calciumfi·om bone and deposit it in the blood. Calcitonin acts to remoue calcium fmm the blood and deposit it in bone.

Figure 37.13 How bonnones control water and salt levels in the blood. Cont1·ol of water (H2 0) and saLt (Na•) baLance within the l<idnev is cente1·ed in the hypothaLamus. The postehoT pituita1Jl pmduces antidiuretic honnone (ADH), which rende1·s the kidnev's coLLecting ductsji·eely penneable to water. As a result. :water leaves tbe ducts andjlows into the blood, increasing wata retention. 'Hihen water rerentwn is too high. blood p1·essvre rises. P7·essure­sensitiue recepton m tbe hypothalamus detect tbis and cause ADH pmduct1on to shut dou•n. If the leueL of salts in the bLood(aLLs. the adrenal cortex uutiates production of the hormone aldostemne. which stimulmes saLt reabso1p1ion by the hdne_r d11cts

G) ADH is released from anterior pituitary.

® ADH causes kidney tubules to release water into blood.

G) High water pressure shuts down ADH.

ADH

ADH

)

G)

Kidney

@) High water pressure dilutes salts in blood; aldosterone is released.

®Aldosterone causes kidney ducts to reabsorb sodium and other salts.

Table 1 Pituitary Hormones

Hormone Target Primary function

Anterior lobe

thyroid-stimulating thyroid gland • stimulates release of thyroxine from

hormone (TSH) thyroid

• thyroxine regulates cell metabolism

adrenocorticotropic adrenal cortex • stimulates release of hormones hormone (ACTH) involved in stress responses

somatotropin (STH), most cells • promotes growth or growth hormone (GH)

follicle-stimulating ovaries, testes • in females, stimulates follicle hormone .CFSH) development in ovaries

• in males, promotes the development of '·· sperm cells in testes

luteinizing hormone (LH) ovaries, testes • in females, stimulates ovulation and formation of the corpus luteum

• in males, stimulates the production of the sex hormone testosterone

prolactin (PRL) mammary glands • stimulates and maintains milk production in lactating females

Posterior lobe

oxytocin uterus, mammary • initiates strong contractions glands • triggers" milk release in lactating females

antidiuretic hormone kidneys • increases water reabsorption by kidneys (ADH)

Hormones That Affect Metabolism

Table 1

Gland Hormone Effect on metabolism

thyroid thyroxine (T4) and • regulates the rate at which glucose ,triiodothyronine (T3) is oxidized within body cells

thyroid calcitonin • lowers calcium levels in the blood

parathyroid glands parathyroid hormone • raises calcium levels in the blood (PTH)

anterior pituitary growth hormone (GH), • promotes protein synthesis .by increasing or somatotropin the uptake of amino acids by cells

• causes a switch in cellular fuels from glucose to fatty acids

UNDERACTIVITY of THYROID

If the THYROID shows atrophy of its secretory cells or is inadequately stimulabzd by the Anterior Pituitary:-

FALL (or absence) LESS (or no) ofTHYROID THYROID

,'HORMONES\ HORMONES\ I in blOod \ I W ter blood \

,' 1 ,' to dczpnzss ~ 1 I I act:ivi ty of I I ~ _)'t_ • ANTERIOR I

~' 1~ PITUITARY /

\ iJ:s~u6ftd~~{al d' / ~ ', ' .......... , .. ·.·--~····:pan " ~~

, to TIIYROID-··----:---- tJody '--- --STIM7iLA'f'/NG J.IORMONE 7iSs-ues

In t~rz ADULT ' I

MYXOEDEMA

_SLOWING UP OF ALL BODILY

PROCESSES

congen/ta/ absence of

Insufficient HORMONAL SECRETION released to Blood Stream. TISSUE OXIDATIONS are depressed. irz. Rate at which cells use energy is reduced. The Basal Metabolic Rak falls. Less Heat is produced. Body T«:mperature fa lis {and person feels COLD). . Energy stores increase (e.g. GLYCOGEN

and FAT). Blood cholesterol increases. Appetite is reduced; Weight increases. Gut movements are sluggish...,..· · Constipation. Heart and Respiratory Rate.s and Blood PrQ:sSure reduced. Thought processes slow down__. Lethargy; Apathy. SKIN- Thick, leathery, puffy. HAI.R- Brittle, ::;parse, dry.

In t~e Cf.IILD -' I

CRETIN thrz gland --i FAILURE t of

DWARFING SKELETAL} SEXUAL MENTAL

GROWTH and DEVELOPMENT

All ''rmlestones" of .Da.Dyhood are delayed.

Tf.IYROID EXTRACT (taken by mouth) .resto.rrzs /nd.r"v.1duals to norn2al.

152

OVERACTIVITY of THYROID If an e:nlarqed THYROID shows increased activity of its secretory cells:-

Great FALLin bl.ood THYROID

1 HORMONES I \ j promotczs 1

1 greater _ \ 1 production 1

Great RISE in blood THYROID HORMONES

depre:ssczs production

: of ~ , of

I TSHbyJ.iS TSHby I ANTERIOR T -~- ANTERIOR I PITUITARY ... ·· : PITUITARY I I \ stimulates 1 \ g rcza tczr 1

production 1 \. and nz/czascz 1

' ,_,, / ::=::;i, ', ~THYROID·:~

, of~--"<· "'-4':~J<>;,

-.. ... _ .HORMONE. ---~.:--, ---

TI-IYROID GLAND

cakrzs up more IOOINE

SPEEDING UP OF ALL

BODILY PROCESSES

EXCESS THYROID HORMONES are distributed by blood stream to the Tissues of the Body. -SPEED up OXIDATIONS in the: cells, i.e. rate at which all cells use

ENERGY

The Basal Metabolic Rate is raised. As a by-product of this increased ce:llular activity more heat is pro­duced----+ rise in BodyTemperature (person frzrzls WARM). t ·

Profuse Sweatinq. Energy stores of body (i.e.GLYCOGEN and FAT) are depleted. -

Appetite increases but wa:ight falls. Movements of digestive tract are increased- Diarrhoea. He:art and Respiratory Rates rise:. Blood Pressure is raised. Muscular tremor and nervousness are marked. Person becomes excitable and

apprehensive.

/EXOPHTHALMOS (protrusion ofeyeha!ls) may be due to an czxcess of some Pituitary Hormone. It is not ducz to an excczss of Thyroid Hormones.}

Surqical removal of" part of the overactive qland reduces thrz Thyroid activity.

153

UNDERACTIVITY of PARATHYROIDS Atrophy or removal of Parathyroid tissue causes a fall in BLOOD CALCIUM level

and increased excitability of Neuromuscular tissue. This leads to severe · · convulsive disorder -TETANY.

PARATHYROID GLANDS I I

(/sua/ Manifestations:­TWITCHINGS, NERVOUSNESS, OCCASIONAL SPASMS OF FACIAL AND LIMB MUSCLES .

• • lnadequat~ Production of BONE~

PTH -- ff ----..- LJi/nin/shed

... .. .. solubil;"ty ...... ',of Ca snd P

4f~;,

Increased ""-·~mountsor

···· Ca and Pin , bones

' ' \

Otmt{JI;J;;dj tubular ;;

reabit;Jrption of G9

: d~::tsed J")~ \ 1 phosph_at-e Increase \ 1 rzxcr~bon · · · . ' 1 tn urtnary '

\ \ \ \

' ' ' ' I I

' ' \ 1 Ca \

\ w \ \ ' ' \

TETANY

lr concrznt:ration of Ca in blood falls below 6mgjl00ml

plasma.

' ' __ ', ', Fall in Concentration of "· ·· ·""'· ' ........... ~ Blood Calcium

, 1 D/minish.rzd ... r, , "'" aasorpt/on of ..... __ .. ~LRise in p;asma

~~~~~~~~~l\, dtiztary Ca ..... - ..... - ... --------..... phosphate} ''' .. ·"'-~, ................. \.\,. ....

{Note the Inverse relat/onshlp .between plasma calc/'vm and /norganlc phosphato/

Symptoms are rel/e:ved hy .inie:.ction of Caldum or of Extract of Parathyroid.

155

OVERACTIVITY of PARATHYROIDS Over activity of the Parathyroids (due often to tumour) leads to rise m

BLOOD CAlCIUM level and eventually to OSTEITIS FIBROSA CYSTICA.

PARATI-IYROID GLANDS •• •• Overproduction ~

of PTH ------ BONE'·,>! ' ~ f_;j Greatly increased

solubi!t:J: or

cf:,~/r: P~'"" C{j t~ OSTEITIS FIBROSA CYSTICA

~\\\ t '\ \ Eventual Solbzmng --~ and derormity of bones

... ·~ \"J.o.. j Greatly incr~asrzd ~ ~ ~~

t-ubular -" ~ ~

::!i~~~c-~\}.\:1 'i•uil/111' ::,;.~

~~ Grrzat: loss or Pin

Urine Great increase in Concentration

~ \r:.rrT

~-.:~ \11, 1 Great' ,~;;i-~ascz in \\ ''"'' absorpt:'/on or

\11,,~ dietary Ca and P ... ,._ .... \ .. ,,,, .... , ... ,, .........

j/ of Ca in Blood l (Plasma Ca may be over 16mq /lOOm!-+ Increased

VIscosity of Pla&ma.) Deposition of Calcium in Unusual Sites· e.g. Kidney.

The increased level of blood calcium ~ventua/ly leads to excessive loss of CALCIUM in URINE and also of WATER since the salts are excreted in solution.

Excision of the overactive Parathyro;'d_t.issue a..Dolishes syndrome.

156

short-term stress response long-term stress response

cells in hypothalamus -------------= i---------- hypothalamus sends releasing hormone to anterior lobe of pituitary send signals to nerve

cells in spinal cord

spinal cord cells -----'<- .,..,._J},.__,.., stimulate adrenal medulla to secrete hormone

.lif'.;i}""'"'""'''w""·'''' ·"""'''" ,,,. ''''''"'"'"•-''''ti!~~·-,

$.'

~ {~· .

epinephrine and norepinephrine response • increase in blood glucose due to

glycogen that has been converted into glucose

• increase in heart rate, breathing rate, and cell metabolism

• change in blood flow patterns that direct more blood to heart and muscle cells

carried by blood to cells in adrenal cortex

mineralocorticoids response • increase in the amounts of sodium ions

and water retained by the kidneys • increase in blood volume and blood

pressure

cells in adrenal cortex secrete mineralocorticoids

r----- and glucocorticoids

glucocorticoids response • increase in blood glucose due to proteins

and fats that are broken down and converted into glucose

• suppression of the inflammatory response of the immune system

Figure 5 Stress responses

-

-SUMMARY Hormones That Affect Blood Sugar

Table 1

Hormone Location ot'- Effect hormone production

insulin islets of Langerhans • increases permeability of cells to glucose; increases glucose uptake (pancreas) • allows for the conversion of glucose to glycogen ·

• brings about a decrease in blood sugar

glucagon islets of Langerhans • promotes the conversion of glycogen to glucose (pancreas) • brings about an increase in blood sugar

epinephrine and adrenal medulla • promotes the conversion of glycogen to glucose norepinephrine • brings about an increase in blood sugar

• brings about an increase in heart rate, and cell metabolism

cortisol (a type adrenal cortex • promotes the conversion of amino acids to glucose of glucocorticoid) • promotes the breakdown of fats to fatty acids

• decreases glucose uptake by the muscles (not by the brain) • brings about an increase in blood sugar in response to stress

382 Chapter 8 NEL

glucagon hormone produced by

the pancreas; when blood sugar

levels are low, glucagon promotes

conversion of glycogen to glucose

Figure 1 Insulin, released when blood sugar

levels are high, increases the perme­

ability of cells to glucose. Glucose is

converted into glycogen within the

liver, thereby restoring blood sugar

levels. Glucagon, released when

blood sugar levels are low, promotes

the conversion of liver glycogen into

glucose, thereby restoring blood

sugar levels.

378 Chapter 8

The pancreas contains two types of cells: one t}rpe produces digestive enzymes; the other type produces hormones. The hormone-producing cells are located in structures called the islets of Langer hans, named after their discoverer, German scientist Paul Langer hans. More than 2000 tiny islets, each containing thousands of cells, are scattered throughout the pancreas. The islets contain beta and alpha cells that are responsible for the pro­duction of two hormones: insulin and glucagon.

Insulin is produced in the beta cells of the islets of Langer hans and is released when the blood sugar level increases. After a meal, the blood sugar level rises and an appropriate amount of insulin is released (Figure 1). The insulin causes cells of the muscles, the liver, and other organs to become permeable to the glucose. In the liver, the glucose is con­verted into glycogen, the primary storage form for glucose. In this way, insulin enables the blood sugar level to return to normal. AI; discussed in Chapter 7, insulin helps maintain homeostasis.

Langerhans in the pancreas release insulin into blood

after a meal. blood sugar level rises

blood glucose level increases to normal level

t liver converts glycogen to glucose and releases

liver converts glucose to glycogen

body cells become permeable to glucose

blood glucose level decreases to normal level

------- after fasting, blood sugar level is low

alpha cells of the islets of Langerhans in the pancreas release glucagon into blood

it into blood ~il!L."'!iii~~~~{g~·-J,2i;mc:.:l~§.Wil!~~ ··,..__.,....,.

NEL

follicle-stimulating hormone (FSH) in females, a gonadotropin that promotes the development of the follicles in the ovary

luteinizing hormone (LH) in

females, a gonadotropin that pro­motes ovulation and the formation ofthe corpus luteum

l hypothalamus 1----

L-----~,-------~· c: (GnRH)

t 0 , I

~- - _,.._! anterior pituitary L.- ~ : : o-~...· r----r-------....\' c:

FSH LH

rl j,,~ l I I growing corpus i i follicle luteum i 1

l j I

: I I I 1 : I I I t t ! I

1-:- estrogen progesterone, I 1

i! 1 some estrogen i 1 I jl

~·------~-----~--__j I

I

t Ovulation T !~creased - -1

progesterone, estrogen after

ovulation inhibit FSH, LH

Increased estrogen at midcycle stimulates LH secretion.

Figure 7

secretion.

Feedback loop showing the regula­tion of ovarian hormones

--,.J hypothalamus _,_ -: c L_ ___ -,-____ .... c: I

I

I

gonadotropin-releasing hormone (GnRH)

t : I a : Ol::.. __ a,..n_t_e_ri_o_r_p_it_u_it_a...,ry _j I

c FSH LH

:0 _l__ ! "§ ~-~ --. testes _____ ]

! ! 1 ,Ls Sertoli interstitial I 1 I- '

i cells cells 1 :

I j L I I: ~ t I I X . }' I

1 testosterone - ;- -l . ~

l influence sperm production ! ' ---'

Figure 2 Negative feedback regulatory system for FSH and LH hormones

gonadotropic hormones hormones produced by the pituitary gland that regulate the functions of the testes in males and the ovaries in females

follicle-stimulating hormone (FSH) in males, hormone that

increases sperm production

luteinizing hormone (LH) in

males, hormone that regulates

the production of testosterone

gonadotropin-releasing hormone (GnRH) chemical messenger from the hypothalamus that stimulates _ .. secretions of FSH and LH from the pituitary

Table 3 IOC (International Olympic Committee) Banned Performance-Enhancing Drugs

Drug Advantage Side effects

Anabolic steroids

• Stanozolol, ' • increases muscle mass • decreased growth, kidney problems, Androstenedoil, and strength hair loss, oily skin, acne, shrinking Nandrolone testes, infertility, and cancer

Peptide hormones

• growth hormone • decreases fat • diabetes, abnormalities of bones, • improves muscle mass liver, heart, and kidneys, and liver

disease • high blood pressure

• erythropoietin • increases red blood • thickens the blood increasing (EPO) cells that carry chances of stroke

greater oxygen • heart problems

Beta blockers

• Atenolol, • slows heart rate • reduces cardiac response time Bisoprolol, • makes skin more sensitive to sun

·.t· Nandolol

Stimulants

• amphetamine • increases endurance • irregular heart beat, nervousness, • relief of fatigue difficulty sleeping • improves reaction time ·~

• caffeine • increases alertness • increases blood pressure

• pseudoephedrine • increases alertness • narrows blood vessels and increases blood pressure

Masking agents

• Bromantan • makes steroid difficult • unknown to detect

• Probenecid • stops excretion of • headache, tissue swelling, nausea steroids for a few hours

ALDOSTERONE and ANTlDIURETIC HORMONE .(ADH)_ and the MAINTENANCE of BLOOD VOLUME

TISSUE FLUIDS

or reduction in VOM~T~NGj

KIDNEY

PULSE PRESSU total volume of EXTRACELLULAR FLUID (such os moy rrzsvlt /'rom loss of ISOTONIC SECRETIONS from Gor )/ o~A~<RI-KJEA

1n AFFERENT-' ARTERIOLE. (,.'e. less stretch o,.o,.ohed to wolls)/

I .{.. I 1 JUXTAGLOMERU I APPARATUS

~releases ,------o;-------RENIN

ENDOCRINES

SUPRARENAL CORTEX Zono Glomeruloso

A1zr~~~ 'f~" /

I /

/ I

/

DISTAL TUBULE ~---------~ ~promotes ;__--------:--- Na+rekntiont

HYPQl~J-4~.lAMU5 I

DOSTERONE

OSM9,;~~0R5 sec,.;g,?:'-?.t·-··· on'c(

POSTER;Jb:R PITUITARY

/ :__ __ ·m:~ /

~--------~QISTALand COLLECTING TUBULES 1 ~ rano'rzrrzd permf2CTb/e to water

:..__-------,----H2 0 reabsorption t I

Aldost:eronrz and AD/-1 co-operat-e In ot-her wsys t-o 177aint-ain salt and water balance e.g. where os177ot:/c pressvre relabonships (.::md not-primarily volumes) are dtst-ur/:)(zd (seepp !4-4_ 145).

172

210

Inhibitory " neurotransmitters GABA --{see chapter 34)

Releasing hormones

hormones

Pituitary

"True" hormones

~-+-Insulin

Second messengers

/

cAMP

IP3

An Overview of Neuroendocrine Control Figure 37.18

Liver

.,.·

.... ...~:·; ..... _~-~-.-~~"-·~--:..~~ ·.-..·. -..-... .... ~--- -------~--- ~-..:.. ...

Peter Raven and George Johnson, Understanding Biology, 3/e. Copyright© 1995 Wm. C. Brown Communicatrons, Inc., Dubuque, Iowa. All Rights Reserved.