Question 1

In the body, the muscles are so positioned that their relaxed length is significantly less than their optimal length

Accepted Answer

Muscles are generally positioned in the body so that their relaxed length is close to their optimal length, allowing for efficient contraction and force generation.

Question 2

The larger the motor units within a muscle, the more precisely controlled the gradations of contraction.

Accepted Answer

The smaller the motor units within a muscle, the more precisely controlled the gradations of contraction.

Question 3

More tension is developed during twitch summation than during a single twitch because the duration of elevated cytosolic Ca²⁺ concentration increases during summation, thus increasing the availability of cross-bridge binding sites.

Accepted Answer

During twitch summation, the frequency of action potentials increases, leading to prolonged calcium release from the sarcoplasmic reticulum. This results in a longer duration of elevated cytosolic Ca²⁺ concentration, which increases the availability of cross-bridge binding sites. As a result, more cross-bridges can form, leading to increased muscle tension.

Question 4

The smaller the load, the lower the velocity at which the muscle fiber shortens during an isotonic tetanic contraction.

Accepted Answer

In an isotonic tetanic contraction, the muscle fiber shortens faster with a smaller load, not slower.

Question 5

The term excitation-contraction coupling refers to the series of events linking signals from the brain to the spinal cord.

Accepted Answer

Excitation-contraction coupling refers to the series of events linking electrical stimulation of muscle cells to contraction.

Question 6

Muscles that have a fine degree of control have small motor units.

Accepted Answer

Muscles that require precise and delicate movements, such as those in the fingers and face, have small motor units. This is because each motor unit only controls a few muscle fibers, allowing for greater control and precision in movement.

Question 7

Tetanus occurs when a muscle fiber is stimulated so rapidly that it is not allowed to relax between stimulations, resulting in a smooth, sustained contraction.

Accepted Answer

Tetanus is a condition of sustained muscle contraction caused by repetitive stimulation, which prevents the muscle from relaxing between contractions.

Question 8

Summation events result from increasing amounts of cytoplasmic calcium levels.

Accepted Answer

Summation events occur when the cytoplasmic calcium levels increase, allowing for multiple action potentials to be generated in rapid succession. This leads to stronger and more sustained muscle contractions.

Question 9

Rigor mortis occurs when Ca²⁺ links actin and the myosin globular head together in a rigor complex.

Accepted Answer

The answer of Rigor mortis occurs when Ca²⁺ links actin...

Question 10

A motor unit is a single muscle plus all of the motor neurons that innervate it.

Accepted Answer

The answer of A motor unit is a single muscle...

Question 11

Muscles with small motor units can be controlled in a precise manner.

Accepted Answer

Small motor units contain fewer muscle fibers and have a smaller neuron-to-muscle fiber ratio. This means that each individual muscle fiber has a more direct connection to a motor neuron, allowing for more precise control over the muscle's movements.

Question 12

With twitch summation, the muscle fiber is stimulated so rapidly that it does not have an opportunity to return to resting potential between stimuli.

Accepted Answer

The answer of With twitch summation, the muscle fiber is...

Question 13

Gradation of muscle contraction can be accomplished by stimulating variable portions of each motor unit.

Accepted Answer

Gradation of muscle contraction is achieved by recruiting different numbers of motor units, not by stimulating variable portions of each motor unit.

Question 14

The greater the load, the lower the velocity at which the muscle fiber shortens.

Accepted Answer

This is known as the force-velocity relationship in muscle physiology. As the load on the muscle increases, the maximum velocity at which it can contract (i.e. shorten) decreases. This means that when a muscle is lifting a heavy load, it will contract more slowly than when it is lifting a lighter load.

Question 15

At Io, a muscle is maximally stretched so that it can develop the most tension upon contraction, because the thin filaments can slide in a maximal distance.

Accepted Answer

The maximal tension is developed when the muscle is at its optimal length, not when it is maximally stretched. At optimal length, there is the greatest overlap between actin and myosin filaments, allowing for maximal cross-bridge formation and tension development.

Question 16

ATP expenditure is required for both contraction and relaxation of a muscle fiber.

Accepted Answer

Contraction and relaxation of a muscle fiber both require ATP expenditure. During contraction, ATP is hydrolyzed to provide energy that powers the sliding of actin and myosin filaments. During relaxation, ATP is needed to pump calcium ions back into the sarcoplasmic reticulum, allowing the muscle to return to its resting state.

Question 17

Increasing the number of recruited motor units in a muscle increases its force or strength of contraction.

Accepted Answer

This statement is true. The more motor units that are recruited in a muscle, the more muscle fibers are activated to contract, resulting in a stronger force of contraction.

Question 18

The metabolic capability of a muscle fiber can affect the degree of tension it can develop.

Accepted Answer

The ability of a muscle fiber to generate tension depends on its metabolic capability, particularly its ability to produce ATP for muscle contraction. Therefore, a muscle fiber with higher metabolic capacity will have the potential to develop greater tension.

Question 19

In general, the contraction of skeletal muscle lasts longer than contraction of smooth muscle.

Accepted Answer

Smooth muscle contractions are generally longer-lasting than skeletal muscle contractions due to differences in their cellular structure and function.

Question 20

The shorter a muscle fiber is before the onset of a contraction, the greater the force that can be developed upon the subsequent contraction because the thin filaments are already partially slid inward.

Accepted Answer

The answer of The shorter a muscle fiber is before...

Quiz 8: Muscle Physiology