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Neural Control of Gait (W6)

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differentiate between locomotion and ambulation
locomotion: movemement across a distance
ambulation: movement over a surface (ie. walking)
what are the 2 major phases of the gait cycle? Which one is longer during walking?
1. stance (extension, both legs on ground, LONGER)
2. swing (flexion, one leg on ground)
all gait combines ________ and __________.
locomotion
posture
what are the 3 variables in the gait cycle?
1. duration and proportion of phases (run vs. walk)
2. relationship btwn. limbs (use different sets of muscles for different gaits)
3. efficiency (sand vs. pavement)
in a run, which phase is shortened?
the stance phase (results in decreased overlap time, decreased double support)
what are the 9 neural components required for gait?
vision, vestibular system, proprioception, basal ganglia, cerebellum, LMN, Primary motor cortex, secondary (association)motor cortex, spinal cord
which neural component of gait contributes to smooth gait over uneven surfaces?
vision (unsmooth gait when walking in the dark).
which neuronal component of gait uses tactile information to find out about limb/joint position and muscle strength/tension?
proprioception
which sensory and motor component of gait is involved in postural maintenance?
Vestibular system. info about position in space relayed to proximal muscles involved in postural maintenance
Which neural component of gait smoothes movement and has a main inhibitory output?
basal ganglia
how exactly does the basal ganglia "smooth movement?"
it inhbits excess mvmnt. by decreasing excess muscle tone and stopping inappropriate muscle movements
Does the basal ganglia execute functions or intitate movement?
NO. this is all integrated by the cortex
the cerebellum is known as the comparator. what does it compare when coordinating motor activity?
compares corticospinal tract to proprioceptive feedback. (this prevents jerky mvmnts and controls accuracy).
proprioceptive motor feedback to the cerebellum is mediated via which 3 tracts/systems?
1. VSCT
2. DSCT
3. vestibular system
what will a midline cerebellar lesion look like vs. a lateral cerebellar lesion?
midline lesion -> gait and posture disorders
lateral lesion -> disorders of ipsilateral limbs, decreased accuracy of mvmnt.
Which neural component of gait is the final output to skeletal muscle? How will damage to this component influence gait?
Lower Motor Neueron. any problem in the LMN will disrupt gait
How will a lesion in the primary motor cortex present?
as a muscle weakness
what is the role of the supplementary motor area?
programs sequence of mvmnts. (It plans, programs and coordinates complex mvmnts)
Apraxia results as a lesion that occurs where? What is apraxia?
result of a supplementary motor area lesion.
impaired ability to plan for movement; failure to perform multi-step tasks
describe the neuronal path through the cortex from sensory input to motor output
sensory input -> primary sensory area -> sensory association areas -> association areas -> secondary motor areas -> primary motor areas -> motor output
The spinal cord it a pretty cool structure. What can and can't it do in regards to gait?
The spinal cord is sufficient for locomotion and can adjust it's speed. It has no volitional control and no balance
Is posture maintained in sleep?
NO, but it is automatically maintained in everything else.
A major component of posture is maintenance of tone in ____________.
antigravity muscles (extensors)
What are the three things needed to maintain posture?
1. proprioception (from limbs/trunk)
2. vestibular system
3. vision
What are the three descending pathways involved with posture control?
1. Reticulospinal
2. Vestibulospinal
3. Tectospinal
The reticulospinal tract: function in posture?
pontine portion: coordinates upper and lower limbs (in walking)
medullary portion: sleep atonia
The vestibulospinal tract: function in posture?
lateral: extensors (antigravity muscles), responsible for upright posture
medial - posture of neck
The tectospinal tract? Where does it begin? function in posture?
superior colliculus
to neck muscles; responsible for reflex head mvmnts to sight/sound
The cerebellum and descending pathways use _________ to maintain posture.
spinal reflexes
Can the cerebellum influence spinal reflexes?
Yes. the cerebellum reinforces beneficial spinal reflexes and supresses harmful spinal reflexes
What is tabes?
sway and fall (often seen during Romberg test)
What are the 4 neural components of locomotion?
1. spinal cord (timing, coordination, speed adjustment)
2. Brainstem (MLR)- initiate and maintain locomotion
3. Cerebellum
4. Cerebral cortex - tonic descending control, intiation, rate
What are central pattern generators?
neuronal circuits that generate rythm: used in locomotion, respiration, mastication
How does the CPG send information superiorly?
via the VSCT
Where does the CPG recieve descending commands from?
from the MLR (mesencephalic locomotor region)
The CPG can choose to reverse or maintain a certain reflex? What is this dependant on?
reflex reversal is dependant of step phase. if stimulation is during flexion: flexion is increased. If stim. is during extension reflex is inhibited
What does an elderly person's gait look like?
decreased velocity
decreased step&stride length
to increase velocity, the # of steps is increased, not the stride length (as would be seen in a younger person)
Define: antalgic
limping to minimize pain: short stance on pain side
define: ataxic
What common condition is ataxia seen in?
unsteady, uncoordinated, wide based gait. Seen in ethanol toxicity
trunkal ataxia is indicative of what kind of lesion?
lesion of cerebellar vermis & pathways
define spastic gait. Where is the problem most likely to be?
stiff legged: circumdiction and toe walking.
UMN lesion - CST problem
define: vertiginous gait. Where is the problem?
wide based and unsteady gait, like walking if very dizzy. Problem with vestibular system
define: frontal gait.
Where is the problem?
a form of apraxia (slow, shuffling) Problem in frontal lobe
define: apraxia
loss of ability to carry out familiar, purposeful movements
define: gait apraxia
can move all muscles individually that are required for gait: just can't combine them to walk
what is a parkisonian gait?
slow, shuffling, narrow base, difficulty initiating, turn around w/o twisting
A dyskinetic gait is due to a problem that is where?
Define: dyskinetic gait
subthalamus problem
choreic, ballistic or athetoid movmnts during walking
high stepping is due to _______? is it unilateral or bilateral?
due to foot drop (loss of fibular nerve function). It is unilateral
tabetic gait is due to a problem in ___________. define: tabetic gait.
dorsal column problem
high stepping bilaterally, foot slapping, need visual feedback
define: paretic gait
what kind of problem?
LMN problem. presents differently depending on which muscles are damaged. trendelenburg, foot drop, bucking etc.
define: functional gait disorder
psychological. highly unbalanced mvmnts without falling
define: trendelenburg gait
weak hip abduction on stance leg of gait (sup. gluteal nerve dysfunction). They throw themselves over affected leg to stop from falling due to xcess pelvic tilt
what controls pelvic tilt?
the hip abductors (gluteus medius and minimus). They contract in stance phase and hold the pelvis level by shifting center of gravity.

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