Hypothalamus and Limbic Systems Flashcards
Lateral zone of the hypothalamus
Contains the median forebrain bundle
Damage results in a decrease in feeding behavior with resultant weight loss
Supraoptic region nuclei
Supraoptic/paraventricular nucleus
Suprachiasmatic nucleus
Anterior nucleus
Supraoptic/paraventricular nucleus
Contain oxytocin and ADH which go to the posterior pituitary
Lesion can result in diabetes insipidus, increased H2O intake, increased urination
Suprachiasmatic nucleus
Receives retinal input and is involved in circadian rhythms
Damage to this area may modify these rhythms
Gene products indirectly control melatonin secretion
Anterior nucleus
Range of visceral/somatic functions
Temperature regulation
Medial zone nuclei
Medial mammillary nucleus in posterior region
Ventromedial and dorsomedial nuclei in tuberal region
Medial mammillary nucleus
Afferents from the hippocampus via the fornix
Efferents to thalamus and brain stem
Lesions result in an inability to process short term events into long term memory
Ventromedial nucleus
Considered to be a satiety center
Lesions cause excessive eating and abnormal weight gain
Dorsomedial nucleus
Subserves function of emotional behavior
Stimulation causes sham rage
Destruction results in decreased aggression and feeding
What nuclei are served by the anterior communicating and anterior cerebral A1 arteries
Preoptic and supraoptic region: supraoptic/paraventricular, suprachiasmatic, anterior nuclei
Rostral part of lateral zone
What nuclei are served by posterior communicating artery and posterior cerebral P1 segment
Rostral posterior communicating artery- tuberal region
Caudal posterior communicating artery- mammillary region
Fornix
Afferent fibers
Arises from subiculum and hippocampus
Largest single input to the hypothalamus
Medial forebrain bundle
Afferent dopaminergic fibers (part of limbic system)
Interconnects septal nuclei, hypothalamus and midbrain tegmentum
Courses through lateral hypothalamic zone
Amygdalohypothalamic fibers
Afferent fibers
Stria terminalis and ventral amydalofugal pathways
Both target septal nuclei, preoptic area and medial hypothalamic zone
Mammillary fasciculus
Efferent fibers
Originates in medial mammillary nucleus
Bifurcates into mammillothalamic and mammillotegmental tracts
Projects to anterior nucleus of thalamus, an important part of the circuit of papez
Hypothalamothalamic fibers
Efferent fibers
From lateral preoptic area to the dorsomedial nucleus of the thalamus and amygdaloid nucleus
Hypothalamomedullary fibers
Direct link to ANS
Travel to solitary nucleus, dorsal vagal motor nucleus and nucleus ambiguus
Hypothalmospinal fibers
Direct link to ANS
Travel to interomediolateral cell column (GVE preganglionics)
Lesions in anterolateral medulla disrupt these fibers and disrupt sympathetic flow to the face (horners syndrome) and the body
Posterior longitudinal fasciculus and mammillotegmental tract
Indirect link to ANS
Both target the PAG
PAG will target other visceral areas of the brainstem and influence autonomic nuclei there
Hippocampal formation
Includes hippocampus, subiculum, entorhinal cortex and dentate gyrus
CA1, CA2, CA3, CA4
Afferent pathway of hippocampal formation
Dentate gyrus –> CA3 —> CA1 –> Subiculum
Efferent pathway of hippocampal formation
Subiculum–>Fornix
Terminates in medial mammillary nucleus, ventromedial nucleus and anterior nucleus of thalamus
Cingulate gyrus
Afferents from thalamus and cortex
Projects to entorhinal cortex via the cingulum
Amygdala afferents
Afferents from inferior temporal association cortex, thalamus, septum and olfactory tract, brainstem
Amygdala efferents
Stria terminalis- outputs to the hypothalamus and basal ganglia to permit motor behavioral responses
Ventral amydalofugal pathway- Major efferent fiber bundle with two general trajectories:
Hypothalamus/septal nuclei, frontal/prefrontal cortex, cingulate and insular cortices
Brainstem to terminate in visceral (dorsal motor vagal) and raphe nuclei
Papez circuit
Simplification of the role of limbic system in modulating feelings
Cingulate gyrus projects–> hippocampal formation (subiculum and entorhinal cortex)
Hippocampus–> fornix–> medial mammillary nucleus
Medial mammillary nucleus–> anterior nucleus of thalamus (via mammillothalamic tract)
Anterior nucleus–> cingulate gyrus
Septal region
Limbic structure thought to help control rage behavior
Nucleus accumbens
Receives input from amygdala and hippocampus
Important role in behaviors related to addiction and chronic pain
Efferents include hypothalamus, brainstem and globus pallidus
VTA ventral tegmental area
Large number of dopaminergic neurons
Form connections with ventral striatum, amygdala, and other limbic structures
Efferents to nucleus accumbens plays important role in reward and motivation, may contribute to addiction
Hippocampal amnesia
Bilateral hippocampal lesions
Deficit in anterograde episodic memory, but spared procedural and working memory
I.Q. and formal reasoning remain about normal
Korsakoffs syndrome
Progressive degeneration of mammillary bodies, hippocampal complex and dorsomedial thalamic nucleus
Impedes retention of new memories - Short term cannot go long term
Difficulty learning new tasks
Difficulty understanding written material or conducting meaningful conversations
Patients combine fragmented memories into a new memory that never occurred
Caused by thiamine deficiency associated with chronic alcoholism
Phantosmia
Olfactory hallucination
Distortion in a smell experience or the perception of a smell when no odor is present
Lesion of anterior/medial temporal lobe can cause this
Or lesion of hippocampus, amygdala or medial dorsal thalamic nuclei
Kluver Bucy syndrome
Bilateral temporal lobe lesions that abolish amygdaloid complex
Visual agnosia - cannot recognize objects
Hyperorality- tendency to examine objects by mouth
Hypermetamorphosis- compulsion to intensively explore the immediate environment or overreact to visual stimuli
Placidity- may not show fear or anger even when appropriate
Hyperaphagia- excessive eating even when not hungry or eating objects that aren’t food
Hypersexuality
Uncal herniation
Dilated pupil with double vision ipsilateral to lesion
Weakness of extremities contralaterally
Respiration can be affected, abnormal reflexes
