Neural Control of Gait (W6)
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- differentiate between locomotion and ambulation
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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?
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1. stance (extension, both legs on ground, LONGER)
2. swing (flexion, one leg on ground) - all gait combines ________ and __________.
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locomotion
posture - what are the 3 variables in the gait cycle?
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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?
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1. VSCT
2. DSCT
3. vestibular system - what will a midline cerebellar lesion look like vs. a lateral cerebellar lesion?
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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?
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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?
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1. proprioception (from limbs/trunk)
2. vestibular system
3. vision - What are the three descending pathways involved with posture control?
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1. Reticulospinal
2. Vestibulospinal
3. Tectospinal - The reticulospinal tract: function in posture?
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pontine portion: coordinates upper and lower limbs (in walking)
medullary portion: sleep atonia - The vestibulospinal tract: function in posture?
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lateral: extensors (antigravity muscles), responsible for upright posture
medial - posture of neck - The tectospinal tract? Where does it begin? function in posture?
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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?
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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?
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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
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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?
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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
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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
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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.
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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.