Question

Why is the posterior pituitary known as a storage release center?

Answer 1

Hint:- Hint- The posterior pituitary or neurohypophysis does not synthesize hormones, It does store and release two hormones: oxytocin and vasopressin. These hormones are actually synthesized by the hypothalamus and are transported axonally to the neurohypophysis. The posterior pituitary is also known as neurohypophysis.

Complete step-by-step solution:-
Two hormones namely oxytocin and antidiuretic hormone (ADH, vasopressin) are produced by the
posterior pituitary gland (neurohypophysis ).
- Oxytocin:
The release of oxytocin from the posterior pituitary gland is caused by the neural impulses of nipple
stimulation. The other stimuli responsible for oxytocin release include vaginal and uterine distinction.
Biochemical functions:
1. Effect on the uterus: oxytocin causes the contraction of the pregnant uterus and includes
labour.
2. Effect on milk ejection in a mammal, oxytocin causes contraction of myoepithelial cells of the
breast. This stimulates the squeezing effect, causing milk ejection from the breast.
3. Óxytocin synthesized in the ovary appears to inhibit the synthesis of steroids.
- Antidiuretic hormone (ADH):
The release of ADH (also called vasopressin) is mostly controlled by osmoreceptors (of the thalamus)
and baroreceptors (of the heart). Any increase in the osmolarity of plasma stimulates ADH secretion.
Biochemical functions: ADH is primarily concerned with the regulation of water balance in the body. It
stimulates kidneys to retain water and, thus, increases the blood pressure.
In the absence of ADH. The urine output would be around 20 1/day. ADH acts on the distal convoluted
tubules of kidneys and causes water reabsorption with result that the urine output is around 0.5 – 1.5/ day. ADH action is mostly mediated through cAMP.
Mechanism of action: ADH stimulates adenylate cyclase causing the production of cAMP. Water
reabsorption is promoted by cAMP. Inhibitors of adenylate cyclase (e.g calcium) inhibit the activity of
ADH. This supports the view.
- Diabetes insipidus: This disorder is characterized by the excretion of large volumes of dilute urine
(polyuria). It may be due to insufficient levels of ADH or a defect in the receptors of target cells.

Note:- Note- The posterior pituitary is a posterior lobe of the pituitary gland. The posterior pituitary does not Secrete hormones, but rather secrets and stores hormones that are produced by the Hypothalamus posterior pituitary response to signals from the hypothalamic neuron. The hormones are released from axon terminals into the bloodstream. The hypothalamus directly sends a message to the posterior lobe through the nerves and then the pituitary gland releases. Therefore, the posterior pituitary is also known as the storage, release center.