Posterior Pituitary Gland

Question 1

• What is produced in the posterior pituitary gland?

Answer 1

ADH & oxytocin

Question 2

• What are the clinical signs of dehydration?

Answer 2

Prolonged skin tent, dry mucous membranes & sunken eyes

Question 3

• What two types of receptors detect dehydration?

Answer 3

Osmoreceptors (hypothalamus) & stretch receptors (atria and veins)

Question 4

• What is the major method of dehydration correction?

Answer 4

Thirst stimulation

Question 5

• How does ADH act?

Answer 5

Acts on the distal tubule and collecting duct to increase permeability to water

Question 6

• What is diuresis?

Answer 6

Increased urine output

Question 7

• Where do water channels present in the DT and CD under the influence of ADH?

Answer 7

Apical membranes

Question 8

• How does ADH activate AQP-2?

Answer 8

Activates adenyl cyclase that initiates the production of cAMP, vesicles contain AQP-2 move to cell surface and insert via exocytosis

Question 9

• What is diabetes insipidus?

Answer 9

ADH deregulation

Question 10

• What are the two types of diabetes insipidus?

Answer 10

Neurogenic – inadequate ADH release from pituitary

Nephrogenic – inadequate response within the kidney

Question 11

• How do you diagnose DI?

Answer 11

Injection of exogenous ADH, response seen in neurogenic patients only

Question 12

• Where does oxytocin act?

Answer 12

Alveoli of mammary glands and uterine muscle during parturition

Question 13

• How is oxytocin regulated?

Answer 13

Regulated by neuronal reflexes

Question 14

• What does prolactin stimulate?

Answer 14

Milk synthesis

Question 15

• What are the effects of oxytocin on the mammary gland?

Answer 15

Increases pressure within alveoli, reduces resistance in excretory ducts, reduces resistance in teat canal – binds receptors on myoepithelial cells, duct becomes shorter and wider

Question 16

• What happens during the preparation for delivery?

Answer 16

Increase ACTH from anterior pituitary gland of the fetus, progesterone converted to oestrogen in placenta, increased prostaglandin released, lysis of the CL

Question 17

• What is the relationship between oestrogen & progesterone?

Answer 17

Progesterone blocks contractility, oestrogen promotes contractility, oestrogen/progesterone ration higher at birth

Question 18

• What does the neuroendocrine reflex stimulate?

Answer 18

Secretion of oxytocin from pars nervosa which acts on oxytocin receptors of myometrium