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Neuroscience > Hypothalamus > Flashcards

Hypothalamus Flashcards

1
Q

What two systems does the hypothalamus link together?

A

Central nervous system and the endocrine system

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2
Q

What brain system is the hypothalamus a part of?

A

The limbic system

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3
Q

What hormones does the hypothalamus synthesise?

A

Releasing hormones/ hypothalamic hormones

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4
Q

What do the neurohormones act on?

A

Pituitary

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5
Q

What are the roles of the hypothalamus? (seven)

A

Maintenance of milieu interne

Behaviour (including attachment and parenting)

Memory

Regulation of energy metabolism (food intake, metabolic rate, temperature regulation, growth)

Reproductive function (including milk production, social interactions)

Biological clock (e.g. sleep-wake cycles, circadian rhythms)

Control of blood flow (cardiac output, blood osmolarity and renal clearance, thirst regulation)

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6
Q

What is the hypothalamus derived from?

A

Diencephalon

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7
Q

What ventricle does the hypothalamus lie near?

A

The third ventricle

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8
Q

What depression separates the thalamus (superior) from the hypothalamus (inferior)?

A

Hypothalamic sulcus

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9
Q

What are the four regions of the hypothalamus?

A

Preoptic

Supraoptic

Tuberal

Mammillary

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10
Q

What nuclei lie in the preoptic area?

A

Preoptic nucleus

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11
Q

What nuclei lie in the supraoptic area?

A

Suprachiasmatic, supraoptic, paraventricular, anterior nuclei

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12
Q

What nuclei lie in the tuberal area?

A

Dorsomedial, ventromedial, arcuate, pre-mammillary, lateral tuberal nuclei

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13
Q

What nuclei lie in the mammillary area?

A

Mammillary, posterior nuclei

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14
Q

What regions does the hypothalamus receive input from?

A 
Retina
Olfactory receptors
Cutaneous receptors
Higher limbic system 
Viscera
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15
Q

What are the two limbic input loops?

A

Fornix (hippocampus to mammillary bodies)

Striae terminalis (amygdala to medial hypothalamus)

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16
Q

What regions does the hypothalamus output to?

A

Thalamus

Midbrain tegmentum

Amygdala

Midbrain PAG

Frontal and parietal lobes, habenular nucleus, midbrain

Blood stream (pituitary)

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17
Q

What are the limbic output loops?

A

Papez circuit, mammillothalamic tract (Mammillary bodies to anterior thalamic nucleus to cingulate gyrus)

Mammillotegmental tract (to tegmentum RF)

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18
Q

What is the retinal input pathway?

A

Retinohypothalamic tract

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19
Q

What nucleus does the retina input into?

A

Suprachiasmatic nucleus

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20
Q

What are the three basic non-specific functions of the hypothalamus?

A

Feed-back

Feed-forward

Anticipation (to meet future needs)

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21
Q

What are the neuroendocrine functions of the hypothalamus?

A

Neurotransmitter release leads to (neuro)hormone release directly into the blood stream.

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22
Q

Where is the site of hormone release as a result of hypothalamus actions?

A

Pituitary

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23
Q

What four nuclei of the hypothalamus have neuroendocrine function?

A

Arcuate
PVN
Anterior HT
Supraoptic nucleus

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24
Q

What hormones does arcuate release?

A

GnRH, GHRH, Dopamine

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25
Q

What hormones does PVN release?

A

CRH, TRH, ADH, oxytocin

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26
Q

What hormones does anterior HT release?

A

Sclerostin

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27
Q

What hormones does SON release?

A

ADH, oxytocin

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28
Q

What two nuclei release ADH and oxytocin?

A

SON, PVN

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29
Q

What nucleus releases sclerostin?

A

Anterior HT

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30
Q

What nucleus releases dopamine?

A

Arcuate

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31
Q

What nucleus releases the Gs (GnRH and GHRH)?

A

Arcuate

32
Q

What nucleus releases CRH and TRH?

A

PVN

33
Q

How does the hypothalamus communicate with the anterior pituitary?

A

Hypothalamic parvocellular neurons secrete releasing or inhibiting hormones into hypothalamo-pituitary portal veins

Hypothalamo-pituitary portal veins carry these hormones to anterior pituitary

34
Q

What neurons secrete releasing or inhibiting hormones into hypothalamo-pituitary portal veins?

A

Hypothalamic parvocellular neurons

35
Q

What vasculature connects the pituitary and hypothalamus?

A

Hypothalamo-pituitary portal veins

36
Q

What stops the release of pituitary hormones?

A

Responsive cells secrete or stop secreting hormones in response to binding of hypothalamic releasing or inhibiting hormones into systemic circulation

37
Q

What is the target cell of sclerostin?

A

Somatotrophs - GH

38
Q

What are the two inhibiting hypothalamic hormones?

A

Sclerostin and dopamine

39
Q

How does the hypothalamus communicate with the posterior pituitary?

A

Hypothalamic magnocellular neurons release hormones directly into systemic veins that drain into the systemic circulation

Hypothalamo-hypophyseal tract (axons of neuroendocrine magnocellular neurons)

40
Q

What neurons release hormones directly into systemic veins that drain into the systemic circulation?

A

Hypothalamic magnocellular neurons

41
Q

What is the name of the tract connecting hypothalamus with posterior pituitary?

A

Hypothalamo-hypophyseal tract

42
Q

What does oxytocin facilitate at the breast?

A

Milk ejection reflex/Letdown reflex: in lactating (breastfeeding) mothers, oxytocin acts at the mammary glands, causing milk to be lactated

43
Q

How does suckling promote lactation?

A

Suckling by the infant at the nipple is relayed by spinal nerves to the hypothalamus (SON and PVN)

The stimulation causes neurons that make oxytocin to fire action potentials in intermittent bursts; these bursts result in the secretion of pulses of oxytocin from the neurosecretory nerve terminals of the pituitary gland.

44
Q

What does oxytocin stimulate at the uterus?

A

Uterine contraction: important for cervical dilation before birth, oxytocin causes contractions during the second and third stages of labor.

45
Q

What does oxytocin stimulate in males?

A

A burst of oxytocin is released during ejaculation in human males; its suggested function is to stimulate contractions of the reproductive tract, aiding sperm release.

46
Q

What does oxytocin support behaviourally?

A

Maternal behavior: Female rats given oxytocin antagonists after giving birth do not exhibit typical maternal behavior.

47
Q

What does ADH promote?

A

ADH promotes water retention in kidneys release is modified when blood osmolarity changes by more than ~ 1% from set point (~ 280 mOsm/kg)

48
Q

What promotes ADH release?

A

Hypertonic conditions stimulate ADH release (water is leaving cells as blood not dilute)

49
Q

What neurons, where, detect changes in osmolarity?

A

Osmosensitive neurons in the: vascular organ of lamina terminalis, subfornical organ (SFO) and NTS

50
Q

Where do osmosensitive neurons project to?

A

Supraoptic and paraventricular nuclei

51
Q

How does hyperosmolarity stimulate release of ADH?

A

Increased blood osmolarity causes osmosensitive (OVLT) neurons to shrink

TRPV1 channels open, leading to depolarisation and eventually firing of (OVLT) neurons (graded response)

(OVLT) neurons make monosynaptic glutamatergic contacts with supra-optic nuclei neurons

This promotes firing of ADH-releasing neurons and hence ADH release

52
Q

What does firing of ADH releasing neurons depend on?

A

Central and peripheral inputs (baroreceptors!) as well as their intrinsic osmosensitivity

53
Q

Are ADH releasing neurons intrinsically osmosensitive?

A

Yes

54
Q

What is the cause of diabetes insipidus?

A

Central DI: failure to secrete ADH, resulting in excess urine output and dehydration

Following pituitary stalk damage (accident)

55
Q

What are the non-neuroendocrine functions of the hypothalamus

A

Food and drink intake

Thermoregulation

Circadian rhythms

ANS control

56
Q

What is the role of the anterior HT nucleus?

A

ANS regulation, endogenous temperature sensor, osmoregulation, energy metabolism, blood flow

57
Q

What is the role of the suprachiasmatic nucleus?

A

Circadian rhythms

58
Q

What is the role of the arcuate nucleus?

A

Food intake

59
Q

What is the role of the ventromedial nucleus?

A

Satiety centre (role in aggression?)

60
Q

What is the role of the lateral HT nucleus?

A

Hunger centre

61
Q

What is the role of the Posterior HT nucleus?

A

ANS regulation (temperature sensor)

62
Q

What is the role of the mammillary bodies?

A

Memory

63
Q

Where is the hunger centre?

A

Lateral HT

64
Q

Where is the satiety centre?

A

Ventromedial

65
Q

Where is the temperature sensor?

A

Posterior HT/ Anterior HT

66
Q

What nucleus receives olfactory input?

A

Lateral HT

67
Q

What nucleus has receptors for leptin and insulin?

A

Arcuate

68
Q

What is the action of central temperature sensor (two models)?

A

Heat directly opens ion channel that then depolarises neuron leading to AP firing

Same principle as peripheral temperature sensing (TRP channels)

Heat indirectly promotes depolarisation of neuron leading to AP firing

Heat-inactivated “leak” K+ channel: increased K+ channel inactivation at high temperature results in decreased hyperpolarisation due to less loss of K+, background depolarising current can now effectively depolarise cell to threshold level for AP firing.

69
Q

Where do lesions cause hyperthermia?

A

Anterior

70
Q

Where do lesions cause hypothermia?

A

Posterior

71
Q

What nuclei do the mammillary bodies contain?

A

Lateral nuclei

Medial nuclei

72
Q

What occurs in Korsakoff’s syndrome?

A

Alcohol-induced Vitamine B1 deficiency: damage to mammillary bodies (but also thalamus)

73
Q

What deficits does Korsakoff’s cause?

A

Anterograde and retrograde amnesia

74
Q

What cells does the lateral nuclei of the mammillary body contain?

A

Head direction cells fire selectively when animal faces specific direction in horizontal plane for navigation

75
Q

What cells does the medial nuclei of the mammillary body contain?

A

Memory formation connected with hippocampus via fornix and fire at theta frequency (4-8Hz), which elicits long term potentiation in hippocampus

76
Q

What is the role of vasopressin in behaviour?

A

Courtship, aggression, territorial defence, paternal care of young and pair bonding

Neuroscience (19 decks)

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