Physiology Review -II
neurophysin II ,
transport the hormone from the cell body to the axon terminals
These are neurosecretory bodies or neurosecretory terminals.
Found in the posterior pituitary.
They represent the terminal end of the axons from the hypothalamus
Hormones are temporarily stored in these locations.
ADH causes water retention and brings osmolality back to normal. ADH secretion
Increased ECF volume,
All of above factors decrease ADH secretion.
Brain - Aquaporin 4
Salivary and Lacrimal glands and respiratory tract- Aquaporin 5
Human leucocytes -Aquaporin 9
polyuria and polydipsia.
Polyuria occurs due to ADH deficiency that promotes water diuresis. Polydipsia occurs secondary to dehydration caused by polyuria.
Diabetes mellitus- Urine is hyperosmolal due to loss of glucose in urine [>1200 mOsm/L]
Nephrogenic Diabetes Insipidus- kidneys fail to respond to ADH
Neurogenic Diabetes Insipidus- deficiency of ADH secretion .
Neurogenic DI is also called central DI
X-linked recessive defect -V2 receptor gene is deficient
Autosomal defect - aquaporin gene is deficient
desmopressin, chlorpropamide, high dose of oxytocin, vincrisitine, phenothiazine, carbamazepine
This escape phenomenon occurs due to down regulation of aquaporins production in collecting duct
Urine output increases despite high ADH levels in plasma
Cervical dilatation - at the time of parturition
1. milk ejection reflex
2. parturition reflex.
uterus contracts severely in response to oxytocic and bleeding vessels are compressed in the contracted uterus that prevents bleeding.