Muscle twitch

Question 1

twitch

Answer 1

contraction in response to a stimulus that causes AP in one or more muscle fibers

Question 2

lag phase

Answer 2

gap between stimulus and beginning of beginning of contraction
–AP traveling across cleft and down sacrolemma

Question 3

contraction

Answer 3

once Ca is released from SR and cross bridge cycling occurs

Question 4

relaxation

Answer 4

longer than contraction bc concentration of Ca decreases slowly and Ca reuptake into SR slow

Question 5

isometric contraction

Answer 5

no change in length but increase in tension
ie postural muscles standing
or when try to lift something and its too heavy

Question 6

isotonic contractoin

Answer 6

muscle shortens and tension constant
ie lifting an object or moving your limbs

Question 7

motor unit

Answer 7

a single motor neuron and all of the muscle fibers it innervates

Question 8

large muscles have motor units with ______fibers

Answer 8

many

Question 9

small muscles have motor units with _____ fibers

Answer 9

few

Question 10

summation

Answer 10

amount of force of an individual muscle fiber

Question 11

recruitment

Answer 11

amount of force of a whole muscle

Question 12

muscles respond to stimuli in ____ fashion

Answer 12

graded

Question 13

to increase the force of a contraction you need to increase the ______

Answer 13

cross bridges

Question 14

to increase the number of cross bridges in a reaction (3 ways)

Answer 14

1. increase frequency of stimulation
2. muscle fiber diameter
3. muscle fiber length at time of contraction

Question 15

treppe phenomenon

Answer 15

muscle fiber force of contraction will increase with each subsequent contraction at high frequency
will eventually become equal
muscle fiber must completely rest followed by immediate stimulus

Question 16

increase in frequency increases force of contraction (treppe) bc

Answer 16

increase of Ca remains in sarcoplasm

Question 17

wave summation

Answer 17

muscle tension increases as contraction frequencies increase

Question 18

incomplete tetanus

Answer 18

muscle partially releaxes

Question 19

complete tetanus

Answer 19

no relaxation between contractions

Question 20

active tension

Answer 20

force applied to an object to be lifted when muscle contracts
increases or decreases as muscle contracts

Question 21

active tension curve

Answer 21

stretched too far–fewer cross bridges can form
not stretched enough-thick filaments touch z disk and little contraction can occur

Question 22

passive tension

Answer 22

tension applied to load when muscle stretches but is not stimulated

Question 23

total tension

Answer 23

sum of active and passive tension

Question 24

subthreshold stimulus

Answer 24

no AP, no contraction

Question 25

threshold stim

Answer 25

AP; contraction

Question 26

submaximal stim

Answer 26

stronger stim that produce AP in axions of additional motor units

Question 27

max stim

Answer 27

AP produced in axons of all motor units

Question 28

multiple motor unit contraction

Answer 28

strength of a contraction depends on recruitment of motor units

Question 29

during recruitment ____ motor units are recruited first followed by _________

Answer 29

small; large

Question 30

muscle tone

Answer 30

tension of relaxing muscle
constant tension by muscles for long periods of time
due to small percentage of all motor units contracting out of phase from one another
–ie keeping head up straight, abdomen flat, back and lower limbs straight

Question 31

isotonic concentric contraction

Answer 31

overcomes opposing resistance and muscle shorten; tension remains constant
ie bicep curl

Question 32

isontonic eccentric

Answer 32

tension constant and muscle lengthens
ie going down a flight of stairs