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Neuroscience Quiz 3 > 4 Hypothalamus I & II > Flashcards

4 Hypothalamus I & II Flashcards

1
Q

Big picture: what’s the role of the hypothalamus?

A
  • controls homeostasis
  • integrates endocrine, autonomic and somatomotor systems
  • also involved w/ affective behavior
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2
Q

define: diencephalon

A

the thalamus, subthalamus, hypothalamus and epithalamus

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3
Q

define: infudibulum

A

“funnel” = pituitary stalk

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4
Q

tuber cinerum

A

“Grey swelling” is region on ventral surface of brain that extends from the optic chiasm to the mammilary bodies

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5
Q

median eminence

A

part of the tuber cinerum that is raised and forms the infundibulum; contains 1° capillary network of the hypophysial portal system

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6
Q

True or False: The neurons of the hypothalamus are nice and neatly ordered?

A

False, unlike the neat rows of neurons in the hippocampus, the neuronal organization of the hypothalamus is highly heterogeneous.

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7
Q

Describe”the”information”integrated”and”affected”by”the”hypothalamus”(e.g.,”sensory,” affective,”motor;”control”of”temperature,”osmolarity”and”salt”balance,”circadian”rhythms,” reproduction,”stress,”arousal).

A

??

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8
Q

Describe the anatomical landmarks of the brain that demarcate the hypothalamus.

A
  • just dorsal to pituitary
  • just ventral to thalamus from which it is separated by the hypothalamic sulcus
  • makes up floor and lateral walls of 3rd ventricle
  • continuous with the pre-optic area anteriorly and the mammillary bodies posteriorly
  • medial and rostral to the subthalamic region
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9
Q

Describe”the”MAJOR”afferents (5) of”the”hypothalamus”and”the”type”of”
information”these”tracts”carry.”

A
  1. mfb* (median forebrain): carry sensory, motor, limbic and autonomic info from the cortex, striatum and septum
  2. retinohypothalamic: carry sensory/circadian info from the retina
  3. dlf* (dorsal longitudinal fasiculus): carry motor, sensory and autonomic info from the brainstem and spinal cord
  4. stria-terminalis*: carries limbic info from amygdala
  5. fornix: carries info from hippocampus (memory?)

*also contain efferents from hypothalamus

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10
Q

Describe”the”MAJOR”efferents (6) of”the”hypothalamus”and”the”type”of”
information”these”tracts”carry.”

A
  1. mfb: carry limbic, autonomic and motor info to median forebrain
  2. tuberoinfundibular tract: endocrine signals to adenohypophysis
  3. supraopticohypophysial: endocrine signals to neurohypophysis
  4. dlf: motor, autonomic, etc. to brainstem and spinal cord
  5. mammillothalamic: limbic info
  6. stria terminalis: limbic info to amygdala
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11
Q

Describe”the”nuclei”and”hormones”that”provide”input”to”the”posterior”pituitary.

A

SO (supraoptic) and PVN (paraventricular) nuclei of hypothalamus project their axons to the neurohypophysis via the supraopticohypophyseal tract.

  • -signal with AVP (arginine vasopressin) and oxytocin–two related nonapeptides
  • -cell bodies in both the SO and PVN make both hormones; each nuclei has 50/50 breakdown of AVP- and oxytocin-producing neurons
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12
Q

What does AVP do?

A

acts on the kidney to promote water reabsorption

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13
Q

Lesions of the ant. hypothalamus that disrupt input to the SO and PVN nuclei lead to ?

A

diabetes insipidus – abnormal production of lots of dilute pee

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14
Q

When is oxytocin released?

A

released in response to: sexual stim, uterine dilation, nursing and, sometimes stress

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15
Q

What does oxytocin do?

A

-stimulates uterine contraction
-stimulates milk secretion
Along with AVP, oxytocin is also involved with:
-maternal instincts, pair bonding, love, empathy, trust, eye contact
-aggressive behaviors, too
-oxytocin deficit in autism may be?

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16
Q

Prairie vs. Montaine voles

A

Have different expression of AVP and oxytocin receptors:

  • prairie voles express these receptors in their nucleus acumbens (part of the mesolimbic reward system); they are monogamous and males show aggression towards other males etc.
  • montaine voles express these in other areas like the lateral septum and the amydala and do not show these parental, partner-preference, mating for life behaviors
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17
Q

Tuberoinfundibular tract definition

A

the name for the collection of axons from periventricular regions of the hypothalamus (paraventricular, arcuate and ventromedial nuclei and the preoptic area) that secrete releasing/inhibitory factors into the anterior pituitary via a vascular connection

18
Q

Describe”the”HPG”axis.

A

[photo]

19
Q

Describe how gonadal steroids and other environmental factors influence GnRH neurons.

A

Kisspeptin neurons integrate information from estrogen, progestins, androgens and other hormones (e.g. leptin, glucocorticoids ) (i.e. they have a high amt of receptors for these hormones) and then serve as presynaptic afferents that innervate GnRH neurons in the hypothalamus.

  • -The secrete kisspeptin which then acts thru G-prot coupled receptors on the GnRH neurons.
  • -It therefore serves as a master regulator of the HPG axis.
  • -These kisspeptide cells are responsible for the onset of puberty and regulation of cycling in adults.
20
Q

Describe the difference between activational and organizational effects of steroids.

A

Organizational effects: permanent effects on hormone on the structure/function of brain regions; leads to sexual dymorphism (e.g. ∆s in size of SDN-POA); will continue to have their effect in the absence of that hormone later

Activational effects: transient effects of hormones involved with normal cyclicity in females sex-specific behavior and ∆s in the HPG axis necessary for parturition
–also involves w/ PMS, PMDD, enhanced sz susceptibility in catamenial epilepsy

21
Q

Name the nucleus that is the master regulator of circadian rhythms and describe how loops of transcription factor expression control the “clock”.

A

Peripheral clocks exists all over the body, but the SCN in the master clock.

  • -In the SCN (suprachiasmatic nucleus), transcription factors (clock, BMAL1, Crypton and Period) encode proteins that regulate each other’s and other downstream proteins’ expression in such a way that you get 24hr periodicity.
  • -the stability of these prots is regulated by casein kinase which is mutated in FASPS (familial advanced sleep phase syndrome)
22
Q

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

A

VMN (ventromedial nucleus of the hypothalamus) and POA (pre-optic area)

23
Q

What is the human equivalent of the SDN-POA?

A

INAH3 (the interstitial nucleus of the anterior hypothalamus 3)

24
Q

Name the molecule that signals peripheral energy stores from white adipose tissue.

A

leptin

25
Q

What are the anorexogenic peptides and what do they do?

A

leptin, POMC, α-MSH; they suppress feeding and stimulate energy expenditure

26
Q

What are orexogenic peptides and what do they do?

A

NPY, orexin and AgRP (agouti-related protein); these increase feeding and suppress energy expenditure

27
Q

Describe the effect of leptin on the opposing orexigenic and anorexigenic neuronal circuits
in the arcuate nucleus.

A

[photo]
when there is decreased food:
1. leptin falls
2. this activates NPY/AgRP neurons and inhibits POMC neurons in the arcuate nucleus
3a. More NPY and AgRP is released; both increase food intake; AgRP also blocks binding of α-MSH to melanocortin receptors which decreases the melanocortin anorexia pathways
3b. α-MSH expression and release is directly decreasd

28
Q

Describe the routes by which peripheral information about energy state gets to the hypothalamus.

A

Info from GI and Pancreas:

  • -insulin: from pancreatic ß-cells
  • -ghrelin: acute signal to increase food intake, decr, energy usage and incr adiposisity
  • -CCK transmits info about stomach filling; via vagus to the nucleus of the solitary tract

From White fat: leptin signals via JAK/STAT on long form leptin receptors

these get into CNS:

  • -in areas where BBB in breached (E.g. posterior pituitary and area postrema)
  • -via active transport
  • -via hypothalamic neurons that project directly into the blood stream
29
Q

What gene codes for leptin?

A

The ob gene

30
Q

What is the primary evolutionary role of leptin?

A

To get us to maintain adequate fat stores when there is enough food around, NOT to diminish energy intake under high food or high already-have-a-lot-stored-up situations.

31
Q

What gene encodes from the leptin receptor?

A

db

32
Q

Describe the routes by which hypothalamic control of energy homeostasis reaches
peripheral structures.

A

Signaling mostly from the arcuate nucleus via POMC and NPY/AgRP neurons (??)

33
Q

Define”the”genetic”deficit”in”ob/ob”and”db/db”mice.”

A

ob/ob mice cannot make leptin while db/db mice cannot make the leptin receptor; both exhibit:

  • obesity
  • hyperphagia
  • low metab rate
  • hypothyroid
  • hypothalamic infertility
  • decr. growth
  • decr. immune f(X)
34
Q

Describe the dysregulation in leptin homeostasis in obese individuals and why clinical trials with leptin have had such a low success rate.

A
  • leptin levels are paradoxically very elevated in obese individuals, so it appears they have become resistant to its effects;
  • only 1-2% of obese individuals are obese 2° to a defects in the genes of leptin and/or its receptor, so clinical trials w/ leptin were not effective for most subjects
35
Q

Describe the relationship between CRF, stress, eating of high fat foods, and reward

A
  • stress incr. CRF (Corticotropin releasing factor) –> incr ACTH from ant. pituitary –> cortisol release –> ∆s energy homeostasis and incr intake of high-fat foods
  • *CRF also involved in anxiety
  • *this path whacked in people w/ anorexia nervosa

**reward??

36
Q

Describe the pathophysiology in hypothalamic function that occurs in anorexia.

A

HPA axis becomes dysregulated and produces too much CRF and cortisol
–HPG also affected: amenorrhea etc.

37
Q

Describe the location of orexin neurons in the hypothalamus

A

orexin neurons are located in the LHA (lateral hypothalamic region of the hypothalamus

38
Q

What is the role of orexin neurons in arousal and the pathophysiological basis for narcolepsy?

A
  • -orexin neurons are a very small group of neurons (only ~6700 in whole brain), but are highly branched and innervate widespread areas of the brain; plays central role in arousal
    a) their signals coordinate vigilance, energy homeostasis (e.g. they activate brown fat cells), reward and emotion
    b) they promote transition between sleep and wakeful state
  • -Narcolepsy is a neurodegenerative disease in which >90% of orexin neurons (again, found in the LHA) are lost.
39
Q

What is the proposed mechanism of drugs like modafinil?

A
  • -stimulates orexin signaling and other stimulatory pathways;
  • -may also augment dopamine (DA) levels in the mesolimbic reward system (i.e. NAc, nucleus acumbens) which means we know that increased DA in the NAc = addiction
40
Q

Describe”the”importance”of”the”discovery”of”brown”fat”in”adults”and”its”relationship”to”
thermoregulation”and”energy”homeostasis”in”women”versus”men.”

A

Brown adipose tissue (BAT) burns calories to generate heat

  • stimulated to do so by orexin
    a) normothermia –> GABAergic neurons in POA inhibit a multisynaptic pathway that controls heat generation in BAT
    b) hypothermia –> sensory info from skin –>activates other GABAergic neurons that suppress the aforementioned tonic inhibition allowing BAT activation –> heat generation

SEX: two times more in women than men; hypothesized that women, who have less muscle mass on avg than men, use this extra BAT to generate heat

Neuroscience Quiz 3 (7 decks)

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