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neuro 2019 Exam 3 > Hypothalamus and Limbic System > Flashcards

Hypothalamus and Limbic System Flashcards

1
Q

Hypothalamus input/ output

A

Hypothalamus receives input from cortical, limbic, and sensory sources, sends output in 3 types of motor control

All sorts of things regulated by hypothalamus:
Secretomotor (neuroendocrine hypothalamus)
Skeletomotor (GSE directly from HT)
Autonomics

At least 3 different types of outputs from the HT.

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2
Q

Traditionally, the hypothalamus has been associated with

A

Drive-related behaviors
Ingestive, reproductive, and defensive behaviors
or feeding, fighting, fleeing and mating
Brain’s center for homeostasis
My own opinion:
Hypothalamus = brain’s chief of staff
Coordinates all major input with the appropriate output to keep things running smoothly
(contrast this role with the thalamus as the brain’s gatekeeper)

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3
Q

4 longitudinal divisions of the hypothalamus contain nuclei with diverse functions

A

Preoptic
Anterior: Anterior, Paraventricular, supraoptic, and suprachiasmatic nucleus
Tuberal (infundibulum): Dorsal medial, ventral medial, arcuate
Posterior

PratP is rostral to caudal

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4
Q

There are 3 mediolateral divisions of the hypothalamus

A 
Periventricular
Few nuclei, mostly DLF fibers
Medial
Most hypothalamic nuclei
Lateral
Separated from medial by the fornix
MFB
Lateral Hypothalamic Area
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5
Q

The hypothalamus has a logical organization

A

Unlike the thalamus, hypothalamic nuclei follow patterns:

Neuroendocrine vs. endocrine output 
Anterior nuclei (parasympathetic) vs. posterior nuclei (sympathetic)
Lateral nuclei = reticular formation/state control
Bidirectional circuitry
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6
Q

The secretomotor (neuroendocrine) hypothalamus

A

Nuclei involved in release of hormones through the hypophysis
Neurohypophysis (posterior pituitary)
Direct release into
Adenohypophysis (anterior pituitary)
Release via a vascular link within the ant. pituitary

Supraoptic and Paraventricular nuclei
Magnocellular	subdivision
Oxytocin
Milk letdown reflex, uterine contractions
ADH (vasopressin)
Water reabsorption
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7
Q

Neural circuit of ADH release(aka preventing urination and inducing drinking behavior when dehydrated)

A

Circumventricular organs (no blood-brain barrier!)

6 in the brain, including OVLT (Organum vasculosum of lamina terminalis), neurohypophysis, median eminence (base of hypothalamus), pineal, SFO (subfornical organ), area postrema
Neuronal and glial structures that abut capillaries and aren’t protected by BBB

Monitoring osmololality
When low blood volume:
A) Kidney secretes renin, converted to angiotensin II, activates receptors in SFO
B) Osmoreceptors in OVLT activated
SFO and OVLT send axons to preoptic nucleus, these neurons send axons to paraventricular and supraoptic nuclei, stimulate ADH release

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8
Q

Adenohypophysis blood supply

A

Internal carotid artery branches into the superior hypophyseal artery that breaks up into a capillary bed in the median eminence

Blood recollects down pituitary stalk in hypophyseal portal vessels to carry releasing hormones and inhibiting hormones to endocrine cells in the anterior pituitary

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9
Q

Signaling molecules through adenohypophysis

A

Parvocellular neurons release the “releasing hormones” via the tuberoinfundibular tract

Hypothalamic nuclei involved are preoptic, supraoptic, paraventricular, ventromedial, and arcuate

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10
Q

Releasing hormones and their anterior lobe hormones(adenohypophysis)

A 
CRH, --> ACTH
TRH, --> Thyrotropin
GHRH, --> Growth hormone
GnRH, --> FSH/ LH
Dopamine --> Prolactin
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11
Q

Preoptic Nucleus/Preoptic area

A 
Parasympathetic centers
Important for maintaining bp/heart rate
Important for maintaining osmolality
Important for induction of sleep
Important for thermoregulation
Important for 
GnRH neurons
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12
Q

Anterior region of the hypothalamus

A

Supraoptic nucleus
Regulates ingestive, reproductive behaviors
Vasopressin (ADH) and oxytocin

Paraventricular nucleus
Regulates ingestive, reproductive and stress behaviors
Vasopressin (ADH), oxytocin, CRH, TRH

Suprachiasmatic nucleus
Sits just on top of optic chiasm, contains body’s master circadian clock
Receives major direct sensory input from the retina

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13
Q

The retinohypothalamic tract (RHT) does what?

A

programs synchrony based on daily light cycles

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14
Q

Major nuclei along the medial axis: Tuberal region of the hypothalamus

A

Dorsomedial nuecleus
Regulates ingestive behaviors

Ventromedial nucleus
Regulates ingestive and reproductive behaviors
“satiety center”

Arcuate nucleus
Regulates ingestive behaviors
Parvocellular neurons to anterior pituitary (dopamine, GHRH)

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15
Q

Posterior region of the hypothalamus

A

Posterior nucleus
Sympathetic center

Mammillary bodies
Prominent posterior landmark
Afferents from hippocampus—damage here affects memory
Efferents to anterior nucleus of the thalamus
Damaged in Korsakoff’s syndrome

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16
Q

korsakoff’s syndrome

A

– alcoholism, some vitamin deficiency, memory loss. Suggests the mammillary bodies are related to memory in some way. Hippocampus to mammillary bodies.

17
Q

Lateral hypothalamus and median forebrain bundle

A

Separated by the fornix
Consists of an ambiguous network—a continuation of the brainstem reticular formation
Contains massive fiber tract:
Median forebrain bundle
Connects brainstem tegmentum with basal forebrain
– Septal nuclei and Basal nucleus of Meynert
Major role in regulated behavioral state changes

18
Q

Behavioral state control in the lateral hypothalamus (histamine and orexin)

A

Tuberomammillary nucleus
Major center of histamine-containing neurons
Project throughout the brain
Important for maintaining consciousness
Histamine neurons are inactive during sleep

Orexin+ neurons perifornical (around the fornix) in the lateral hypothalamus
Project to many targets
Active when emotionally aroused
Loss of orexin neurons is the cause of narcolepsy
3rd most common neurodegenerative disorder

19
Q

Hypothalamic control of visceromotor circuits:

A

Paraventricular nucleus = “king” of the autonomic nervous system

Efferents to:
Reticular formation
Parasympathetic cranial nerve nuclei
Lateral horn of spinal cord

20
Q

Hypothalamic inputs

A

Dorsal longitudnal fasciculus
Fibers from around the periaqueductal grey in the brainstem that fan out in the hypothalamic wall of the 3rd ventricle

Retina (only directly transduced sensory input)

Ascending reticular activating system
Catches a ride to the hypothalamus with the Median forebrain bundle

Cortex

Hippocampus and amygdala–LIMBIC

21
Q

Rule of thumb for hypothalamic output:

A

If it sends something to the hypothalamus, it receives something from the hypothalamus
Exception with the retina as input
Neuroendocrine outputs

22
Q

Hypothalamus is integrated into the center of the

A

limbic system

23
Q

Amygdala is collection of nuclei. 2 pathways:

A

1 involves basolateral nucleus to central nucleus indirect

  • This is slow response
  • Fear association that isn’t immediate

1 involves visceral responses, direct

  • This is a fast response
  • Think “what happens when I see a snake”
24
Q

Hippocampus has 4 major subregions

A 
Dentate gyrus (DG)
Hippocampus proper
CA1-3 (Cornu ammonis)
Subiculum
Entorhinal cortex
25
Q

Parahippocampal gyrus

A

is where diverse cortical info is brought into (and carried out) of hippocampus

Transitional zone from neocortex to paleocortex
Instead of 6 layers, 3 layers
Entorhinal cortex (“within the nose”)
Subiculum (“supporting”)

26
Q

Pathway of information flow through parahippocampal gyrus:

A

How declarative memories are consolidated and retrieved

NEocortex –> parahippocampal region–> entorhinal cortex–> dentate gyrus–> CA 3–> CA1–> subiculum–> entorhinal cortex and back to parahippo and neocortex

27
Q

Septohippocampal pathway and parahippocampal gyrus are

A

the outs and ins of the hippocampus

28
Q

Septohippocampal pathway is bi-directional

A

Info leaves HC via fornix—”fimbria”
Fornix travels around to septal nuclei
Bifurcates on the way there, sends other arm to Mammillary bodies

29
Q

Papez circuit:

A

A circuit to connect the hippocampus to the rest of the limbic lobe

Original circuit tied to emotion (1930’s)
Cingulate gyrus—Parahippocampal region—hippocampus—fornix—mammillary body—ant nuc. Thal.—cingulate gyrus

neuro 2019 Exam 3 (17 decks)

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