Types of Muscle Tissue

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Questions and Answers

What is the primary function of skeletal muscles?

To enable voluntary body movements (correct)

To pump blood throughout the body

To line the digestive tract

To facilitate involuntary movements in organs

Which of the following is a characteristic of smooth muscles?

Involuntary control and non-striated appearance (correct)

Specialized to contract rapidly and fatigue quickly

Striated appearance and voluntary control

Highly vascularized and multinucleated fibers

What role does cardiac muscle play in the body?

Pumps blood through the circulatory system (correct)

Controls voluntary movements of limbs

Supports the movement of air in the lungs

Facilitates digestion by moving food

What is the action of actin and myosin in muscle contraction?

They interact to cause the contraction of muscles Signup and view all the answers

Which statement regarding cardiac muscle is true?

It has a striated appearance similar to skeletal muscle Signup and view all the answers

What is the primary role of myoglobin in muscle fibres?

To store oxygen for use during muscle contractions Signup and view all the answers

Which component regulates the entry and exit of materials in muscle fibres?

Sarcolemma Signup and view all the answers

What is the function of the sarcoplasmic reticulum in muscle contraction?

Storage and release of calcium ions Signup and view all the answers

What occurs when myosin heads attach to actin during muscle contraction?

They pull actin filaments inward Signup and view all the answers

What initiates the sliding process of actin and myosin during muscle contraction?

Binding of calcium to troponin Signup and view all the answers

What prevents contraction when a muscle is relaxed?

Troponin-tropomyosin complex covering actin sites Signup and view all the answers

Which proteins block myosin attachment sites on actin when muscle contractions are not occurring?

Tropomyosin and troponin Signup and view all the answers

The shortening of the muscle occurs due to which mechanism during contraction?

Pulling the actin past myosin Signup and view all the answers

What structure within muscle fibres contains organized bundles of myofilaments?

Myofibrils Signup and view all the answers

When calcium ions are released from the sarcoplasmic reticulum during contraction, what is the consequence?

The troponin-tropomyosin complex exposes actin binding sites Signup and view all the answers

Study Notes

Types of Muscle Tissue

Skeletal muscles are responsible for movement of the skeleton.
Smooth muscles are found in internal organs and blood vessels.
Cardiac muscles are found in the heart.

Traits of Skeletal Muscles

Voluntary control
Striated appearance
Multi-nucleated cells
Responsible for locomotion and movements of the skeleton

Traits of Smooth Muscles

Involuntary control
Non-striated appearance
Single-nucleated cells
Responsible for involuntary movements in internal organs

Traits of Cardiac Muscles

Involuntary control
Striated appearance
Single-nucleated cells
Responsible for pumping blood throughout the body

Skeletal Muscle Structures and Functions

Muscle fiber: Single muscle cell responsible for muscle contractions.
Myoglobin: Stores oxygen for muscle contractions.
Sarcolemma: Membrane of the muscle fiber, regulates material exchange.
Sarcoplasm: Cytoplasm of a muscle fiber, site of cellular processes and stores glycogen (energy source).
Sarcoplasmic Reticulum: Smooth endoplasmic reticulum in muscle fiber, stores calcium ions.
Myofibrils: Bundles of myofilaments, cylindrical structures within muscle fibers, containing protein filaments responsible for contractions.
Myofilament (thick) – Myosin: Protein filaments (~11 nm), bind to actin and cause contractions.
Myofilament (thin) – Actin: Protein filaments (~5 nm), bind to myosin and cause contractions.
When muscles contract, they shorten, causing movement.
Muscles are arranged in antagonistic pairs (e.g., biceps and triceps), where one muscle contracts while the other relaxes.

Mechanism of Muscle Fibre Contraction

Structure of Myofilaments

Actin Myofilaments: Composed of globular actin proteins; contain tropomyosin (blocks myosin binding sites when needed) and troponin (calcium-binding protein).
Myosin Filaments: Two polypeptide chains wrapped around each other, with globular heads (myosin heads) protruding at regular intervals, capable of binding to actin and causing motion.

The Sliding Filament Model of Muscle Contraction

During muscle contraction, the actin filaments slide past the myosin filaments, shortening the muscle fiber.
Myosin Attach: Myosin heads bind to actin binding sites.
Myosin Flex: Myosin heads pivot, pulling the actin filaments.
Myosin Release: Myosin heads detach from actin sites.
Myosin Reattach: Myosin heads reattach to new actin sites further along the filament.
The actin filaments are pulled towards the center of the sarcomere, and the Z lines move closer together. The sarcomere shortens, and the muscle fiber contracts.
The myosin heads are alternately pulling opposite sides of the actin filament.
Muscle shortening causes change in the arrangement of molecules in the plasma membrane.

Muscle Contraction

Relaxed muscle: Tropomyosin blocks actin binding sites, preventing myosin interaction.
Muscle contraction: Calcium ions bind to troponin, causing a shift in the position of tropomyosin, exposing the binding sites on actin for myosin.
Calcium ions are stored in the sarcoplasmic reticulum. The release of calcium ions is triggered by nerve impulses causing a signal cascade leading to the release.
Calcium ions are released into the sarcoplasm which causes contraction.

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Description

This quiz covers the three main types of muscle tissue: skeletal, smooth, and cardiac. You will learn about their traits, structures, and functions, enhancing your understanding of how they contribute to bodily movements and functions.