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What type of matter is the semioval center of the telencephalon?
white matter
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The semioval center of telencephalon is white matter w/in what structure?
cerebral hemispheres
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What is the semioval center made of?
cellular processes (myelinated axons and dendrites)
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Where is the the semioval center?
extends between cerebral cortex, basal ganglia, and ventricular system
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What are the types of fibers in the semioval center?
- commissural fibers
- association fibers
- projection fibers
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What do the commissural fibers do?
connect corresponding cortical regions of the two hemispheres
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What are the types of commissural fibers?
- corpus callosum
- anterior commissure
- posterior commissure
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What does the corpus callosum look like?
overturned canoe
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Which type of commissural fibers is the largest?
corpus callosum
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What is the corpus callosum?
millions of fibers that are a primary means of communication between right and left hemispheres
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What are the parts of the corpus callosum?
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Rostrum of corpus callosum:
connects frontal lobes
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Genu of corpus callosum:
connects frontal lobes
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Body of corpus callosum:
connects frontal and parietal lobes
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Splenium of corpus callosum:
connects temporal and occipital lobes
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What is the largest portion of the corpus callosum?
body
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Directional terms
Rostral:
towards the nose
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Directional terms
Caudal:
towards the tail
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Where is the anterior commissure?
crosses midline rostrally through the fornix to connect portions of temporal lobe
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The anterior commissure is part of what pathway?
olfactory pathway
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Is the posterior commissure in the telencephalon or diencephalon?
diencephalon
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Posterior commissure:
visual reflexes that rely on optical info
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What does the posterior commissure connect?
interconnects superior calliculi and pretectum of the midbrain (reciprocal pathways)
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What do association fibers connect?
cortical regions in same hemisphere
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What are the types of association fibers?
- short association fibers
- long association fibers
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How are short association fibers named?
not specifically named
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What do short association fibers do?
arch the floor of each sulcus to connect adjacent gyri
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Are long association fibers reciprocal?
always reciprocal
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What does reciprocal mean?
runs both ways
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What are long association fibers?
cables that connect cortical regions in different lobes w/in same hemisphere
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Fasciculus:
named long association fibers that form bundles (reciprocal)
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What are the types of fasciculus?
- uncinate fasciculus
- arcuate fasciculus
- cignulum fasciculs
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Uncinate fasciculs:
frontal lobe to temporal lobe
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What is another name for the arcuate fasciculus?
superior longitudinal fasciculus
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Arcuate fasciculus:
- frontal, temporal, and occipital lobes
- major fasciculs that connects Broca's and Wernicke's area
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Cingulum fasciculus:
- primary association bundle on medial side of hemisphere of brain; connects parietal, temporal, and frontal lobes
- can be surgically removed to decrease pain
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Deep to the insula are 2 association areas:
- external capsule
- extreme capsule
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What are the external and extreme capsules?
white matter structures that contain association fibers deep to insula
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What is the thin band of grey matter b/w the external and extreme capsules called?
claustrum
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Superficial to deep, the sequence of association structures:
insula -> extreme capsule -> claustrum -> external capsule -> corpus striatum -> internal capsule
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What is the claustrum a part of?
basal ganglia
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What is the corpus striatum a part of?
basal ganglia
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Projection fibers are mostly axons that converge on the:
brainstem
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What do projection fibers connect?
one specific part of the cerebral cortex and another specific part of the CNS (and vice versa)
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Are projection fibers reciprocating?
yes
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Where do projection fibers project?
- to different places
- (unlike commissural fibers; not in same hemisphere like association)
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Afferent projection fibers:
going to cortex
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Efferent projection fibers:
leaving cortex
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Corona radiata:
radiating mass of afferent/efferent projection fibers going into and out of the brain stem (everything has to narrow when passing through brain stem)
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Internal capsule:
- compact band of efferent and afferent projection fibers formed rostrally
- condensed area that allows fibers to narrow and go into brain stem or widen to go out of brain stem
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What is the appearance of the internal capsule?
white 'H'
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Where is the internal capsule?
corpus striatum in a transverse section of the brain
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What does the internal capsule contain?
- anterior limb
- genu (transition)
- posterior limb
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What are the boundaries of the internal capsule?
- flanked medially and laterally by the basal ganglia
- medially by head of caudate nucleus
- laterally by putamen
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What does it mean that the internal capsule is somatotopically organized?
damage to specific part causes a specific impairment that it controls
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What are the limbs does the internal capsule form?
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What does the anterior limb separate?
partially separates caudate nucleus and putamen
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The caudate nucleus and putamen are what type of structures?
basal ganglia
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What is the anterior limb medially?
caudate nucleus of basal ganglia
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What is the anterior limb laterally?
putamen of basal ganglia
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What types of fibers does the internal capsule contain?
afferent and efferent fibers
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What percent of the anterior limb fibers are afferent?
90%
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What do afferent anterior limb fibers have?
sensory structure
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Thalamocortical projection fibers:
afferent projection fibers that originate in thalamus and are projected to various parts of the cortex
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What happens if thalamocortical afferent projection fibers are damaged?
sensation is affected
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What percentage of the anterior limb fibers are efferent?
10%
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Frontopontine projection fibers:
efferent projection fibers that come from frontal lobe (cortex) and travel to pons
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What is the posterior limb of the internal capsule?
motor limb
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What is the medially boundary of the posterior limb?
thalamus
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What is the lateral boundary of the posterior limb?
globus pallidus
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What does the posterior limb contain?
afferent and efferent fibers
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What are the afferent (sensory) fibers of the posterior limb?
thalamocortical
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What percentage of posterior limb fibers are afferent?
10%
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What percentage of posterior limb fibers are efferent?
80-90%
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Where do the efferent motor fibers of the posterior limb originate?
from cerebral cortex to nuclear masses in brain, brain stem, and spinal cord
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What are the efferent motor fibers of the posterior limb called?
corticofugal fibers
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What are the types of corticofugal fibers in the posterior limb?
- corticothalamic
- corticopontine
- corticobulbar
- corticospinal
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Corticothalamic:
- efferent posterior limb fibers
- go to thalamus
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Corticopontine:
- efferent posterior limb fibers
- go to pons
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Corticobulbar:
- efferent posterior limb fibers
- go to motor nuclei of CNs in the brain stem
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corticospinal:
- efferent posterior limb fibers
- go to ventral horns of spinal cord
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What does a stroke in the posterior limb cause?
loss of movement
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Genu of internal capsule:
transition (bent) area b/w anterior and posterior limb
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What types of fibers does the genu of the internal capsule contain?
afferent and efferent fibers
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What makes up the fornix?
commissural and projection fibers
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What does the fornix connect?
telencephalon and diencephalon
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How does the fornix connect the telencephalon and diencephalon?
w/ 2-way reciprocal movement of info (both communicate w/ each other)
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What forms the fimbria of the fornix?
axons of pyramidal neurons of hippocampus
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Where is the hippocampus?
temporal lobe of telencephalon
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Fibers spread over the ventricles to form:
fimbria of fornix
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Where do axons of the fimbria proceed?
forward until they reach the posterior end of the hippocampus
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Once the fimbria axons reach the hippocampus, what happen?
arch beneath splenium of corpus callosum
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What do the fimbria axons become when they arch beneath splenium of corpus callosum?
crura of the fornix
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Is the crura of the fornix unilateral or bilateral?
bilateral structure
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The crura of the fornix converge and form:
body of fornix
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Between the two converging crura is a thin sheet of tissue called:
fornical commissure
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What is another name for the fornical commissure?
hippocampal commissure
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What type of fibers are found in the fornical commissure?
commissural fibers
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Where is the body of the fornix?
runs forward under corpus callosum to rostral margins of the thalamus
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The body of the fornix bifurcates and forms:
2 anterior columns of the fornix
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The anterior colums of the fornix arch:
ventrally
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Half of the anterior column fibers descend behind what?
anterior commissure
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The half of the anterior column fibers that descend behind the anterior commissure are called:
postcommissural fibers
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The postcommissural fibers terminate in what?
thalamus and mammillary bodies of hypothalamus
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The other half of anterior column fibers descend in front of what?
anterior commissure
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The half of anterior column fibers that descend in front of then anterior commissure are called:
precommissural fibers
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Precommissural fibers terminate where?
thalamus
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What is the function of the fornix?
- major input/output structure associated w/ limbic system
- allows communication of the telencephalon with diencephalon for emotional responses
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What is the limbic system?
cortical and subcortical structures which are active w/ emotions and visceral and behavioral responses associated w/ those emotions
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What is the limbic lobe?
collection of specific structures in telencephalon/diencephalon
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What are the parts of the limbic lobe?
- hippocampal formation
- amygdaloid nuclear complex
- anterior nucleus of thalamus
- hypothalamus
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Where is the hippocampal formation?
temporal lobe
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What are the parts of the hippocampal formation?
- gentate gyrus
- hippocampal gyrus
- parahippocampal gyrus
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Where is the amydaloid nuclear complex?
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What is the amygaloid nuclear complex?
- memory stored and processed
- memories are a big part of emotions
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Where is the anterior nucleus of thalamus?
part of limbic lobe in diencephalon
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Where is the hypothalamus?
part of limbic lobe in diencephalon
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What is the hypothalamus?
- ANS
- controls visceral responses (tears, sweat, etc.)
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What are the connecting pathways of the limbic system?
- fornix
- stria terminalis
- mammilothalamic tract
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What does the fornix connect?
telencephalon to diencephalon
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What is the stria terminalis?
- lateral border of diencephalon
- reciprocal connection b/w amygdala and hypothalamus
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What does the mammilothalamic tract connect?
mammillary nuclei of hypothalamus and thalamus
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