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30 Cards in this Set

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

T or F
1. frequency of stimulation
2. # of motor units recruited
3. degree of muscle stretch
What are the three factors which affect muscle tension in a whole muscle?
muscle twitch
A muscle contraction in response to a single stimulus of adequate strength is called a __________________.
1. latent period
2. Contraction period
3. Relaxation
What are the three phases of a muscle twitch?
contraction
myosin cross bridge cycling causes sarcomeres to shorten
latent period
no visible shortening of the muscle
relaxation
calcium ions are actively transported back into the terminal cisternae
relaxation
cross bridge cycling decreases and ends
latent period
the sarcolemma and the T tubules depolarize
relaxation period
muscle to return to its original length
slow twitch fibers & fast twitch fibers
What two factors will cause the speed of the contraction phase of a muscle twitch to vary?
Temporal (wave) stimulation
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?
Because an influx of Ca++ promotes 2nd contraction, which is added to the 1st contraction.
In temporal summation, why is the second peak is higher than the first?
a. 50 millisecond apart
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
Because cross bridge cycling has stopped & Ca++ ions have already been actively transported back into the terminal cisternae.
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?
e. complete tetanus
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
d. treppe
.) 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
a. temporal summation
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
e. incomplete tetanus
.) 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
c. depletion of calcium ions in the cytosol
.) 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
d. they are all factors
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
false
A given muscle always uses the same number of motor units, no matter what the muscle is trying to accomplish.

T or F
a. threshold
.) 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
c. a subthreshold stimulus
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
b. a maximal stimulus
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
treppe
• 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".
temporal summation
• 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.
incomplete summation
• 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.
complete summation
• 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.
fatigue
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.