4.2 Muscles A

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Questions and Answers

What is one of the primary functions of skeletal muscle?

Regulate blood pressure

Generate heat (correct)

Store excess lipids

Facilitate hormonal secretion

Which component is found at the neuromuscular junction?

Tendon fibers

Synaptic cleft (correct)

Sarcomeres

Myofibrils

What type of muscle tissue is involved in involuntary control and is responsible for pumping blood?

Smooth muscle

Skeletal muscle

Cardiac muscle (correct)

Striated muscle

What is the role of the H band in the sarcomere structure?

Only contains myosin filaments Signup and view all the answers

Which connective tissue surrounds individual muscle fibers?

Endomysium Signup and view all the answers

Which of the following describes the process of muscle contraction?

Filaments slide and shorten the muscle Signup and view all the answers

What type of muscle fibers are primarily responsible for voluntary movements?

Skeletal muscle fibers Signup and view all the answers

Which part of the sarcomere marks the boundary between adjacent sarcomeres?

Z line Signup and view all the answers

What triggers the release of acetylcholine (ACh) from the axon terminal?

The arrival of an electrical impulse Signup and view all the answers

What occurs when an action potential reaches the axon terminal?

Vesicles containing ACh undergo exocytosis Signup and view all the answers

How does ACh affect the muscle action potential?

It triggers a sudden influx of sodium ions Signup and view all the answers

What is the role of the synaptic cleft in neurotransmission?

It serves as the site of neurotransmitter release Signup and view all the answers

How is acetylcholine removed from the synaptic cleft?

By enzymatic breakdown and diffusion Signup and view all the answers

What defines an action potential in a neuron?

A sudden change in membrane potential Signup and view all the answers

What happens to the axon's permeability when ACh binds to receptors on the motor end plate?

It increases permeability to sodium ions Signup and view all the answers

Which ions are primarily responsible for the generation of an action potential in muscles?

Sodium ions Signup and view all the answers

What is the primary role of acetylcholinesterase (AChE) in the motor end plate?

To break down acetylcholine (ACh) Signup and view all the answers

Which characteristic distinguishes cardiac muscle tissue from other muscle types?

Found only in the heart Signup and view all the answers

What is the function of intercalated disks in cardiac muscle?

They provide electrical connectivity between cells Signup and view all the answers

How are smooth muscle contractions primarily controlled?

Hormonal signals Signup and view all the answers

Which feature is associated with the spontaneous activity of cardiac muscle cells?

Function of pacemaker cells Signup and view all the answers

Which of the following correctly describes smooth muscle tissue?

Typically has a sheathing role around organs Signup and view all the answers

Which factor affects the rate of heart contractions in cardiac muscle?

Nervous system action Signup and view all the answers

What is a primary distinguishing feature of skeletal muscle compared to cardiac muscle?

Multinucleated fibers Signup and view all the answers

Study Notes

Muscle Tissue Types

Muscle is one of the four primary tissue types.
There are three types of muscle tissue: skeletal, smooth, and cardiac.
Each type plays a vital role in the body, such as movement, circulation, and organ function.

Functions of Skeletal Muscle

Skeletal muscle is responsible for producing movement of the skeleton.
It helps maintain body posture and position.
Skeletal muscle supports soft tissues.
It guards body entrances and exits.
Skeletal muscle helps regulate body temperature.
It can act as a nutrient store.

Skeletal Muscle Structure

Skeletal muscle tissue is composed of muscle fibers, connective tissue, blood vessels, and nerves.
Connective tissue surrounds and supports muscle fibers, including the epimysium (outermost), perimysium (surrounding bundles), and endomysium (around individual fibers).

Skeletal Muscle Fibers

Each skeletal muscle fiber is composed of myofibrils, which are bundles of protein filaments.
Myofibrils contain two types of protein filaments: thin filaments (actin) and thick filaments (myosin).
Myofibrils are divided into segments called sarcomeres, which are the functional units of muscle contraction.

Sarcomere Structure

A band: Contains both thick and thin filaments, including the M line (center of the band) and H band (thick filaments only).
I band: Only contains thin filaments.
Z line: Marks the boundary between adjacent sarcomeres.

Sliding Filament Model

Muscle contraction is achieved through the sliding of thin and thick filaments over each other.
This sliding causes the sarcomere to shorten and the muscle to contract.

Muscle Action

Muscle contraction is an active process that involves muscle shortening.
Muscle lengthening occurs passively due to external forces.
Muscles can only pull, not push.

Neuromuscular Junction

This is the point where nerve signals are transmitted to muscle fibers.
The process involves the release of a neurotransmitter, acetylcholine (ACh), from the axon terminal of a motor neuron.
ACh diffuses across the synaptic cleft and binds to receptors on the muscle fiber.
This binding triggers an influx of sodium ions, generating an action potential that travels along the sarcolemma (muscle fiber membrane).
The action potential ultimately leads to muscle contraction.

Cardiac Muscle Tissue

Cardiac muscle is found only in the heart.
It is excitable tissue, meaning it can generate electrical signals.
Cardiac muscle cells are short and small, with a striated appearance.
Cells are connected via intercalated disks, which allow for electrical continuity.
Cardiac muscle relies heavily on aerobic metabolism for energy production.

Cardiac Muscle Activity

Intercalated disks allow the heart to function as a single, coordinated unit.
Cardiac muscle cells are spontaneously active, generating their own electrical impulses.
The heart has both faster (pacemakers) and slower cells (triggered), setting the rhythm of contraction.
The nervous system can modulate the heart rate and force of contraction.

Smooth Muscle Tissue

Smooth muscle differs from skeletal and cardiac muscle.
It plays a regulatory role in the body, found in organs like blood vessels, the integumentary system, and digestive tract.
Smooth muscle does not have striations, and its cells are smaller and elongated.
Contractions are often spontaneous and controlled primarily by hormones rather than nerve signals.
Smooth muscle has a ‘bunching-up’ effect as it contracts.

Comparing Muscle Tissue

skeletal muscle: Attached to bones, voluntary movement, striated
cardiac muscle: Found only in the heart, involuntary movement, striated, connected by intercalated disks
smooth muscle: Found in walls of organs, involuntary movement, not striated, cells are spindle-shaped

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Description

Explore the different types of muscle tissue, focusing primarily on skeletal muscle. Learn about the structure and functions of skeletal muscle, including its role in movement, posture, and temperature regulation. Test your knowledge about these vital tissues in the body.