Question 1

Which of the following would increase the tension produced by a skeletal muscle contraction?

Accepted Answer

The answer of Which of the following would increase the...

Question 2

When you bend your arm at the elbow, the movement is known as

Accepted Answer

Flexion is the proper term for the movement of bending your arm at the elbow. Agonism refers to the action of a muscle contracting, extension refers to the movement of straightening the arm, and pronation refers to the rotation of the forearm so that the palm faces down.

Question 3

Which of the following defines a motor unit?

Accepted Answer

A motor unit consists of a single motor neuron and all of the muscle fibers it innervates. When the motor neuron fires an action potential, all of the muscle fibers it innervates contract together.

Question 4

The force a motor unit exerts depends on the rate at which the somatic motor neuron discharges action potentials because calcium is released from the sarcoplasmic reticulum faster than it is pumped back by the Ca²⁺-ATPase pump.

Accepted Answer

This statement is true. The rate of action potential firing in the somatic motor neuron determines the amount of calcium released into the cytoplasm of the muscle cell. The faster the neuron fires, the more calcium is released, leading to a greater force of contraction. The Ca2+-ATPase pump then works to remove calcium from the cytoplasm, but it operates more slowly than the release of calcium, so the force of contraction will still depend on the rate of action potential firing.

Question 5

Which type(s) of muscle fibers is/are most fatigue resistant?

Accepted Answer

Slow oxidative muscle fibers are the most fatigue-resistant due to their high concentration of mitochondria and myoglobin, which allows for sustained aerobic energy production. They also have a high resistance to fatigue-causing substances like lactic acid.

Question 6

Which event does NOT occur during the relaxation period?

Accepted Answer

During the relaxation period, calcium is pumped out of the sarcoplasm by the Ca2+-ATPase pump (Choice A), myosin-binding sites are covered by tropomyosin (Choice B), and actin filaments return to their resting position (Choice C). Therefore, the event that does NOT occur during the relaxation period is the rising of calcium levels in the sarcoplasm (Choice D).

Question 7

Concentric and eccentric are types of ______ contractions.

Accepted Answer

Concentric and eccentric contractions are both subtypes of isotonic contractions, which involve changes in muscle length while maintaining a constant load or tension. Isometric contractions, on the other hand, involve maintaining a constant muscle length while generating tension against an immovable object. Elastic contractions also refer to a different mechanism altogether, involving the stretching and subsequent release of elastic tissues like tendons.

Question 8

Competitive weight lifters often try to exceed their own limits of performance by lifting heavier and heavier weights. Dwight is attempting to set his new personal record on the bench press and as he lowers the bar to his chest, he pushes it back up about halfway and begins to struggle. His spotter waits for two seconds while Dwight continues to work by himself, and suddenly the bar begins to move upwards again until it is fully extended, without the intervention of the spotter. Describe the types of muscle contractions that occurred while Dwight was struggling and while he followed through, respectively.

Accepted Answer

When Dwight was struggling with the weight without moving it, his muscles were engaged in an isometric contraction, where the muscle length does not change despite force being applied. As he managed to push the bar upwards until it was fully extended, his muscles were performing a concentric isotonic contraction, where the muscles shorten while generating force.

Question 9

You are holding a small textbook in your hand, and you begin to flex your elbow to raise the book. You stop with your elbow flexed at about 90 degrees, and the book held out in front of you. What is occurring in your biceps muscle at this time?

Accepted Answer

When you flex your elbow and hold the textbook out in front of you, your biceps muscle is contracting, but not fully tetanic (unfused tetanus). At the same time, the concentrations of Ca^{2 and} are elevated in the biceps muscle fibers, indicating increased activation and utilization of the muscle. Therefore, choice D is the best answer. Choice A is incorrect because the biceps is not in a fully tetanic state. Choice B is not a known physiological term. Choice C does not provide enough information to make a conclusion. Choice E is incorrect because the term "latched" is not a known physiological term.

Question 10

The muscle action potential travels down the T tubule system during the _____ period.

Accepted Answer

The answer of The muscle action potential travels down the...

Question 11

A whole muscle is controlled by activation of a single motor unit.

Accepted Answer

A whole muscle is controlled by the activation of multiple motor units. Each motor unit contains a single motor neuron and the muscle fibers it innervates. The activation of multiple motor units allows for coordinated and graded muscle contractions.

Question 12

Imagine you want to produce a finely controlled movement (like picking up a wine glass by the stem). Would it be better to recruit a motor unit with a lower number of muscle fibers, or a motor unit with a higher number of muscle fibers?

Accepted Answer

Recruiting a motor unit with a lower number of muscle fibers will allow for finer control and a more precise movement. This is because the smaller motor unit will produce a smaller amount of force, allowing for more precise adjustments in movement. If a motor unit with a higher number of muscle fibers was recruited, it would produce a greater force and could result in an overcompensation or a less controlled movement.

Question 13

A competitive marathon runner will likely have a higher than average number of which type of muscle fiber?

Accepted Answer

Slow oxidative fibers are more prevalent in endurance athletes like marathon runners because these fibers are more efficient at using oxygen to generate ATP for long-duration, low-intensity activities.

Question 14

Although an individual person's distribution of skeletal muscle fiber types is primarily genetically determined, there exists some evidence that fiber types can change in response to exercise to a limited degree (ie. a slow glycolytic fiber can change to a fast oxidative fiber). If such a change were to occur, which of the following proteins MUST change in some manner as the transition from one muscle type to another occurs?

Accepted Answer

Myosin is the motor protein responsible for muscle contraction, and different types of myosin are present in different muscle fiber types. Therefore, if a slow glycolytic fiber were to transition to a fast oxidative fiber, the myosin isoform present in the muscle would need to change to one that is better suited for oxidative metabolism. While changes in the other proteins listed may also occur during this transition, myosin is the most critical protein for determining muscle fiber type.

Question 15

Which of the following is correct regarding unfused tetanus in a skeletal muscle fiber?

Accepted Answer

Unfused tetanus occurs when a muscle fiber is stimulated at a high rate but still has a slight amount of time to relax between stimuli, leading to a situation where the muscle does not fully relax before the next stimulus arrives. This results in a tension that is higher than a single twitch but not as high as in complete (fused) tetanus.

Question 16

No energy is expended during an isometric contraction because no actual movement is occurring.

Accepted Answer

During an isometric contraction, muscles generate force without changing length, and energy is expended to maintain the contraction, even though there is no movement.

Question 17

Jimothy is out cutting firewood with his dad and when they finish they need to carry it back to their campsite. Jimothy wants to impress his dad with how much would he can carry. What would be the most efficient way for him to carry the most wood while using the least amount of energy?

Accepted Answer

Carrying logs close to the elbows reduces the moment arm, which is the distance between the point of force application and the pivot (in this case, the shoulder joint), thereby reducing the torque and the amount of energy required to carry the logs. This method allows for carrying more wood efficiently compared to the options that involve carrying with hands or making multiple trips.

Question 18

When the body produces movements, ______ function as fulcrums for levers and ______ act as the levers.

Accepted Answer

The answer of When the body produces movements, ______ function...

Question 19

Why do fast glycolytic skeletal muscle fibers have the greatest cross sectional area?

Accepted Answer

Fast glycolytic skeletal muscle fibers are designed for producing a high amount of force. This is achieved through a larger cross-sectional area, which allows for more myofibrils and sarcomeres to be packed into the muscle fiber, resulting in a greater amount of force production.

Question 20

A competitive sprinter will likely have a higher than average number of which type of muscle fiber?

Accepted Answer

Fast glycolytic muscle fibers are responsible for quick and powerful movements such as sprinting. Therefore, a competitive sprinter will likely have a higher percentage of fast glycolytic muscle fibers in their muscles.

Quiz 11: Muscle

Which of the following would increase the tension produced by a skeletal muscle contraction?

When you bend your arm at the elbow, the movement is known as

Which of the following defines a motor unit?

The force a motor unit exerts depends on the rate at which the somatic motor neuron discharges action potentials because calcium is released from the sarcoplasmic reticulum faster than it is pumped back by the Ca²⁺-ATPase pump.

Which type(s) of muscle fibers is/are most fatigue resistant?

Which event does NOT occur during the relaxation period?

Concentric and eccentric are types of ______ contractions.

You are holding a small textbook in your hand, and you begin to flex your elbow to raise the book. You stop with your elbow flexed at about 90 degrees, and the book held out in front of you. What is occurring in your biceps muscle at this time?

The muscle action potential travels down the T tubule system during the _____ period.

A whole muscle is controlled by activation of a single motor unit.

Imagine you want to produce a finely controlled movement (like picking up a wine glass by the stem) . Would it be better to recruit a motor unit with a lower number of muscle fibers, or a motor unit with a higher number of muscle fibers?

A competitive marathon runner will likely have a higher than average number of which type of muscle fiber?

Which of the following is correct regarding unfused tetanus in a skeletal muscle fiber?

No energy is expended during an isometric contraction because no actual movement is occurring.

Jimothy is out cutting firewood with his dad and when they finish they need to carry it back to their campsite. Jimothy wants to impress his dad with how much would he can carry. What would be the most efficient way for him to carry the most wood while using the least amount of energy?

When the body produces movements, function as fulcrums for levers and act as the levers.

Why do fast glycolytic skeletal muscle fibers have the greatest cross sectional area?

A competitive sprinter will likely have a higher than average number of which type of muscle fiber?

Quiz 11: Muscle

Which of the following would increase the tension produced by a skeletal muscle contraction?

When you bend your arm at the elbow, the movement is known as

Which of the following defines a motor unit?

The force a motor unit exerts depends on the rate at which the somatic motor neuron discharges action potentials because calcium is released from the sarcoplasmic reticulum faster than it is pumped back by the Ca2+-ATPase pump.

Which type(s) of muscle fibers is/are most fatigue resistant?

Which event does NOT occur during the relaxation period?

Concentric and eccentric are types of ______ contractions.

You are holding a small textbook in your hand, and you begin to flex your elbow to raise the book. You stop with your elbow flexed at about 90 degrees, and the book held out in front of you. What is occurring in your biceps muscle at this time?

The muscle action potential travels down the T tubule system during the _____ period.

A whole muscle is controlled by activation of a single motor unit.

Imagine you want to produce a finely controlled movement (like picking up a wine glass by the stem) . Would it be better to recruit a motor unit with a lower number of muscle fibers, or a motor unit with a higher number of muscle fibers?

A competitive marathon runner will likely have a higher than average number of which type of muscle fiber?

Which of the following is correct regarding unfused tetanus in a skeletal muscle fiber?

No energy is expended during an isometric contraction because no actual movement is occurring.

Jimothy is out cutting firewood with his dad and when they finish they need to carry it back to their campsite. Jimothy wants to impress his dad with how much would he can carry. What would be the most efficient way for him to carry the most wood while using the least amount of energy?

When the body produces movements, ______ function as fulcrums for levers and ______ act as the levers.

Why do fast glycolytic skeletal muscle fibers have the greatest cross sectional area?

A competitive sprinter will likely have a higher than average number of which type of muscle fiber?

The force a motor unit exerts depends on the rate at which the somatic motor neuron discharges action potentials because calcium is released from the sarcoplasmic reticulum faster than it is pumped back by the Ca²⁺-ATPase pump.

When the body produces movements, function as fulcrums for levers and act as the levers.