Descending Motor Pathways Flashcards
one nerve communicating to the next - comes down from cortex and when gets to sc synapses on one neuron and then goes out to create an action
monosynaptic
comes down and synapses in grey matter on interneuron which then will synapse onto the cell that sends the info out to create the action
interneurons
the pathway that comes out of sc to the final destination - the final path
lower motor neurons
what type of lesion do we see if it is in the LMN?
ispilaterally symptoms
because it stays on that side and has already crossed over in the body since it is in the periphery
stab wound severs dorsal root and neuron = loss of motor and sensory function
these lesions show muscles involved individually and patterns of associated sensory loss follow dermatome patterns
LMN
These lesions result in muscles being affected in groups, an entire extremity or even half of the body (associated sensory loss does not follow dermatome patterns)
UMN
Descending motor pathways from the cortex and brainstem to the spinal cord
Upper motor neurons
what type of symptoms do we see with UMN?
happens before the crossing over so the symptoms we see are usually contralateral
stroke in M1 of area in the arm in the left hemisphere, will have a contralateral issue with my left arm
what is the largest and clinically important descending motor tract
corticospinal tract (pyramidal tract)
what is the function of corticospinal tract (pyramidal tract)
voluntary and fine motor skilled
talk, chew, write, type, sew, = skilled movements of muscles that we need them to do
what is the dorsal horn composed of
lamina I-VI (Projection neurons receiving synapses from primary afferent axons from the dorsal root –somatic and visceral sensory information– and interneurons)
Lamina VII is the intermediate zone (containing autonomic neurons),
what is the ventral horn composed of
Lamina VIII (containing interneurons associated with motor reflexes) and
IX (motor neurons leaving the CNS—not one discrete “ribbon”, but multiple locations in the ventral horn).
Lamina X surrounds the central canal and contains cells important for the perception of visceral pain
function of the rubrospinal tract
Control of dextrous movement
of the upper extremity (mediation of skilled voluntary movements)
describe the reticulospinal tracts
Participating in the control of movement
*Connecting to the spinal cord and cerebellum
*From Nolte text “The reticulospinal tracts are a major alternate route (to the pyramidal tract) by which spinal motor neurons are controlled, both influencing motor neurons directly and regulating the sensitivity of spinal reflex arcs.”
The anterolateral system (also called the Lateral Spinothalamic Tract) of the spinal cord…
is an ascending somatosensory pathway carrying information regarding pain and thermal sensations.
Damage to corticobulbar tract above the
nucleus results in
UMN signs (paresis
contralateral to side of lesion)
~ Tongue deviates away from the side of lesion
what is the function of rubrospinal tract
Upper fine movements
Control of dextrous movement
of the upper extremity (mediation of skilled voluntary movements - in M1)
dextrous - more in hands so it makes sense that m1 can do the job and this helps refine skilled movements for neurosurgery
to help with area that has the most finest movements is assisted by this tract
M1 is the main one and this tract assist it in fine movements
What is the function of reticulospinal
tying in sc and cerebellum info in lower to help us be ready for big muscles to have the right amount of tone we need and be ready for movements
Participating in the control of movement
*Connecting to the spinal cord and cerebellum
*From Nolte text “The reticulospinal tracts are a major alternate route (to the pyramidal tract) by which spinal motor neurons are controlled, both influencing motor neurons directly and regulating the sensitivity of spinal reflex arcs.”
Tectospinal tract function
Neurons have cell bodies in the superior colliculus (in the midbrain tectum)
Mediates reflex postural movements of the head &
neck in response to novel visual stimuli
In area of tectorial plate
known as primary antigravity pathway with muscle groups known as antigravity muscles
lateral vestibulospinal tract
Antigravity pathway for upper extremities
VCR
medial vestibulospinal tract
What is the vestibulo-ocular reflex
if head goes right, eyes go left
goes equal and opposite of head movement - eye movement
same amount of degrees in the opposite direction
if move head 10 degrees to right, eyes go ten degrees to left
sends down to sc predominantly to cervical and high thoracic level = keeps head and eyes on stable platform
sends it ascending and descending
controls VOR ascending
MVST
ends down to all levels of sc ot help with anti gravity muscles to respond to where we are in space and how we are moving (if I lean left, this responds)
go down and ready to send command out of sc, they go to ventral grey horn and synapse on interneurons adn motor to send command out to the muscles
LVST
What are the vestibular nuclei
scarpa’s ganglion
Acts on gamma and alpha motor neurons in spinal cord
- Facilitates lower extremity extensors (increases lower extensor muscle tone)
pontine (medial) reticulospinal tract
acts primarily on gamma motor neurons (also on alpha motor neurons) in SC
- Inhibits lower extremity extensors (reduces extensor tone in lower extremities)
- Facilitates lower extremity flexors
(increases flexor tone
in lower extermities)
medullary (lateral) reticulospinal tract
Called postural pathways
Lateral and Medial Vestibulospinal Tracts
