Physiology of the Posterior Pituitary The posterior pituitary

Physiology of the Posterior Pituitary • The posterior pituitary gland secretes two hormones which are: • oxytocin , • increase uterine contractions during parturition • Contraction of mammary glands to secret milk • and vasopressin or arginine vasopressin (AVP) (or Antidiuretic Hormone ‘ADH’) • contract vascular smooth muscle and thus raise blood pressure • promote reabsorption of water by renal tubules 2

Posterior Pituitary and Hypothalamic Hormones • Oxytocin and ADH • Each composed of nine amino acids • Almost identical – differ in two amino acids © 2013 Pearson Education, Inc.

Physiology of the Posterior Pituitary • Oxytocin and ADH are stored in and secreted by the posterior pituitary gland, but are synthesized by the hypothalamus 4

The Pituitary Gland: • Posterior pituitary • Vasopressin • Oxytocin Figure 7 -12 (1 of 4)

The Pituitary Gland: Figure 7 -12 (2 of 4)

Figure 7 -12 (3 of 4)

The Pituitary Gland: Figure 7 -12 (4 of 4)

The Pituitary Gland: Figure 7 -12

Maintaining Water Balance • • As in lose water, the concentration of dissolved materials in our blood rises. The hypothalamus signals the pituitary gland to release a hormone— antidiuretic hormone (ADH).

Maintaining Water Balance • ADH is carried by the blood to the kidneys, where it slows the removal of water from the blood. • Later, we experience a sensation of thirst.

• When we take a drink, most of that water is quickly absorbed into the blood.

Maintaining Water Balance When the water content of the blood rises, the pituitary releases less ADH. Less ADH causes the kidneys to remove water from the blood.

The blood is then restored to its proper concentration.

Maintaining Water Balance Less water = more ADH = kidneys conserve water. More water = less ADH = kidneys remove water

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