DSA Hypothalamic and Limbic systems Flashcards
What is the primary role of the Hypothalamus
Maintenance of homeostasis
water and electrolyte balance, food intake, temperature, BP, circadian rhythm, stress responses, body metabolism
Location of the tuber cinereum
small swelling between the mamillary bodies and the optic chiasm and tract
Location of the median eminence
arises from the tuber cinereum and narrows into the infundibulum and attaches to the pituitary gland
What are the longitudinal divisions of the hypothalamic nuclei
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
What are the medial to lateral divisions of the Hypothalamic nuclei
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
What are the three zones of the hypothalamic nuclei
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
What nuclei are found in the supraoptic region and what are their functions
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
What nuclei are found in the Mamillary/posterior region and what are their functions
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
What nuclei are found in the tuberal region and what are their functions
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
Blood supply to the anteromedial and posteromedial groups of the hypothalamus
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)
What are three major afferent routes to the hypothalamus
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
What are the two major efferent hypothalamic pathways
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
What are the Direct links to the ANS via the hypothalamus
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
What are the indirect links to the ANS via the hypothalamus
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
What is the significance of the supraopticohypophysial tract
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
What is the significance of the Tuberoinfundibular tract
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
Purpose of the suprachiasmatic nucleus
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
What gland controls melatonin secretion
pineal gland via indirect circadian genes
What is the purpose of the Hippocampus and what are its afferent and efferent pathways
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
What are the afferents and projections of the cungulate gyrus
afferents: from thalamus and cortex
projects to the entorhinal cortex cia the cingulum
What is the purpose of the amygdala and what are its afferent and efferent pathways
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
Oversimplified Papez circuit and what is it carrying
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
WHat does the septal region of the limbic system do?
small are just rostral to the anterior commissure thought to control rage behavior
What does the medial forebrain bundle of the limbic system do
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
WHat does the nucleus accumbens of the limbic system do
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
What does the Ventral tegmental area do
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
Hippocampa amnesia
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
Korsakoffs syndrome
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
2 Disorders of OLfaction
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
Kluver bucy syndrome
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
Uncal Herniation
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
