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Neuro Quiz 3 > 36_Hypothalamus_Jullet > Flashcards

36_Hypothalamus_Jullet Flashcards

1
Q

What regions make up the preoptic regions? (2) Tuberal regions? (3)

A

PREOPTIC: medial preoptic area + suprachiasmatic nucleus. TUBERAL: LHA, VMN, arcuate nucleus

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2
Q

What is the pre-optic region of the hypothalamus involved in?

A

thermosensation + gonadotropin secretion

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3
Q

What is the suprachiasmtic nucleus of the hypothalamus involved in?

A

circadian rhythms

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4
Q

What is the LHA region of the hypothalamus involved in?

A

food intake/arousal + sensitization

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5
Q

What is the ventromedial nucleus (VMN) of the hypothalamus involved in?

A

reproductive/sexual behaviors, glucose homeostasis, food intake

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6
Q

What is the arcuate nucleus of the hypothalamus involved in?

A

glucose homeostasis, food intake

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7
Q

The hypothalamus has connections with the retina via this tract:

A

retinothalamic tract

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8
Q

The hypothalamus has connections with the cortex, striatum, and septum via this tract:

A

median forebrain bundle

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9
Q

The hypothalamus has connections with the hippocampus and thalamus via this tract:

A

fornix

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10
Q

The hypothalamus has connections with the amygdala via this tract:

A

stria terminalis

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11
Q

The hypothalamus has connections with the brainstem/spinal cord via this tract:

A

dorsal longitudinal fasciculus (DLF)

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12
Q

What is the HPA axis?

A

Hypothalamus Pituitary Adrenal Axis: CRH -> ACTH -> Cortisol release from adrenal cortex

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13
Q

What is the HPG axis?

A

Hypothalamic Pituitary Gonadal Axis: GnRH -> FSH/LH -> Estrogen/Progesterone (F) or Testosterone (M)

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14
Q

What is the supraopticohypophyseal tract?

A

axons of SUPRAOPTIC and PARAVENTRICULAR nuclei project to neurophypophysis/posterior pituitary.

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15
Q

What hormones are produced from the supraopticohypophyseal tract?

A

vasopressin (AVP) and oxytocin

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16
Q

What regulates oxytocin and AVP?

A

gonadal hormones

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17
Q

Deficits in oxytocin has been associated with:

A

autism spectrum disorders/social deficits

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18
Q

Why is that oxytocin and AVP have roles in mating/bonding and social behavior?

A

cognate receptors for AVP/oxytocin are expressed in the nucleus accumbens (mesolimbic reward circuitry). Mating causes release of AVP/oxytocin, which activates the reward circuitry, thus imprinting “pleasure” with the affiliative social behaviors

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19
Q

Why is that montaine voles are promiscuous while prarie voles are monogamous?

A

PRARIE VOLES: cognate receptors for AVP/oxytocin are expressed in the nucleus accumbens (mesolimbic reward circuitry). Mating causes release of AVP/oxytocin, which activates the reward circuitry, thus imprinting “pleasure” with the affiliative social behaviors. MONTAINE VOLES: cognate receptors are expressed in areas of the lateral septum and amygdala

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20
Q

What is the tuberoinfundibular tract?

A

axons of PARVOCELLULAR neurons (from paraventricular, arcuate, ventromedial, preoptic nuclei) project to the adenohypophysis/anterior pituitary and influence release of inhibitory/releasing hormones (FLAT PG)

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21
Q

How is the hypothalamus regulated?

A

via steroid hormone receptors (androgens, estrogens, progestins, glucocorticoids, minerocorticoids) and peptide hormone receptors

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22
Q

Androgens/Estrogens have two roles:

A

1) transient ACTIVATIONAL effects of hormones, 2) permanent ORGANIZATIONAL effects on neural structures that underlie sexual dimorphic behavior in neonates

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23
Q

What are the two sexually differentiated regions of the hypothalamus/forebrain?

A

VMN and POA

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24
Q

What does the POA contain? What regulates it?

A

neuroeffector cells that synthesize + release GnRH (HPG axis). Activity indirectly regulated by fluctuations in gonadal steroids (via kisspeptin neurons)

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25
Q

The POA does not contain any gonadal receptors, but its activity is influenced by gonadal steroids. How is this possible?

A

gonadal hormones regulate kisspeptin neurons that synapse onto GnRH cells.

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26
Q

What are kisspeptin neurons?

A

key sensors of the environment that ensure that reproduction does not proceed when the body’s state is not conducive to support the reproduction of healthy offspring. Relay signals from the periphery (via gonadal steroid hormones) to GnRH neurons (influencing its activity)

27
Q

What influences kisspeptin neurons? (4)

A

1) circadian rhythm, 2) body fat/leptin, 3) stress hormones, 4) gonadal hormones

28
Q

What is leptin and its role in reproductive behavior/sexual differentiation?

A

important regulator of PUBERTY and REPRODUCTIVE COMPETENCE via regulation of kisspeptin neurons and their influences on GnRH neurons

29
Q

What are activational effects of gonadal steroid hormones? What are they required for? (3)

A

Transient flucutations in gonadal steroids that affect brain/behavior; effects are transitory. REQ’D for: 1) normal cycling in females, 2) sex-specific behaviors in M/F, 3) hypothalamic control of pituitary gland (necessary for partiuition)

30
Q

What are organizational effects of gonadal steroid hormones? What are they required for? (2)

A

gonadal steroids impart PERMANENT and SEX-SPECIFIC differences in brain organization and function, which leads to sexual dimorphism. REQ’D for: 1) sex-specific behaviors, 2) changes that enable the system to be responsive to activational effects during adulthood.

31
Q

What is the critical period in terms of organizational effects? What happens if changes are made after the critical period?

A

DURING: time during perinatal development where gonadal steroids impart PERMANENT and SEX-SPECIFIC differences in brain organization and function, which leads to sexual dimorphism. AFTER: organization is not established

32
Q

Where does the suprachiasmtic nucleus of the hypothalamus receive input from? (1) Output? (3)

A

INPUT: retina via retinohypothalamic tract. OUTPUT: PVN, VMN, LHA of hypothalamus to mediate circadian control of eating, sleeping, energy homeostasis, reproduction

33
Q

What is the key circuit of the SCN?

A

Remember the SCN is the master circadian regulator: SCN -> dorsomedial nucleus of hypothalamus -> pineal gland -> melatonin -> sleep/wake cycles

34
Q

When is melatonin prouction highest? What other physiological signs are associated with this?

A

Night. Decreased core body temp + arousal. Increased Fatigue

35
Q

Where are melatonin receptors expressed? How many type are there and what are their functional roles?

A

SCN. 2 types: MT1 - regulate onset of sleep. MT2 - regulate circadian rhythm

36
Q

What is an agonist of melatonin receptors?

A

Rozerem (ramelton)

37
Q

What is the molecular control of circadian rhythms?

A

clock/bmal -> per + cry -> per-cry complexes (which inhibit clock/bmal.

38
Q

What are the two key regulators of the circadian rhythm cycle?

A

1) degradation of clock/bmal and per/cry and 2) Ck1 kinase that influnces stability of per/cry complexes

39
Q

What two syndromes are associated with circadian rhythm disorders?

A

1) metabolic syndrome (linked to diabetes/obeisty), 2) Familial Advanced Sleep Phase Syndrome (mutation in CK1 or per)

40
Q

What are two regions of the hypothalamus involved in food intake? What are their effects on food intake?

A

VMN/ARCUATE: decrease food intake. LHA: increase food intake

41
Q

A lesion in the VMN/Arcuate results in:

A

hyperphagia/obesity (VMN/Arcuate normally decreases food intake)

42
Q

A lesion in the LHA results in:

A

aphagia/weight loss (LHA normally increase food intake)

43
Q

Peptides that regulate feeding/body weight via hypothalamus fall under these two categories:

A

Orexigenic (stimulates appetite) and Anorexigenic (suppresses appetite)

44
Q

What is Ghrelin?

A

GI peptide that stimulate food intake

45
Q

What is CCK?

A

Gi peptide that provides info about GI fill via vagal afferents that project to the nucleus of the solitary tract (medulla); limits food intake

46
Q

What is leptin?

A

produced by white adipose tissue and can cross the BBB to access the hypothalamic nuclei to regulate feeding/energy utilization. ROLE: HIGH leptin BLOCKS ANOREXIGENIC and STIMULATES OREXIGENIC pathways, resulting in weight gain.

47
Q

What do leptin receptors signal through?

A

JAK/STAT pathways

48
Q

Where are leptin receptors?

A

hypothalamus: VMN nucleus, Arcuate nucleus, and LHA “VAL-leptin”

49
Q

Leptin receptor(s) of VMN nucleus:

A

SF1 - steroidogenic factor 1.

50
Q

Leptin receptor(s) of Arcuate nucleus:

A

AgRP (agouti-related peptide) and NPY (neuropeptide Y)

51
Q

Leptin receptor(s) of LHN nucleus:

A

neurotensin

52
Q

Mice missing leptin receptors are generally:

A

obese/hyperphagic.

53
Q

If leptin stimulates weight loss, how is it possible that obese people have high leptin levels?

A

the CNS in obese individuals is resistant to leptin

54
Q

Decreased leptin ultimately results in:

A

food intake (since decrease in fat cell mass results in decreased leptin; want to increase fatc cell mass by increasing food intake)

55
Q

Increase leptin ultimately results in:

A

limited food intake (since increased leptin means that there is increased fat cell mass; no need to take in more)

56
Q

Howdoes the HPA axis affect food intake?

A

CRF -> ACTH -> Cortisol -> Gluconeogenesis + Food intake -> decrease anxiety

57
Q

What is the profile of anorexia nervosa in terms of: 1) CRH/cortisol, 2) LH/FSH, 3) GH, 3) orexigenic and anorexigenic peptides, 4) leptin, 5) peptide YY, and 6) ghrelin (orexigenic)?

A

1) excess CRH/cortisol, 2) suppression of HPG axis (decreased LH/FSH), 3) resistance to GH, 3) alterations in orexigenic and anorexigenic peptides 4) decreased leptin 5) increased peptide YY (anorexigenic) 6) increased ghrelin (orexigenic)

58
Q

What is orexin?

A

expressed by orexigin neurons of LHA; regulates 1) weight/food intake by establishing an INTERNAL BASELINE and 2) transitions between sleep/wake cycles - (proof: orexigin neurons are absent in narcopletic goats), 3) stimulates calorie-burning brown fat

59
Q

What does orexin signal through?

A

GPCR

60
Q

What regulates orexin? (2)

A

inhibited by leptin (duh - since high levels of leptin indicate increase fat cell mass) and increased by ghrelin (hunger, indicating increased energy demand of the body)

61
Q

What happens if there is no orexin produced? (2)

A

decreased caloric utilization by brown fat + weight gain

62
Q

How does temperature affect the utilization of brown adipose tissue (BAT) to generate heat?

A

NORMOTHERMIC: preoptic area contains GABAergic neurons that tonically inhibit a pathway that controls heat generation of BAT. COLD: skin GABAergic neurons inhibit GABAergic neurons of the preoptic area, thus reducing the tonic inhibition -> BAT is used to generate heat

63
Q

What type of neurons is missing in narcolepsy?

A

orexigin neurons - result in 1) premature entry to REM sleep and 2) cataplexy (rapid muscle weakness w.o loss of consciousness)

64
Q

How does Modafinil work for narcolepsy? How does it promote addictive behavior?

A

1) stimulates orexin signaling and 2) increase dopamine levels in the mesolimbic reward system by interfering with the dopamine transporter.

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