Functional hierarchy of motor control Flashcards
what is responsible for direct control of muscles
a motoneurones
where do reflexes occur
autonomously at each segmental spinal level
what are higher order reflexes and what do they control
spinal reflexes that have been integrated at the brainstem nucleii
involve trunk and limb muscles
control posture and balance
what do the brainstem nucleii control
cerebral cortex
basal ganglia
cerebellum
what are the 4 systems that control movement
descending control pathways
basal ganglia
cerebellum
local spinal cord and brainstem circuits
what do lower motor neurones do
innervate muscles, initiate reflexes, voluntary movements
all at the SPINAL LEVEL
what do LMN lesions cause
flaccid paralysis and muscle atrophy
what do upper motor neurones do
synapse with lots of lower circuit neurones and REGULATE a motoneurone activity
in the BRAINSTEM OR CORTEX
what do UMN lesions cause
spasticity, paralysis, spastic paralysis
if corticospinal lesion = weakness not paralysis
how is the spatial map of the body in the spinal cord arranged
medio-laterally
eg proximal shoulder = medial motoneurones
eg finger muscles = lateral motoneurones
what input does the spinal cord receive
descending input via neurones in the brainstem
direct cortical input from the corticospinal/pyramidal tracts
where does sensory input enter
at all levels
spinal cord, brainstem and cortex
what is the sensory input at the spinal cord
proprioception, touch, pain
what is the sensory input at the brainstem
balance from the vestibular system
what is the sensory input at the cortex
visual, olfactory, auditory, emotional, intellectual
what does damage to sensory inputs at the spinal cord cause
paralysis as if the motoneurones were damaged
what is a reflex arc
the nerve pathway involved in reflex action
what is the stretch reflex
simplest form of reflex - involves a sensory nerve, a motor nerve and the synapse between them
in every muscle in the body e.g. patellar tendon reflex
what happens during the stretch reflex
- initial stimulus - muscle stretch in spindles
- excitatory afferent impulse - stretch receptor to spinal cord
- excitatory efferent impulse to a motoneurone - causes contraction of stretched muscle
- inhibitory efferent impulse to antagonist muscle - dampened action - reciprocal inhibitio
what spinal levels can different reflexes test for
biceps jerk = C6
triceps jerk = C7
patellar tendon = L4
achilles tendon = S1
what can reflexes help detect
level of spinal cord damage
impaired reflex areas = areas of nerve damage
what must you be sure to do when testing reflexes
distract patient to avoid voluntary influence
what is the flexor (withdrawal) reflex
polysynaptic and protective reflex that uses info from pain receptors (nociceptors) to withdraw the body away from painful stimuli
what is the flexor-crossextensor reflex
when painful stimuli very large - larger response from flexor reflex
e.g. move whole arm and side of body away
if that is the only action - loss of balance - can fall
so when flexor response is large in ipsilateral side of body - cross extensor action of the contralateral side of the body occurs to maintain balance
e.g. move right side back - extend left leg to balance
