unit 2 review - motor

Question 1

agonists/synergists are?

Answer 1

muscles that contract together

Question 2

axial muscles vs. proximal vs. distal

Answer 2

axial= center: trunk and posture

proximal=shoulder, pelvis, elbow, knee; locomotion

distal=digits, fine motor skills, specialized in humans

Question 3

how to motor neuron axons get to the brain?

Answer 3

by going through the ventral horn

Question 4

what areas of the spinal cord are enlarged and why?

Answer 4

cervical and lumbar
- fine motor control, enlarged because of more motor neurons

Question 5

what is contained in the lateral ventral horn?

Answer 5

lateral muscles
- like hands

Question 6

what is contained in the medial ventral horn?

Answer 6

medial muscles
- like torso

Question 7

where are flexors vs. extensors on the ventral horn spectrum?

Answer 7

flexors are more dorsal to neurons innervating extensors

Question 8

what is a muscle fiber innervated by?
how many, what is the NT?

Answer 8

innervated by 1 alpha motor neuron
- NT=ACh

Question 9

where does the muscle fiber synapse?

Answer 9

motor end plate

Question 10

what is a motor unit?

Answer 10

• 1 alpha motor neuron
• all the muscle fibers it innervates

Question 11

how many muscle fibers can an alpha motor unit innervate?

Answer 11

a muscle fiber can only be innervated by 1 alpha motor unit, but
- 1 alpha motor unit can innervate many muscle fibers

Question 12

what is a motor pool?

Answer 12

all the alpha motor units that innervate 1 muscle

Question 13

what determines slow vs. fast twitch?
can a motor unit have more than 1 type?

Answer 13

alpha motor unit determined fast/slow twitch type

Question 14

what are the two ways that more muscle force can be generated?

Answer 14

1) increasing the firing rate of active motor neurons
- fasciculation=twitches
- temoral summation of twitches
2) increase number of active motor neurons
- size princliple

Question 15

where are alpha motor neurons located?
where do they send their axons?

Answer 15

spinal cord
- send axons down to muscles to cause contraction

Question 16

what are the 3 components that modulate alpha motor neurons?

Answer 16

1) sensory input
2) input from same and nearby spinal segments
3) brain
- upper motor neurons

Question 17

where do muscles get sensory input from?

Answer 17

Aa and Ab
- fastest conduction

Question 18

what two organs give muscles proprioceptive input?

Answer 18

• golgi tendon organs
• muscle spindles

Question 19

what are golgi tendon organs?
where are they located in comparison to the muscle?

Answer 19

force/tension receptors
- located in series, at the junction between the muscle and tendon

Question 20

what are golgi tendon organs innervated by?

Answer 20

Ab/1b axons

Question 21

what is the purpose of golgi tendon organs?

Answer 21

allow us to regulate how much force is needed for different tasks

Question 22

describe the 4 steps of the GTO pathway?
whats the recap?

Answer 22

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

Question 23

what is the negative feedback present in the GTO?

Answer 23

GTO innervates inhibitory interneurons which reduces alpha motor neuron activity
- thus reducing muscle tension if its overloaded

Question 24

what are muscle spindles?

Answer 24

stretch receptors

Question 25

where are muscle spindles located in comparison to muscle?

Answer 25

in parralell witch muscle fibers - within the muscle

Question 26

what are muscle spindles innervated by?

Answer 26

Aa/1a axons

Question 27

what is the purpose of muscle spindles?

Answer 27

sense changes in the length of the muscle

Question 28

what are the muscle fibers that are within the muscle spindle called?

Answer 28

intrafusal muscle fibers - extra fusal=outside

Question 29

what is the muscle spindles mechanism?

Answer 29

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

Question 30

what do gamma motor neurons do?

Answer 30

innercate intrafusal fibers and make them contract/re-adjust until Aa/1a fibers come online again - they respond to chnages in length

Question 31

recap intra vs. extra fusal fibers?

Answer 31

intra - innervated by gamma motor neurons - located within muscle spindles - sense changes in length extra - innervated by alpha motor neurons - generate force

Question 32

what does the stretch reflex involve? what is its goal?

Answer 32

1 synapse - no interneurons or brain goal - to maintain neurons at a constant length

Question 33

what is reciprocal inhibition?

Answer 33

when agonists contract antagonists relax

Question 34

flex-crossed extensor reflex pathway? *right foot*

Answer 34

excited - r leg flexors, l leg extensors inhibited - r leg extensors, l leg flexors

Question 35

what motor cortex area is involved in strategy?

Answer 35

area 6, basal ganglia, higher order association orders

Question 36

what motor cortex area is involved in tactics? (how to execute movement smoothly) movement and movement control

Answer 36

area 4

Question 37

what area of the brain is involved with execution?

Answer 37

brainstem, cerebellum, spinal cord

Question 38

what are the 2 descending pathways?

Answer 38

lateral pathway ventromedial pathway

Question 39

what do the 2 descending pathways control?

Answer 39

lateral - voluntary movement - distal muscles ventromedial - posture, gait, balance, head position - axial muscles

Question 40

what are 5 signs of motor tract damage? PPSS = peepees lol

Answer 40

- paresis - plegia/hemiplegic gait - spasticity - sign of babinsky

Question 41

what are the 5 signs of cerebellar damage? AIDMH?!

Answer 41

- ataxia - intention tremor - drunken gait - melagraphia - hypotonia

Question 42

what are basil ganglia diseases?

Answer 42

- parkingsons=hypokenesia, not enough movement - hungtingtons=hyperkinesia, excess movement

Question 43

what are treatments for parkinsons?

Answer 43

- ldopa - pallidotomy/lesion of global pallidus - deep brain stimulation

Question 44

where do the ventro medial pathways originate?

Answer 44

brainstem

Question 45

what does the corticospinal tract control? where does it decussate?

Answer 45

controls - voluntary movements decussates - caudal medulla

Question 46

what does the cerebellum control?

Answer 46

the ipsilateral side of your body

Question 47

what is area 6 involved with? what is it named?

Answer 47

motor planning, intent to move, strategy - SMA, PMA

Question 48

what is area 4 involved with? what is it named?

Answer 48

execution - primary motor cortex