Muscle Physiology Quiz

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Questions and Answers

What is the primary characteristic of fast-twitch muscle fibers?

Adapted for sustained endurance activities

Have a large number of mitochondria

Rich in glycogen and generate power quickly (correct)

High oxidative capacity

How does endurance training affect intermediate fibers?

Decreases their number significantly

Turns them into slow-twitch fibers

Increases their resistance to fatigue (correct)

Has no impact on their oxidative capacity

What factor primarily contributes to muscular hypertrophy?

Reduction in muscle use

High-resistance exercises leading to myofibril thickening (correct)

High-repetition resistance training

Frequent endurance training

What is a consequence of muscular atrophy?

Reduction in the size and power of a muscle Signup and view all the answers

What role does glycogen depletion play in exercise limitation?

Limits exercise due to lactic acid buildup Signup and view all the answers

How do skeletal muscles assist in maintaining body temperature?

By causing shivering which generates heat Signup and view all the answers

What role do intercostal muscles play in the respiratory system?

They assist in the movement of oxygen into the bloodstream Signup and view all the answers

Which of the following best describes the muscular system's relationship with the circulatory system?

Muscles help return venous blood to the heart Signup and view all the answers

What is the function of smooth muscle contraction in the digestive system?

To assist in the movement of food through peristalsis Signup and view all the answers

How do smooth muscles help in the excretory system?

By aiding in the regulation of bladder sphincters Signup and view all the answers

What characterizes the latent period in a muscle twitch?

It is the time from nerve stimulation to contraction. Signup and view all the answers

Which statement accurately describes muscle contraction strength?

It varies based on the number of muscle fibers contracting. Signup and view all the answers

What happens during summation in muscle fibers?

Muscle twitches add together to produce a stronger contraction. Signup and view all the answers

What best describes the muscle condition known as tetanus?

A state of constant contraction with fused twitches. Signup and view all the answers

Which type of muscle fibers are associated with endurance activities?

Slow-twitch fibers (Type I) due to their resistance to fatigue. Signup and view all the answers

What is the primary energy production method for slow-twitch muscles?

Aerobic metabolism for prolonged ATP production. Signup and view all the answers

Which factor differentiates slow-twitch fibers from fast-twitch fibers?

The amount of myoglobin present. Signup and view all the answers

What effect does fatigue have on muscle contraction?

Stops contractions despite stimulation. Signup and view all the answers

What happens to muscle fibers if they start dying?

They cannot be replaced and it leads to permanent loss of function. Signup and view all the answers

Which condition is characterized by skeletal muscle degeneration replaced by fatty and fibrous tissue?

Dystrophy Signup and view all the answers

What causes the paralysis associated with botulism?

Toxin that inhibits the release of acetylcholine Signup and view all the answers

Which of the following can trigger muscle cramps?

Low blood glucose Signup and view all the answers

What is a characteristic of fibromyalgia?

It causes chronic muscular pain and tenderness. Signup and view all the answers

What occurs in crush syndrome?

High fever and heart irregularities from potassium release. Signup and view all the answers

When does delayed muscle soreness typically occur?

From several hours to a day post-exercise. Signup and view all the answers

What role do muscles play in maintaining homeostasis?

Muscles allow movement to respond to environmental changes. Signup and view all the answers

Signup and view all the answers

Study Notes

Muscle Twitch

A muscle twitch occurs when a nerve stimulates the muscle to contract
The twitch has a latent period, the time between nerve stimulation and the start of contraction
The latent period is followed by a contraction period and then a relaxation period
The contraction results in a maximal, all-or-none response
The strength of contraction varies depending on the number of muscle fibers contracting

Muscle Twitch Summation and Tetanus

If stimuli reach a muscle fiber continuously, the twitches are added together in a process called summation
A sustained contraction, or tetanus, occurs when the muscle is in a constant state of contraction
Individual twitches are fused into a straight line on a graph, during a state of tetanus
Tetanus continues until the muscle fatigues; then no contraction can occur

Skeletal Muscle Fibre Types

There are two main types of skeletal muscle fibers: slow-twitch and fast-twitch
Slow-twitch (Type I) fibers are dark in color, contain lots of myoglobin, and have many surrounding capillaries
Fast-twitch (Type II) fibers are light in color, contain little or no myoglobin, and have fewer blood vessels
Slow-twitch fibers contract slowly but resist fatigue, have more endurance, produce ATP aerobically and are best suited for endurance activities (e.g., biking, swimming)
Fast-twitch fibers are adapted for rapid generation of power but fatigue quickly, depend on anaerobic energy production putting them at risk of lactate accumulation and are suited for short-term, power activities (e.g., sprinting, tennis)

Intermediate Fibres

Intermediate muscle fibres are fast-twitch but have a high oxidative capacity
More resistant to fatigue
Endurance training increases the proportion of intermediate fibers
Genetics also plays a role in the proportion of different fiber types

The Value of Exercise

The depletion of muscle glycogen and the build-up of lactic acid limits exercise capacity
Frequent exercise increases aerobic capacity, allowing more exercise before fatigue occurs
Endurance training does not increase the size of muscles, but resistance training does
Resistance training thickens fast-twitch muscle fibers through hypertrophy (growth of myofibrils)
Myofibrils increase in size and number, leading to increased muscle size

Complications of the Muscular System

Muscles are vulnerable to injuries from sudden stress
Lack of use can impair muscle activity
Regular exercise allows muscles to develop and use energy more efficiently

Muscular Atrophy

Atrophy is a reduction in the size, tone, and power of a muscle, coming from the Greek meaning "without nourishment"
Even temporary reduced muscle use can lead to atrophy
Atrophy can be reversed if the muscle fibers are not dying
Permanent loss of function can occur if muscle fibers start dying and are not replaced

Muscular System Disorders

Muscular dystrophy is a collective term for several hereditary conditions where skeletal muscles degenerate
Botulism is a potentially fatal muscular paralysis caused by a toxin produced by the bacterium Clostridium botulinum
Muscle cramps are painful muscle spasms caused by strenuous exercise, dehydration, etc.
Muscle contractures are abnormal muscle shortening not caused by nerve stimulation, resulting from inability to remove calcium ions

Common Injuries to Muscular System

Common injuries to the muscular system include torn muscles, stretched tendons, torn ligaments, and joint sprains. Tendons connect muscles to bones, ligaments connect bones to bones (within joints)

Muscles and Homeostasis

Movement is essential for maintaining homeostasis; the body responds to environmental changes through movement (e.g., seeking shade from sun)
The muscular system is connected to all other body systems.
The circulatory, respiratory, digestive, and excretory systems have relationships with the muscular system.

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Description

Test your knowledge on muscle twitch mechanisms, including the phases of contraction, summation, and the types of skeletal muscle fibers. Understand how nerve stimulation leads to muscular responses and the differences between slow-twitch and fast-twitch fibers.