Motor systems I Flashcards
the corticospinal tract arises from what parts of the brain?
cortex of frontal and parietal lobes
the corticospinal tract splits into what tracts in the caudal medulla?
anterior and lateral corticospinal tracts
where does the anterior corticospinal tract terminate? what is its function?
- C and upper T spinal cord levels (gray matter - only UMNs that decussate in spinal cord) 2. skilled, voluntary movement of axial muscles (neck, shoulder, upper trunk) on OPPOSITE side of the body
where does the lateral corticospinal tract terminate? what is its function?
- all spinal cord levels (mostly for UL and LL) 2. skilled, well defined, voluntary movement on OPPOSITE side of the body (especially fingers)
where does the desire to initiate a movement originate?
association cortex
what areas are involved in the orientation of the trunk and upper limbs in the direction of intended movement / program the design and sequence of complex movements?
SMA and premotor cortex
what is the function of the posterior parietal cortex?
- sensory integration and visual guidance of movement2. evaluates location or position of body 3. forms movement plan that would accomplish a task
what is the function of the SMA and premotor cortex?
orientation of the trunk and upper limbs in the direction of intended movement / program the design and sequence of complex movements
SMA and PMC correspond to which Brodman’s area?
6
FEF corresponds to what Brodman’s area?
8
the posterior parietal cortex corresponds to what Brodman’s area?
7
the primary motor cortex corresponds to what Brodman’s area?
4
how does S-1 influence movement?
by modulating the relay of sensory input from visceral and somatic structures to the spinal cord
where are the pyramidal cells located? what is their function?
- layer 5 (internal pyramidal layer of cerebral cortex) 2. give rise to axons that form descending motor pathways (UMNs)
where are the LMNs that control movement of the body located?
ventral horn of spinal cord
what are the specific origins of the corticospinal tract?
- 1/3 from Brodman’s area 4 2. 1/3 from Brodman’s area 6 3. 1/3 from Brodman’s areas 5, 7 and 3, 1, 2
what is the course of the corticospinal tract?
descends through corona radiata - posterior limb of internal capsule - basis pedunculi - pons - medulla (pyramids)
what are the phases of an UMN lesion?
- initial paresis / hypotonia / hyporeflexia 2. eventual hypertonicity
what is the reason for eventual hypertonicity in an UMN lesion?
descending inhibitory influences are diminished or eliminated (overactive gamma neurons, cerebellar input)
what is the reason for spasticity (severe hypertonicity) of distal limbs in an UMN lesion?
exaggeration of stretch reflex
what is the reason for eventual hyperreflexia in an UMN lesion?
excess stimulation of gamma motor neurons
what is the result of a LMN lesion? why?
- hypotonia, hyporeflexia, areflexia, fibrillations, fasciculations 2. alpha and gamma motor neurons are both damaged
what is the blood supply to the medial surface of the precentral gyrus (hip, leg, foot)?
anterior cerebral
what is the blood supply to the lateral surface of the precentral gyrus (trunk, upper limb, head)?
middle cerebral
