#25 - Hypothalamus

Question 1

Functions of Hypothalamus

Answer 1

• Body temperature and the febrile response
• Food, salt, and water intake
• Sexual cycles, sexual orientation, and the onset of sexual milestones
• Circadian rhythms
• Sleep
• Body weight
• Stress response

Question 2

Body Temp, Serum Osmolality Set Points

Answer 2

• Temp: 98.6
• Serum osmolality: 275-295 mOsm/Kg H2O

Question 3

Median Eminence Functino

Answer 3

• Major source of signaling to hypothalamus
• Releases hormones into bloodstream

Question 4

Preoptic Nucleus

Answer 4

• Medial hypothalamus
• Set point generator
  
  • Integrates sensory info needed to judge deviations from set points
• Involved in thermoregulation, salt water intake, and sleep

Question 5

Paraventricular Nucleus

Answer 5

• Medial hypothalamus
• Decreases appetite (POMC)
• Is the key hypothalamic nucleus directly interfacing with the endocrine and autonomic systems
• Has glucose-sensitive neurons
  
  • Is the source of the most hypothalamospinal axons (controls IML for sympathetics)
• Similar to the supraoptic nuclei; is an important area for humans for the release of vasopressin (antidiuretic hormone)

Question 6

Mammillary Bodies

Answer 6

• Participate in memory functions
• Located at termination point of fornix
  
  • Bidirectional contact with hippocampus
• Linked to anterior thalamus via the mammillothalamic tract
• Degenerated in Korsakoff’s (confusion from alcoholism)

Question 7

Fornix

Answer 7

• Bidirectlonally onnects hippocampus to mammillary bodies
• Cuts hypothalamus into medial and ventral parts
• Plays a part in memory
• Degenerated in Korsakoff’s (confusion from alcoholism)

Question 9

Lateral Hypothalamus

Answer 9

• Keeps you awake (orexin)
• Keeps you eating (orexin)
• Outputs to cerebral cortex, basal forebrain, amygdala

Question 10

Mammillothalamic tract

Answer 10

• Links mammillary bodies to anterior thalamus
• Memory
• Connects hippocampus and anterior thalamus

Question 11

Sexually dimoprhic nuclei

Answer 11

• Sex behaviors
• Larger in males

Question 12

Suprachiasmatic nucleus

Answer 12

• Circadian rhythms
• Respondible for release of melatonin

Question 13

Arcuate nucleus

Answer 13

• In wall of tuber cinereum
• Feeding/appetite

Question 14

Hypothalamo-hypophyseal Tract

Answer 14

• Axons running from paraventricular nucleus and supraoptic nuclei to posterior pituitary
• Releases vasopressin (to block fluid loss)

Question 15

Dorsomedial, posterior nuclei

Answer 15

Maturation and thermogenesis

Question 16

Tubermammillary Nucleus

Answer 16

• Lateral hypothalamic nuclei
• Sleep/wake/circadian rhythm
• Histaminergic axons for wake, sleep, circadian rhythms

Question 22

Ventromedial Nucleus

Answer 22

• Superior to arcuate nucleus
• Regulates satiety/stop eating
• DAMAGE = obesity, aggression

Question 23

Medial Forebrain Bundle

Answer 23

• Bidirectionally connects forebrain (amygdala, cerebral cortex) to brainstem via lateral hypothalamus
• Damage = affects appetite due to LHA

Question 24

Tuberoinfundibular Tract

Answer 24

• Runs from arcuate nucleus to median eminence
• DA released here regulates secretion of prolactin from the anterior pituitary
  
  • Prolactin: provides body with sexual gratification

Question 25

Hypothalamic Inputs

Answer 25

• Neural
  
  • Retina: light info to suprachiasmatic nuc.
  • Olfactory
  • Spinohypothalamic: pain/temp from STT
  • Viscerosensory
    
    • Gi tract, liver
    • Baroreceptors (blood pressure) and chemoreceptors (pCO2) from heart reach HT via NTS axons
• Chemosensory
  
  • Circumventricular organs:
    
    • Subfornical organ: CSF monitoring
    • Vascular organ of the lima terminalis (VOLT): CSF monitoring
    • Median eminence: brings blood born stuff to arcuate nucleus
  • Hypothalamic chemosensory neurons:
    
    • Glucose (paraventricular organs), osmolality (supraoptic nucleus), temp (anterior hypothalamus)
  • Hormone and steroid receptors

Question 26

Hypothalamic Outputs

Answer 26

• Autonomic nervous system
  
  • Paraventricular nucleus, arcuate and ventromedial nuclei, and lateral hypo.
  • DLF
  • Hypothalamospinal pathway
• Endocrine system (via anterior and posterior pituitary)
• Direct neural connections to cortex and brainstem

Question 27

Dorsal Longitudinal Fasciculus

Answer 27

• Located in PAG
• Connects hypothalamic axons to parasympathetic brainstem targets

Question 28

Hypothalmospinal Pathway

Answer 28

• Runs in CTT
• Connects hypothalamus to pregnanglionic axons for control over:
  
  • blood pressure
  • sweating
  • vasoconstriction
  • release of epi and norepi

Question 29

Lateral Hypothalamus projections

Answer 29

• Mesopontine cholinergic cells (acetylcholine) -> forced attention
• Ventral tegmental area (dopamine) -> motivation
• Locus coeruleus (norepinephrine) -> vigilance
• Midbrain dorsal raphe (serotonin) -> mood
• Tuberomammillary nucleus (histamine) -> wakefulness