BIO 253 Midterm Exam Questions With
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What are the main causes of fatigue addressed for each of the variables tested? -
answerEncouragement: Change in motivation or central drive
Visual Feedback: Sense of effort
Rest: Build-up of lactic acid and a reduction in blood flow
What would you...
What are the main causes of fatigue addressed for each of the variables tested? -
answer✔✔Encouragement: Change in motivation or central drive
Visual Feedback: Sense of effort
Rest: Build-up of lactic acid and a reduction in blood flow
What would you expect from a person's EMG who has Muscular Dystrophy who is asked to lift a
weight? How would that differ from a person with Myasthenia Gravis? - answer✔✔Muscular
Dystrophy: EMG would look the same as normal individual despite the muscle cells dying, the
nerve signal is unaffected.
Myasthenia Gravis: EMG would look weaker and fatigue faster than a normal individual
The muscle cell doesnt stockpile large quantities of ATP. How does the muscle ensure enough
ATP for intense exercise? - answer✔✔At rest, some ATP transfers a phosphate to creatine and
creates phosphocreatine. This can be used to resynthesizes ATP during intense exercise for the
contraction to continue.
During repeated skeletal muscle contraction, what happens to calcium within a single motor unit
that may lead to fatigue? What is it's overall effect? - answer✔✔A reduction in calcium ion
release due to depletion of Ca2+ ions from intracellular stores: The SR inhibits excitation-
contraction coupling.
If EMG electrodes were placed on the flexor digitorum superficialis (one of the muscles involved
in maintaining grip) while applying sustained max force, what would the EMG trace look like as
you encounter fatigue for both the raw data and the RMS data? - answer✔✔Raw data would be
spikey, and then get smaller.
RMS data would be a nice curve that starts as a plateau and then slopes down
Why is high intensity anaerobic exercise limited in duration? - answer✔✔Lactic acid breaks
down and contributes to fatigue by interfering with contractile processes and by changing the pH
of the muscle cell. The tolerance for decreasing pH in muscle cells is limited. As pH decreases,
enzymes denature and anaerobic respiration becomes inefficient.
Define isometric contraction and describe an example - answer✔✔An isometric contraction is a
muscle contraction that sees the muscle remain at the same length in which there is no movement
of the joint.
Holding a wallsit is an example
When the current reached the following stages, what proportion of fibers in the muscle were
contracting?
- At threshold
- At max
- Above the maz - answer✔✔- At threshold only a few of the fibers are being recruited.
- 100% of the fibers are being recruited and contracting
- still 100% because all of the fibers are being used
A short period of rapid electrical stimuli is used to observe muscle fibers contracting
continuously (tetanus). Chemical agents can cause tetanus by interfering with the motor neurons.
These agents include a toxin produced by the soil bacterium Clostridium tetani which produces a
toxin that blocks inhibitory signals to motor neurons. One of the symptoms of these agents is
called "spastic paralysis". Explain how the nervous system effects of clostridium tetani toxin
would result in tetanus in a muscle. How might this lead to a life threatening condition? -
answer✔✔If the muscles required for breathing were involved death could follow
Explain what is happening at the synaptic clef during summation, incomplete tetanus, and
tetanus. - answer✔✔During summation, stimuli occur one after the other, but they do not reach
the intensity or frequency to reach tetanus. The second stimulus does not happen until the
refractory period is almost over from the first. At this time, the action potential has reached the
synaptic cleft and ACh is released. ACh at the synaptic cleft is quickly degraded, though not
fully. A very small amount still remains and is added on, i.e. summated, with each subsequent
stimulus received.
During incomplete tetanus, stimulus frequency has increased. Muscle fibers are now reaching
tetanus but cannot maintain tetanus between impulses. There is an additive, stair-step effect of
each twitch that occurs since the muscle has not yet fully relaxed. There is more ACh being
released and less time for it to get degraded between impulses
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