BIO 253 MIDTERM QUESTIONS &
ANSWERS(RATED A+)
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 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? -
ANSWERMuscular 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? - ANSWERAt 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? - ANSWERA 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? - ANSWERRaw 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? - ANSWERLactic 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.
In the image above, why is there a delay in the evoked EMG and the subsequent
force produced? Explain this in terms of acetylcholine and acetylcholinesterase. -
ANSWERAcetylcholinesterase is always present and breaking down acetylcholine.
The delay happens because after the electrical impulse, enough acetylcholine must
be released and build up in order to overwhelm the acetylcholinesterase present.
ACh then binds to the motor end plate receptor, initiating excitation-coupling
reaction.
When taking blood pressure, what are the sounds that appear between systolic and
diastolic measurements. What causes them? Do we hear them when the cuff is not
, inflated? Why? - ANSWERThe sounds heard are the Korotkoff sounds. These
sounds are caused by the turbulent blood flow that results from the occlusion in the
brachial artery. We do not hear the Korotkoff sounds when the cuff is not inflated
because there is no resistance to blood flow, thus there is not turbulence to disrupt
laminar flow.
What could be some sources of error (that do not include improper use of the
equipment or not following procedure correctly) in this whole lab that could have
affected your data? (LAB one) - ANSWERInterference due to movement or sounds
Placement error (human error)
Define isometric contraction and describe an example - ANSWERAn 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? - ANSWERIf the muscles
required for breathing were involved death could follow
Explain what is happening at the synaptic clef during summation, incomplete
tetanus, and tetanus. - ANSWERDuring 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
During tetanus, the muscle has no relaxation between impulses because the stimuli
are arriving very shortly after one another. There is no time for ACh in the synaptic
cleft to degrade, causing more ligand-gated sodium channels to open. There is
ANSWERS(RATED A+)
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 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? -
ANSWERMuscular 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? - ANSWERAt 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? - ANSWERA 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? - ANSWERRaw 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? - ANSWERLactic 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.
In the image above, why is there a delay in the evoked EMG and the subsequent
force produced? Explain this in terms of acetylcholine and acetylcholinesterase. -
ANSWERAcetylcholinesterase is always present and breaking down acetylcholine.
The delay happens because after the electrical impulse, enough acetylcholine must
be released and build up in order to overwhelm the acetylcholinesterase present.
ACh then binds to the motor end plate receptor, initiating excitation-coupling
reaction.
When taking blood pressure, what are the sounds that appear between systolic and
diastolic measurements. What causes them? Do we hear them when the cuff is not
, inflated? Why? - ANSWERThe sounds heard are the Korotkoff sounds. These
sounds are caused by the turbulent blood flow that results from the occlusion in the
brachial artery. We do not hear the Korotkoff sounds when the cuff is not inflated
because there is no resistance to blood flow, thus there is not turbulence to disrupt
laminar flow.
What could be some sources of error (that do not include improper use of the
equipment or not following procedure correctly) in this whole lab that could have
affected your data? (LAB one) - ANSWERInterference due to movement or sounds
Placement error (human error)
Define isometric contraction and describe an example - ANSWERAn 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? - ANSWERIf the muscles
required for breathing were involved death could follow
Explain what is happening at the synaptic clef during summation, incomplete
tetanus, and tetanus. - ANSWERDuring 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
During tetanus, the muscle has no relaxation between impulses because the stimuli
are arriving very shortly after one another. There is no time for ACh in the synaptic
cleft to degrade, causing more ligand-gated sodium channels to open. There is
