ADH DAN OKSITOSIN

ST. RAHMAWATI (P 1502208005)ALIA ANDRIANY (P 1502208002)

PROGRAM STUDI BIOMEDIK JUR. FISIOLOGIPROGRAM STUDI BIOMEDIK JUR. FISIOLOGIPASCASARJANA UNHASPASCASARJANA UNHAS

Posterior Pituitary (neurohypophysis)

• Cell bodies in SON (ADH) & PVN (Oxytocin) of hypothalamus

•Consists of neural endings withassociated blood vessels

•Acts as storage area, secretory granules travel down axon

•Connects to hypothalamus via hypothalamic-hypophyseal

tract

• Processes extend through infundibulum and end in Post. Pit

Amino acid sequence in oxytocin Amino acid sequence in oxytocin & vasopressin& vasopressin

http://www.neurosci.pharm.utoledo.edu/MBC3320/vasopressin.htm

The posterior pituitary gland hormones

Posterior pituitary gland releases 2 hormones:

1. Antidiuretic hormone (ADH), or arginine vasopressin (AVP). 2. Oxytocin

Both hormones are produced in hypothalamic nuclei: - Supraoptic nucleus (ADH + 1/6 oxytocin) - Paraventricular nucleus (Oxytocin + 1/6 ADH)

1. Oxytocin:

Action of oxytocin

1. Contraction of smooth muscles of the uterus

enhance labor.2. Contraction of mammary gland myoepithelial cells of the alveoli & the ducts Ejection of milk as a reflex in lactating women.

3. In men ejaculation.

Remember: Oxytocin is concerned with releasing or ejection of milk, while prolactin is

concerned with synthesis & production of milk.

Control of oxytocin release

1. Stimulation of nipple (suckling reflex) oxytocin.

2. Visual or auditory stimuli from the baby oxytocin secretion.

3. Distension of uterus & stretching of cervix during delivery oxytocin release.

4. During coitus oxytocin secretion.

5. Psychological & emotional factors, e.g. Fear, anxiety & pain

oxytocin.6. Alcohol oxytocin secretion.

7. Hormones: a. progesterone uterine sensitivity to oxytocin.

b. estrogen uterine sensitivity to oxytocin.

Neuroendocrine Reflex Arc of Milk Let-Down

Takes only milliseconds from suckling to hypothalamus

OT reaches its target a few seconds later

OT binds receptors on myoepithelial cells of mammary

gland

NeuroendocrineReflex

Neuroendocrine Reflex

The posterior pituitary hormones – 2. ADH (vasopressin):

Antidiuretic hormone (ADH), or arginine vasopressin

(AVP), is produced mainly in SON of hypothalamus.

ADH activates (2) second messenger systems: 1. cAMP 2. IP3

Action of ADH

ADH has 2 main effects:

1. water re-absorption (retention) by distal tubules & collecting ducts of the kidneys decrease osmotic pressure of the blood.

* This effect is regulated by V2 receptors, through the

action of cAMP.2. Contraction of vascular smooth muscles generalized vasoconstriction.

* This effect is regulated by V1 receptors, through the action

of IP3/Ca2+.

Control of ADH release1. in osmotic pressure of the ECF ( in plasma

osmolality), as in dehydration which will stimulate osmoreceptors in the hypothalamus ADH. Hyperosmolarity of

ECF

Receptors in hypothalam

us

More ADH release

Thirst

Collecting ducts of kidneys

Reabsorption of water

Water intake

Dilution of ECF

-ve feedback

Control of ADH release … cont.

Loss of ECF volume

Less pressure in Rt. atrium & great

vessels

Less nerve impulse to the

hypothalamus

Thirst

More ADH release

More water reabsorption by kidneys

Water intake

Maintains ECF volume

2. blood volume ( 10%) stimulate mechanoreceptors in the great arteries (aorta & carotids) & right atrium ADH.

Control of ADH release …cont.

3. arterial blood pressure, due to blood volume ADH.

4. Age: ADH secretion water retention & hyponatremia.

5. Pain, emotional stress & physical trauma ADH secretion.

6. Drugs, e.g. morphine, barbiturates, & nicotine ADH

secretion.7. Alcohol ADH secretion.

Abnormalities of ADH release – Hyposecretion:

Lack of ADH Diabetes insipidus.

2 types of DI: a. Neurogenic (central, or cranial) … Problem in Hypothalamus or Post

pituitary gland

b. Nephrogenic … in collecting ducts of the kidneys.

Symptoms: Polyurea 20 L/day (N 1.5 L/d), Polydepsia,

specific gravity of urine (diluted urine),

plasma osmolality.

Abnormalities of ADH release – Hypersecretion:

ADH, ‘Schwartz-Bartter Syndrome’: - occurs after surgery. - adenoma, ectopic kidney. - Bronchial carcinoma.

Signs & Symptoms:

- Hyponatremia, i.e. [Na+] extracellularly to 110 mM.

(N = 140 mM); resulting in: - Mental confusion. - Coma. - Death, due to ventricular fibrillation.

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