Gamma motor neurons (yMNs) (365/351)

Question 1

where do dynamic yMNs connect

Answer 1

more dynamic / elastic nuclear bag fibres

Question 2

where do static yMNs connect

Answer 2

less dynamic nuclear chain fibres (help measure length)

Question 3

what would happen without yMNs

Answer 3

when the skeletal muscle contracts, the intrafusal fibres would become slack

muscle spindle would stop providing feedback about limb position

Question 4

what happens when aMNs and yMNs are stimulated at the same time (role of yMNs)

Answer 4

intrafusal fibres contract along with the skeletal muscle (extrafusal)

allows the muscle spindle to keep responding during contractions

Question 5

what is alpha gamma coactivation

Answer 5

both neurons stimulated together from one motor command

Question 6

why does alpha gamma coactivation occur

Answer 6

same motor commands from cerebral cortex connect to both aMNs and yMNs therefore they contract together

Question 7

which “code” does dynamic yMN activation enhance

Answer 7

velocity code

Question 8

what “code” does static yMN activation enhance

Answer 8

length code

Question 9

why at height would we want independent control of aMNs and yMNs

Answer 9

want to increase yMN input to be more sensitive

don’t want to change aMN input because it could lead to over correction and larger forces

Question 10

in independent control, which yMN turns on first

Answer 10

static yMN (dynamic isn’t useful in slow movement patterns)

Question 11

in independent control, which yMN is more likely to turn on during fast movement and why

Answer 11

dynamic yMNs - more likely to have a faster stretch in the muscle