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Neuro > Hypothalamus > Flashcards

Hypothalamus Flashcards

1
Q

what are the functions of the hypothalamus?

A

regulates and integrates autonomic and endocrine functions with behavior that are primarily concerned with homeostasis

does this by regulating:

  • BP and electrolyte balance (drinking, salt appetite)
  • body temp (behavior, ANS- shivering, endocrine)
  • energy metabolism (feeding, digestion, metabolic rate)
  • reproduction (hormone- mating, pregnancy and lactation)
  • emergency responses (BF to ms, secretion of adrenal stress hormones)
  • mediation of emotional responses
  • controls the release of 8 major hormones by the hypophysis (pituitary)
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2
Q

what are the 3 mechanisms that the hypothalamus uses?

A

1- receives sensory signals from all parts of the body

2- compares these sensory signals with biological set points

3- if a deviation is detected- homeostasis is restored by:

  • adjusts in the ANS
  • endocrine system
  • behavior
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3
Q

what are the 2 lobes? of the hypophysis (pituitary)?

A

adenohypophyseal system

neurohypophyseal system

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4
Q

what is the adenohypophyseal system?

A

endocrine
regulates what you need (thyroxine for metabolism)

hypothalamus neurons produce releasing factors or inhibiting factors into the portal system

–>adenohypophysis (anterior pituitary lobe) produces and stores other releasing factors

–> peripheral glands- produces hormones and release them into systemic circulation

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5
Q

what is the neurohypophyseal system?

A

hypothalamus produces hormones

axoplasmic flow to neurohypophypophsis where hormones are stored (posterior lobe of pituitary)

to release hormones, these cells fire off APs in hypothalamus and fire off cells in post pituitary to release ADH and oxytocin into systemic blood supply

hypohypophseal tract –> neurohypophsis (releases stored hormone into the systemic circulation)

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6
Q

what is the biggest function of oxytocin?

A

lactation, suppress hypothalamic function

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7
Q

what do vasopressins do?

A

regulate blood volume and salt concentration

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8
Q

coronal anatomy:

A 
nuclear masses:
-medial
-lateral
-periventricular
names from columns of fornix surrounding 3rd ventricle
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9
Q

how does the hypothalamus control hormonal and hypothalamic regulation of body fat?

A

body fat and foot consumption:

  • lipostatic hypothesis
  • Leptin
  • Leptin depletion– incites adaptive responses to fight starvation
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10
Q

what is leptin?

A

the hormone responsible for regulating body mass

decreases appetite

increases energy expenditure

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11
Q

a lesion of the lateral hypothalamus would make an animal:

A

lose weight

feeding centers are in the lateral hypothalamus

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12
Q

a lesion of the medial hypothalamus would make an animal:

A

gain weight

satiety centers are in the medial hypothalamus

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13
Q

what are the effects of elevated leptin levels on the hypothalamus?

A

a rise in leptin levels in the blood is detected by neurons in the arcuate nucleus that contain the peptides aMSH and CART. (located at the base of the 3rd ventricle)

these neurons project axons to:

  • the lower BS and SC
  • the paraventricular nuclei of the hypothalamus
  • the lateral hypothalamic area

each of these connections contributes to the coordinated humoral, visceromotor and somatic motor responses

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14
Q

what are the effects of decreased leptin levels on the hypothalamus?

A

activation of arcuate neurons that release NPY and AgRP

effects on energy balance: opposite to the effects of aMSG and CART

orexigenic peptides- increase appetite
-NPY and AgRP inhibit secretion of TSH and ACTH

activate parasympathetic division of ANS
-stimulate feeding behavior

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15
Q

how can you control feeding by the lateral hypothalamic peptides?

A

lateral hypothalamus: motivation to eat
-electrical stimulation: triggers feeding behavior in satiated animals

neurons intrinsic to lateral hypothalamus; axons passin through the lateral hypothalamus

MCH: peptide neurotransmitter

  • informs cortex about leptin levels
  • motivates the search for food
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16
Q

what does the motivation to eat depend on?

A

time and quantity of last meal

17
Q

are the 3 phases of appetite, eating, digestion and satiety?

A

1-cephalic

2-gastric

3-substrate
increases blood insulin levels

18
Q

what is the short term regulation of feeding behavior?

A

appetite

eating (cephalic)

digestion

satiety

  • gastric distension
  • cholecystokinin (CKK)- hunger suppressant
  • increases insulin

CCK–> gastric distension–> vagus nerve–> nucleus of solitary tract –> SATIETY

19
Q

why do we eat?

A

reinforcement and reward (reward hormones are released when eating (dopamine and serotonin)– why depressed ppl are overweight - food activates reward systems
dopamine motivates to eat, serotonin spikes when you eat . no serotonin-don’t want to eat

liking-hedonic

wanting- drive reduction

electrical self stimulation- experiments to identify sites of reinforcement

effective sites for self stimulation- trajectory of dopaminergic axons in the ventral segmental area projecting to the forebrain

drugs that block dopamine receptors: reduce self stimulation

20
Q

what is the role of dopamine in motivation?

A

old belief: dopamine projection served hedonic reward

new understanding:

  • dopamine-depleted animals “like” food but “do not want” food
  • lack motivation to seek food, but enjoy it when available

stimulation of the dopamine axons
-craving for food without increasing the hedonic impact

21
Q

how does serotonin affect food and mood?

A

serotonin as a neuromodulator

serotonin levels:

  • low- postabsoptive period
  • rise: in anticipation of food
  • spike: during meals

mood elevation: rise in blood tryptophan and brain serotonin

drugs that elevate serotonin levels: dexfenfluramine (redux)

22
Q

what are disorders and treatment concerning serotonin?

A

disorders:
-anorexia nervosa
-bulimia nervosa
both often accompanied by depression

treatment:
- antidepressant drugs- elevate brain serotonin levels

23
Q

what is another motivating factor besides dopamine?

A

drinking

1-hypovolemia (decrease in blood volume)

2- hypertonicity (increase in the concentration of dissolved substances in the blood)

no water- kidney regulates- releases angiotensin II to blood supply. heart is affected, goes up vagus nerve to solitary to hypothalamus. hypovolemia goes to subfornix which regulates water

salt content- too much–>need more water - produces ADH, too little salt= inhibit ADH

24
Q

what is volumetric thirst?

A

thirst triggered by hypovolemia

25
Q

what is the subfornical organ?

A

highly vascularized
does not have BBB
responsive (sensory) to a wide variety of hormones

regulates water content

bloodbourne angiotensin II signals reduced blood flow to kidneys

mechanoreceptors in walls of major BV and heart detect drop in BP –> vagus–> solitary

26
Q

what is osmometric thrist?

A

OVLT-vascular organ of the lamina terminals
-regulates the osmolarity of the blood
(too little salt= inhibit ADH; too much= facilitate ADH)

role of OLVT neurons

  • excite magnocellular neurosecretory cells
  • stimulate osmometric thirst

diabetes insipidus
-tx: replace missing vasopressin

27
Q

temperature regulation:

A

cells fine tuned for constant temp- 37 degrees C (98.6 degrees F)

neurons for temperature homeostasis

  • clustered in anterior hypothalamus
  • humoral and visceromotor responses (neurons in the medial pre optic area of the hypothalamus)
  • somatic motor (behavioral responses)- (neurons of lateral hypothalamic area

process during a fall in temp

visceromotor response: goosebumps

involuntary somatic motor response: shivering, seeking warmth

rise in tmep: metabolism slowed by reducing TSH release
TSH released by ant pituitary–>TSH stimulates release of thyroxin from thyroid gland –> increase in cellular metabolism

28
Q

what is sleep?

A

a readily reversible state of reduced responsiveness to and interaction with the environment

29
Q

how does the hypothalamus play a central role in the regulation of sleep?

A

RF runs it but it is governed by the hypothalamus (pre optic and suprachiasmatic areas)

neuroendocrine, autonomic, and somatic function

suprachiasmatic nucleus-circadian signals

pre-optic area- switch from wakefulness to sleep- inhibit BS and other area neurons that maintain arousal

pineal gland releases melatonin

30
Q

what is the first stage of sleep?

A

4-5%
light sleep

muscle activity slows down
occasional muscle twitching

high amp theta waves

31
Q

what is the second stage of sleep?

A

45-55%
breathing pattern and heart rate slows
slight decrease in body temp

theta with rapid sleep spindles

32
Q

what is the 3rd stage of sleep?

A

4-6% deep sleep begins

brain begins to generate slow delta waves

33
Q

what is the 4th stage of sleep?

A

12-15%

very deep sleep
rhythmic breathing
limited muscle activity
brain produces delta waves

34
Q

what is the 5th stage of sleep?

A 
20-25% 
REM sleep 
rapid eye movement
brainwaves speed up and dreaming occurs
muscles relax and HR increases
breathing is rapid and shallow

if you wake up in stage 5 you remember your dreams
delta wave sleep

35
Q

what is NREM?

A

4 recognized stages of sleep

  • the 1st is the “lightest stage” to the deepest 4th
  • -as you progress from 1-4 in the first hour of sleep and spend the rest of the night cycling up and down between 1-4

the EEG gets progressively more synchronous with each deeper stage

EEG activity is larger and slower than in the awake state– this pattern is called SYNCHRONOUS and is high amplitude but low frequency

36
Q

what is REM sleep?

A

characterized by profound muscle relaxation, alterations in BP, pulse rate, respiration

EEG activity is called DESYNCHRONOUS and is low amplitude by high frequency

REM sleep is also called paradoxical sleep because the body appears to be more deeply asleep than in any other stage but the EEG looks very much like the waking brain

37
Q

what is the difference between awake and asleep?

A

ACh system:

awake: active
asleep: inactive

sensory thalamus:

awake: facilitated
asleep: inhibited

reticular nucleus:
awake inhibited
asleep active

thalamocortical neurons:
awake active
asleep: in slow rhythm

EEG:
awake desyncrhonous
asleep: synchronous

Neuro (48 decks)

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