Functional Properties of Muscle and Motor Units

Question 1

What 2 factors is force/tension production dependent on?

Answer 1

• the initial starting length

- the number of independently cycling actin-myosin crossbridges

Question 2

(slow twitch/fast twitch) muscle fibers are relatively larger in diameter

Answer 2

fast twitch

Question 3

(slow twitch/fast twitch) muscle fibers are relatively smaller in diameter

Answer 3

slow twitch

Question 4

3 factors that effect the number of independently cycling actin-myosin cross-bridges

Answer 4

• pattern of stimulation of firing frequency of the motoneurons
• number of motoneurons recruited simultaneously
• cross-sectional area of the muscle fibers recruited

Question 5

_________contraction: in which there is increasing force, but muscle length remains constant (load does not move)

Answer 5

isometric

Question 6

_______contraction: in which a constant force is exerted, resulting in a changing length of the muscle

Answer 6

isotonic

Question 7

_______ both origin and insertion are stabilized or fixed and a force transducer is applied to one of the tendons

Answer 7

isometric

Question 8

maximum force is produced at length with maximum ____________

Answer 8

overlap

Question 9

_______ the origin is fixed and the insertion is loaded

Answer 9

isotonic

Question 10

shortening curves and the force-velocity diagram are examples of _______ recording

Answer 10

isotonic

Question 11

_______ contraction is a ‘shortening’ contraction

Answer 11

concentric

Question 12

_______ contraction is a ‘lengthening’ contraction

Answer 12

eccentric

Question 13

________: the time to reach maximum tension

Answer 13

twitch contraction time

Question 14

_______ is the series-elastic component of muscle

Answer 14

titin

Question 15

titin is in series with the ______ filaments in a sarcomere

Answer 15

myosin

Question 16

twitch contraction times are a function of the _____________ in muscle

Answer 16

type of myosin ATPase

Question 17

twitch contraction times

FF -
FR -
S -

Answer 17

FF - 30ms
FR - 40 ms
S - 70 ms

Question 18

increased frequency of stimulation in muscle fibers results in ___________

Answer 18

twitch summation

Question 19

a muscle will always go through recruitment of the ________ muscle fibers first

Answer 19

slow twitch

Question 20

2 mechanisms of force modulation in skeletal muscle

Answer 20

• increase stimulation frequency of motor units presently recruited (unfused tetani vs. fused tetani)
• increase recruitment of more motor units (S first, FR, FF last)

Question 21

central recruitment of more motor units results in ___________

Answer 21

more force production

Question 22

size of motor neurons is __________ proportional to the size of the muscle fibers they innervate

Answer 22

directly

Question 23

the larger a motor neuron, the ____ input it will need to get going

Answer 23

more

Question 24

twitch contraction time is determined by the rate of ___________

Answer 24

crossbridge recycling

Question 25

Which type of fibers have greater myosin ATPase activity?

Answer 25

Type II (F)

Question 26

___________ fibers are more dependent on aerobic metabolism and have a high mitochondria content

Answer 26

slow twitch, type I

Question 27

What type of muscle fiber is described?

• low tetanic fusion frequency
• fatigue resistant
• high oxidative capacity

Answer 27

slow twitch, type I

Question 28

What type of muscle fiber is described?

• high tetanic fusion frequency
• able to maintain a tetanic contraction for only short periods of time

Answer 28

fast twitch

Question 29

What is meant by the homogeneity of motor units?

Answer 29

a single motor neuron will only innervate muscle fibers of a single type

Question 30

Maximum force production occurs during what kind of contraction?

Answer 30

isometric tetanic contraction

Question 31

differentiation of muscle fiber typing is dependent upon both _________ and _________

Answer 31

• genetic programming

- neural innervation