Unraveling the Secrets of Muscle Tension Quiz 4 (p 16-21)

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Questions and Answers

During the relaxation phase of muscle contraction, what happens to the actin filaments?

They overlap one another

They extend from two successive Z discs

They barely overlap one another (correct)

They shorten

What is the maximum strength of tetanic contraction of a muscle operating at a normal muscle length?

7-8 kg/cm²

1-2 kg/cm²

5-6 kg/cm²

3-4 kg/cm² (correct)

What is treppe, also known as the 'staircase effect'?

The decrease in muscle strength at the onset of contraction

The increase in muscle strength at the onset of contraction (correct)

The decrease in muscle strength during relaxation

The plateau in muscle strength during contraction

What occurs after the first five stimuli during temporal summation?

Increase in tension Signup and view all the answers

What are some factors that contribute to muscle fatigue?

All of the above Signup and view all the answers

What happens to the forcefulness of muscle contraction depending on the length of the sarcomeres within a muscle?

It decreases with longer sarcomeres Signup and view all the answers

Which type of motor units are recruited first during a muscle contraction?

Small motor units Signup and view all the answers

What is the purpose of the size principle of motor unit recruitment?

To conserve energy Signup and view all the answers

What happens to muscle tone when a nerve is damaged?

Muscle tone becomes flaccid Signup and view all the answers

What occurs during the latent phase of muscle twitch?

Depolarization of sarcolemma and T-tubules Signup and view all the answers

What is the mechanism of tetanization?

Fusing together successive contractions Signup and view all the answers

How does frequency summation contribute to muscle contraction?

By increasing the frequency of contraction Signup and view all the answers

Which type of muscle fiber arrangement has a parallel fiber arrangement and is capable of greater range of motion?

Strap/fusiform Signup and view all the answers

Which type of muscle fiber arrangement has an oblique arrangement resembling that found in a feather?

Pennate Signup and view all the answers

Which type of muscle is responsible for mobility (rotatory) and has its proximal attachment far from the joint axis?

Spurt muscles Signup and view all the answers

Which type of muscle fiber has a high proportion of FG fibers and is located superficially?

Phasic muscles Signup and view all the answers

Which architectural characteristic directly determines the amount of shortening or lengthening of a muscle fiber?

Fiber length Signup and view all the answers

What is the measure of the cross-sectional area of a muscle perpendicular to the orientation of the muscle fibers?

Physiologic cross-sectional area Signup and view all the answers

Which of the following factors can affect muscle strength?

Fiber composition Signup and view all the answers

In a first-class lever, where are the two resultant forces applied?

On opposite sides of the axis Signup and view all the answers

Which lever class has the moving force closer to the axis than the weight or resistance?

Third-class lever Signup and view all the answers

What is the formula for mechanical advantage in a lever system?

MA = FA/WA Signup and view all the answers

Which lever class provides a force advantage so that large things can be moved by a small force?

Second-class lever Signup and view all the answers

What is an example of a second-class lever in the human body?

Calf muscles lifting the body around the axis of the toes Signup and view all the answers

Which of the following is true about tension in an unstretched muscle that is stimulated?

Tension decreases due to overlapping thin filaments Signup and view all the answers

Which of the following is true about tension in a moderately stretched muscle that is stimulated?

Tension increases due to optimum overlapping of thick and thin filaments Signup and view all the answers

Which of the following is true about tension in an overstretched muscle that is stimulated?

Tension decreases due to crumpling thick filaments Signup and view all the answers

Which of the following is true about isotonic contraction?

The tension on the muscle remains constant throughout the contraction Signup and view all the answers

Which of the following is true about hypertrophy?

It occurs as a response to maximal contractions Signup and view all the answers

Which of the following is true about atrophy?

It results in a decrease in the quantity of actin and myosin filaments Signup and view all the answers

Study Notes

Muscle Contraction

During relaxation phase, actin filaments slide back to their original position.
Maximum strength of tetanic contraction of a muscle operating at a normal muscle length is 4-5 times the maximum strength of a single twitch.

Muscle Physiology

Treppe, also known as the 'staircase effect', is a gradual increase in muscle contraction force due to repeated stimulation.
After the first five stimuli during temporal summation, the muscle contraction force increases.
Factors that contribute to muscle fatigue include depletion of ATP and CP, increase in lactic acid, and decrease in pH.

Muscle Mechanics

Forcefulness of muscle contraction depends on the length of the sarcomeres within a muscle, with optimal force generated at resting length.
Slow-twitch motor units are recruited first during a muscle contraction.
The size principle of motor unit recruitment ensures that the smallest motor units are recruited first to achieve precise movements.
When a nerve is damaged, muscle tone decreases.

Muscle Twitch

During the latent phase of muscle twitch, there is a delay between the stimulation and the contraction of the muscle.
Mechanism of tetanization involves the rapid stimulation of a muscle, resulting in the summation of individual muscle twitches.

Muscle Fibers

Frequency summation contributes to muscle contraction by increasing the force of contraction through rapid stimulation.
Parallel fiber arrangement is found in muscles capable of greater range of motion.
Oblique fiber arrangement, resembling that found in a feather, is found in muscles with a complex architecture.
Rotatory muscles, responsible for mobility, have their proximal attachment far from the joint axis.
Superficial muscles with a high proportion of FG fibers have a high proportion of fast-twitch fibers.

Muscle Architecture

The amount of shortening or lengthening of a muscle fiber is directly determined by its architectural characteristic.
Cross-sectional area of a muscle perpendicular to the orientation of the muscle fibers is known as the physiological cross-sectional area (PCSA).

Muscle Strength

Factors that can affect muscle strength include muscle length, muscle fiber type, and neural drive.
In a first-class lever, the two resultant forces are applied on either side of the fulcrum.
Second-class lever has the moving force closer to the axis than the weight or resistance, providing a force advantage.
The formula for mechanical advantage in a lever system is output force / input force = distance of effort arm / distance of resistance arm.
Third-class lever provides a force advantage, allowing large things to be moved by a small force.
An example of a second-class lever in the human body is the wheelbarrow-like movement of the foot during plantarflexion.

Muscle Tension

In an unstretched muscle that is stimulated, tension increases rapidly to a maximum and then plateaus.
In a moderately stretched muscle that is stimulated, tension increases to a maximum and then decreases as the muscle shortens.
In an overstretched muscle that is stimulated, tension is minimal due to the decreased overlap of actin and myosin filaments.
Isotonic contraction is a type of muscle contraction where the muscle shortens while generating a constant tension.
Hypertrophy occurs when muscle fibers increase in size, leading to an increase in muscle strength.
Atrophy occurs when muscle fibers decrease in size, leading to a decrease in muscle strength.

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Description

Test your knowledge on the tension development in unstretched muscles and the factors that contribute to relatively weak contractions. This quiz explores the impact of overlapping thin filaments and crumpled thick filaments on cross bridge binding and sarcomere length.