Question 1

An important difference between single-unit and multiunit smooth muscle is the

Accepted Answer

The numerous gap junctions in single-unit smooth muscle allow many cells to work together as a sheet, resulting in coordinated contractions. In contrast, multiunit smooth muscle fibers function independently and do not have as many gap junctions between them.

Question 2

The force generated by a single muscle fiber can be increased by

Accepted Answer

The force generated by a single muscle fiber can be increased by increasing the frequency of action potentials only. This is known as temporal summation, where the muscle fiber is stimulated repeatedly and the force of contraction increases. Increasing the muscle length beyond optimal (option B) would actually decrease the force generated as it would result in a reduced overlap between the actin and myosin filaments. Increasing the asynchrony of recruitment (option C) would also not increase the force generated by a single muscle fiber. Option D is partially correct in that increasing the frequency of action potentials would increase the force generated, but increasing muscle length beyond optimal would not. Therefore, the best choice is A.

Question 3

Briefly compare and contrast the structure and behavior of cardiac, smooth, and skeletal muscles.

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Question 4

List, compare, and contrast the types of skeletal muscle fibers based on their speed of contraction and resistance to fatigue.Give examples of where each type might be found, and why it is advantageous for each type to occur there.

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Question 5

Define and explain the differences between slow wave potentials and pacemaker potentials in smooth muscle cells.

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Question 6

Compare and contrast the structural and functional differences between single-unit and multi-unit smooth muscle fibers, particularly in regard to their ability to vary their force of contraction.

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Question 7

Describe the process of relaxation of a skeletal muscle fiber.

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Question 8

List and explain the functions of the regulatory molecules in a sarcomere, specifying how the on and off positions are controlled and its impact on the crossbridges formed.

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Question 9

Relative to skeletal muscle, smooth muscle

Accepted Answer

Smooth muscle is more energy-efficient than skeletal muscle, allowing it to sustain contractions for longer periods without fatigue. Additionally, smooth muscle utilizes calcium ions from both the sarcoplasmic reticulum and the extracellular space to initiate and maintain contraction, unlike skeletal muscle which primarily relies on calcium from the sarcoplasmic reticulum.

Question 10

Myasthenia gravis is a disease characterized by reduction in the number of acetylcholine receptors on skeletal muscles.Which physiological process would be affected? What would someone afflicted by this disease experience? How may this disease be treated?

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Question 11

A construction worker entered the emergency room after an accident in which his leg was crushed by falling beams.A color of the urine sample is noticeably reddish brown.Assuming that color is related to the accident, what molecule could have been released from the damaged muscle cells that colored the urine? What is the function of this molecule?

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Question 12

The factor(s)that determine the duration of a twitch in various types of fibers is the speed of the

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Question 13

Put these myofibers in the order they would be recruited as the body moves from a weak to a strong stimulus:
1)glycolytic fast-twitch fibers
2)fatigue-resistant oxidative fast-twitch fibers
3)fatigue-resistant slow-twitch fibers

Accepted Answer

The myofibers would be recruited in the following order:
1) Fatigue-resistant slow-twitch fibers: These fibers are recruited first as they have a low threshold for activation and contribute to low-intensity activities or initial stages of exercise.
2) Fatigue-resistant oxidative fast-twitch fibers: As the intensity of the exercise increases, these fibers are recruited, which are more powerful than slow-twitch fibers but fatigue-resistant.
3) Glycolytic fast-twitch fibers: These fibers are recruited last as they have a high threshold for activation and are only activated during high-intensity activities or when the body is under extreme physiological stress.

Question 14

Explain the events leading up to a skeletal muscle twitch, starting with the arrival of neurotransmitter in the neuromuscular junction.

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Question 15

Outline and explain the cellular event that affects the force generated by smooth muscle cells.What are the initiating events, and how do these events affect force production by the smooth muscle cell? How can this process be activated without changes in membrane potential?

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Question 16

Describe the muscle condition called tetanus.Is this a normal or a pathological event? If it is normal, what is the function? If it is pathological, what is the cause? The bacterium Clostridium tetani causes a disease called tetanus or lockjaw; you may have been vaccinated against tetanus, especially if you ever had hospital treatment for a skin wound.Speculate on whether or not the name of this disease is related to the muscle condition and why the disease can be fatal.

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Question 17

Sketch and label a relaxed sarcomere, then draw the same sarcomere in a contracted state.The myofilaments may be represented as simple lines.

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Question 18

Factors playing a role in fatigue can be classified into two categories.Define those two categories and provide an example of each.

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Question 19

Skeletal muscle fibers with the greatest endurance rely on ________ for energy.

Accepted Answer

Skeletal muscle fibers with the greatest endurance rely on oxidative phosphorylation for energy. This is because oxidative phosphorylation produces ATP through the use of oxygen and a series of biochemical reactions that occur in the mitochondria. This process is more efficient and can produce ATP for longer periods of time compared to anaerobic glycolysis, which produces ATP through the breakdown of glucose without oxygen, and can lead to the accumulation of lactic acid. Ketone body degradation is not a significant source of energy for skeletal muscle fibers.

Question 20

Define and explain the difference between isotonic, isometric and eccentric contractions and give an example of a specific movement for each.What is the role of series elastic elements in muscle contraction?

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Quiz 12: Muscles