Hypothalamus Flashcards
Zones of Hypothalamus
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
Function of Limbic System
o Emotions (fear, aggression, and anger)
o Sexual behaviors
o Feeding behaviors (satiety and hunger)
o Learning and memory
Mammillarybodies(MB) FUNCTION:
Part of the hypothalamus involved in:
o Memory consolidation (episodic memory) o Reflex with olfaction
Memory of smells
Hippocampus function:
Projects to the mammillary bodies through the fornix
Also involved in memory
(iii) Mammillothalamictract(MTT) function:
Connects the MB and the anterior thalamic nucleus
What is Papezcircuit(PC) ?
Connection of the thalamus, cingulate gyrus back to the hippocampus
Involved in memory
o Damage results in Alzheimer’s and Wernicke’s
encephalopathy
Amygdala Function
Involved in fear, aggression, and olfaction
Connects to the hypothalamus (via MB) through the stria
terminalis (ST
What is Arcuate nucleus (ARC) ?
o Receives signals from different parts of the body o Primarily connects and modulates the activity of:
Ventromedial nucleus
Lateral hypothalamic nucleus
What is Connection between the hypothalamus, satiety and hunger. ?
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
Function of Dorsomedial Nucleus
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
Lesion in the ventromedial nucleus
impaired satiety → constant feeling of hunger → obesity and hyperphagia
Lesion in the lateral hypothalamic nucleus
impaired hunger sensation leading to:
o Failure to thrive (FTT) in infants o Anorexia nervosa in adults
Lesion in the dorsomedial nucleus
savage behaviors o Individuals become very rude and aggressive
Lesion in the mammillary bodies
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)
Anterior hypothalamic nucleus function :
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
Nucleus tractus solitarius function :
o Located in the medulla
o Projects ascending fibers back to the anterior
hypothalamic nucleus → sends information about taste sensations, cardiovascular and visceral sensations
Sympathetic Activity : Posterior hypothalamic nucleus
o Sends axons down to the preganglionic sympathetic neurons (T1-L2)
o Hypothalamospinal tract: connects the hypothalamus to the spinal cord
Thermal Regulation:
Anterior hypothalamic nucleus function :
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
Posterior hypothalamic nucleus function :
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
Connections of the hypothalamus in the limbic system:
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
Connections of the hypothalamic nuclei to the pituitary gland :
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
Connections of the hypothalamus to the autonomic nervous system :
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
