Question 1

Following death, rigor mortis occurs due to a lack of (calcium / ATP).

Accepted Answer

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Question 2

While muscle cells respond in an all -or -nothing manner to a single action potential, the extent of force that they generate can be modified by a number of factors. Describe the mechanisms whereby individual skeletal muscle cells can modify force development.

Accepted Answer

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Question 3

Smooth and cardiac muscle are innervated by the autonomic nervous system, whereas skeletal muscle is innervated by the somatic nervous system.

Accepted Answer

Smooth and cardiac muscles are controlled involuntarily by the autonomic nervous system, while skeletal muscle is controlled voluntarily and innervated by the somatic nervous system.

Question 4

There is no summation of cardiac muscle.

Accepted Answer

Cardiac muscle cells are connected by intercalated discs that allow for rapid transmission of electrical impulses, enabling the heart to contract as a unit without the summation of contractions seen in skeletal muscle.

Question 5

The speed with which smooth muscle cells contract is similar to fast glycolytic skeletal muscle cells.

Accepted Answer

Smooth muscle cells contract more slowly than fast glycolytic skeletal muscle cells, which are designed for quick, powerful movements.

Question 6

Another name for a muscle cell is (myofibril / muscle fiber).

Accepted Answer

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Question 7

Spontaneous depolarization of smooth muscle cells is mediated by pacemaker cells.

Accepted Answer

Pacemaker cells, which are specialized cells capable of spontaneous depolarization, help regulate the contraction of smooth muscle cells in certain organs, such as the gastrointestinal tract, by setting the pace for their rhythmic activity.

Question 8

In order for skeletal muscle to develop force, a muscle cell must be able to convert the action potential generated at a neuromuscular junction into crossbridge cycling. Describe the process of excitation -contraction coupling in skeletal muscle, including all of the important ion channels and the structures involved in this process.

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Question 9

In human skeletal muscle, a number of different fiber types exist. Describe the properties of the fibers that make them unique and how that is linked to motor units.

Accepted Answer

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Question 10

Energy in the form of ATP is essential to the contractile process. Describe the cellular sources of energy for skeletal muscle fibers and how those energy sources play a role maintaining muscle activity at low -and high -intensities of activity.

Accepted Answer

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Question 11

Force development by muscle cells requires an interaction between actin and myosin. Describe the proteins involved in the development of force through the process of the sliding -filament theory, including crossbridge cycling.

Accepted Answer

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Question 12

Action potentials in cardiac muscle last longer than action potentials in skeletal muscle.

Accepted Answer

Cardiac muscle action potentials have a longer duration due to a plateau phase, which is not present in skeletal muscle action potentials. This plateau is caused by prolonged calcium ion influx, extending the total duration of the action potential in cardiac cells.

Question 13

While contractile proteins are similar in skeletal and smooth muscle cells, the structure and regulation of muscle contraction is quite different. Describe the arrangement of contractile proteins in smooth muscle cells and how contraction is mediated.

Accepted Answer

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Question 14

(Dihydropyridine / Ryanodine) receptors are located on the sarcoplasmic reticulum.

Accepted Answer

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Question 15

Oxidative phosphorylation is the primary energy source for cardiac muscle.

Accepted Answer

Cardiac muscle relies heavily on oxidative phosphorylation for its energy needs due to its constant activity and high demand for ATP, utilizing oxygen and nutrients from the blood to generate energy efficiently.

Question 16

Slow -wave potentials are caused by cyclical fluctuations in opening and closing of potassium channels.

Accepted Answer

Slow-wave potentials are primarily caused by cyclical fluctuations in the opening and closing of calcium channels, not potassium channels.

Question 17

Receptor types at the motor end plate are (muscarinic / nicotinic) cholinergic receptors.

Accepted Answer

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Question 18

Training induces a number of changes within skeletal muscle that are specific to the type of training employed. Describe the changes that occur in skeletal muscle in response to training.

Accepted Answer

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Question 19

Pacemaker activity occurs in certain smooth muscle cells and cardiac muscle cells.

Accepted Answer

Pacemaker activity refers to the ability of certain cells to spontaneously generate electrical impulses that trigger muscle contractions. This activity is characteristic of some smooth muscle cells, such as those in the gastrointestinal tract, and cardiac muscle cells, particularly those in the sinoatrial node of the heart, which acts as the heart's natural pacemaker.

Question 20

Irrespective of an individual muscle cell's ability to regulate the amount of force developed by that cell, the force generated by a skeletal muscle is also controlled at the whole muscle level. Describe the mechanism whereby force of a whole muscle can be modified, including a discussion on motor units.

Accepted Answer

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Quiz 12: Muscle Physiology