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Neuroscience Unit 2 > Hypothalamus > Flashcards

Hypothalamus Flashcards

1
Q

A line between what two structures separates the midbrain from the diencephalon?

A

Posterior commissure and mamillary bodies

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2
Q

A line between what two structures separates the hypothalamus and the thalamus?

A

Posterior and anterior commissure

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3
Q

From rostral to caudal, what are the landmarks of the anterior, middle, and posterior hypothalamus?

A

Anterior - Optic chiasm
Middle - Infundibulum
Posterior - Mammillary bodies

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4
Q

Why does the fornix course through the hypothalamus? What does it divide?

A

Contains postcommissural fibers from the subiculum, divides the hypothalamus into medial and lateral area

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5
Q

What nuclei are in the anterior division of the hypothalamus, and what is their relative position (medial / lateral)? What is their general function overall?

A

All four nuclei control the pituitary

Medial:
1. Preoptic area (POA) - ventral to PVN, dorsal to SCN
2. Suprachiasmatic nucleus (SCN) - onto of the optic chiasm
3. Paraventricular nucleus (PVN) - near fornix and third ventricle
Lateral:
4. Supraoptic nucleus (SON) - atop the optic tracts

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6
Q

What nuclei are in the middle division of the hypothalamus, and what is their relative position (medial / lateral)?

A

Medial:
1. Arcuate nucleus (ARC) - directly above infundibulum
2. Ventromedial nucleus (VM) - ventral to fornix
3. Dorsomedial nucleus (DM) - dorsal to fornix
Lateral:
4. Lateral hypothalamic area (L) - lateral to fornix

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7
Q

What nuclei are in the posterior division of the hypothalamus, and what is their relative position (medial / lateral)?

A

Medial:

  1. Mammillary bodies (MB)
  2. Posterior nucleus (P)

Lateral:
3. Tuberomammillary nucleus (TM)

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8
Q

What neuron types mediate the anterior and posterior pituitary?

A

Anterior - parvocellular

Posterior - magnocellular

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9
Q

What nuclei control the anterior pituitary?

A

All in anterior division of hypothalamus minus supraoptic, and + arcuate

So: ARC, SCN, POA, PVN

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10
Q

What nuclei control the posterior pituitary?

A

just supraoptic and paraventricular: SON / PVN

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11
Q

What is special about the paraventricular nucleus?

A

Contains both parvocellular and magnocellular neurons projecting to anterior and posterior pituitary

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12
Q

What are the afferent inputs to the hypothalamus for SANS and PANS?

A
  1. Solitary nucleus - caudal part

2. Reticular formation - medulla, pons, and midbrain

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13
Q

What parts of the hypothalamus regulate SANS and PANS?

A

SANS - middle / posterior part - includes DM / P nuclei extending backwards in the same area

PANS - anterior - PVN

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14
Q

What are the efferent output examples for SANS and PANS?

A

SANS - intermediolateral cell column through reticulospinal tract (dorsolateral tegmentum)

PANS - dorsal motor nucleus of X

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15
Q

What part of the hypothalamus functions in heat dissipation? What will lesion cause?

A

Preoptic area - includes blood vessel dilation and sweating / panting. More typically viewed as a sympathetic function, but is located anteriorly to lower body temperature

Lesion makes you feel hot

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16
Q

What part of the hypothalamus functions in heat conservation?

A

Posterior nucleus - results in vasoconstriction, shivering, and piloerection to raise body temp

17
Q

What relays information about blood volume to the hypothalamus?

A

NTS (caudal part) and RF (reticular formation), due to baroreceptors in heart and great vessels

18
Q

Where are the osmoreceptors located in the brain?

A

Directly on the supraoptic and paraventricular neurons which contain vasopressin

19
Q

How is vasopressin release normally controlled, and what happens if those neurons are lesioned?

A

SON / PVN neurons with vasopressin are tonically active, (vs oxytocin is not).

If lesioned - diabetes insipidus due to lack of aquaporins loss in kidneys

20
Q

What nuclei control feeding?

A

All mid-hypothalamic nuclei except DM

21
Q

What will destruction of VM hypothalamus cause and why?

A

Cause hyperphagia - since VM thalamus is the satiety center

22
Q

What will destruction of LH hypothalamus cause and why?

A

Aphagia - since LH hypothalamus is the feeding center (motivation to eat)

23
Q

What is the mechanism by which feeding is thought to be stimulated?

A

Arcuate nucleus detects a drop in circulating leptin levels, indicating a drop in fat storage and a need to eat.

Arcuate nucleus releases orexigenic neuropeptides like NPY / AgRP to stimulate lateral hypothalamus

24
Q

What is the mechanism by which feeding is inhibited?

A

Solitary nucleus receives info from vagus nerve about gut distention which projects to mid-hypothalamus

Blood leptin levels increase, releasing anorexigenic peptides (i.e. alpha-MSH) to lateral hypothalamus to stop feeding

25
Q

How are certain foods craved?

A

There are specific neurotransmitters in hypothalamus corresponding to certain nutrient deficiencies (carbs, fat, proteins)

26
Q

What is the function of the SCN? Where does it project?

A

Receives direct retinal inputs for circadian rhythms. Lesions will disrupt 24-hr pattern of sleep-wake.

Projects to POA (VLPO) and DM

27
Q

What nuclei are involved in the ascending arousal system (reticular activating system)? How does this relate to consciousness?

A
  1. Locus ceruleus
  2. Dorsal raphe
  3. PPN - releases ACh
  4. DM / TM nuclei of hypothalamus - histamine

If these cannot reach the hypothalamus, there will be no consciousness (brainstem injury rostral to the pons causes impairment of consciousness)

28
Q

What exhibits inhibitory control over the ascending arousal system during sleep?

A

POA (specifically VLPO)

  • keep in mind this also functions to decrease temp, regulate reproductive behaviors, and projects to anterior pituitary
29
Q

What influences POA / VLPO neurons?

A

Acetylcholine from basal forebrain (septal nucleus + nucleus basalis). Inhibition via ACh declines with increasing adenosine levels, which is a somnogen

30
Q

What is orexin and what releases it?

A

Peptide which activates the ascending arousal system and inhibits REM sleep

released by lateral hypothalamus + DM at mid levels, and partially via posterior hypothalamus

31
Q

Why do subregions of the POA differ in size?

A

They are sexually dimorphic, and they influence reproductive behaviors / reproductive hormones differentially in males and females

32
Q

What does the VM hypothalamus control, other than feeding?

A

Subregions will control sexual receptivity and mating behaviors by expressing progesterone receptors. Ablation of these areas will lead to sexual disinterest in both males and females

33
Q

What is the function of POA, other than sleep, for females? What neurotransmitter influences it?

A

It is directly connected to PVN neurons releasing oxytoxin, which increases maternal behaviors and nursing / infant care. Important in bonding

34
Q

Why are mammillary bodies not necessarily considered part of the hypothalamus?

A

They have far fewer intrahypothalamic connections than other nuclei, and function in memory. They are more limbic in function

35
Q

What caused sham-rage in cats and why?

A

Lesion above the hypothalamus, disconnecting it from the cortex. The hypothalamus controls the autonomic responses to rage, but not the physical actions, so cats wouldnt actually attack

The limbic cortex acts as a “braking system” to prevent hypothalamus stimulation of the brainstem autonomics for rage

36
Q

What are the rostromedial vs caudolateral divisions of the hypothalamus, generally?

A

Rostromedial - more PANS, satiety and ‘contentment’, decreasing body temperature, passivity

Caudolateral - ‘anxiety’ and SANS, increasing body temperature, aggressive behavior. Also happens to contain the feeding center

Neuroscience Unit 2 (19 decks)

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