animal physiology notes in Endocrine system

Endocrinology

Homeostasis is the maintenance of the dynamic equilibrium of internal milieu at a particular physiological range. It is achieved through 2 integrating systems:1. Endocrine system2. Nervous systemBoth of which are controlled by the Central Nervous System (CNS)They are both anatomically and physiologically distinct from one another

Nervous system is localized, more rapid and release neurotransmitters (neurohumor)Endocrine system is prolonged, slower and release hormones

Endocrine: duct-less glands such as the pineal body, parathyroid, hypothalamohypophysial system, pancreatic islets, testis, adrenal cortex, adrenal medulla, thyroid, ovaries |PHOTAPTAP|: glands are modified neurons

Origin of the Endocrine System primarily for coordination and integration

Some neurons: evolved a secondary function which is secretory and/or morphologically distinct

(neurosecretory cells)

Neurohormone e.g. neurosecretory nuclei (nuclei in vertebrates and invertebrates)[somatic tissue achieved secretory capabilities]

Endocrine glands ES: neurosecretory nuclei + ductless glands:long term control over many ?cyclic?

Nature of a neurosecretory cell and concept of neurotransmissionNeurosecretory cell: modified neuron

:has neuronal function as well (normal features: axon, cylinders, neurofibrils, Nissl bodies):secondary function: responds to afferent stimulation efferently releasing a chemical

molecule (neurohormone) [vs neurons whose primary function is transmission of electrical impulses]

:has elaborate axon system :have membrane bound vesicles under electron microscopy:appear through selective staining which are design to stain the neurohormones

Secretion of neurohormone (3 steps)I Synthesis of neurosecretory material

Precursor neurohormone: synthesized in the perikaryon

Transported to the Golgi bodies [for concentration and fabrication of secretory material]

Membrane bound vesicles containing active or precursor neurosecretory material:the process of synthesis is backed by evidences from Electron microscopy

II Axonal transport of neurosecretory material

notes in animal physiology under Dr. Campos. Prepared by Bryan Atas

Transport of neurosecretory material:Site of synthesisaxoplasmic flow processessite of release:proof is found in cytological observation of stained axons “string of pearls”

III Release of neurosecretory material:from axonal bulbs3 views:1. Intact granules

-proof: in earthworms and insects2. Exocytosis

-granules fuse with the membrane then discharge their contents into the intracellular space-inverse pinocytosis

3. Diffusion-neurosecretory granules disrupt and neurosecretory material diffuses out of the membrane-the membrane inhibits the passage of granules but allows the passage of neurosecretory materials

Hormones:come from the German word “ horman” which means “to excite” or “stimulate”:chemical transmitter excreted by endocrine source into the circulatory which on reaching an active site, influences a target tissue or organ responsive to it:has some degree of specificity:bond to blood plasma proteins:some are Generalized while some have Specific effect

-thyroxine is one example of a Generalized effect as it an stimulate many tissues

-oxytocin is Specific such that it targets and acts on only a few cell types (uterus, mammary gland)

Mechanism of hormonal action:mediated through adenosine-3’-5’cyclic monophosphate (CAMP) which acts as a 2nd messenger

:stimulation varies depending on cell type:CAMP relies on adenyl cyclase


EShormonereceptor sitestimulate adenyl cyclasemore CAMP

Physiological responsehydrolysed by phosphodiesterase

4 proposed General Action of hormones1. Hormone affects the enzyme system of the cell

Proof: hormonesquantitative effectintracellular enzyme systemEpinephrine and glucagonphosphorylaseactive form

2. Membrane system of cellHormones control permeability (cell surface or elsewhere): Therefore this leads to indirect condition of enzymatic reactions:such as insulin: promotes transfer of glucose to cells and certain muscles

3. Genes:from chromosomal puff studies: hormones produce their effects directly by activating or suppressing specific gene loci:e.g. effect of Ecdysone on giant chromosome of insect salivary glands such as in Chironom

4. Controlled Release of Ions:e.g. Thyroid Stimulating Hormone (TSH)- control the release and uptake of ions which are important in the synthetic process and metabolism

Concept of feedback mechanismendocrineblood

:feedback controls the pressure for circulating substancesreciprocal relationship: in concentration leads to + feedback (increase rate of release)

in concentration leads to - feedback (decrease rate of release):i.e. in beta cells of the pancreas which secrete insulin: blood sugar insulin

Four Different types of feedback mechanismsI. Simplest type: wherein the endocrine gland directly regulates the amount of hormones reaching

the target cell:examples: insulin & blood sugar,

glucagon & blood sugar,parathromone & plasma Ca2+

aldosterone & plasma Na+


II. :feedback mechanism involves the EOA which secretes enzymes to process or convert the inactive hormone precursor (harmonogen) to its active state

III. :the hormone indirectly regulates the hypothalamic acitivy

IV. :such as in the hypothalamic control of the anterior pituitary

Hypothalamic region: primitive part of the brain, connected to all parts of the brain


e.g. Angiotensinogen (hormone precursor from EOB) Angiotensin (tropic hormone) [EG: adrenal cortex] Aldosterone

e.g. posterior pituitary neurohypophysis (EG)

Vasopressin or ADH

Kidney (cell)

%H2O in plasma (x)

Hypothalamus

<EG loop>

:controls or directs the pituitary:ultimate source of neurohormones:removal of hypothalamusatrophy endocrine glandsimpairment of functions

Hypophysis/Pituitary gland: 1. Anterior lobe: adenohyposhyisis2. Posterior lobe: neurohypophysis

Hypothalamo-neuro-hypophysial complex:has direct connections with the neurohypophysis (direct pathway):has indirect connections with the adenohypophysis (indirect pathway)

Hypophysis: 2 secretory nuclei:1. supra-optic: has more neurosecretory cells ~100+k2. para-ventricular: has ~39 to 40k neurosecretory cells:both nuclei (1&2) has terminals in the hypothalamohypophysial systems thereby reaching the adenohypophysis and neurohypophysis

Localization through electrical stimulation of regions:Hypothalamic region releasing factor hypothalamohypophysial portal system

adenohypophysis adenohypophysial hormone

Example: Thyroid releasing factorthyroid stimulating

hormoneadenocotricotropic hormonecortisone


Mechanism Action of Releasing Factor

Hypothalamic releasing factor

Interacts with plasma membrane of adenohypohysis

Mediated thru the action of Prostaglandins

Activates adenyl cyclase

Conversion of ATP of cyclic AMP

Change in intracellular distribution of Calcium

Activation of cyclic AMP dependent protein kinase

Bring about protein synthesis

Acts on contractile microtubules and extrusion of hormone (containing granules)

Pituitary Gland_________________________________________________________________ ____ :the pituitary gland is also known as the hypophysis:it is the chief secretory gland which is the center of the endocrine system

CNS hypothalamus hypophysis endocrine glands

Anatomy :small, nut-like structure:in males: 0.5g 10x6x13mm at the floor of the IV ventricle:in females: increases in size and weight during pregnancy

Anterior lobe: adenophypophysis:pars distalis:pars tubularis

Posterior lobe: neurohypophysis:pars intermedia:pars nervosa


:infundibulum-the neurohypophysis is very important in the development of poikilotherms

Hypothalamo-hypophysial portal system:delivers substances from the hypothalamus to the hypophysis<refer to hand outs: table of adenohypophysis hormones>

Two categories of adenohypophysis hormones:1. tropic hormone :activates another endocrine gland or target organ2. gonadotropin :concerned with the normal function of gonads or accessory reproductive organs

Growth Hormone (GH) or somatotropin hormone (STH)too much causes increase in size in ratsPars intermedia :greatly functions in cold blooded animals

:secrete Melanophore stimulating hormone (MSH) – melanophores can change the animals’colors

-two kinds in man:1. alpha ( )α2. beta ( )β

Neurohypophysial hormones1. Andti-diuretic hormone (ADH) or vasopressin

:role in osmoregulation (water balance):its effect on the kidneys is that it causes the kidney to produce concentrated urine thereby decreasing the volume of the urinee.g. hypothalamic lesions diabetes insipidus diuresis/produces dilute urine-administration of ADH corrects effects of diabetes insipidus from hypothalamic lesions

Kangaroo rate (Dipodomys) and camel can tolerate the lack of H2O because of their developed pituitary gland which produces more ADH (+long loops of Henle)

-camels can lose up to 40% of their normal H2O levels2. Oxytocin

a. oxytoxic effect :act on uterine musculaturei. facilitates the ascent of the spermatozoa in the female reproductive tractii. contracts the uterine muscles, expels the fetus at the time of parturition

b. galactogogic effect: brings about milk ejection from the mammary glands


Thyroid________________________________________________________________________________Anatomy :bi-lobed in mammals

:lobes on each sides of the trachea immediately below the larynx, :lobes connected by isthmus

Histology :collection of ovate follicles filled with colloid lined with cuboidal epithelial cells:thyroglobulin make up the colloid:highly vascularized connective tissues in between the follicles:asinus (ultimate microscopic unit which secretes thyroxine) are lined by epithelium:thyroxine is similar to those hormones secreted by closely related organisms

Synthesis, Secretion and Metabolism of ThyroxineThyroxine :is an iodinated protein which simply means that it requires iodine for its synthesis

:man’s iodine requirement: ~1mg/week or ~ 3550mg/year:half of the iodine taken in orally is used in the synthesis of thyroxine

Iodidethyroid gland cells [peroxidase]thyroxine synthesis

Iodine pumps control the uptake + concentration of iodine Hyperplacia

:condition wherein the cells enlarge:more secretion of TSH causes more epithelial cells due to mitosis:results to goiter


:is usually caused by the lack of tyrosine so the levels of TSH increase to compensate for the deficiency

Hyperthyroidism :leads to high basal metabolic rate (BMR) [BMR exceeds 60% of the normal activity:bad for the body’s visceral organs except brain, testis, muscle, kidney:growth is enhanced:increase in blood pressure and cardiac output

Thyroxine Physiology |CHAMN|1. hormone influence on a specific metabolite

a. carbohydrates :increase adsorption of monosaccharidesincrease glycogenolysis hypoglycemiathyroxine effect on blood sugar level: --antagonistic-- with insulin:b. fats: indirect effect: thyroxine, rapid CHO utilizationmobilization of fats to liverc. protein :effect on body growth (protein anabolic effect)d. effect on Vitamin Metabolism especially vitamin B1[thiamine], B12 [cyanocobalmin], Ce. effect on electrolyte and H2O metabolism: Na+ and Cl- in hypothyroidism (extracellular

H2O retention)2. calorigenesis

:role in thermoregulation of homeotherms:high BMRhigh temperature :in fishes, thyroid glands are more involved in osmoregulation:in animals living in temperate regions, more active in winter and is inactive during

hibernation and activity peaks in spring3. molting

:periodic shedding of the exoskeleton:plays a role in the regenerative process:hair replacement in mammals:skin replacement in amphibians:in anurans and urodels –toads undergo rhythmic molting which can be stopped by hypophysectomy

4. amphibian metamorphosis:removal of thyroxine source prevents metamorphosis:exogenous injection of thyroxine stimulates premature metamorphosis

5. neoteny :neoteny is the condition where most of the larval characteristics are retained in the adult (sexually mature)e.g. in Amblystoma tigrinum (tiger salamander) and A. mexicanum:

axolotle (neotenous larvae) [+thyroxine] metamorphosis


Clinical considerations of thyroid in man1. Hypothyroidism :subnormal functioning of the thyroid

:CRETINISM in children:cretins show arrested growth, squat and flabby body, mentally retarded, usually deaf-mutes and pale skin; dry, coarse, sparse hair; sexually underdeveloped and low BMR :main cause of cretinism: dietary iodine deficiency which is curable by exogenous iodine supply except if the thyroid gland is functionally defective [requires thyroxine injections]:MYXEDEMA in adults:myxedemic adults show depressed mental functions, subnormal BMR, sparse hairs, dry and puffy skin,:treatment of myxedema: intake of tyroxine

2. Hyperthyroidism:BMR and heart rate (HR):exhibits trembling limbs, extreme nervousness, exophthalmic bulges :treatment: drugs such as thiomec, thiouracid, etc.

Parathyroid glands____________________________________________________________________Anatomy: located close to the posterior surface

of the thyroid in mammals:paired lobes, one on each side (left and right):located anterior and posterior

Histology: densely packed cells:chief cells and oxyphilic cells:chief cells:

-light:gly, secretory granules-dark: gly, secretory granules

:oxyphilic cells: -appear after puberty-much smaller than chief cells-no special function

:main hormone of the parathyroid is the Parathormone which is secreted by the chief cells:control: negative feedback: between parathyroid & calcium levels in the blood

Hypocalcemiahyperactivity of the parathyroidHypercalcemiahypoactivity of the parathyroid

:not influenced by the tropic hormone of the pituitary galnd Parathormone (PTH) :straight chain polypeptide with MW ~9000

:functions in mineral metabolism specifically calcium phosphate:skeleton is the main site of PTH action

-the skeleton holds 99% of the body’s calcium and 90% of the body’s phosphateA. Calcium metabolismnotes in animal physiology under Dr. Campos. Prepared by Bryan Atas

:most numerous cation in the human body:average adult has 1, 200-1, 400g Ca in the skeleton, intercellular deposit, blood extracellular fluids :intestinal uptake of Ca is the basic step in calcium metabolism and is therefore Calcium in the blood: 9-11mg/100mL plasmaIn 3 forms |NCI|1. nondiffusable form :~35%, bounded to plasma albumin2. complex Ca :combined with citrate, bicarbonate and phosphate, no physio. importance3. ionized Ca : diffusible and physiologically significant

B. Phosphorous metabolism:in the form of HPO4

-, H2PO4- in the plasma

:amount depends on the blood pH:quantity dependent on the pH of the medium:in young: 5-7mg/100mL plasma:in adults: 3-4.5mg/100mL plasma:requirement:

-childhood: 1g/day-pregnancy: 1.5g/day

:phosphorous absorption is facilitated by acids:uptake is facilitated by dietary uptake of calcium and vitamin D:3/4 of the dietary phosphate is removed by the kidney to maintain homeostasis

-failure of the kidney to remove the phosphates results to hyperphosphatemia:diet poor in phosphorous leads to osteoporosis where bones become brittle

Solubility Product (Solubility Product): definite ratio between serum calcium phosphate levels and phosphate in mg/100mL of plasma

If SP<30: decalcificationSP=50: equilibriumSP>50: deposition

Bone and mineral Metabolism:main site of calcium and phosphate ion turnover:65% of which is inorganic:35% of which is organic:salt deposition is more prominent during growth:when maximum growth is already achieved, i.e. maximum height, the rate of resorption and decalcification is equal to the rate of deposition:osteoblasts are involved in the rate of deposition and osteoclasts are involved in the rate of resorption:osteoclasts become more active as the animal ages

Three important sites of Calcium metabolism:1. bone2. kidney


3. intestine

:increase in serum calcium levels causes increase in the level of parthormone which induces bone resorption, breakdown of calcium apatite and release of calcium and phosphate ions:retention of phosphates leads to deposition in tissues:parathormone acts on the kidneys for the removal of excess phosphate

Parathyroidectomy symptoms1. calcium blood levels2. blood citrate since calcium is bound to citrate3. calcium in the urine (urinary excretion of calcium ions)4. serum level of phosphate5. urinary excretion of phosphate:may result to asphyxia due to tetany:remedy: ingestion of calcium of parathormone

Parathormone (PTH): maintain circulatoty levels of calcium and phosphate in the blood in a physiological range:acts mainly on bone, kidney and intestine

hypercalcemiasecrete PTHbone, kidneyincrease blood calcium levels’bone resorptionincrease phosphate levels [hyperphosphatemia] diuresis in kidneyPTH lowers the renal threshold of phosphorous in the kidney also enhances diuresis

Thyrocalcitonin (TCT) :antagonistic with PTH:hypocalcemic:antagonistic with PTH (which is hypercalcemic):source of this hormone is not fully known but evidences point that it comes from thyroid or parathyroid:distinct from thyroxine:further evidences also suggest that parathyroid is not the source of the TCT:it is suggested that the thyroid secretes it with stimulation from the parathyroid

Pancreas_______________________________________________________________________________

:compound gland which has both an exocrine and endocrine gland:exocrine function: released from asinus which has a digestive function (secrete digestive juice):endocrine function: islet of Langerhans secrete 2 hormones (insulin and glucagon) which acts on the liver

Three types of islets of Langerhansnotes in animal physiology under Dr. Campos. Prepared by Bryan Atas

1. alpha ( ) cells: glucagon-hyperclycemic [α blood sugar]2. beta ( ) cells: insulin-hypoglycemic β

-most studied hormone because the lack thereof leads to diabetes mellitus

3. C cells: few in number and have no secretory functions

Insulin (hypoglycemic blood sugar levels):2 chain polypeptide (A and B chain):possess specific amino acid (a.a.) sequence in different organismse.g. ox insulin: A chain: 20 a.a.’s B chain:30 a.a.’shyperglycemia cellsβ insulin secretionnormalizes hyperglycemia:it returns the blood sugar levels back to normal through:

a. enhances glucose utilization of tissuesb. gluconeogenesis (converts excess glucose to other forms)

-protein synthesis and glycogenesisc. enables extraordinary retention of glycogen in the liver

Glucagon (hyperglycemic blood sugar levels):composed of straight chain amino acids:29 amino acids:molecular weight is ~3485MW :peculiar since it has no disulphide bonds:acts mainly on the liverincrease glycogenolysisincrease amount of glucose:at the molecular level, it acts on the enzyme system…… which converts glucose to glucose-1-6 phosphate

Glucose metabolism:glucose concentration in the blood is 90-100mg/100mL plasma

-change in the levels leads to hyperglycemia or hypoglycemia:hyperglycemia 1. Glycosuria :dehydration of cellular compartments

2. Polyurea :urinary loss of glucose:hypoglycemia :fainting:storage is in the form of glycogen in the liver and muscles through the process of glycogenesis:pancreatomy leads to increase in blood sugar levels

diabetes mellitus :urine loss of glucose:initial –polyurea (excretion of abnormally high volume of urine)


–polyphagia (feeling of being constantly hungry):leads to dehydration, imbalances, weakness, etc

Adrenal Glands________________________________________________________________________:paired:lying in the superior poles of the kidney:2 layers

-cortex – mesodermal cell mass in origin: homologous with testis and ovaries-medulla – neural crest origin: homologous with the sympathetic and autonomic system

:each layer have a different embryology:medulla with chromaffin cells

Histology of the adrenal glands::cortex:

1. zona glomerulosa: secrete mineralocorticoids (aldosterone, DOC)2. zona fasciculata: secrete glucocorticoids3. zona regularis: secrete glucocorticoidsAdrenocroticotrpic hormone (ACTH): regulates adrenal cortex

-effects mainly on the zona fasciculata and zona regularisAdrenoglomerulotropin and angiotensin regulate zona glomerulosa

-adrenoglomerulotropin is secreted from the pineal body-angiotensin is secreted from the kidney

:medulla:-chromaffin cells are so named because they are easily stained with chromate-the medulla is regulated by the hypothalamus

ADRENAL CORTEX____________________________________________________________________________________________

Hormones of the adrenal cortex are classified under four groups:1. 11-oxygenated corticosteroids

:potent in affecting carbohydrate and protein versus water and electrolyte metabolisme.g. cortisol, corticosterone

2. corticoids that lack Oxygen at the 11 position: influence water and electrolyte metabolism e.g. 11-deoxycorticosterone (DOC)

3. aldosterone: the most effective adrenocortical steroid regulating electrolyte metabolism4. gonadal hormones:

e.g. androgens, progesterone, estrogennotes in animal physiology under Dr. Campos. Prepared by Bryan Atas

Adrenal cortex is the accessory endocrine source of gonadal hormones:removal of adrenal cortex results to death in 10 days

Addison’s disease:result of chronic adrenal malfunction/hypofunctioning:insufficient secretion of glucocorticoids and mineralocorticoids:features:

1. appetite, vomiting, blood pressure, weakness2. temperature and basal metabolic rate3. renal loss of sodium and bicarbonate, potassium clearance4. hypoglycemia5. renal failure

Cushing’s syndrome:result of adrenal over activity/hyperfunctioning:features:1. weakness of the limbs2. centripetal distribution of fats, moon shaped face, pendulous abdomen3. hyperglycemia (can be counteracted by pancreas activity)4. in plasma ionic concentration

Mineralocorticoids:1. aldosterone2. 11-DOC:influence sodium retention and potassium loss in urine

-potassium is allowed to pass out of the urine:selective enhancement of sodium reabsorption in the distal convoluted tubule: energy supply for the sodium pumps in the membrane

-therefore the plasma clearance of sodium decreases (Na+ inside cell) and K+ in the system and H+ are allowed to escape

:regulated by angiotensin and anglomerulotropinSummary

Two basic effects of mineralocorticoids1. enhancement of tubular reabsorption of Na+ [ in the renal tubules]2. increase renal excretion of K+

Side effect: increase in Cl- uptake as it accompanies increase in Na+ uptake


Glucocorticoids (cortisol and corticosterone)A. Corticosterones

:weak gluconeogenetic effect:slight mineralocorticoid activity:important in glucose metabolism

-primary site in liver (gluconeogenesis) -corticosterone and cortisol hyperglycemia

:antagonist to insulin and STHB. Cortisol

:glycogenolysis-glycogen is converted to glucose in the liver under the influence of epinephrine and glucagon

:glucocorticoids, glucagon, epinephrine – maintain blood sugar level, selective in functioning of glucongenolysis, glycogenolysis

Glucocorticoids:promote protein catabolism:induce centripetal distribution (lipolysis) of fats (Cushing’s disease):effect on electrolyte and H2O metabolism (~aldosterone)

Seyle’s concept of stress influenceGeneral Adaptation syndrome (Seyle et. al.)“The adaptive mechanism set into action during exposure to nonspecific stress, on one hand help the animal withstand stress and on the other hand, may derail or cause disease.”

Stress pituitary adrenal axis steroid withstand stress


ADRENAL MEDULLA__________________________________________________________________________________________:large ovoid and columnar cells:sympathetic innervation:produces catecholamines (25% epinephrine and 75% norepinephrine)

Epinephrine :increases blood sugar – glycogenolysis:differs from norepinephrine in the side chains that they posses

-differs in nature in magnitude, and their action

Epinephrine Norepinephrineheart rate

systolic blood pressure diastolic blood pressure - +

blood flow through the liver, muscles, brain

- or

cutaneous vasoconstriction renal blood flow

general vasodilation general vasoconstriction

O2 consumption and glucose output from the liver

strong weak

promotes hyperglycemiavascular flow to vital organs

from the skin

aids in maintaining blood pressure (vasoconstriction

effect)

Chief function of the catecholamines:1. maintain blood pressure2. alterations in the carbohydrate metabolism3. assist in systemic adjustments to certain kinds of stress

Epinephrine: circulatory adjustmentsNorepinephrine: metabolic adjustments

∴ allows the body to face emergency situations

Cannon’s concept of emergency hormones:“In physiological and emotional stress, catecholamines acts as emergency hormones to

bring about a number of internal adjustments enabling the body to deal more adequately with the state of emergancy”


Urophysis: in fishes a part of the spinal cord (ventral part of the distal end):composed of neurosecretory modified unmyelinated neurons with a tract of secretion bearing fibers (Dahlgren cells):the caudal neurosecretory system (CNSS) of fishes, neurohormonal organ:in teleosts, elesmobranchs, chondrosteans

-not conclusively proven in lungfishes and rat fishes-CNSS cells histologically recognizable in teleosts, urophysis is an enlargement of the posterior spinal cord, neurons are aggregated in caudal-most spinal cord and organized in definite nuclei, neurohemal are is definite-neurosecretoty cells are scattered in elasmobranchs, diffused neurohemal area-poorly developed in isospondylous teleosts

:Neurosecretoy cells under Electron Microscope:granules are found in the 1. cell body and 2. end bulb with uniform diameter:change in granular diameter during axonal trasnsport:cell body end bulb: neurosecretion undergoes some changes in its physiochemical characteristics before subsequent release, association with Zinc:some structural analogy between hypothalamus-hypophyseal neurosecretory system with caudo-urophysis neurosecretory system

Principles which strengthen the caudo-hypophyseal system/neuroendocrine function1. well-developed NSC as a rule termination in rich vascular beds2. ubiquitousness of the system3. regenerative capacity suggests functional significance4. no seasonal variation in its activities5. information is transmissible, presence of axo-denritic and –somatic terminals upon the caudal NSC6. system is drained by the caudal veins and renal portal system

Functional significance of the C audal N euro s ecretory S ystem 1. osmoregulation

:Borr and Takasugi (1962): in Tilapia mossambica-fish is highly euryhaline-urophysis involved in blood chlorine regulation-urosectomy leads to decrease in the amount of chlorine in the blood-injection of urophysis extract causes the chlorine levels in the blood to shoot up -also in other fishes ??lack specific scientific names??

2. Gas metabolism and buoyancy: carbonic anhydrase activity in the swimming bladder and gills

3. acts as corticotropic releasing factor (CRF): strong ACTH-hypophysiotropic activity:extra hypothalamic ACTH reserves

4. Pharmacological actionsa) smooth muscle contraction activity


b) water retentionc)strong pharmacological action

Bern and Lederis: urotensinI for influencing blood pressure activityII for smooth muscle contractionIII for Na movement influencing activityIV for hydroosmotic activity

Organs of Uncertain status1. Pineal Body

:small nervous stalk in the diencephalon:slightly flattened and cone shaped structures in man:in lower vertebrates such as the Sphenodon

-there are two bodiesa. parapineal: “ third eye” which is sensitive to photoperiods and temperaturesb. epiphysis: deep lying

:pineal influence on gonads: inhibitor:increase amounts of hydroxyindole-O-methyltransferase (HIOMT):serotoninmelatonin and methoxytryptophol:in rats: HIOMT activity follows the circadian rhythm

-increase melatonin at night time than at daytime-in estrus cycle: increase activity at diestrus and decrease at proestrus and estrus-pinealectomy results to abnormally enlarged ovaries, which can be counteracted by melatonin injections

:pineal acts as a neuroendocrine transducerPhotoperiod and lightingvisual receptionPineal bodygonads, etc

2. Thymus:behind the upperplate of the breast bone in man:shrinks with age2 zones:

a) cortex: masses of lymphocytes supported by a meshwork of slender binding cellsb) medulla: contains relatively fewer lymphocytes

:primary center for the production of small lymphocytes during fetal and early post-natal life:essential for the establishment or maintenance of immunologic competence in neonatal stage:thymectomy in newly born mice results to the complete loss of the ability to form antibodies against antigens (as in skin grafts):thyemectomy in adult mice leads to a decrease in the number of lymphocytes:2 ways by which the thymus functions in immunologic response:

1. source of immunologically competent cells (lymphocytes)2. secrete thymic principle which conditions proliferation and maturation of potential immunologically competent cells in many tissues and organs


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animal physiology notes in Endocrine system