Lecture 12: Hypothalamic, Thalamus and Limbic Systems Flashcards
What are the 5 thalamic nuclei of the functional lateral nuclear group and what are their functions?
- Ventral anterior: basal ganglia and primary/supplementary motor areas
- Ventral lateral: basal ganglia, cerebellum, and primary/supplementary motor areas
- VPM/VPL: spinothalamic tracts, medial lemniscus, and trigeminothalamic tracts
- LGN: visual afferents
- MGM: auditory afferents
The anterior and medial nuclear groups and intralaminar groups of the thalamic nuclei are considered non-specific and are involved in what kind of behavior?
Instinctive drives, mood, emotional behavior
The reticular nuclei collectively make up the RAS, which controls what?
States of conciousness, sleep, REM, heart rate and respiration
The descending reticulospinal tracts originate where and influence what?
- Originate from the medullary and pontine RAS
- Influence muscle tone and posture
The ascending fibers (cholinergic) of the RAS, mainly the intralaminar nuclei is responsible for causing activation of what?
The cerebral cortex and heightened arousal
What are the serotonergic nuclei that exist as a series of midline nuclei extending the length of the brainstem and are part of the RAS; what are they involved in?
- Raphe nuclei
- Involved in mood and cognitive function and in the neural mechanisms of sleep
What nuclei of the preoptic area of the Hypothalamus contains neurons that make GnRH?
Medial preoptic nucleus
Which zone of the hypothalamus contains the Supraoptic (chiasmatic) region, Tuberal region, and Mammillary region?
Medial zone
The lateral hypothalamic nucleus is a large cell group that constitues what functional center?
The feeding center
Where does the Fornix arise from and why is it significant?
- From neurons in the subiculum and hippocampus
- LARGEST single input to the hypothalamus
What are the 2 bundled divisions of the Fornix and where does each arise from and terminate?
- Precommissural bundle (Hippocampus) = distributed to the septal nuclei, medial areas of frontal cortex, hypothalamus, and nucleus accumbens
- Postcommissural bundle (Subiculum) = terminate in the medial mamillary nucleus, ventromedial nucleus of hypothalamus, and anterior nucleus of the dorsal thalamus
Korsakoff’s Syndrome results from progressive degeneration of what structures; what deficit is seen; what is a common cause?
- Degeneration of mammillary bodies, hippocampal complex, and dorsomedial thalamic nucleus
- Impeded retention of newly acquired memories; unable to transform new information into long-term memories
- Patients will confabulate, combining fragmented memories into synthesized memory of an “event” that never occurred.
- Caused by thiamine deficiency, due to chronic alcoholism
What is the Amygdala vital to?
Vital to the motivational and emotional connotations of experience
What is the primary efferent pathway of the Amygdala and to where?
- Primary = Ventral amygdalofugal pathway
- To the Septal areas
Where does the Stria Terminalis Efferent pathway go?
- Hypothalamus and basal ganglia
- Permit motor behavioral responses
What bundle is the major conduit for septal nuclei and hypothalamus to communicate with the brainstem; dopamine-containing fibers in this area are though to be responsible for what?
- Medial forebrain bundle - VTA (dopaminergic)
- Related to perceptions of pleasure or drive reduction
Major input of Afferents to the Hippocampus is from cells of which cortex via what pathway; where do most of these afferent inputs terminate?
- Cells of the entorhinal cortex via the perforant pathway
- Most terminate in the molecular layer of the Dentate Gyrus
- Few in the subiculum and hippocampus
After receiving afferents the Dentate gyrus projects to which area of the hippocampus and what is the rest of this pathway until reaching the Subiculum?
Granule cells of Dentate gyrus —> Molecular layer of CA3 region of hippocampus —> CA3 projects —> CA1 of the hippocampus –> Subiculum
The Hippocampal efferents originate primarily from which cells, what do axons coalesce to form and then continue as what?
- From the Subiculum and Pyramidal cells of the hippocampus the axons leave, and coalesce to form the fimbria, and then continue as the fornix
- The Fornix is the MAJOR output of the hippocampus and the MAJOR input to the hypothalamus
The initial segment of the Papez circuit is from where to where?
The SUBICULUM of HIPPOCAMPUS to the Medial Mammilary nucleus (postcommissural fornix)
From the Medial Mammillary nucleus how is the Circuit of Papez completed?
- Mammillothalamic tract that connects the medial mammillary nucleus to the anterior nucleus of the thalamus
- Thalamocortical fibers from the anterior nucleus to cortex of the cingulate gyrus
- Projection from the cingulate cortex (via cingulum) to entorhinal cortex, subiculum and hippocampus
*The subiculum (via fornix) returns info to the mammillary body
The Cingulate gyrus and Parahippocampal gyrus are continous around what; how does the cingulate gyrus relay to the parahippocampal gyrus?
- Continous around splenium of Corpus Callosum
- Projects to the parahippocampal gyrus via the fibers of the cingulum
- The principle structures of the limbic system are thus linked by a seies of connections, which constitute the Papez circuit
