lecture 3

Question 1

what is a motor unit?

Answer 1

a motor neuron and all the fibers it innervates

Question 2

what are the MU types

Answer 2

fast fatiguable, fast resistance, slow twitch

Question 3

muscle tension is proportional to ?

Answer 3

the size

Question 4

the size of a MU is dependent on?

Answer 4

the amount to muscle fibers it innervates

Question 5

what are the three criteria for MU classifications

Answer 5

speed, maximal titanic force, fatigue index(how much force is lost, how fast it is fatiguing)

Question 6

if there is an increase in force then?

Answer 6

there is an increase in MU recruitment

Question 7

is there an order for MU recruitment?

Answer 7

yes there is and it is orderly meaning that the smallest MU are recruited first then the largest after. also during derecruitments, the largest are derecruited first then the smallest.

Question 8

why are smaller mU recruited first?

Answer 8

they have higher synaptic density and excitatory current is concentrated along a smaller membrane so it can reach threshold faster

Question 9

why orderly recruitment

Answer 9

limiting fatigue since the smallest MU are fatigue resistance

fine force control since weakest are recruited first

simplifies motor control schemes

Question 10

how is temporal summation studied for force gradation?

Answer 10

recording muscle force response from artificial electrical stimulation or record EMG firing rates of MY actions potential during voluntary contractions

Question 11

temporal summations

Answer 11

there is no full relaxation before calcium is released and contraction occurs again

Question 12

what is unfused tetanus

Answer 12

there is no full relaxation. but there are series of muscle twitches with barely any relaxation

Question 13

what is fused tetanus

Answer 13

no time to relax at all. all the contractions are fused together

Question 14

force frequency curves

Answer 14

describes the relationship between electrical stimulation frequency input and force output.

Question 15

increasing the calcium in the muscle does what?

Answer 15

increases the frequency and force of contraction

Question 16

what is the concept of rate coding?

Answer 16

so when the there is an increase in force and additional motor unit cannot be recruited, the nervous system basically increase the firing rate of the already active MU to generate more force.