2 Hypothalamus II Flashcards by Jake Evans

What is the main pattern generator for thermogenesis?

nucleus raphe pallidus

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What do thermogenic neurons in the nucleus raphe pallidus receive inhibitory inputs from? excitatory?

-heat sensitive anterior hypothalamus

- -cold sensitive posterior hypothalamus

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What does the medial pre optic area send inhibitory neurons to during warmth sensing?

Inhibits the raphe pallidus and the dorsomedial posterior hypothalamus with GABA

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What does the dorsomedial hypothalamus do when it senses cold ?

excites the raphe pallidus

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Where are heat sensitive neurons located in the anterior hypothalamus?

medial preoptic area

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Increases in core temperature lead to inhibition of the raphe pallidus and activation of what?

endocrine/specific autonomic responses (cooling the body–sweating, decreased metabolism, peripheral vasodilation)

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Excitement of of RPa leads to what?

SELECTIVE sympathetics–peripheral vasoconstriction and piloerection, inhibition of sweating,

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Lesions affecting the anterior hypothalamus lead to what?

hyperthermia

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Lesions to the posterior hypothalamus lead to what?

hypothermia (body temperature matching the surrounding)

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What neurons are sensitive to circulating pyrogens and promote thermogenesis by raising the set point for warm response?

medial preoptic area

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What special receptor does medial pre optic area neurons have for fever production?

EP3 receptor activated by prostaglandin 2 produced in the capillary walls

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What are cyclical behaviors entrained to the daily light-dark cycle?

circadian rhythms

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What nucleus acts as an endogenous circadian oscillator?

suprachiasmatic nucleus

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What is the most important external timing cue for circadian rhythms?

light

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What does the suprachiasmatic nucleus receive direct input from?

photosensitive retinal ganglion cells- retinohypothalamic tract

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Where does the suprachiasmatic nucleus project to?

extensively throughout the hypothalamus

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what secretes melatonin?

pineal gland–[suprachiasmatic nuc.–> dorsomedial hypothalamus—> hypothalamospinal pathway—> sympathetics—>pineal]

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What is the brains expression of darkness?

melatonin

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What is production of melatonin inhibited by?

light

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Does the total melatonin production decrease or increase with age?

decreasese- nightly schedule of peak production shifts to earlier in the evening

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What does melatonin act through?

melatonin receptors MT1 and MT2

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Review of all the things melatonin acts on–

thyroid
liver
pancreatic islets to inhibit insulin
adrenal cortex
kidney
pituitary
and suprachiasmatic nucleus

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What does disruption of cyclic release of melatonin through travel and artificial indoor lighting responsible for?

jet lag, sleep disorders, and seasonal affective disorder

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What nucleus is active during sleep and reciprocally connected with the tuberomammillary nucleus TMN?

ventrolateral preoptic nucleus VLPO

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What types of neurons does the TMN contain that project through the entire cerebral cortex and to components of the ascending reticular activating system for arousal?

histamine neurons

Two way reciprocal connection between TMN and VLPO create what?

switch that is in either the awake or sleep position

Do the VLPO have histamine receptors?

No--inhibited by GABA also made from TMN

T-F---norepinephrine and serotonin released by axons from the locus ceruleus and median raphe nuclei excite the VLPO during the awake state?

False---they inhibit during awake state

Neurons in the lateral hypothalamus around the fornix are active during wakefulness---their neurons contain what?

orexin peptides [which keep the awake switch on and is absent in patients with narcolepsy]

The SCN regulates the timing of sleep, but does it directly effect sleep itself?

Lesions of the anterior hypothalamus effect sleep in what way?

insomnia

Damage to the posterior hypothalamus leads to what sleep problems?

sleepiness

Besides sleep, orexin-containing neurons under normal circumstances will generate what? projects to where for motivation?

an appetite and projects to basal forebrain dealing with motivation

The hypothalamus controls food intake by modulating which part of the hypothalamus?

lateral hypothalamus [orexin containing] and further by influencing endocrine/autonomic function and behavior

what does pro-opiomelanocortin (POMC) do?

inhibit feeding

The system in the arcuate nucleus promoting feeding uses what neurotransmitter?

neuropeptide Y [NPY]

what receptors in the lateral hypothalamus are acted on by POMC to inhibit lateral hypothalamus LH? what does the effect have?

melanocortin receptors | satiety

Mutations in MC4R are associated with what disease state?

obesity

What does NPY do to MC4 receptor in the LH?

blocks the MC4 receptor and blocks the action of POMC neurons [NPY neurons also release GABA that block POMC]

whate is ghrelin to NPY neurons?

excitatory

what hormone is produced in the duodenum and inhibits gastric emptying and gastric acid secretion and causes release of other digestive enzymes/

cholecystokinin

does cholecystokinin inhibit the POMC and act as a hunger suppressant?

no- it excites it and suppresses hunger

what is an important signaling protein produced by white fat and tells the brain how much energy is available

leptin

can loss of inhibition of feeding by obese individuals be due to leptin resistance?

yes

T-F---insulin modulates effects of ghrelin and leptin but does not have a glucoregulatory function on the hypothalamus?

false-- it does have a glucoregulatory function and controls glucose output by the liver

does central norepinephrine or serotonin decrease feeding?

serotonin, the other increases feeding

What nucleus plays a strong role in satiety by sending excitatory inputs to the POMC neurons in the arcuate nucleus?

ventromedial nucleus

How is the strength of ventromedial nucleus to POMC neurons diminished?

by fasting

Lesions of the lateral hypothalamus have what effect on eating?

abolish eating (aphasia) and drinking (adipsia) from destruction of orexin neurons

lesions of the medial hypothalamus has what effects on eating…especially in the ventral part?

uncontrollable eating (hyperphagia) [can lead to people eating photographs of food]

what is an eating disorder that may be caused by receptor function changes following a forced starvation? ghrelin carrier antibody affinity is effected, reducing ghrelin delivery to hypothal.

anorexia

What are the 2 types of thirst the hypothalamus regulates?

volumetric and osmotic

What type of thirst comes from the loss of body fluid.

volumetric thirst

What part of the pituitary releases vasopressin?

posterior pituitary [baroreceptor --> NTS --> median preoptic area --> supraoptic and paraventricular nuclei ---> posterior pituitary]

Angiotensin II ---> subfornical organ ---> median preoptic area --> lateral hypothalamus ---> ??

thirst sensation promoting drinking behavior and salt appetite

What is activated in decreased serum osmolality and leads to osmotic thirst through the anterior hypothalamus to increase salt appetite via the lateral hypothalamus?

vascular organ of the lamina terminals (volt)

Volt---> median preoptic area --> lateral hypothalamus ---> ??

increased salt appetite

what does destruction of the anterior hypothalamus due to drinking?

partial or total loss of desire to drink

the hypothalamus can control what in order to modulate the baroreflex?

rostral ventrolateral medulla RVLM

what portion of the pituitary is involved in reproductive function?

anterior pituitary

what is the axis that controls the reproductive milestones and cycles?

hypothalamo-pituitary-gonadal axis

can the hypothalamus adjust its reproductive control from body mass signals, light signals and even stress?

yes

Hypothalamic lesions can lead to what in sexual development?

advanced or arrested sexual development

What neurons in the arcuate nucleus send axons to the medial pre optic nucleus and drive sexual behaviors?

pro-opiomelanocortin neurons

T-F-- the arcuate nucleus also sends dopaminergic projections to the median eminence during arousal and inhibits prolactin release? what cells release prolactin?

True- lactotroph cells | [prolactin leads to sexual gratification which counteracts dopamine]

Lesions to the medial hypothalamus (ventromedial hypothalamus) can do what to sex drive? what other problems in general?

hypersexuality---uncontrollable hunger and rage

Does a lesion to the hypothalamus produce one sign at a time?

No, often multiple signs with odd symptom patterns that aren't intuitive