Spinal Cord Descending Pathways Flashcards
1
Q
Descending Motor Tracts
A
- originate from cerebral cortex and brainstem
- functions: control movement, muscle tone, spinal reflexes, spinal autonomic functions, modulation of sensory transmission to higher centers
2
Q
General Pathway of Primary Motor Cortex
A
-projects down –> crosses over –> goes down to level it needs to be in anterior horn –> acts on neuron that’s already down there (doesn’t cross over) –> acts on peripheral nerve –> acts on muscle –> contraction
3
Q
General Organization of Motor Systems
A
-cerebral cortex and brainstem have interactions with thalamus, pons, cerebellum and basal ganglia in modification of movement
4
Q
Apraxia
A
-normal strength but difficulty performing motor plan –> can’t put all the pieces together
5
Q
Motor and Somatosensory Cortical Areas
A
- primary motor cortex-Brodmann’s Area 4
- motor association cortex-higher order motor planning and projects to primary motor cortex: supplementary motor area-Brodmann’s Area 6; premotor cortex-Brodmann’s Area 6 (both of these are in front of precentral gyrus)
- primary somatosensory cortex: Brodmann’s Areas 3, 1, 2
- somatosensory association cortex: receives inputs form primary somatosensory cortex: parietal association cortex-Brodmann’s Areas 5, 7; secondary somatosensory area
- lesions in these areas present with contralateral symptoms
6
Q
Medial Motor System
A
- travels in anteromedial spinal cord columns to synapse on medial ventral horn motor neurons and interneurons
- controls proximal axial and girdle muscles for tone, balance, orienting movements of head and trunk and automatic gait
- consists of: anterior corticospinal tract, vestibulospinal tracts, reticulospinal tracts, tectospinal tract
- lateral controls more distal extremities while medial controls more trunk/axial skeleton
7
Q
Anterior Corticospinal Tract
A
- control of bilateral axial and girdle muscles
- originates in primary motor cortex
- terminates cervical and upper thoracic spinal cord
- runs ipsilaterally and acts a little bilaterally
- stays ipsilateral going down anterior-medial motor column in SC, synapses on medial aspect of ventral horn, some crosses over and acts on interneurons to supply other side of trunk
- it is the uncrossed corticospinal fibers going down-don’t decussates at medulla keeping our trunk upright
8
Q
Vestibulospinal Tract
A
- positioning of head and neck
- controls limb extensor tone to maintain posture
- balance
- originates at vestibular nuclei of pons/medulla
- runs entire cord
- runs ipsilaterally and contralaterally
- received input from cerebellum and ear
- lots of cross innervation
9
Q
Reticulospinal Tract
A
- automatic posture and gait-related movements
- originates: pontine and medullary reticular formation
- runs entire cord
- runs ipsilaterally
10
Q
Tectospinal Tract
A
- coordination of head and eye movements
- originates at superior colliculus
- terminates at cervical cord
- decussates at midbrain
11
Q
Lateral Motor System
A
- travels in lateral column of spinal cord and synapse on lateral groups of ventral horn motor neurons and interneurons
- controls movement of extremities
- consists of lateral corticospinal tract (rapid dextrous movement at individual digits or joints) and rubrospinal tract
12
Q
Lateral Corticospinal Tract
A
- aka pyramidal tract: triangular shape in medulla
- movements of contralateral limbs
- originates in primary motor cortex and other frontal and parietal areas
- runs entire cord
- most fibers cross over (pyramidal decussation) at junction between medulla and spinal cord
- lesions above decussation would produce contralateral weakness
- lesions below would produce ipsilateral weakness
- middle 1/3 of basis pedunculi is where lateral corticospinal tract runs
- in medulla it runs in pyramids
- decussates at cervicomedullary junction where brainstem ends and goes through foramen magnum
13
Q
Corticospinal Course
A
- cerebral cortex to corona radiata
- descend into internal capsule
- continues into midbrain cerebral peduncles “feet of brain”
- basis pedunculi-ventral portion: middle 1/3 contains corticospinal and corticobulbar fibers
- descend thru ventral pons to ventral medulla to form medullary pyramids
- at cervicomedullary junction decussates to lateral white matter columns of cord forming lateral corticospinal tract
- descends and enters gray matter of spinal cord to synapses on anterior horn cells
14
Q
Internal Capsule
A
- looks like two V’s with points facing in
- thalamus and caudate medial
- globus pallidus and putamen are lateral
- 3 parts: anterior limb separates head of caudate from gp and putamen, genu transition between (at level of foramen of monro), posterior limb separates thalamus from gp and putamen (corticospinal tract lies in this limb)
- lesion in this area can cause weakness in contralateral body or more selective
- gp and putamen are part of basal ganglia
- head of caudate is in floor of lateral ventrical
15
Q
Corticobulbar
A
- fibers projecting from cortex out to brainstem (bulb)
- called corticobulbar rather than corticospinal because they project to the bulb
- acts on neurons in brainstem (CN are in brainstem –> supply face)
