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Neuro Exam III > 4-13 Hypothalamus and Limbic System > Flashcards

4-13 Hypothalamus and Limbic System Flashcards

1
Q

Behavior is expressed in what type of commands?

A

ALL behavior expressed in motor commands

Skeletomotor

Secretomotor

Visceromotor

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2
Q

In a general sense, what does the hypothalamus do?

A

Receives info:

basic sensory, cognitive, behavioral state, limbic

Integrates info

Sends output:

hormonal, adrenaline/cortisol release, ANS, muscle tension

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3
Q

What does the hypothalamus work on in order to do skeletomotor, visceromotor, and secretomotor outputs?

A

Skeletomotor - reflexes, motor programs, reticulospinal tracts

Secretomotor - hypothalamus, pituitary, adrenal axis (HPA axis)

Visceromotor - ANS ganglia

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4
Q

What types of behaviors has the hypothalamus been associated with?

A

Drive related: ingestive, defensive, reproductive

4 F’s

Works to maintain homeostasis

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5
Q

What are the longitudinal divisions of the hypothalamus?

A

Preoptic

Anterior

Tuberal/infundibulum

Posterior

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6
Q

What are the 3 mediolateral divisions of the hypothalamus?

A

Periventricular

Medial

Lateral

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7
Q

What is the makeup and innervation of the periventricular division of the hypothalamus?

A

Few nuclei

Mostly DLF fibers

DLF pathway is connection between PAG - periaqueductal gray - and hypothalamus

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8
Q

What does the DLF do?

A

DLF - communication between hypothalamus and PAG

PAG regulates many behaviors and staes

DLF does visceral and survival related behaviors between hypothalamus ad PAG

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9
Q

What does the medial division of the hypothalamus contain?

A

Most hypothalamic nuclei

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10
Q

What does the lateral division of the hypothalamus do? What does it contain?

A

Lateral is separated from the medial division by the fornix

Contains:

Medial Forebrain Bundle

Lateral Hypothalamic area

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11
Q

What do the following areas in the hypothalamus tend to do:

anterior nuclei

lateral nuclei

posterior nuclei

A

Anterior nuclei - parasympathetics

Lateral nuclei - reticular formation and state control

Posterior nuclei - sympathetic

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12
Q

What patterns of activity would you expect to see in the hypothalamus of someone who is asleep?

A

More activity anteriorly

Less activity posteriorly

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13
Q

What changes does Fatal Familial Insomnia cause in the hypothalamus? Sleeping sickness?

A

FFI: Lesions in anterior hypothalamus

  • this portion has many parasympathetic nuclei
  • Inability to sleep, always fatal

Sleeping sickness: lesions in the posterior hypothalamus

  • poor ability to maintain wakefulness
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14
Q

What is another name for the secretomotor hypothalamus? What are the 2 parts of it?

A

Secretomotor = neuroendocrine hypothalamus

Neurohypophysis

Adenohypophysis

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15
Q

How does the neurohypophysis secrete hormones?

A

Secretes directly into posterior pituitary and capillary beds

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16
Q

How does the adenohypophysis secrete hormones?

A

Directly via a vascular link within anterior pituitary

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17
Q

How many nuclei does the neurohypophysis have? What do these nuclei have in common?

A

2: Supraoptic and paraventricular nuclei

Both have magnocellular and parvocellular neurons

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18
Q

What does the supraoptic nuclei make? What behaviors does it regulate?

A

Magnocellular neurons release ADH/arginine vasopressin

Regulates ingestive and reproductive behaviors

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19
Q

What does the paraventricular nuclei make? What behaviors does it regulate?

A

Oxytocin via magnocellular division

Also makes ADH, CRH and TRH

Regulates ingestive, reproductive and stress behaviors

  • regulates HPA axis, very important in stress response
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20
Q

What does the basal forebrain (FB) do?

A

Sends AcH into cortex to increase wakefulness

Considered an extension of the reticular formation

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21
Q

What are the circumventricular organs in the brain?

A

OVLT - Organum vasculosum of Lamina Terminalis

Neurohypophysis

Median eminence - base of hypothalamus

Pineal gland

SFO - SubFornical Organ

Area Postrema

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22
Q

What is the purpose of circumventricular organs in the brain?

A

Monitor osmolality

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23
Q

What is the sequence of events that is kicked off by low blood volume/high osmolality leading to ADH release?

A

low blood volume/high serum osmolality

kidney secretes renin

renin converted to ANG II

ANG II activates receptors in SFO

Osmoreceptors in OVLT also activated

SFO and OVLT send axons to preoptic nucleus

Preoptic nucleus sends fibers to paraventricular and supraoptic nuclei

ADH release stimulated

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24
Q

What can happen to the pathway from SFO and OVLT to the paraventricular and supraoptic nuclei as we age?

A

Pathway can break down, leading to less release of vasopressin

Pathway can break down as a result of age, resulting in nocturnal polyuria - frequent nighttime urination

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25
Q

What makes up the capillary bed in the median eminence? Why is this important?

A

Internal carotid artery branches into superior hypophysial artery, breaks into a capillary bed in the median eminence

Releasing hormones are leaked into this capillary bed by parvocellular neurons. Releasing hormones are carried to anterior pituitary, and cause release of actual hormones.

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26
Q

How are releasing hormones carried from parvocellular neurons to the capillary beds?

A

Via tuberoinfundibular tract

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27
Q

What are the major nuclei along the medial axis of the hypothalamus?

A

Preoptic

Anterior

Tuberal

Posterior

28
Q

What are the functions of the preoptic nucleus?

A

Parasympathetic centers

Maintains BP, heartrate, osmolality, induction of sleep, thermoregulation

Also has GnRH neurons

29
Q

What happens when the temperature of the area in and around the preoptic nucleus drops?

A

Sleep is induced

Vasodilation is induced in the brain so that the temp rises

30
Q

What is Kallmann’s syndrome?

A

Lack of GnRH neurons in the preoptic nucleus, no GnRH hormone to start puberty. Can be treated in males with exogenous testosterone, and person will develop normally.

31
Q

What nuclei are in the anterior region of the hypothalamus?

A

Supraoptic nucleus

Paraventricular nucleus

Suprachiasmatic nucleus

32
Q

What does the suprachiasmatic nucleus do?

A

Runs the body’s master circadian clock

Sits right on top of optic chiasm, receives input from retina directly

33
Q

How does the retina send info to the SCN?

A

Via the retinohypothalamic tract (RHT).

Helps program synchrony based on daily light schedules

34
Q

What major nuclei are in the tuberal region of the hypothalamus?

A

Dorsomedial nucleus

Ventromedial nucleus

Arcuate nucleus

35
Q

What is the function of the dorsomedial nucleus?

A

Regulates ingestive behaviors

36
Q

What is the function of the ventromedial nucleus? What does it release?

A

Regulates ingestive and reproductive behaviors

Satiety center - releases ghrelin, neuropeptide Y

Lesion here will make you overeat compulsively

37
Q

What is the function of the arcuate nucleus?

A

Regulates ingestive behaviors

  • contains neurogenic neurons - can generate new neurons
  • inability to generate new neurons here leads to obesity, ceases satiety

Parvocellular neurons to anterior pituitary

  • releases dopamine (inhibits PRL), GHRH
38
Q

What nuclei do the posterior region of the hypothalamus have?

A

Posterior nucleus - sympathetic center

Mammillary bodies

39
Q

What is the function of the mammillary bodies?

A

Prominent posterior landmark

No relation to sympathetics

Receives afferents from hippocampus - helps with memory and learning

Efferents to anterior nucleus of the thalamus

Contains tuberomammillary nucleus

40
Q

What is the function of the tuberomammillary nucleus?

A

Secretes histamine

promotes consciousness, wakefulness

Projects throughout the brain

These neurons are inactive during sleep

41
Q

What is Korsakoff’s syndrome?

A

Lesion of mammillary bodies due to thymine deficiency secondary to EtOH overconsumption

Difficulty in forming new memories, creating working memoreis

42
Q

What is the median forebrain bundle and where does it go?

A

Runs through fornix

Connects brainstem tegmentum with basal forebrain

(specifically septal nuclei and Basal nucleus of Meynert)

Has a major role in regulated behavioral state changes - helps release AcH to cortex to promote wakefulness

43
Q

What is the lateral zone in the lateral hypothalamus?

A

Poorly defined, mostly an extension of the reticular formation, helps promote wakefulness

44
Q

Where do orexin containing neurons exist? When are they active?

A

Exist in the perifornical area in hte lateral hypothalamus

Tend to be active when you are emotionally aroused

45
Q

What causes narcolepsy?

A

Loss of orexin neurons

3rd most common neurodegenerative disorder

Sleep happens when you are active

46
Q

What does orexin do?

A

Orexin is a neuropeptide that has feeding, reward, and staying awake capabilities

47
Q

What is cataplexy? What causes it, and how does it differ from narcolepsy?

A

Cataplexy is loss of muscle tone and subsequent collapse from a potent emotional stimulus - frightened, laughing, surprised

People will collapse but will still be conscious

Caused by complete loss of orexin neurons, frequently co-morbid with narcolepsy

narcolepsy = disordered sleep, cataplexy = transient paralysis

  • locus coeruleus ends up being inhibited, inhibition of reticulospinal pathways happens, motor pathways freeze
48
Q

What entities, together, regulate wakefulness?

A

Asecending Reticular Activating System

Medial Forebrain Bundle

Basal Forebrain

49
Q

What is the king of the ANS?

A

Paraventricular nucleus

50
Q

What does the PVN send efferents to?

A

Reticular formation

Parasympathetic CN nuclei

Lateral horn of spinal cord

51
Q

The stress response in the brain is bidirectionally mediated. Explain.

A

HPA (hypophysis - pituitary - adrenal) axis

CNS innervation causing release of CRH, which works on adrenal medulla to cause global release of NE and epinephrine

Direction innervation to sympathetic chain, and subsequent innervation of adrenal medulla

52
Q

What are the inputs to the PAG to regulate behavior?

A

Limbic cortex

Amygdala

Hypothalamus

Spinal Cord

Regulates defensive reactions, vocalizations, mating behavior

53
Q

What are the 5 inputs to the hypothalamus?

A

Dorsal longitudinal fasciculus

Retina

Ascending Reticular activating system

Cortex

Hippocampus and Amygdala - limbic lobe

54
Q

What is the path of the DLF?

A

Fibers from around PAG will fan out to hypothalamic wall of 3rd ventricle

55
Q

What paths does the amygdala take into the hypothalamus?

A

Stria Terminalis - c-shaped pathway, goes many places

Amygdalofugol pathway, faster

56
Q

What is the rule of thumb for hypothalamic outputs?

A

If it receives something from the hypothalamus, it also sends something to the hypothalamus.

57
Q

What are the physical parts of the limbic system related to the hippocampus? Amygdala?

A

Hippocampus:

posterior cingulate gyrus

parahippocampal gyrus

Amygdala:

anterior cingulate gyrus

uncus

subcortical areas

58
Q

The amygdala evolved with the BG. Why?

A

BG - helps with smooth, repetitive motions, like running

Amygdala - processes fear and emotions. Amygdala speeds up decision making process significantly by adding emotional inputs.

If you need to run away from a hungry bear/Dr. Buck/neuro course, you rely on both these systems.

59
Q

The amygdala has 2 important pathways. What are they?

A

Basolateral Nuclei Group - BNG

multimodal association cortex - assigns value judgement to scary/stressful stimuli

-slow, fear response that isn’t immediate

Projects to central nucleus, indirect

Central Nucleus of Amygdala - CNA

  • fast, learned fear response, direct response

(What happens when someone sees a snake, spider, etc.)

60
Q

What are the afferent pathways to the amygdala?

A

thalamus

hypothalamus

OFC

olfactory tract

Association cortices

61
Q

What are the 4 major subregions of the hippocampus?

A

Dentate gyrus

Hippocampus proper (CA 1-3)

Subiculum

Entorhinal cortex

62
Q

What is the path of the parahippocampal gyrus?

A

Diverse cortical info is brought in and out of hippocampus

Neocortex –> parahippocampal region –> Entorhinal cortex –> dentate gyrus –> CA 1-3 –> subiculum –> fimbrae or back out the way it came

63
Q

What is the septohippocampal pathway out of the hippocampus?

A

Info leaves hippocampus via fornix fimbria

Fornix travels around to septal nuclei

Bifurcates on the way there, sends other arm to mammillary bodies

64
Q

What is the papez circuit?

A

Circuit to connect hippocampus to rest of the limbic lobe.

Cingulate gyrus –> parahippocampal region –> hippocampus –>fornix –> mammillary bodies –> anterior nucleus of the thalamus –> cingulate gyrus

65
Q

What is Kluver-Bucy syndrome? What does it tell us about goal driven behavior?

A

Loss of limbic lobes, resulting in fearlessness, placidity, hypersexuality, curiousity

Drives are still intact, but ability to satisfy the drives isn’t

Also, poor ability to learn and learn from mistakes.

Emotional component essential to learning, learning from mistakes, and satisfying wants.

Neuro Exam III (9 decks)

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