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Neuro Endo 3 > Hypothalamic and Limbic Systems > Flashcards

Hypothalamic and Limbic Systems Flashcards

1
Q

What part of the brain is the hypothalamus?

A

Diencephalon

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2
Q

Where does the hypothalamus receive and integrate information from?

A

forebrain, brainstem, spinal cord

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3
Q

Main role of hypothalamus

A

Homeostasis: water and electrolyte balance, food intake, temperature, BP, circadian rhythm, stress response, body metabolism

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4
Q

Where does the hypothalamus connect to rostrally?

A

optic chiasm

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5
Q

Where does the hypothalamus connect to caudally?

A

merges into tegmentum and PAG (midbrain)

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6
Q

The hypothalamus form the floor and ventral wall of what?

A

3rd ventricle

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7
Q

What is the hypothalamus continuous with?

A

posterior pituitary through infundibular stalk

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8
Q

What forms the posterior part of the hypothalamus and are next to the cerebral peduncles?

A

Mammillary bodies

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9
Q

What is the small swelling between the mammillary bodies and optic chiasm and tract?

A

Tuber cinereum

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10
Q

What arises from the tuber cinereum and narrows into the infundibulum, and attaches to the pituitary gland?

A

Median eminence

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11
Q

How are the hypothalamic nuclei divided?

A

Longitudinal divisions

Medial to lateral divisions

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12
Q

What are the longitudinal divisions?

A

Anterior region: superior to optic chiasm, extending anteriorly to the lamina terminalis
Tuberal region: superior to and including the tuber cinereum
Mammillary/posterior region: superior to and including the mammillary bodies

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13
Q

What are the medial to lateral divisions?

A

Periventricular zone: periaqueductal gray (midbrain) through the wall of the 3rd ventricle
Fornix is used to divide the remainder of the hypothalamus into medial and lateral zones

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14
Q

What does the lateral zone consist of?

A
  • diffusely arranged neurons with few “named” nuclei
  • contains median forebrain bundle
  • damage results in a decrease of feeding behavior with a resultant weight loss
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15
Q

What does the medial zone consist of?

A
  • overlaps with anterior to posterior regions

- where neurons are arranged in distinct nuclei

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16
Q

What are the regions of the medial zone?

A

1) supraoptic region
2) Mammillary/posterior region
3) Tuberal region

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17
Q

Name the specific nuclei of the supraoptic region and their function

A

1) supraoptic/paraventricular nucleus- contain oxytocin (PVN) and ADH (SON) to send to posterior pituitary (lesions in these nuclei can result in diabetes insipidus, increased water intake, and increased urination
2) suprachiasmatic nucleus- receives retinal input and is involved in circadian rhythms
3) anterior nucleus- range of visceral/somatic functions, temperature regulation

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18
Q

Name the specific nuclei of the mammillary/posterior region and their function

A

1) medial mammillary nucleus- afferents from the hippocampus via the fornix, efferents to the thalamus and brainstem (lesions= inability to process short term events and put them in long term memory)

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19
Q

Name the specific nuclei of the tuberal region and their function

A

1) Ventromedial nucleus- satiety center (lesions = excessive eating an abnormal weight gain)
2) Dorsomedial nucleus- subserves functions of emotional behavior; stimulation causes sham rage (lesion = decreased aggression and feeding)

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20
Q

What is the blood supply to the hypothalamus?

A

small perforating arteries from circle of wills

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21
Q

Blood supply to anteromedial group of hypothalamus?

A

branches from anterior communicating and anterior cerebral arteries (A1)

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22
Q

What parts of the hypothalamus are supplied by the anterior communicating and anterior cerebral arteries?

A
  • preoptic region
  • supraoptic region
  • septal nuclei
  • rostral portions of lateral hypothalamic area
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23
Q

Blood supply to posteromedial group of hypothalamus

A

perforating arteries from the posterior communicating artery and posterior cerebral artery (P1)

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24
Q

What parts of the hypothalamus are supplied by the posterior communicating artery?

A
  • rostral portion of posterior communicating artery = tuberal region
  • caudal portion of posterior communicating artery = mammillary region
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25
Q

What is the function of the fornix?

A

-largest single afferent input to the hypothalamus from the subiculum and hippocampus

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26
Q

What is the function of the medial forebrain bundle?

A
  • afferents
  • interconnects septal nuclei, hypothalamus, and midbrain tegmentum
  • courses through lateral hypothalamic zone
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27
Q

What is the function of the amygdalohypothalamic fibers?

A
  • afferents
  • stria terminalis and ventral amygdalofugal pathways
  • both target septal nuclei, preoptic area, and medial hypothalamic zone
28
Q

What are the major afferent routes to the hypothalamus?

A

1) fornix
2) medial forebrain bundle
3) amygdalohypothalmic fibers

29
Q

What are the major efferents of the hypothalamus?

A

1) mammillary fasciculus

2) hypothalmaothalamic fibers

30
Q

What is the function of mammillary fasciculus?

A
  • efferents
  • originates as well defined bundle from the medial mammillary nucleus
  • bifurcates into mammillothalamic and mammillotegmental tracts
  • projects to anterior nucleus (thalamus), an important part of circuit of papez
31
Q

What are the functions of the hypothalamothalamic fibers?

A
  • efferents
  • from later preoptic area
  • project to dorsomedial nucleus (thalamus) and amygdaloid nucleus
32
Q

How are the vital functions of the hypothalamus controlled?

A

reflexes mediated by autonomic or endocrine systems

33
Q

What are the two direct links to the ANS and where do they project to?

A

1) hypothalamomedullary fibers project to the solitary nucleus, dorsal vagal motor nucleus, nucleus ambiguus
2) hypothalamospinal fibers project to the intermediolateral cell column (GVE preganglionics)

34
Q

What would a lesion to the anterolateral medulla disrupt?

A
  • direct link fibers to the ANS

- disrupts sympathetic outflow to face and head (Horner’s)

35
Q

What is the indirect link to the ANS and where does it project to?

A

1) posterior longitudinal fasciculus and mammillotegmental tract project to target the PAG
- PAG will target other visceral areas of the brainstem (solitary and dorsal motor vagal nuclei)

36
Q

What is the supraopticohypophusial tract made of?

A

axons and neurons in SON and PVN

37
Q

What do the SON and PVN produce?

A
  • oxytocin and ADH to posterior pituitary

- stored in Herring bodies and released into capillary plexus of posterior pituitary

38
Q

What are the inputs to the tuberinfundibular tract?

A
  • inout from neurons located in periventricular zone, PVN, and others
  • convey releasing hormones to median eminence and infundibulum
39
Q

What is the function of the suprachiasmatic nucleus?

A
  • receives direct input from the retina to mediate circadian rhythms, hormonal fluctuations secondary to light-dark cycles
  • conveys circadian info to other hypothalamic regions, influencing sleep-wake transitions
  • opposes drive for sleep
  • essential for timing of rest vs. activity
40
Q

How do cells maintain 24 hour periodicity of circadian genes?

A

transcription/translational control

41
Q

Gene products indirectly control the secretion of what?

A
  • melatonin from pineal gland
  • increases just prior to normal sleep onset
  • internal indicator of circadian time and feedback to SCN
42
Q

What does the limbic system include?

A

-subcallosal area, cingulate gyrus, parahippocampal gyrus, uncus, hippocampal formation, and subcortical nuclei

43
Q

Function of limbic system?

A
  • receives input from and projects to diverse brain areas

- connections influence behavior, memory, and pain perception

44
Q

What is included in the hippocampal formation?

A
  • hippocampus
  • subiculum (transitional area between hippocampus and entorhinal cortex)
  • entorhinal cortex
  • dentate gyrus
  • CA1, CA2, CA3, CA4 (CA= cornus ammonis; 2 and 4 are modulatory)
45
Q

Importance of hippocampal formation

A

learning and memory

46
Q

Hippocampal formation afferent pathway

A

dentate gyrus > CA3 > CA1 > subiculum

47
Q

Hippocampal formation efferent pathway

A

subiculum > fornix

  • terminates in medial mammillary nucleus, ventromedial nucleus, and anterior nucleus
  • other projections: septal nuclei, frontal cortex, preoptic and anterior nuclei, nucleus accumbens
48
Q

Cingulate gyrus function

A
  • receives afferents from thalamus and cortex

- projects to entorhinal cortex via cingulum

49
Q

Function of amygdala

A
  • vital to emotional and motivational connotations of experience
  • located deep and medially within temporal lobes
50
Q

Where does the amygdala receive afferents from?

A

-inferior temporal association cortex, thalamus, septum, brainstem, and olfactory tract

51
Q

Where does the amygdala send efferents?

A
  • stria terminalis sends outputs to hypothalamus and basal ganglia to permit motor behavioral response
  • ventral amygdalofugal pathway sends major efferent fiber bundle with two general trajectories: hypothalamus, septal nuclei, frontal and prefrontal, cingulate, insular cortices; brainstem to terminate in visceral nuclei and raphe nuclei
52
Q

What is the papez circuit?

A

-role of limbic system in modulating feelings

53
Q

Papez circuit

A

1) cingulate gyrus projects to hippocampal formation
2) hippocampus to fornix to medial mammillary nuclei
3) medial mammillary nucleus to anterior nucleus
4) anterior nucleus projects to cingulate gyrus

54
Q

Septal Region

A

-small area just rostral to anterior commissure thought to control rage behavior

55
Q

Medial Forebrain Bundle

A
  • diffuse group of dopaminergic fibers that courses rostrocaudally through the lateral hypothalamic area
  • major conduit for septal nuclei and hypothalamus to communicate with brainstem
56
Q

Nucleus Accumbens

A
  • receives input from amygdala and hippocampus
  • important role in behaviors related to addiction and chronic pain
  • sends efferents to hypothalamus, brainstem, globus pallidus
57
Q

Where is the VTA located?

A

medial to substantia nigra, contains large number of dopaminergic neurons

58
Q

What does VTA do?

A

forms connections with ventral striatum, amygdala, and other limbic structures

59
Q

Where does VTA send efferents to?

A

-nucleus accumbens which plays an important role in reward and motivation and may contribute to addiction

60
Q

What is hippocampal amnesia?

A
  • bilateral lesions of hippocampi
  • deficit in anterograde episodic memory (cannot learn new material)
  • spared procedural and working memory
  • normal IQ and formal reasoning
61
Q

What is Korsakoff’s Syndrome?

A
  • progressive degeneration of the mammillary bodies, hippocampal complex, and dorsomedial thalamic nucleus
  • impedes retention of newly acquired memories
  • cannot form long term memories from short term
  • difficulty understanding written material and conducting meaningful conversations
  • confabulate = combine fragmented memories into a synthesized memory of an “event” that never occurred
  • caused by thiamine deficiency (alcoholism)
62
Q

Anosmia

A
  • loss of smell due to viral infection of olfactory mucosa, obstruction of nasal passages, congenital
  • lesions due to shearing of CN1 or tumors in floor of anterior cranial fossa
  • do not recover sense of smell
63
Q

Phantosmia

A
  • distortion in smell experience or perception of smell when no odor is present
  • abnormal sequence of neuronal activity
  • lesion is anterior/meidal temporal lobe
  • hippocampus, amygdala, or medial dorsal thalamic nuclei
64
Q

Kluver Bucy

A
  • bilateral temporal lobe lesions that abolish amygdaloid complex
  • visual agnosia
  • hyperorality
  • hypermetamorphosis
  • placidity
  • hyperphagia
  • hypersexuality
65
Q

Uncal Herniation

A
  • movement of uncus over edge of tentorium cerebelli
  • initially compress midbrain, may move to lower brainstem regions
  • dilated pupil
  • abnormal eye movements
  • weakness of extremities opposite to dilated pupil
  • can affect respiration as it progresses toward medulla
  • abnormal reflexes appear

Neuro Endo 3 (13 decks)

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