Limbic System Flashcards
the four functions of the limbic system
HOME: homeostasis, olfactory processing, memory processing, emotional content of memories
the cingulate gyrus above the corpus collosum, the parahippocampal gyrus on the medial aspect of the temporal lobes, and the orbitofrontal gyri above the orbits are related in that they are all a part of the….
limbic lobe
buried deep inside the parahippocampal gyri on the medial aspect of each temporal lobe are an array of structures associated with the ___
hippocampus
the most medial part of the temporal lobe is known as the
uncus
underneath the uncus (the most medial part of the temporal lobe) is the ____, which lies anterior to the hippocampal formation
amygdala
the subcortical structures on the medial aspect of each hemisphere but on the most inferior parts of each frontal lobe are the ____ nuclei
septal nuclei, involved in emotional response and reward
the olfactory mucosa contain what type of neurons?
bipolar neurons, which give rise to olfactory receptors embedded in mucosal lining of nasal cavity, and also to central processes that pass through the cribriform plate
the bipolar neurons pass through this sieve-like bone found between the superior aspect of the nasal cavity and the anterior cranial fossa. what is the?
cribriform plate
T/F: the olfactory nerve (CN I) is not a single nerve
TRUE: simply a bunch of bipolar neurons that send their central processes through the cribriform plate to synapse on 2nd neuron in overlying olfactory bulb (containing mitral cells)
cribriform plate fracture results in this symptom
CSF rhinorrhea
the ___ cells in the olfactory bulb send their axons through the olfactory tract to the primary olfactory cortex
mitral cells
the olfactory bulb (mitral cells) and tract axons project to the ____ in the olfactory cortex, the ____ in the medial temporal lobe, and the ____ in the hippocampal formation in the parahippocampal gyrus
the olfactory bulb (mitral cells) and tract axons project to the PIRIFORM CORTEX in the olfactory cortex, the AMYGDALA in the medial temporal lobe, and the ENTORHINAL CORTEX in the hippocampal formation in the parahippocampal gyrus
the only sensory system that reaches cortical area without relaying through the thalamus
olfactory system
what are the neurons in the olfactory pathway?
- bipolar neurons in nasal mucosa
- mitral cells in olfactory bulb
- piriform cortex in olfactory cortex, amygdala, entorhinal cortex in hippocampal formation
major location for developing emotional content memories
amygdala
what are the three components of the hippocampus, forming the shape of a seahorse?
hippocampus proper (Ammon’s horn)
dentate gyrus
subiculum
lying adjacent to the hippocampus (proper, dentate gyrus, and subiculum) is the ____ cortex of the parahippocampal gyrus
entorhinal cortex
the ____ cortex in the parahippocampal gyrus provides virtually all daily input that is arriving and being processed by hippocampus
entorhinal cortex
besides the entorhinal cortex (parahippocampal gyrus), the hippocampus proper also receives some input from these two places:
septal nuclei (medial and most inferior of temporal lobe) amygdala
these nuclei are a major location in the brain of cholinergic neurons that project their axons via the fornix into the hippocampal formation, and they play a role in enhancing memory consolidation. what are?
septal nuclei (including within the basal nucleus of Meynert)
the axons leaving the entorhinal cortex headed to the hippocampus proper exit via the ____
perforant path (perforates the hippocampal formation) these synapse with granule cells in dentate gyrus of hippocampus
the axons of the entorhinal cortex exit via the perforant path and synapse on the ___ in the ___
granule cells in the dentate gyrus. granule cells then project to cornu ammonis region 3 (CA3) pyramidal cells in hippocampal formation
after receiving input from entorhinal cortex, the granule cells of the dentate gyrus (hippocampus) synapse on the cornu ammonis region 3 (CA3) pyramidal cells in the hippocampal formation, which then synapse on ____ (also in hippocampal formation)
pyramidal cells
where are the 3 levels that long-term potentiation occurs in the hippocampus?
- granule cells (receiving input from entorhinal cortex)
- CA3 pyramidal cells
- CA1 pyramidal cells
the outflow of newly-consolidated memories within the hippocampus project to the ____
subiculum- major destination of hippocampal formation outflow
major destination of hippocampal formation outflow
subiculum (Latin for “support”)
the axons that leave the subiculum (major destination of hippocampal formation outflow) do what?
coalesce on the surface to form the alveus (located on the lateral ventricle surface of the hippocampal formation)
alveus axons then coalesce to form fimbria, and ultimately fornix
major efferent pathway of the hippocampal formation?
fornix
what are the neurons of the Papez circuit?
- memories consolidated in hippocampal formation (granule cells, CA3, CA1), input from entorhinal cortex
- axon outflow via fornix (subiculum)
- post-commissural fornix axons project to mammillary body (diencephalon)
[pre-commissural fornix project to septal nuclei and nucleus accumbens, but not main projection] - mammillary body projects to anterior nucleus (thalamus)
- cingulate gyrus (limbic associated cortex), which closes circuit by projecting back to entorhinal cortex (parahippocampal gyrus)
the pre-commissural axonal projections of the fornix project where?
septal nuclei and nucleus accumbens
post-commissural fornix is major output, going to mammillary body
on the medial aspect of the frontal and parietal lobes above the corpus collosum is the end destination of the Papez circuit. what is the?
cingulate gyrus
a chronic abuser of alcohol or someone deficient in thiamine (Vit B1) develops selective degeneration of what set of neurons? what is this condition called?
mammillary body in hypothalamus (diencephalon)
–> Korsakoff psychosis
irreversible degenerative loss of mammillary neurons bilaterally
Korsakoff psychosis
alcoholism or vitamin B1 (thiamine) deficiency
a person who develops Korsakoff syndrome may develop long-term gait problems (gait ataxia) due to neural changes in what area?
anterior vermis of cerebellum
where does Alzheimer’s dementia develop initially?
entorhinal cortex (subiculum of hippocampus) neurofibrillary tangles and senile plaques here
over time, a patient with Alzheimer’s may develop what kind of preferential aphasia?
Wernicke’s (fluent) aphasia
what are the two regions of the amygdala? what inputs do they receive?
basolateral region- external stimuli
corticomedial region- visceral input
Kluver-Bucy syndrome
bilateral lesion of amygdala, usually includes nearby hippocampus–>
profound amnesia (anterograde and retrograde)
placid or docile- lacking appropriate emotional responses (esp. fear)
oral tendencies (putting things in mouth), hypersexuality
possible visual agnosia
a patient presents with anterograde and retrograde amnesia, a placid disposition, hypersexual comments, and prosopagnosia (inability to recognize familiar faces). where is the lesion?
bilateral lesion of amygdala, and lesion of nearby hippocampus
Kluver-Bucy syndrome
near the septal nuclei of the anterior basal part of the forebrain, right near the juncture between the putamen and the caudate nucleus, just underneath the anterior limb of the internal capsule is the….
nucleus accumbens
what are the 3 sources of input to the mesolimbic projection in the basal ganglia as part of the reward circuit?
amygdala, hippocampus, prefrontal cortex
