Hypothalamus and posterior pituitary caves notes only so far

Question 1

Give five functions of the hypothalamus

Answer 1

1. Control of anterior pituitary hormone secretion via hormone release
2. Control of appetite
3. Role in cyclic phenomena e.g. circadian rhythms, body temperature
4. Control of thirst
5. Control of posterior pituitary secretion

Question 2

How is appetite controlled?

Answer 2

The lateral feeding centre is chronically active but suppressed by satiety centre and possible CCK and leptin. The ventrolateral satiety centre senses glucose utilisation and is insulin sensitive

Question 3

How is thirst controlled?

Answer 3

1. By sensing changes in plasma olsmolarity through osmoreceptos (anterior hypothalamus)
2. By sensing blood volume changes through angiotensin II
3. By sensing blood volume changes through baroreceptos peripherally ->nerves

Question 4

Name three posterior pituitary hormones whose secretion is controlled by the hypothalamus

Answer 4

Vasopressin, ADH, oxytocin. Formed as preprohormones

Question 5

Where is vasopressin released from? What stimulates its release?

Answer 5

Vasopressin is released by the posterior pituitary. Release is stimulated by anti-urination mechanisms i.e.

1. Increasing plasma osmotic pressure (sensed by ant. hypothalamus)
2. Decreasing plasma volume (sensed by baroreceptors and overrides osmotic effect)
3. Stress
4. Drugs (morphine, nicotine)
5. Angiotensin II
6. Sleep
7. Pain

Question 6

What is vasopressin release inhibited by?

Answer 6

Pro-urination hormones

1. A decrease in plasma osmotic pressure
2. An increase in plasma volume
3. Alcohol

Question 7

How is vasopressin bound in the plasma?

Answer 7

Vasopressin is not bound in plasma. It is readily distributed and degraded by proteolysis

Question 8

Name four actions of vasopressin

Answer 8

1. Antidiuretic action
2. Vasoconstriction
3. Stimulation of ACTH release
4. Stimulation of Glycogen breakdown in the liver

Question 9

Via what mechanism does vasopressin have antidiuretic activity?

Answer 9

Vasopressin acts on the collecting ducts to increase permeability to water, with matter passing from urine to medullary fluid (via V2->cAMP->increase water channels from endosomes

Question 10

Via what mechanism does vasopressin cause vasoconstriction?

Answer 10

Via V1a->G-protein->PpC->increases in Ca2+ -> blood vessel constriction

Question 11

Where is the vasopressin vasoconstrictor response seen?

Answer 11

The liver, brain, kidney, and mesangial cells

Question 12

How does vasopressin stimulate ACTH release?

Answer 12

Vasopressin stimulates ACTH release by corticotrophins in the anterior pituitary via V1b ->G protein ->Ca2+ release

Question 13

What may diabetes insipid us be due to?

Answer 13

Destruction via neoplasm or trauma of the hypothalamus, or due to the inability of the kidney to respond to ADH (genetic)

Question 14

By what other name is vasopressin known?

Answer 14

ADH

Question 15

What hormone is related to ADH?

Answer 15

Oxytocin

Question 16

What stimulates oxytocin release?

Answer 16

Vaginal distension, nipple stimulation, stress

Question 17

What inhibits oxytocin release?

Answer 17

alcohol

Question 18

What are the actions of oxytocin?

Answer 18

1. Contraction of myoepithelial cells in the breast leading to milk discharge
2. Contraction of smooth muscle in the uterus
3. Oxytocin has an ADH effect in high concentrations

Question 19

What mediates the effects of oxytocin?

Answer 19

Effects of oxytocin are mediated by specific receipts ->G protein ->Ca2+ release

Question 20

What happens in the late stages of pregnancy?

Answer 20

The number of oxytocin receptors increases dramatically

Question 21

What does the pineal gland do?

Answer 21

The pineal gland secretes melatonin cyclically (high levels at night, low levels during the day.