DSA Hypothalamic and Limbic systems

Question 1

What is the primary role of the Hypothalamus

Answer 1

Maintenance of homeostasis

water and electrolyte balance, food intake, temperature, BP, circadian rhythm, stress responses, body metabolism

Question 2

Location of the tuber cinereum

Answer 2

small swelling between the mamillary bodies and the optic chiasm and tract

Question 3

Location of the median eminence

Answer 3

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

Question 4

What are the longitudinal divisions of the hypothalamic nuclei

Answer 4

Anterior region: superior to optic chiasm, estending anteriorly to the lamina terminalis

Tuberal region: superior to and including the tuber cinerum

Mamillary /posterior region: superior to and including the mammillary bodies

Question 5

What are the medial to lateral divisions of the Hypothalamic nuclei

Answer 5

Periventricular zone: periaqueductal gray through to the wall of the 3rd ventricle

Fornix then divides the remainder of the hypothalamus into the medial and lateral zones

Question 6

What are the three zones of the hypothalamic nuclei

Answer 6

Lateral zone: contains the median forebrain bundle
-damage results in a decrese in feeding behavior with a resultant weight loss

Medial zone: overlaps with anterior and posterior regions (supraoptic region, tuberal region, mammillary region)

Periventricular zone

Question 7

What nuclei are found in the supraoptic region and what are their functions

Answer 7

found in the medial zone:

supraoptic/paraventricular nucleus: contain oxytocin(SO) and ADH(PVN) send this to the posterior pituitary
-lesions can result in diabetes insipidus, increase in H2O intake and increase in urination

Suprachiasmatic nucleus: recieves retinal input and is involved in circadian rhythms
-damage here may modify circadian rhythms

Anterior nucleus: range of visceral/ somatic functions, temperature regulateion

Question 8

What nuclei are found in the Mamillary/posterior region and what are their functions

Answer 8

Found in medial zone:

Medial mammillary nucleus:

• afferents from the hippocampus via the fornix
• efferents to the thalamus and brainstem
• lesions result in an inabillity to process short term events into long term memory

Question 9

What nuclei are found in the tuberal region and what are their functions

Answer 9

Found in the medial zone:

Ventromedial nucleus: considered to be a satiety center
-lesions cause exessive eating and abnormal weight gain

Dorsomedial nucleus: sub serves functions of emotional behavior

• stimulation causes sham rage
• destruction results in decreased aggression and feeding

Question 10

Blood supply to the anteromedial and posteromedial groups of the hypothalamus

Answer 10

anteromedial group: branches from anterior communicating and anterior cerebral arteries
(preoptic area, supraoptic area, septal nuclei, lateral hypotjhalamic area)

posteromedial group: perforating arteries from the posterior communicating artery and posterior cerebral artery
(tuberal and mamillary region)

Question 11

What are three major afferent routes to the hypothalamus

Answer 11

Fornix: arises from the subiculum and hippocampus

Medial forebrain bundle: interconnects septal nuclei, hypothalamus and midbrain tegmentum
-goes through lateral hypothalamic zone

Amygdalohypothalamic fibers: stria terminalis and ventral amydalofugal pathways
-both target septal nuclei, preoptic area and medial hypothalamic zone

Question 12

What are the two major efferent hypothalamic pathways

Answer 12

Mamillary fasciculus: originates as a well-defined bundle from the medial mammillary nucleus

• bifurcates into mammillothalamic and mammillotegmental tracts
• projects to the anterior nucleus (part of circuit of papez)

Hypothalamothalamic fibers:
-lateral preoptic area to the dorsomedial nucleus and amygdaloid nucleus

Question 13

What are the Direct links to the ANS via the hypothalamus

Answer 13

Hypothalamomedullary fibers: go to the solitary nucleus, dorsal vagal motor nucleus, nucleus ambiguus

Hypothalamospinal fibers: interomedial cell column containing GVE preganglionics

Lesions to anterolateral medulla disrupts these fibers leading to horners syndrome

Question 14

What are the indirect links to the ANS via the hypothalamus

Answer 14

Posterior Longitudinal fasciculus and the mammilotegmental tract

both target the PAG which will target other visceral areas of the brainstem affecting the Autonomic nuclei in the brainstem

Question 15

What is the significance of the supraopticohypophysial tract

Answer 15

tract that goes from the Paraventricular nucleus and the supraoptic nucleus to the posterior pituitary gland

produce oxytocin and ADH

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

Question 16

What is the significance of the Tuberoinfundibular tract

Answer 16

recieves input from the neurons located in the periventricular zone, paraventricular nucleus, and others and conveys releasing hormones to median eminence and the infundibulum

ends up in the anterior pituitary

Question 17

Purpose of the suprachiasmatic nucleus

Answer 17

recieves input from the retina to mediate circadian rhythms

conveys this information to other hypothalamic regions influencing sleep and wake transitions

SCN activity opposes drive for sleep and is essential for timing of rest vs activity

Question 18

What gland controls melatonin secretion

Answer 18

pineal gland via indirect circadian genes

Question 19

What is the purpose of the Hippocampus and what are its afferent and efferent pathways

Answer 19

Important for learning and memory

Afferent pathway: Dentate gyrus to CA3 to CA1 to subiculum

Efferent pathways: subiculum to the fornix
-terminates in the medial mammillary nucleus, ventromedial nucleus, and anterior nucleus

CA means cornus ammonis

Question 20

What are the afferents and projections of the cungulate gyrus

Answer 20

afferents: from thalamus and cortex

projects to the entorhinal cortex cia the cingulum

Question 21

What is the purpose of the amygdala and what are its afferent and efferent pathways

Answer 21

Vital to motivational and emotional connotations of experience

afferents: from the inferior temporal association cortex, the thalamus, septum, olfactory tract, and the brainstem

Efferent projections:
-Stria terminalis: output to the hypothalamus and basal ganglia to permit motor behavioral responses
-Ventral amydalofugal pathway: to the hypothalamus, septal nuclei, frontal and prefrontal, cingulate and insular cortices
also the Brainstem to terminate with the dorsal motor vagal nuclei and the raphe nuclei

Question 22

Oversimplified Papez circuit and what is it carrying

Answer 22

Modulates feelings

Cingulate gyrus to the hippocampal formation (subiculum and entorhinal cortex)

then to the fornix and to the medial mammillary nuclei

from the medial mammillary nucleus to the anterior nucleus via the mammillothalamic tract

then from the anterior nucleus it projects bact to the cingulate gyrus

Question 23

WHat does the septal region of the limbic system do?

Answer 23

small are just rostral to the anterior commissure thought to control rage behavior

Question 24

What does the medial forebrain bundle of the limbic system do

Answer 24

Diffuse group of dopaminergic fibers that courses rostrocaudally through the lateral hypothalamic area

major conduit for septal nuclei and hypothalamus to communicate with the brainstem

Question 25

WHat does the nucleus accumbens of the limbic system do

Answer 25

Recieves input from the amygdala and the hippocampus

play an important role in behaviors related to addiction and chronic pain

Efferents include hypothalamus, brainstem and glbus pallidus

Question 26

What does the Ventral tegmental area do

Answer 26

Contains large numbers of dopaminergic neurons (located next to the substantia nigra)

Forms connections with the ventral striatum, the amygdala and other limbic system structures

Efferents to nucleus accumbens play an important role in reward and motivation and may contribute to addiction

Question 27

Hippocampa amnesia

Answer 27

Bilateral lesions of the hippocampus

profound deficit in anterograde episodic memory (cant learn new material) combined with spared procedural and working memory

patients I.Q. and formal reasoning is normal

Question 28

Korsakoffs syndrome

Answer 28

progressive degeneration of the mammillary bodies, hippocampal complex and the dorsomedial thalamic nucleus
-impedes the retention of newly acquired memory and cant turn short term memory into long term memory

difficulty in understanding written material and conducting meaningful conversations

patient will confabulate, combine fragmented memories into a synthesized memory of an event that nerver occurred

caused by thiamine deficiency and associated with chronic alcoholism

Question 29

2 Disorders of OLfaction

Answer 29

Ansomia: loss of smell due to a viral infection of the olfactory mucosa, obstruction of the nasal passages or may be congenital
-could also be a tumor lesioning CNI

Phantosmia: olfactory hallucination
distortion in a smeel experience or the perception of a smell when no odor is present
-lesion of anterior/medial temporal lobe
-lesion of hippocampus, amygdala or medial dorsal thalamic nuclei

Question 30

Kluver bucy syndrome

Answer 30

bilateral temporal lobe lesion that abolishes the amygdaloid complex

Visual agnosia: inabillity to reckognze an object by sight

Hyperorality: tendency to examine object by mouth

Hypermetamorphosis: compulsion to intensively explore the immediate environment or overreact to visual stimuli

Placidity: may or may not show fear or anger when such reaction is appropriate

Hyperphagia: eating excessive amounts even when not hungry

Hypersexuality: suggestive behavior and talk with vague or ill-conceived attempts at sexual contact

Question 31

Uncal Herniation

Answer 31

Movement of the uncus and parahippocampal gyrus, downward over the edge of the tentorum cerebelli

damage due to compression of the midbrain

dilated pupil and abnormal eye movements with double vision

weakness of the extremities opposite to dilated pupil

as it progresses respiration is affected and abnormal reflexes