10. Hypothalamus Flashcards

1
Q

homeostasis:

define

A
  • integrated physiological processes to maintain the internal environment of the body w/in narrow physiological range in response to changing environment
  • based on theory of milieu interieur (constant internal environment)
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2
Q

key fxn of hypothalamus?

A

to maintain homeostasis, which means “similar position”

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3
Q

what allows the hypothalamus to maintain homeostasis?

A

broad circuitry of inputs/outputs of hypothalamus

  • inputs: peripheral sensory information, cortex, limbic areas
  • outputs: ANS and Pituitary
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4
Q

hypothalamus: general functions

A

Control:

  • BP & electrolyte come
  • body temp
  • energy metabolism
  • reproduction
  • emergency responses to stress
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5
Q

what is found at the anterior-most aspect of the hypothalamus?

A

anterior commissure, lamina terminalis, and optic chiasm

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6
Q

what is found at the posterior-most aspect of the hypothalamus?

A

mamillary bodies

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7
Q

divisions of hypothalamus, from medial –> lateral

A
  • medially: periventricular zone, and the arcuate nucleus
  • then, ventromedial and dorsomedial nuclei
  • the lateral zone incl. the supraoptic nucleus
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8
Q

hypothalamic nuclei to know, from ANTERIOR –> POSTERIOR

A
  1. preoptic
  2. suprachiasmatic
  3. paraventricular
  4. supraoptic
  5. arcuate
  6. mamillary

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9
Q

important tracts and other structures to know for hypothalamus

A
  1. column of fornix (tract)
  2. anterior pituitary
  3. posterior pituitary
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10
Q

brief location of hypothalamus in relation to other structures

A

optic chiasm –> anterior portion

optic tract –> intermediate portion

mamillary bodies –> posterior portion

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11
Q

anterior division of hypothalamus:

nuclei and functions

A

In general: controls behaviors more aligned w/ rest/digest type fxns

  • preoptic –> heat loss
  • supraoptic & paraventricular –> water balance, milk ejection, uterine contraction
  • suprachiasmatic –> circadian rhythm

Other fxns: thirst, sleep, parasympathomimetic

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12
Q

intermediate division of hypothalamus:

nuclei and functions

A
  • tuberal and arcuate nuclei –> endocrine activity

Other fxns: satiety, feeding, emotions

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13
Q

posterior division of hypothalamus:

nuclei and functions

A
  • mammilary nuclei –> consolidation of memory (pt of Papez circuit)

Other fxns: heat conservation, arousal, aggressive behavior, analgesia, sympathomimetic

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14
Q

match key function w/ corresponding hypothalamic nuclei:

heat loss

A

preoptic nuclei

(anterior division)

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15
Q

match key function w/ corresponding hypothalamic nuclei:

water balance, milk ejection, uterine contraction

A

supraoptic & paraventricular

(anterior division)

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16
Q

match key function w/ corresponding hypothalamic nuclei:

circadian rhythm

A

suprachiasmatic nuclei

(anterior division)

17
Q

match key function w/ corresponding hypothalamic nuclei:

endocrine activity

A

arcuate and tuberal nuclei

(intermediate division)

18
Q

match key function w/ corresponding hypothalamic nuclei:

consolidation of memory

A

mammillary nuclei

(posterior division) – part of broader circuitry in the Papez circuit

19
Q

rhythms such as diurnal rhythms (sleep/wake cycle) and hormonal rhythms are controlled by which nucleli?

A

suprachiasmatic nucleus in anterior hypothalamus;

  1. receives visual inputs from the retina –> allows body to synchronize intrinsic pacemaker to the day/night cycle based on light
  2. *Synchronizing with wake/sleep cycle is the key function of circadian system
20
Q

where do axons of the optic nerve terminate w/in the brain?

A

4 nuclei

  • lateral geniculate nuclei (LGN) of thalamus
  • superior colliculus of midbrain
  • pretectum of midbrain
  • suprachiasmatic nucleus of hypothalamus
21
Q

functions of the 4 nuclei where the optic nerve terminates?

A
  • LGN –> visual perception
  • superior colliculus –> control of eye movements
  • pretectum –> control of pupillary light reflex
  • suprachiasmatic nucleus –> control of diurnal rhythms and hormonal changes
22
Q

entrainment:

definition

A

occurs when rhythmic physiological or behavioral events match their period to that of an environmental oscillation

(caused by suprachiasmatic nucleus)

23
Q

association of light and rhythms

A
  1. light –> synchronizes pacemaker-like activity in Suprachiasmatic Nucleus (SCN) –>
  2. outputs of SCN –> neural, hormonal, and behavioral outputs
24
Q

leptin:

define

A

protein produced by fat cells;

if increase in # of fat cells –> more leptin

25
Q

relationship of leptin & feeding

A

(inc. in fat cells) –> increase in leptin –> decrease in feeding

(inversely related)

26
Q

what happens if mouse LACKS leptin gene

A

–> increase in feeding –> mouse becomes obese

27
Q

fxn of arcuate nucleus

A

integrates multiple satiety and hunger signals

28
Q

2 major arcuate projections and respective effects

A
  • paraventricular nucleus (PVN): effects on cellular metabolism via regulation of endocrine system and ANS
    • (TSH and ACTH)
  • lateral hypothalamic area (LHA): effects on feeding behaviors
29
Q

thermoregulation pathway:

inputs to hypothalamus

A
  • thermoreceptors in skin
  • blood temp monitored by central thermoreceptors of hypothalamus

Either can detect inc or dec in body temperature

30
Q

heat loss response (if body temp is inc)

triggered by hypothalamus

A
  • vasodilation of surface blood capillaries –> to inc heat loss by radiation
  • increased sweating
  • relaxation of erector pili muscles –> hairs lie flat
  • dec metabolic rate
  • (and behavioral component, like taking off jacket if too hot)
31
Q

heat conservation response (if body temp is dec)

triggered by hypothalamus

A
  • vasoconstriction of surface blood capillaries –> reduce heat loss by radiation
  • reduce sweating
  • contract erector pili muscles – hairs pulled upright
  • shivering
  • increased metabolic rate
32
Q

regulation of water intake:

2 types of thirst

A
  • volumetric thirst <– from decreased blood volume (i.e. hemorrhage)
  • osmometric thirst <– from dehydration/ hypertonicity (inc. in blood solutes)
33
Q

outputs of hypothalamus from thirst:

PVN

A
  • paraventricular nucleus (PVN) in hypothalamus –>
  • increases antidiuretic hormone (ADH)/vasopressin
  • inc water retention; and dec urine production –>
  • returns fluid volume to homeostatic levels
34
Q

outputs of hypothalamus from thirst:

lateral hypothalamic area (LHA) of hypothalamus

A
  • lateral hypothalamic area (LHA) of hypothalamus –>
  • directly stimulates thirst and drinking

(promote the sensation of thirst to encourage the behavior)

35
Q

hypovolemic thirst:

inputs to hypothalamus

A
  • KIDNEYS detect reduced blood flow –> inc renin –> inc angiotensin ii –> act on hypothalamus –> release ADH/vasopressin –> inc water retention/ dec urine production
  • CARDIOVASCULAR SYSTEM detects reduced BP –> vasoconstriction to counteract blood loss –> hypothalamus –> (same final steps as other)
36
Q

how is hypothalamus related to emotion?

A
  • hypothalamus is connected to limbic system structures by the fornix
  • hypothalamus mediates autonomic manifestations of emotion