unit 2 review - motor Flashcards
agonists/synergists are?
muscles that contract together
axial muscles vs. proximal vs. distal
axial= center: trunk and posture
proximal=shoulder, pelvis, elbow, knee; locomotion
distal=digits, fine motor skills, specialized in humans
how to motor neuron axons get to the brain?
by going through the ventral horn
what areas of the spinal cord are enlarged and why?
cervical and lumbar
- fine motor control, enlarged because of more motor neurons
what is contained in the lateral ventral horn?
lateral muscles
- like hands
what is contained in the medial ventral horn?
medial muscles
- like torso
where are flexors vs. extensors on the ventral horn spectrum?
flexors are more dorsal to neurons innervating extensors
what is a muscle fiber innervated by?
how many, what is the NT?
innervated by 1 alpha motor neuron
- NT=ACh
where does the muscle fiber synapse?
motor end plate
what is a motor unit?
- 1 alpha motor neuron
- all the muscle fibers it innervates
how many muscle fibers can an alpha motor unit innervate?
a muscle fiber can only be innervated by 1 alpha motor unit, but
- 1 alpha motor unit can innervate many muscle fibers
what is a motor pool?
all the alpha motor units that innervate 1 muscle
what determines slow vs. fast twitch?
can a motor unit have more than 1 type?
alpha motor unit determined fast/slow twitch type
what are the two ways that more muscle force can be generated?
1) increasing the firing rate of active motor neurons
- fasciculation=twitches
- temoral summation of twitches
2) increase number of active motor neurons
- size princliple
where are alpha motor neurons located?
where do they send their axons?
spinal cord
- send axons down to muscles to cause contraction
what are the 3 components that modulate alpha motor neurons?
1) sensory input
2) input from same and nearby spinal segments
3) brain
- upper motor neurons
where do muscles get sensory input from?
Aa and Ab
- fastest conduction
what two organs give muscles proprioceptive input?
- golgi tendon organs
- muscle spindles
what are golgi tendon organs?
where are they located in comparison to the muscle?
force/tension receptors
- located in series, at the junction between the muscle and tendon
what are golgi tendon organs innervated by?
Ab/1b axons
what is the purpose of golgi tendon organs?
allow us to regulate how much force is needed for different tasks
describe the 4 steps of the GTO pathway?
whats the recap?
1) alpha motor neuron -> muscle contracts which pulls GTO
2) GTO squeezes collegen fibrils
3) 1b axons interwoven with collagen deform
4) mechanosensitive ion channels on Ab/1b open, and 1b depolarizes -> fire AP
more force more depolarization
what is the negative feedback present in the GTO?
GTO innervates inhibitory interneurons which reduces alpha motor neuron activity
- thus reducing muscle tension if its overloaded
what are muscle spindles?
stretch receptors
where are muscle spindles located in comparison to muscle?
in parralell witch muscle fibers
- within the muscle
what are muscle spindles innervated by?
Aa/1a axons
what is the purpose of muscle spindles?
sense changes in the length of the muscle
what are the muscle fibers that are within the muscle spindle called?
intrafusal muscle fibers
- extra fusal=outside
what is the muscle spindles mechanism?
1) when muscle stretches, they also pull the spindles and intrafusal fibers
2) this stretch opens mechanoreceptive ion channels in Aa/1a fibers
3) Aa/1a fibers depolarize and fire more
what do gamma motor neurons do?
innercate intrafusal fibers and make them contract/re-adjust until Aa/1a fibers come online again
- they respond to chnages in length
recap
intra vs. extra fusal fibers?
intra
- innervated by gamma motor neurons
- located within muscle spindles
- sense changes in length
extra
- innervated by alpha motor neurons
- generate force
what does the stretch reflex involve?
what is its goal?
1 synapse
- no interneurons or brain
goal
- to maintain neurons at a constant length
what is reciprocal inhibition?
when agonists contract antagonists relax
flex-crossed extensor reflex pathway?
right foot
excited
- r leg flexors, l leg extensors
inhibited
- r leg extensors, l leg flexors
what motor cortex area is involved in strategy?
area 6, basal ganglia, higher order association orders
what motor cortex area is involved in tactics? (how to execute movement smoothly) movement and movement control
area 4
what area of the brain is involved with execution?
brainstem, cerebellum, spinal cord
what are the 2 descending pathways?
lateral pathway
ventromedial pathway
what do the 2 descending pathways control?
lateral
- voluntary movement
- distal muscles
ventromedial
- posture, gait, balance, head position
- axial muscles
what are 5 signs of motor tract damage?
PPSS = peepees lol
- paresis
- plegia/hemiplegic gait
- spasticity
- sign of babinsky
what are the 5 signs of cerebellar damage?
AIDMH?!
- ataxia
- intention tremor
- drunken gait
- melagraphia
- hypotonia
what are basil ganglia diseases?
- parkingsons=hypokenesia, not enough movement
- hungtingtons=hyperkinesia, excess movement
what are treatments for parkinsons?
- ldopa
- pallidotomy/lesion of global pallidus
- deep brain stimulation
where do the ventro medial pathways originate?
brainstem
what does the corticospinal tract control? where does it decussate?
controls
- voluntary movements
decussates
- caudal medulla
what does the cerebellum control?
the ipsilateral side of your body
what is area 6 involved with?
what is it named?
motor planning, intent to move, strategy
- SMA, PMA
what is area 4 involved with?
what is it named?
execution
- primary motor cortex
