Module 3 Flashcards
Name the 3 groups of white matter fibers also know as the medullary core
Projection
Association
Commissural
Where is white matter found?
In all areas of the cerebrum
EXCEPT the cortex and basal ganglia
Describe the projection group
Group of white matter pathway
Vertically organized
Connects the cortex to the Brainstem and spinal cord
Carries sensory and motor information
Describe the association group
Group of white matter pathway
Interconnects cortical area
Run within same hemisphere
Horizontally organized
Describe the commissural group
Group of white matter pathway
Interconnect cortical areas
Runs BETWEEN two hemispheres
Horizontally organized
What is the function of the groups of white matter pathways?
Informs brain on activity in and out of CNS
mediate info transfer between modalities
Coordinate activities between hemispheres
How are gross anatomy structures paired?
Bilaterally
What is the pyramidal pathway?
Major Motor projection system Pyramidal tract (direct motor pathway) Voluntary motor pathway Initiation & control of skilled movements Goes from the cortex to BS & SC
What does the pyramidal tract include?
Corticospinal
Corticobulbar
Where do the pyramidal tract originate from?
Primary motor cortex: 30%
Motor association cortex: 30%
Somatosensory cortex: 40%
Describe the corticospinal pathway
Cortex to spinal cord motor nuclei Inner bates skeletal muscles of limbs Carries motor commands Runs from cortex to spinal cord Carrie motor commands from cortex to SC motor neurons
Where does the decussation of the pyramids happen?
Lower medulla
Lateral corticospinal crossed (90%)
Anterior corticospinal uncrossed (10%)
Describe the corticobulbar pathway
Runs from cortex to BS cranial nerves motor neuron nuclei
Innervates the speech muscles
Carries motor commands
Where does the decussation of the corticobulbar pathway happen?
*TRICK QUESTION**
This pathway has no major decussation
Neurons exit at various levels
Neurons exit pathway then cross to motor nucleus
Predominately contralateral innervation to speech muscles
What type of neurons does the pyramidal tracts have?
Upper motor neurons
What is the significance of the UMN?
Run from cortex to motor neuron cell body in the BS/SC
Within CNS but influence LMN
What is the significance of them LMN?
A peripheral motor neuron
Cell body in the BS/SC
Sends axons out to the muscles it serves
“The final common path”
Includes spinal and cranial motor neurons
How do the projection pathways reach different areas?
Through levels of the pyramidal tract:
Corona radiata
Internal capsule
Cerebral peduncles
what is the corona radiata?
Radiating projection system Contains sensory/motor pathways Between cortex and internal capsule Diverges above Converges below
What is the internal capsule?
Bundle of nerve fibers
Same level of diencephalon
Both sensory/motor pathways
Part of continuous sheet of fibers to/from cerebral cortex
What are the 3 main parts of the internal capsule?
Anterior limb
Knee (genu)
Posterior limb
What is the function of the anterior limb of IC?
Carries motor data
Carries affective and emotional data
Which pathways are used to carry motor data of the anterior limb?
Frontopontine (cortex to pons)
Corticostriate (cortex to BC/striatum)
Describe the genu knee of IC
Corticobulbar pathway (cortex to BS cranial nerve nuclei & motor commands for speech)
Corticoreticular pathway
What is the corticoreticular pathway?
Cortex to BS reticular formation
Arousal and alertness
Describe the posterior limb IC: Motor
Corticospinal path
Innervates limb and trunk muscles
Travels through rostral end of Posterior limb
Describe the posterior limb IC: sensory
Project first to thalamus
Travel thru caudal end of post. Limb
Carry general/special sensory
Corticopontine projections
Do ALL of the pathways to/from IC go through corona radiata?
True
What is the area below the IC?
Cerebral peduncles
A.k.a crus cerebri
A.k.a pea pedunculi
What is a projection system?
A continuous pathway
Level of lesion significant (outcomes)
Motor and sensory components
Name the 2 smaller white matter capsules
External capsule
Extreme capsule
What are association pathways?
Connect areas within the same hemisphere
Gives bidirectional communication between cortical areas
Have: long and short groups
Name the 4 important association pathways
Arcuate fasciculus
Inferior occipital fasciculus
Uncinate fasciculus
Cingulum
What is the function of the arcuate fasciculus?
Interconnects all of the cortices of the 4 main lobes (fron, par, occ, temp)
Connects wernicke’s area and Broca’s area
What is conduction aphasia?
Disconnection syndrome (arcuate syndrome)
Posterior disconnected from anterior areas (wernickes/ Broca’s areas disconnect)
Good comprehension, reduced and impaired speech output
What is the function of the inferior occipital fasciculus?
Connects frontal lobe to occipital lobe and to inferior temporal lobes
Crosses below lateral sulcus
What is the function of the uncinate fasciculus?
Connect orbital frontal with anterior temporal lobe cortex
What is the function of the cingulum?
Connects frontal, parietal and temporal areas with limbic lobe
Follows cingulate gyrus
Lesions impair emotion and affective behavior
Describe commissural pathways
Travel between hemispheres (interhemispheric pathways)
Connect homologous structures in each hemisphere
Makes bidirectional communication
Name the 3 brain commissures
Corpus callosum
Anterior commissure
Posterior commissure
What are the parts of the corpus callosum?
Rostrum (frontal areas)
Genu (frontal areas)
Body (parietal areas)
Splenium (visual areas)
Lesions to the corpus callosum cause…
Communication impairment and coordination between hemispheres
Impact depends in location of lesion
Sectioning prevents spreading of seizures from one hemisphere to the other
What is the anterior commissure?
Interconnects temporal lobes
Anterior to thalamus
What is the posterior commissure?
Involved with midbrain visual (pupillary) reflexes
Posterior to thalamus
White Matter forms what part of the brain?
Medullary core
