The Hypothalamus

Question 1

What is the hypothalamus?

Answer 1

a bilateral paired structure that occupies the side walls and floor of the third ventricle

Question 2

What separates the thalamus and hypothalamus?

Answer 2

hypothalamic sulcus

Question 3

What does the hypothalamus have control over?

Answer 3

• reproduction
• growth and metabolism
• food and fluid intake
• attack and defence
• temperature control
• sleep-wake cycle
• memory

Question 4

How are most of the hypothalamic functions expressed?

Answer 4

through its control of the pituitary gland and the ANS

Question 5

Where are parvocellular neuroendocrine cells found?

Answer 5

the preoptic and tuberal regions of the hypothalamus

Question 6

What are parvocellular neuroendocrine cells sensitive to?

Answer 6

the blood concentration of hormones that are secreted by the anterior pituitary

Question 7

What is the stalk of the pituitary gland called?

Answer 7

the infundibulum

Question 8

What is the tuberoinfundibular tract?

Answer 8

the pathway of axons from the tuberal region of the hypothalamus to the infundibulum

Question 9

What do action potentials travelling down the tuberoinfundibular tract cause?

Answer 9

calcium-dependent exocytosis of releasing or inhibitory hormones (mostly releasing) from the neuroendocrine cells

Question 10

What happens to releasing hormones of the hypothalamus?

Answer 10

they are picked up and secreted into the capillaries to the anterior pituitary, where they release their hormones via the pituitary portal system

Question 11

What does each hormone of the anterior pituitary have?

Answer 11

a separate releasing factor of hypothalamic origin responsible for its secretion except for FSH

Question 12

Where does the arterial supply of the pituitary gland come from?

Answer 12

branches of the internal carotid artery

Question 13

What happens to the capillaries that supply the pituitary gland?

Answer 13

they drain into portal vessels which pass into the anterior pituitary then break up to form a second capillary bed which bathes the endocrine cells and eventually drains into the cavernous sinus

Question 14

What are the 6 hormones secreted by the anterior pituitary and what do they do?

Answer 14

• prolactin - for the development of mammary glands and lactation
• TSH - stimulates thyroid gland to synthesise and release T3 and T4
• ACTH - stimulates the release of certain adrenal cortical steroids
• GH - for growth of long bones and some tissues
• FSH - for growth of ovaries and development of sperm ducts
• LH - induces ovulation with FSH

Question 15

Where are magnocellular neurons found?

Answer 15

in the supraoptic and paraventricular nuclei

Question 16

What do magnocellular neurons give rise to?

Answer 16

the hypothalamo-hypophyseal tract

Question 17

Where does the hypothalamo-hypophyseal tract terminate?

Answer 17

in the posterior pituitary

Question 18

What are the 2 hormones secreted by the posterior pituitary?

Answer 18

ADH and oxytocin

Question 19

What are Herring bodies?

Answer 19

axonal swellings that contain ADH and oxytocin and provide a local depot for release by smaller, terminal swellings into the capillary bed

Question 20

What happens to hormones released from both the anterior and posterior pituitary?

Answer 20

they drain into capillaries which drain into the cavernous sinus and then into general circulation

Question 21

What does ADH act on?

Answer 21

the distal convoluted tubules and collecting ducts of the kidneys

Question 22

What happens if ADH is not produced?

Answer 22

it can result in diabetes insipidus

Question 23

What is the principal function of oxytocin?

Answer 23

to participate in a neurohormonal reflex to cause the release of milk when an infant is breastfeeding

Question 24

What are the 4 steps of breastfeeding?

Answer 24

1. stimulation of the mother’s nipple by the infants suckling produces brain activity
2. hypothalamic cells are stimulated to release oxytocin from the posterior pituitary
3. oxytocin causes cells of the mammary glands to contract which releases milk
4. the baby receives milk and continues suckling until sated

Question 25

How does oxytocin cause expression of milk?

Answer 25

it enters general circulation and stimulates myoepithelial cells surrounding the lactiferous ducts of the breast

Question 26

What are other functions of oxytocin?

Answer 26

stimulating action on uterine muscle contractions during labour

Question 27

What are the mechanisms that facilitate heat loss?

Answer 27

• dilation of peripheral blood vessels beneath the skin to increase heat radiation
• increased sweating
• increased respiratory rate

Question 28

What is heat conservation controlled by?

Answer 28

the posterior hypothalamic area

Question 29

What does regulation of food intake involve?

Answer 29

satiety centres in the hypothalamus which are very sensitive to blood glucose levels

Question 30

What are the mechanisms that help with heat conservation?

Answer 30

• peripheral vasoconstriction with a subsequent decrease in the heat lost by radiation
• increased body metabolism
• shivering of voluntary muscles
• decreased respiratory rate

Question 31

How does the hypothalamus provide a baseline for caloric and nutrient intake?

Answer 31

by interaction between the lateral and ventromedial nuclei, which make up the appestat

Question 32

What does stimulation and destruction of the lateral hypothalamic satiety centre cause respectively?

Answer 32

• stimulation - excessive eating
• destruction - refusal to eat

Question 33

What does stimulation and destruction of the ventral hypothalamic satiety centre cause respectively?

Answer 33

• stimulation - inhibits the urge to eat
• destruction - overeating and gross obesity

Question 34

What does stimulation of the anterior and posterior hypothalamic areas produce respectively?

Answer 34

• anterior - parasympathetic effects
• posterior - sympathetic effects