Muscle Types and Contraction Mechanism

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Questions and Answers

What are the three types of muscles?

Skeletal, Cardiac, Smooth (correct)

Skeletal, Cardiac, Striated

Cardiac, Nervous, Smooth

Skeletal, Elastic, Nervous

What type of muscle is multinucleate?

Skeletal muscle

How many nuclei does cardiac muscle have?

Generally one nucleus

How many nuclei do smooth muscles have?

One nucleus Signup and view all the answers

What is muscle contraction?

Movement of microfilaments Signup and view all the answers

What do tendons connect?

Muscle to the bone Signup and view all the answers

What encloses a single muscle fiber?

Endomysium Signup and view all the answers

What wraps around a fascicle of muscle fibers?

Perimysium Signup and view all the answers

What covers the entire skeletal muscle?

Epimysium Signup and view all the answers

What do motor neurons stimulate to contract?

Skeletal muscles Signup and view all the answers

What neurotransmitter is associated with skeletal muscle?

Acetylcholine Signup and view all the answers

What is the function of myofibrils?

Long organelles inside the muscle cell Signup and view all the answers

Muscle contraction occurs when myosin heads attach to actin filaments.

True Signup and view all the answers

What is the bare zone that lacks actin filaments?

H Zone Signup and view all the answers

What is responsible for releasing and storing calcium in muscle cells?

Sarcoplasmic reticulum Signup and view all the answers

What is the ability of a muscle to shorten when stimulated?

Contractility Signup and view all the answers

What occurs in isotonic contractions?

Myofilaments slide past each other and the muscle shortens. Signup and view all the answers

What is muscle tone?

Different fibers contract at different times. Signup and view all the answers

What enhances muscle flexibility and resistance to fatigue?

Aerobic exercise Signup and view all the answers

What increases muscle size and strength?

Resistance exercise Signup and view all the answers

What are the five golden rules of skeletal muscle activity?

All muscles cross joints; bulk of muscle at proximal end; at least 2 attachments; muscles only pull; muscle insertion moves towards origin Signup and view all the answers

What is the term for decreasing the angle of a joint?

Flexion Signup and view all the answers

What is the term for increasing the angle of a joint?

Extension Signup and view all the answers

What combines flexion, extension, abduction, and adduction in a circular movement?

Circumduction Signup and view all the answers

Study Notes

Muscle Types

Three types of muscles: skeletal, cardiac, smooth.
Skeletal muscle is multinucleate; cardiac muscle generally has one nucleus; smooth muscle has one nucleus.

Muscle Structure

Skeletal and smooth muscle cells are elongated.
Striations present in skeletal and cardiac muscles.
Endomysium surrounds individual muscle fibers; perimysium wraps around fascicles; epimysium covers the entire skeletal muscle.
Fascia is located outside the epimysium.
Tendons connect muscles to bones and cross joints due to toughness.

Muscle Cells and Contraction Mechanism

Muscle contraction results from the movement of microfilaments.
Sarcolemma is a specialized plasma membrane in muscle cells.
Myofibrils, long organelles in muscle cells, contain distinct light (I band) and dark (A band) bands.
Sarcomeres are the contractile units with thick (myosin) and thin (actin) filaments.

Muscle Filaments

Myosin filaments contain ATPase enzymes and overlap slightly with actin filaments, which are anchored to the Z disc.
H Zone is a bare zone of the sarcomere that lacks actin filaments at rest.
Sarcoplasmic reticulum stores and releases calcium.

Muscle Properties

Excitability: ability to respond to stimuli.
Contractility: ability to shorten in response to stimuli.
Extensibility: capability to stretch.
Elasticity: ability to return to resting length after stretching.

Neural Stimulation

Motor neurons are necessary for skeletal muscle contraction.
The neuromuscular junction is the site where nerve impulses stimulate muscle contraction through neurotransmitters like acetylcholine.
Transmission of nerve impulses involves the release of neurotransmitters, generating action potential, and thereby facilitating muscle contraction.

Muscle Contraction Mechanisms

Sliding filament theory explains muscle contraction through the binding of myosin heads to actin, resulting in myofilament sliding and muscle shortening.
Muscle contractions can be graded by varying frequency and the number of muscle fibers stimulated.
Tetanus results from the summation of contractions, leading to sustained contraction.

Energy for Contraction

Initially, muscles use stored ATP for energy.
Creatine phosphate transfers energy to ADP, regenerating ATP quickly before depletion.
Aerobic respiration uses glucose to produce ATP requiring continuous oxygen; anaerobic glycolysis produces ATP rapidly but leads to lactic acid buildup.

Muscle Fatigue

Muscle fatigue occurs when muscles cannot contract even with stimulation, primarily due to oxygen debt and accumulating lactic acid.
Increasing acidity and lack of ATP diminish muscle contraction efficacy.

Types of Muscle Contractions

Isotonic contractions result in muscle shortening with movement.
Isometric contractions involve increased tension without muscle shortening.

Muscle Tone and Exercise

Muscle tone is maintained through the involuntary contraction of different fibers.
Aerobic exercise enhances muscle strength, flexibility, and overall metabolism.
Resistance exercise (Isometric) increases muscle strength and size.

Muscle Movement and Terms

Flexion decreases the joint angle, while extension increases it.
Abduction moves limbs away from the midline; adduction brings them closer.
Rotation occurs around a bone's axis; circumduction is a circular movement.
Various movements include dorsiflexion (lifting foot) and plantar flexion (pointing toes).

Muscle Anatomy

Key muscles include:
- Frontalis (raises eyebrows)
- Orbicularis oculi (closes eyes)
- Masseter (closes jaw)
- Pectoralis major (adducts humerus)

Muscle Classification

Muscles are named based on direction, size, location, number of origins, attachments, shape, and action.

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Description

This quiz explores the different types of muscles, their structures, and the mechanisms of contraction. Learn about skeletal, cardiac, and smooth muscles, along with the cellular components involved in muscle contraction. Test your knowledge on muscle anatomy and physiology.