L2

Question 1

What is a motor unit

Answer 1

an alpha motor neuron and all the muscle fibers it innervates

Question 2

what is a motor neuron pool

Answer 2

in the ventral horn of the spinal cord cell bodies reside forming the MN pool, and exit through the ventral root

Question 3

what does the dorsal root carry

Answer 3

sensory or afferent axons

Question 4

how do motor neurons exit the anterior horn

Answer 4

via the ventral root, efferent axons

Question 5

describe mediolateral somatotopic arrangement

Answer 5

is the specific arrangement in the spinal cord for distribution of motor pool. allows system to organize in an efficient way. Proximal muscles are located in the center (postural muscles) distal in the spinal cord is the motor neuron pools for the limbs

Question 6

what is neuromuscular compartmentalization

Answer 6

a compartment contains a unique population of MU, confined to a certain region of the muscle.

concept of task groups. so some MUs active during supination, others active during elbow flexion = two physiological muscles

Question 7

Explain innervation ratio

Answer 7

the number of muscle fibers innervated by a single motor unit
Varies for different muscles

Question 8

T or F: number of MUs increases with age while the number of fibers per MU decreases

Answer 8

F: number of MUs decreases with age while the number of fibers per MU decreases

Question 9

what are the implications for motor control if there is a loss of the amount of MUs

Answer 9

lose the ability to preform fine motor control tasks due to too much force generation

Question 10

what are the three types of skeletal muscle fibers

Answer 10

1. slow oxidative
2. fast oxidative-glycolytic
3. fast glycolytic

Question 11

The three skeletal muscle fibers and their MU size/innervation ratio

Answer 11

1. FF = large MU and high innervation ratio
2. FFR = medium MU and medium innervation ratio
3. SO = small MU and low innervation ratio

Question 12

twitch response and fatigability of each of the muscle fiber types

Answer 12

1. FF = fast twitch but easily fatigable
2. in between
3. SO = slow twitch but fatigue resistant

Question 13

what is the latent period

Answer 13

the time between action potential and onset of torque - speed of binding

Question 14

what is the force of contraction peak dependent on

Answer 14

the number of cross bridges able to form

Question 15

what is the contraction phase in the tension time graph

Answer 15

the speed of power stroke, dependent on cycling rate of myosin

Question 16

what is the relaxation phase in the tension time graph

Answer 16

phase based on requestering of Ca2+ (measured by the half relaxation time)