Hypothalamus

Question 1

What are the anterior and postero-inferior borders of the hypothalamus?

Answer 1

The lamina terminalis borders the hypothalamus anteriorly.

The mammillary bodies mark the end of the hypothalamus posteriorly.

Question 2

What is the blood supply of the hypothalamus?

Answer 2

Small perforating arteries from the circle of willis.

Question 3

What is the sella turcica?

What is the tuber cinereum?

Answer 3

The bony identation of the anterior cranial fossa in which the pituitary gland sits.

A bulge of gray matter that sits posterior to the optic chiasm.

Question 4

Lateral Preoptic Nucleus

Is it located anteriorly or posteriorly?

What is it derived from?

Answer 4

Lateral Preoptic Nucleus

Anterior (“preoptic”)

Derived from the telencephalon, unlike most of the hypothalamus.

Question 5

Lateral Hypothalamic Nucleus

What functions does it regulate?

What happens when it is ablated?

Answer 5

Lateral Hypothalamic Nucleus

Feeding.

Ablation results in decreased appetite (anorexia).

Question 6

Tuberomammilary Nucleus

What process does it regulate?

What is the chemical basis for this control?

Answer 6

Tuberomammillary Nucleus

Wakefullness and sleep.

The neurotransmitter is histamine.

Presumably, H1 blockers cause sedation due to effects here.

Question 7

Medial Preoptic Nucleus

What process does it regulate?

Answer 7

Medial Preoptic Nucleus

Release of gonadotropins (GnRH), influencing the anterior pituitary to release FSH/LH.

Note: This structure is sexually dimorphic.

Question 8

Suprachiasmatic Nucleus

What process does it regulate?

Answer 8

Suprachiasmatic Nucleus

Circadian rhythm. Note that it receives direct input from the retinas.

Question 9

Anterior Hypothalamic Nucleus

What process does it regulate?

Answer 9

Anterior Hypothalamic Nucleus

Warmth regulation (ablation = hyperthermia).

Question 10

Paraventricular Nucleus

What processes does it regulate?

Answer 10

Paraventricular Nucleus

1. Release of vasopressin/oxytocin (magnocellular).
2. Release of CRF (parvocellular).
3. Regulation of ANS outflow (parvocellular).

Question 11

Supraoptic Nucleus

What process does it regulate?

Answer 11

Supraoptic Nucleus

Release of vasopressin/oxytocin.

Note that like the magnocellular cells from the paraventricular nuclei, these nerves travel into the pituitary, and don’t rely on portal vessels.

Question 12

Dorsomedial Nucleus

What process does it regulate?

Answer 12

Dorsomedial Nucleus

Blood pressure regulation, and maybe aggression.

Question 13

Ventromedial Nucleus

What process does it regulate?

Answer 13

Ventromedial Nucleus

Feeding–but specifically satiety, unlike the lateral hypothalamic.

Question 14

Arcuate Nucleus

What process does it regulate?

Answer 14

Arcuate Nucleus

Complex regulation of anterior pituitary.

Question 15

Posterior Nucleus

What process does it regulate?

Answer 15

Posterior Nucleus

Cold sensation. Ablation results in poikilothermia.

Question 16

Mammillary Body

What process does it regulate?

Answer 16

Mammillary Body

Since it is linked with the hippocampus as part of the Papez circuit, it is involved in memory and learning.

Question 17

Describe the papez circuit, starting at the hippocampus and ending in the cingulate gyrus.

Answer 17

Hippocampus signals via the fornix to the mammilary bodies. These signal via the mammillothalamic tract to the anterior thalamic nuclei, and then to the cingulate gyrus.

Question 18

What does the stria terminalis connect?

What is the medial forebrain bundle?

Answer 18

Stria terminalis connects the amygdala and hypothalamus.

Medial forebrain bundle is a fiber pathway common to many different signaling tracts.

Question 19

Does the posterior pituitary involve the hypophyseal portal vessel system or the tuberoinfundibular tract?

What other pathway does it involve?

Answer 19

Posterior pituitary is signaled from higher structures via the tuberoinfundibular and supraopticohypophyseal tracts.

Question 20

What is carried on the hypothalamospinal tract?

What can result from a lesion here?

Answer 20

Hypothalamospinal tract carries ANS efferents from the PVN to the spine.

Lesions can cause horner’s syndrome.

Question 21

What processes are triggered by the hypothalamus to reduce temperature? To increase it?

Why does a bilateral lesion of the posterior hypothalamic nucleus cause poikilothermia rather than hypothermia?

Answer 21

Reduce temperature via sweating, panting, and cutaneous vasodilation. Incrase via shivering, thyroid upregulation, and cutaneous vasoconstriction.

This region also carries fibers extending from the anterior nucleus.

Question 22

What three structures seem to play a role in feeding urges?

In which of these are AgRP/NPY and POMC/CART neurons found?

On which structure do those neurons synapse?

Answer 22

The ventromedial and lateral hypothalamic nuclei, and the arcuate nucleus too.

The arcuate nucleus.

The nucleus tractus solitarius.

Question 23

Which mediates hunger: Leptin or ghrelin?

Which is secreted by adipocytes?

Answer 23

Ghrelin induces hunger. Leptin mediates satiety.

Leptin is produced by adipocytes when they take up metabolites.

Question 24

In what patients are craniopharyngiomas found?

What symptoms are associated with them?

Answer 24

Newborns or young children (congenital tumor).

Bitemporal hemianopia (loss of lateral vision) due to pressure on the optic chiasm. Hypothalamic syndrome eg adiposity, diabetes insipidus, temperature dysregulation, and somnolence.

Question 25

What results from a lesion of the mammillary body?

Why might alcoholics experience similar symptoms?

Answer 25

Lesion of the mammillary complex causes inability to form new memories (anterograde amnesia).

Chronic alcoholism results in malabsorption (or general deficiency) of thiamine, resulting in Korsakoff’s psychosis.

Question 26

What is Klein-Levin syndrome?

Answer 26

A hypothalamic lesion, especially in young men, which causes excessive eating, sleeping, and sexual drive.

Associated with decrease in dopamine.