8 - Contraction Of Whole Muscle

Front 1

false

Back 1

The level of muscle tension that can be developed within a given muscle is always constant.

T or F

Front 2

1. frequency of stimulation
2. # of motor units recruited
3. degree of muscle stretch

Back 2

What are the three factors which affect muscle tension in a whole muscle?

Front 3

muscle twitch

Back 3

A muscle contraction in response to a single stimulus of adequate strength is called a __________________.

Front 4

1. latent period
2. Contraction period
3. Relaxation

Back 4

What are the three phases of a muscle twitch?

Front 5

contraction

Back 5

myosin cross bridge cycling causes sarcomeres to shorten

Front 6

latent period

Back 6

no visible shortening of the muscle

Front 7

relaxation

Back 7

calcium ions are actively transported back into the terminal cisternae

Front 8

relaxation

Back 8

cross bridge cycling decreases and ends

Front 9

latent period

Back 9

the sarcolemma and the T tubules depolarize

Front 10

relaxation period

Back 10

muscle to return to its original length

Front 11

slow twitch fibers & fast twitch fibers

Back 11

What two factors will cause the speed of the contraction phase of a muscle twitch to vary?

Front 12

Temporal (wave) stimulation

Back 12

What is it called when a second stimulus of the same intensity is applied to a muscle before the completion of the relaxation period of the first stimulus resulting in increased muscle tension?

Front 13

Because an influx of Ca++ promotes 2nd contraction, which is added to the 1st contraction.

Back 13

In temporal summation, why is the second peak is higher than the first?

Front 14

a. 50 millisecond apart

Back 14

If two stimuli are given to the same muscle, which will result in a more intense second contraction?
a. If the stimuli are given 50 milliseconds apart
b. If the stimuli are given 70 milliseconds apart

Front 15

Because cross bridge cycling has stopped & Ca++ ions have already been actively transported back into the terminal cisternae.

Back 15

If you wait until relaxation is complete from the first stimulus, then give a second stimulus to the same muscle, why won't temporal summation occur?

Front 16

e. complete tetanus

Back 16

In which of the following states does the muscle stay contracted, with no apparent relaxation?

a. temporal summation
b. fatigue
c. incomplete tetanus
d. treppe
e. complete tetanus

Front 17

d. treppe

Back 17

.) In which of the following states does the muscle relax totally between stimulations?

a. temporal summation
b. fatigue
c. incomplete tetanus
d. treppe
e. complete tetanus

Front 18

a. temporal summation

Back 18

In which of the following states does the strength of contraction increase with each stimulation because of a gradual accumulation of calcium ions in the cytosol?

a. temporal summation
b. fatigue
c. complete tetanus
d. treppe

Front 19

e. incomplete tetanus

Back 19

.) In which of the following states does the strength of contraction decrease with each stimulation?
a. temporal summation
b. fatigue
c. complete tetanus
d. treppe
e. incomplete tetanus

Front 20

c. depletion of calcium ions in the cytosol

Back 20

.) Which of these is not a reason for muscle fatigue?
a. ionic imbalances resulting from membrane activities
b. relative but not total lack of ATP
c. depletion of calcium ions in the cytosol
d. a build-up of acidic compounds

Front 21

d. they are all factors

Back 21

Which of these is not a factor which affects the development of muscle tension:
a. Number of Motor Units Recruited
b. Degree of Muscle Stretch
c. Frequency of Stimulation
d. they are all factors

Front 22

false

Back 22

A given muscle always uses the same number of motor units, no matter what the muscle is trying to accomplish.

T or F

Front 23

a. threshold

Back 23

.) The minimum stimulus (voltage) which can evoke a response is applied to a muscle. This is called _________.
a. threshold
b. a maximal stimulus
c. a subthreshold stimulus
d. recruitment

Front 24

c. a subthreshold stimulus

Back 24

The stimulus (voltage) is applied to a muscle and there is no visible response. This is called
a. threshold
b. a maximal stimulus
c. a subthreshold stimulus
d. recruitment

Front 25

b. a maximal stimulus

Back 25

The stimulus (voltage) is applied to a muscle. When another, more intense stimulus does not evoke greater tension the original stimulus would be called
a. a threshold stimulus
b. a maximal stimulus
c. a subthreshold stimulus
d. recruitment

Front 26

treppe

Back 26

• The frequency of stimulation was so slow here that relaxation was complete between contractions. Note that the curve goes down to the baseline after each contraction
• The strength of contraction did increase because muscle contraction causes heat to build up in the muscles and muscles then work better when they are warmer. Enzymes can work faster and more efficiently when a muscle is "warmed up".

Front 27

temporal summation

Back 27

• Now the frequency of stimulation is increased to the point where relaxation cannot totally occur.

• The result is a continual increase in tension which may result from increased availability of intracellular calcium.

Front 28

incomplete summation

Back 28

• Now the frequency of stimulation is increased to the point where the muscle exhibits even shorter contraction-relaxation cycles, but there is still some degree of relaxation after each contraction.

Front 29

complete summation

Back 29

• When the frequency of stimulation becomes fast enough, the contractions fuse into a smooth, continuous, total contraction with no apparent relaxation.

• This state is due to a continual depositing of calcium ions in the cytosol. As a result, the binding sites on actin continually stay exposed.

Front 30

fatigue

Back 30

Tetanus cannot continue forever. With continued rapid stimulation, there is a build-up of acidic compounds which affect protein functioning, a relative but not total lack of ATP, and ionic imbalances resulting from membrane activities. This causes muscle fatigue and the gradual inability of the muscle to respond to stimulation.