A&p Chapter 10 - Muscular Tissue | Attempts: 1524

1.

A single somatic motor neuron and all of the muscle fibers it stimulates is known as a .

Explanation
A single somatic motor neuron and all of the muscle fibers it stimulates is known as a motor unit.

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2.

The wasting away of muscle due to lack of use is known as while the replacement of skeletal muscle fibers with scar tissue is known as .

Explanation
Muscular atrophy refers to the wasting away or decrease in size of muscle tissue due to lack of use or physical activity. This can occur as a result of immobilization, prolonged bed rest, or certain medical conditions. On the other hand, fibrosis is the replacement of skeletal muscle fibers with scar tissue. This can happen as a result of chronic inflammation, injury, or certain diseases. Fibrosis can lead to decreased muscle function and flexibility.

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1

3.

The synaptic end bulbs of somatic motor neurons contain synaptic vesicles filled with the neurotransmitter .

Explanation
The synaptic end bulbs of somatic motor neurons contain synaptic vesicles filled with the neurotransmitter acetylcholine. Acetylcholine is the primary neurotransmitter involved in transmitting signals from motor neurons to muscle fibers, allowing for muscle contraction and movement. When an action potential reaches the synaptic end bulb, it triggers the release of acetylcholine from the synaptic vesicles into the synaptic cleft, where it binds to receptors on the muscle fiber, initiating a muscle contraction. Therefore, acetylcholine plays a crucial role in the communication between motor neurons and muscles.

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4.

The ability of muscle cells to respond to stimuli and produce electrical signals is known as excitability.

A.

True
B.

False

Correct Answer
A. True

Explanation
Excitability refers to the ability of muscle cells to respond to stimuli and generate electrical signals. This is a fundamental characteristic of muscle cells that allows them to contract and produce movement. When a muscle cell receives a stimulus, such as a nerve impulse, it responds by generating an electrical signal called an action potential. This electrical signal then triggers a series of events that lead to muscle contraction. Therefore, the statement that the ability of muscle cells to respond to stimuli and produce electrical signals is known as excitability is true.

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1

5.

The sequence of events resulting in skeletal muscle contraction are: a) generation of a nerve impulse; b) release of the neurotransmitter acetylcholine; c) generation of a muscle action potential; d) release of calcium ions from the sacroplasmic reticulum; e) calcium ion binding to troponin; f) power stroke with actin and myosin binding and release.

A.

True
B.

False

Correct Answer
A. True

Explanation
The given answer is true because it accurately describes the sequence of events that occur during skeletal muscle contraction. First, a nerve impulse is generated, which triggers the release of the neurotransmitter acetylcholine. This neurotransmitter then stimulates the generation of a muscle action potential. The muscle action potential leads to the release of calcium ions from the sarcoplasmic reticulum. These calcium ions then bind to troponin, which allows for the power stroke to occur. During the power stroke, actin and myosin bind and release, resulting in muscle contraction.

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6.

In muscle physiology, the latent period refers to:

A.

The period of lost excitability that occurs when two stimuli are applied immediately one after the other
B.

The brief contraction of a motor unit
C.

The period of elevated oxygen use after exercise
D.

An inability of a muscle to contract forcefully after prolonged activity
E.

A brief delay that occurs between application of a stimulus and the beginning of contraction

Correct Answer
E. A brief delay that occurs between application of a stimulus and the beginning of contraction

Explanation
The latent period in muscle physiology refers to a brief delay that occurs between the application of a stimulus and the beginning of contraction. This delay is necessary for the excitation-contraction coupling process to occur, where the electrical signal from the stimulus is transmitted to the muscle fibers and triggers the release of calcium ions. These calcium ions then bind to the contractile proteins in the muscle, initiating the contraction. Therefore, the latent period represents the time it takes for this process to happen before the muscle actually starts to contract.

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2

7.

Which of the following muscle proteins and their descriptions are mismatched?

A.

Titin: regulatory protein that holds troponin in place
B.

Myosin: contractile motor protein
C.

Tropomyosin: regulatory protein that blocks myosin-binding sites
D.

Actin: contractile protein that contains myosin-binding sites
E.

Calsequestrin: calcium-binding protein

Correct Answer
A. Titin: regulatory protein that holds troponin in place

8.

During muscle contraction all of the following occur except

A.

Cross-bridges are formed when the energized myosin head attaches to actin's myosin-binding site
B.

ATP undergoes hydrolysis
C.

The thick filaments slide inward toward the M line
D.

Calcium concentration in the cytosol increases
E.

The Z discs are drawn toward each other

Correct Answer
C. The thick filaments slide inward toward the M line

Explanation
During muscle contraction, several events occur. Cross-bridges are formed when the energized myosin head attaches to actin's myosin-binding site. ATP undergoes hydrolysis to provide energy for muscle contraction. Calcium concentration in the cytosol increases, which is necessary for the contraction process. The Z discs are drawn toward each other, causing the muscle to shorten. However, the thick filaments do not slide inward toward the M line during muscle contraction. Instead, the thin filaments slide over the thick filaments, resulting in the muscle contraction.

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9.

Which of the following is not true concerning sarcomeres (before contraction begins) and muscle fiber length-tension relationships?

A.

If sarcomeres are stretched, the tension in the fiber decreases
B.

If a muscle cell is stretched so that there is no overlap of the filaments, no tension is generated
C.

Extremely compressed sarcomeres result in less muscle tension
D.

Maximum tension occurs when the zone of overlap between a thick and thin filament extends from the edge of the H zone to one end of a thick filament
E.

If sarcomeres shorten, the tension in them increases

Correct Answer
E. If sarcomeres shorten, the tension in them increases

Explanation
Sarcomeres are the basic contractile units of muscle fibers. When sarcomeres shorten, it means that the muscle is contracting. During contraction, the thick and thin filaments slide past each other, causing the sarcomeres to shorten. As the sarcomeres shorten, the tension in them increases, leading to muscle contraction and the generation of force. Therefore, the statement "if sarcomeres shorten, the tension in them increases" is true, as it aligns with the basic principles of muscle contraction.

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3

10.

Which of the following are sources of ATP for muscle contraction? 1) creatine phosphate, 2) glycolysis, 3) anaerobic cellular respiration 4) aerobic cellular respiration, 5) acetylcholine

A.

1,2, and 3
B.

2,3, and 4
C.

2,3 and 5
D.

1,2,3, and 4
E.

2,3,4, and 5

Correct Answer
D. 1,2,3, and 4

Explanation
The correct answer is 1,2,3, and 4. Creatine phosphate, glycolysis, anaerobic cellular respiration, and aerobic cellular respiration are all sources of ATP for muscle contraction. Creatine phosphate is used as a quick source of ATP during short bursts of intense activity. Glycolysis breaks down glucose to produce ATP in the absence of oxygen. Anaerobic cellular respiration also produces ATP from glucose, but without the need for oxygen. Aerobic cellular respiration is the most efficient way to produce ATP and requires oxygen. Acetylcholine is a neurotransmitter that is involved in muscle contraction, but it is not a direct source of ATP.

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11.

What would happen if ATP were suddenly unavailable after the sarcomere had begun to shorten?

A.

Nothing, the contraction would proceed normally
B.

The myosin heads would be unable to detach from actin
C.

Troponin would bind with the myosin heads
D.

Actin and myosin filaments would separate completely and be unable to recombine
E.

The myosin heads would detach completely from actin

Correct Answer
B. The myosin heads would be unable to detach from actin

Explanation
If ATP were suddenly unavailable after the sarcomere had begun to shorten, the myosin heads would be unable to detach from actin. ATP is required for the detachment of myosin heads from actin during muscle contraction. Without ATP, the myosin heads would remain bound to actin, preventing the relaxation of the muscle and leading to a continuous state of contraction.

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