Week 5: Hypothalamus and Pituitary

Question 1

Compare neuroendocrine neurons vs normal neurons of the CNS.

Answer 1

Neuroendocrine neurons

• multipolar with branching dendrites (same as normal)
• axon terminals are in close proximity to capillaries so that transmitters enter capillary lumen
• most neuroendocrine neurons release products at the median eminence near base of hypothalamus
• stimulate release of trophic hormones from pituitary

Question 2

What is the function of the hypothalamus?

Answer 2

Hypothalamus controls:

• Social behavior: aggression, sexual behavior, maternal behavior
• Ingestive behavior: feeding and drinking
• Homeostatic mechanisms: circadian rhythms, thermoregulation, stress

Question 3

What are the nuclei and the function of the pre optic region of the hypothalamus?

Answer 3

1. Medial pre-optic area (MPOA): sexual and parental behavior with reproductive function. stimulate gonadal function.
   - responds to testosterone and stimulates male sex behavior
   - receives sensory input from olfactory, visual, SS, projections from amygdala
   - output: GnRH neurons have humoral output, projections to other hypothalamic nuclei, to midbrain for motivation and reward
2. Median preoptic nucleus (MePO): sensation of thirst
   - receives info from hind brain (which senses increases in blood osmolarity and decreases in blood volume)

Question 4

What are the nuclei and the function of the anterior region of the hypothalamus?

Answer 4

1. Anterior hypothalamic area (AHA): aggressive behavior. Inputs: amygdala, sensory, testosterone
   - AHA and MPOA also= Heat Loss center
2. Paraventricular and supraoptic nuclei (PVN, SON): release hormones involved in milk release and uterine contraction (Oxytocin) and water balance (vasopressin)
   - projections in posterior pituitary
   - PVN: response to chronic stress, controls secretion of cortisol
3. Suprachiasmatic nucleus (SCN): brain’s master oscillator, regulates rhythms, particularly circadian rhythms.
   - inputs: retina (light)
   - controls secretion of melatonin from pineal gland

Question 5

What are the nuclei and the function of the tuberal region of the hypothalamus?

Answer 5

Ingestive behavior

1. Ventromedial nucleus (VMH): satiety center
   - lesions increase food intake
   - important for female sexual behavior (animals)
   inputs: from arcuate nucleus about metabolic state, estrogen receptors, SS from pudendal area
2. Arcuate nucleus (ARC): hunger, satiety, metabolism
   - insulin, leptin, glucose, fat
   - regulate prolactin and growth hormone secretion from anterior pituitary
3. lateral hypothalamus
   - activates hunger
   - involved in body regulation

Question 6

What are the nuclei and the function of the mammillary region of the hypothalamus?

Answer 6

1. Posterior Nucleus (PN): body temperature regulation
   - Heat gain center
   - outputs: spinal sympathetic neurons

Question 7

Body temperature regulation involves which nucleus in the hypothalamus?

Answer 7

lateral hypothalamus (also involved in hunger) and posterior nucleus (heat gain center)

Question 8

Stress response involves which nucleus in the hypothalamus?

Answer 8

paraventricular nucleus

Question 9

Regulation of circadian rhythms involve which nucleus in the hypothalamus?

Answer 9

suprachiasmatic nucleus

Question 10

Regulation of thirst which nucleus involve which nucleus in the hypothalamus?

Answer 10

Periventricular nucleus (also involved in stress)

Question 11

Regulation of appetite which nucleus involve which nucleus in the hypothalamus?

Answer 11

lateral hypothalamus=activates hunger

ventromedial nucleus controls satiety

Question 12

Which nuclei control sex behavior in men, which in females, and which nucleus controls aggression, which controls maternal behavior?

Answer 12

MPOA controls male sex behavior & maternal behavior, anterior hypothalamus controls aggression, female sex behavior is in VMH