Hypothalamus

Question 1

Zones of Hypothalamus

Answer 1

Preoptic zone
-Medial preoptic nucleus (MPON)

Supraoptic zone
-Suprachiasmatic nucleus (SCN)
-Supraoptic nucleus (SON)
-Paraventricular nucleus(PVN)
-Anterior hypothalamic nucleus (AHN)

Tuberal zone
Arcuate nucleus (ARC)
Ventromedial nucleus (VMN)
Dorsomedial nucleus (DMN)

Mammillary zone
Mammillary nuclei
Posterior hypothalamic nucleus (PHN)

Lateral portion of the hypothalamus
Lateral hypothalamic nucleus

Question 2

Function of Limbic System

Answer 2

o Emotions (fear, aggression, and anger)
o Sexual behaviors
o Feeding behaviors (satiety and hunger)
o Learning and memory

Question 3

Mammillarybodies(MB) FUNCTION:

Answer 3

Part of the hypothalamus involved in:
o Memory consolidation (episodic memory) o Reflex with olfaction
Memory of smells

Question 4

Hippocampus function:

Answer 4

Projects to the mammillary bodies through the fornix
Also involved in memory

Question 5

(iii) Mammillothalamictract(MTT) function:

Answer 5

Connects the MB and the anterior thalamic nucleus

Question 6

What is Papezcircuit(PC) ?

Answer 6

Connection of the thalamus, cingulate gyrus back to the hippocampus
Involved in memory
o Damage results in Alzheimer’s and Wernicke’s
encephalopathy

Question 7

Amygdala Function

Answer 7

Involved in fear, aggression, and olfaction
Connects to the hypothalamus (via MB) through the stria
terminalis (ST

Question 8

What is Arcuate nucleus (ARC) ?

Answer 8

o Receives signals from different parts of the body o Primarily connects and modulates the activity of:
Ventromedial nucleus
Lateral hypothalamic nucleus

Question 9

What is Connection between the hypothalamus, satiety and hunger. ?

Answer 9

ARC releases α-MSH and CART to VMN → stimulates VMN → VMN releases CRH → induces satiety
o VMN = satiety center

ARC releases NPY and AsRP to LHN → stimulates LHN → LHN releases orexins → induces hunger
o LHN = hunger center

Ventromedial nucleus. Lateral hypothalamic nucleus

Question 10

Function of Dorsomedial Nucleus

Answer 10

Involved in non-specific behaviors
o Feeding, drinking, body weight regulation, and
circadian activity [Chou et al., 2003]

In rats, lesions in DMN prevented food entrainment of wakefulness, locomotor activity, and core body temperature

Question 11

Lesion in the ventromedial nucleus

Answer 11

impaired satiety → constant feeling of hunger → obesity and hyperphagia

Question 12

Lesion in the lateral hypothalamic nucleus

Answer 12

impaired hunger sensation leading to:
o Failure to thrive (FTT) in infants o Anorexia nervosa in adults

Question 13

Lesion in the dorsomedial nucleus

Answer 13

savage behaviors o Individuals become very rude and aggressive

Question 14

Lesion in the mammillary bodies

Answer 14

Wernicke’s or Korsakoff syndrome which presents with confabulation o Confabulation: defect in the recall and reproduction
of memories that had been formed several days, weeks, or even years [Ropper et al, 2019]
 In return, patient generates a false memory without the intention of deficit [Wiggins, 2020]

Korsakoff syndrome
o Due to degeneration of MB
o Results from thiamine deficiency, accompanying
alcoholism [Martin, 2021]
o Individuals with this disorder have profound memory
loss
 Newly presented material appears to be correctly
registered but cannot be retained for more than a few minutes (anterograde amnesia)

Question 15

Anterior hypothalamic nucleus function :

Answer 15

o Involved in the parasympathetic NS (craniosacral outflow)
o Projects axons to the brainstem nuclei and the sacral area through the dorsal longitudinal fasciculus
o Connects with the following:
Edinger-Westphal nucleus (CN III)
* Responsible for pupil constriction
Superior salivatory nucleus (CN VII)
Inferior salivatory. nucleus (CN IX)
Dorsal nucleus of vagus (CN X)
 Preganglionic parasympathetic neurons (S2-S4)
 Reticular formation
* Important in alertness and arousal of the cerebral cortex for different sensory information

Question 16

Nucleus tractus solitarius function :

Answer 16

o Located in the medulla
o Projects ascending fibers back to the anterior
hypothalamic nucleus → sends information about taste sensations, cardiovascular and visceral sensations

Question 17

Sympathetic Activity : Posterior hypothalamic nucleus

Answer 17

o Sends axons down to the preganglionic sympathetic neurons (T1-L2)
o Hypothalamospinal tract: connects the hypothalamus to the spinal cord

Question 18

Thermal Regulation:
Anterior hypothalamic nucleus function :

Answer 18

o Responsible for decreasing the body temperature o How?
 Causes vasodilation of the cutaneous vessels → allows heat to radiate off the skin surface → ↓body temperature
* Recall that the blood is warm
 Can induce sweating (from eccrine sweat glands)
→ sweat coats the skin → ↓body temperature * Evaporative cooling: ↓body temperature
whenever heat hits perspiration

Question 19

Posterior hypothalamic nucleus function :

Answer 19

Responsible for increasing the body temperature o How?
 Can induce vasoconstriction of the cutaneous vessels → no heat radiated off the skin → shunts blood to the internal organs → ↑body temperature
 Can induce shivering → generates heat → ↑body temperature

Question 20

Connections of the hypothalamus in the limbic system:

Answer 20

Stria terminalis (long) and ventro amygdalofugal pathway (short)
o Connects amygdala to the hypothalamus
o Involved in emotions and olfaction

Fornix
o Connects the hippocampus and hypothalamus o Involved in memory

Median forebrain bundle
o Connects the reticular formation and the prefrontal cortex to the hypothalamus

Question 21

Connections of the hypothalamic nuclei to the pituitary gland :

Answer 21

Hypothalamic-hypophyseal tract
o Connects the supraoptic nucleus and paraventricular nucleus to the posterior pituitary

Hypothalamic-hypophyseal portal system
o Vascular connection between the arcuate nucleus, medial preoptic nucleus, and the anterior pituitary

Question 22

Connections of the hypothalamus to the autonomic nervous system :

Answer 22

Hypothalamospinal tract
o Connects the PHN to the lateral gray horn of T1-L2 (sympathetic NS)

Dorsal longitudinal fasciculus
o Contains the following:
 Connection of the AHN, cranial nerve nuclei, and
the sacral neurons of the spinal cord (S2-S4)
 Connection of the nucleus tractus solitarius back
to the AHN