Hypothalamus Flashcards
Functions of the hypothalamus
Homeostasis, body temp, hunger, thirst, metabolism, emotional states, circadian rhythms, sleep/wakefulness, reproductive functions.
Ach synthesized in
Nucleus basalis of meynert
Histamine synthesized in
Tuberomamillary nucleus
Functions of preoptic area and anterior hypothalamus
Thermoregulation (fever)
Fluid balance
Sexual behavior
Includes ventrolateral preoptic area – sleep!
Function of the suprachiasmatic nucleus
Site of master circadian clock that entrains with environmental light.
Function of the arcuate nucleus in the infundibulum
Regulation of feeding and body weight via CNS projections, neuroendocrine regulation via the anterior pituitary
Ventromedial nucleus
Feeding/drinking/body weight (reduces feeding)
thermoregulation
sexual behavior
Dorsomedial nucleus
Regulation of feeding/drinking/body weight (reduces feeding)
Lateral hypothalamus
Increases feeding, regulation of sleep-wakefulness
Paraventricular nucleus
Contains Magno and Parvocellular neurons that project to the pituitary
Magnocellular neurons
In the paraventricular nucleus and supraoptic nucleus, Make oxytocin and ADH and project directly to posterior pituitary
Parvocellular neurons
In the paraventricular nucleus, make releasing factors that influence the anterior pituitary (CRF, TRF, GNRF). Project to the pituitary portal system, which brings releasing hormones to the anterior pit.
Mammillary Nuclei
Considered part of the limbic system, thought to be important in memory (olfactory memories) Also has fornix, major output of hippocampus carrying axons to mammillary nuclei as well as to septum and nucleus accumbens.
HPA Axis
Excited by amygdala, inhibited by the hippocampus. PVN releases CRF to the anterior pituitary, releases ACTH to adrenals, makes glucocorticoids.
High TSH
Can mean HYPOthyroidism because of lack of inhibition
Autonomic inputs and outputs
Input to hypothalamus from RAS and NST, output via Vagus
Circadian rhythms controlled by
Suprachiasmatic nucleus. Optic nerve innervates the SCN directly and indirectly via the thalamus. SCN innervates the superior cervical sympathetic ganglion, which projects to the pineal gland. SO sympathetic activation releases melatonin, but light turns off superior cervical ganglion.
Molecular clock
Clock and BMal are TFs that activate period/cryptochrome, period inhibits clock and bmal and is degraded. As period degrades, it relieves in inhibition.
Where is the molecular clock located?
Everywhere! Very ubiquitous
Orexin created in?
Lateral hypothalamus – induces wakefulness
Where do orexigenic neurons project to?
Cortex and thalamus, also projects to ARAS to cause REM-OFF
Narcolepsy
Caused by the death of orexigenic neurons, which quiets the thalamocortical circuits, causing synchronized EEGs.
Sleep and arousal
Both active processes, sleep is not just the removal of arousal.
Brain structure that drives REM sleep?
PPT (pontine tegmentum), ACh. Wake the thalamus during sleep to cause awake-like EEG.
VLPO-
Ventrolateral preoptic area, causes sleep. Activated by general anesthetics
How do antidepressants disrupt REM sleep?
By activating the ARAS
Production of leptin
By fat cells to reduce appetite. Works via JAK-Stat
Db mouse
Has loss of function at leptin receptor (hyperphagia, obesity, diabetes)
Can leptin explain obesity?
No, leptin levels are appropriately high in obese.
Where does leptin act?
In the arc nucleus where it inhibits orexigenic factors (NPY and AgRP) and stimulates anorexigenic factors (MSH, CART)
Hormones in medial hypothalamus, lateral hypothalamus
Medial: Corticotropin releasing factor
Lateral: Melanin Concentrating hormone.
NPY
Most orexigenic factor known
MSH
Melanocortin derived from POMC, M4 receptor, Gs Linked
AgRP
Antagonist of M4 (MSH receptor)
MCH
Melanin concentrating hormone. Gi linked receptors. Major orexigen
Are brain actions of insulin required for full glucose metabolism?
Yes.
Ghrelin
Secreted by stomach as a function of fasting, orexigenic.
GLP-1
Strongly anorexigenic. Promotes insulin, reduces glucagon.
Feeding and the mesolimbic pathway
Food is rewarding, increases DA in VTA NACC. Leptin and ghrelin act here.
SSRIs and appetite?
Suppress it! Maybe at 5ht2c
CB1 receptors and appetite?
Activate CB1, get the munchies.