Muscular System Overview

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Questions and Answers

What triggers the muscle contraction process?

Acetylcholine diffusing across the gap (correct)

The release of ATP

Calcium ions leaving the sarcolemma

Increase in muscle fiber temperature

The I band in a sarcomere contains only thick filaments.

False

What is the role of calcium ions (Ca2+) in muscle contraction?

Calcium ions expose binding sites on actin for myosin to attach.

At the neuromuscular junction, the neurotransmitter that signals muscle contraction is called __________.

acetylcholine Signup and view all the answers

Match the following structures with their functions:

Z line = Defines the boundary of a sarcomere T-tubules = Transmit the nerve impulse to the muscle fibers SR (Sarcoplasmic Reticulum) = Stores calcium ions Myofibrils = Contractile units of muscle fibers Signup and view all the answers

Which type of muscle is responsible for heat generation?

Skeletal muscle Signup and view all the answers

Smooth muscle is primarily under voluntary control.

False Signup and view all the answers

What is the primary function of cardiac muscle?

Pumping blood throughout the body Signup and view all the answers

During muscle contraction, muscle fibers are activated by __________.

signals from the nervous system Signup and view all the answers

Match the following muscle components with their descriptions:

Epimysium = Outer layer covering of a muscle Perimysium = Surrounds bundles of muscle fibers Endomysium = Covers individual muscle fibers Sarcoplasm = Cytoplasm of a muscle cell Signup and view all the answers

Which characteristic of muscle cells allows them to stretch without damage?

Extensibility Signup and view all the answers

The neuromuscular junction is involved in the contraction of smooth muscle.

False Signup and view all the answers

Name the muscle responsible for chewing.

Masseter Signup and view all the answers

Which of the following best describes cardiac muscle?

Involuntary, striated, and contains intercalated discs Signup and view all the answers

Smooth muscle cells have more than one nucleus per cell.

False Signup and view all the answers

What is the function of desmosomes in cardiac muscle cells?

To anchor actin and prevent cells from separating during contraction. Signup and view all the answers

Smooth muscle is responsible for involuntary actions such as ______ in the stomach.

churning food Signup and view all the answers

Match the muscle type with its characteristic:

Cardiac muscle = Involuntary, striated Skeletal muscle = Voluntary, striated Smooth muscle = Involuntary, non-striated Cardiac muscle cells = Contract without external signals Signup and view all the answers

Study Notes

Muscular System Overview

The muscular system is responsible for movement, posture, and heat generation.
Muscle cells are excitable, contractible, extensible, and elastic.
Muscle cells do not change length unless signaled.

Types of Muscle Tissue

Skeletal Muscle: Voluntary, striated, multinucleated, long cylindrical cells.
Cardiac Muscle: Involuntary, striated, branched, uni- or binucleate cells connected by intercalated discs. Found only in the heart.
Smooth Muscle: Involuntary, non-striated, fusiform, uninucleated cells. Found in the walls of internal organs and blood vessels.

Skeletal Muscle Structure

Epimysium: Outermost layer of connective tissue surrounding the entire muscle.
Perimysium: Connective tissue surrounding fascicles (bundles of muscle fibers).
Endomysium: Connective tissue surrounding individual muscle fibers (cells).
Muscle fiber (cell): Contains myofibrils.
Fascicles: Bundles of muscle fibers.

Skeletal Muscle Fiber Detail

Sarcolemma: Muscle cell membrane.
Sarcoplasmic Reticulum (SR): Stores calcium ions.
T-tubules: Extensions of sarcolemma, rapidly transmitting signals into the cell.
Myofibrils: Long protein filaments, containing sarcomeres.
Sarcomeres: Functional units of muscle contraction, composed of thick and thin filaments.
Actin (thin) filaments: Attached to Z lines.
Myosin (thick) filaments: Between actin filaments.
Z lines: Boundaries of sarcomeres.

Myofibril Structure Detail

I band: Light band, contains only actin filaments.
A band: Dark band, contains both actin and myosin filaments.
H zone: Middle of A band, contains only myosin filaments.
M line: Middle of H zone, connecting myosin filaments.
Sarcomere Shortening: Shortening of the sarcomere during muscle contraction—actin and myosin filaments slide past each other.

Muscle Contraction Mechanism

Neuromuscular Junction: Where nerve impulses stimulate muscle cells.
Acetylcholine (ACh): Released neurotransmitter.
Calcium Ions (Ca2+): Released from SR, initiates contraction.
ATP: Necessary for the sliding of actin and myosin filaments.

Chemistry of Muscle Contraction

ATP production: ADP + P = ATP.
Energy sources: Creatine phosphate, glycogen, myoglobin, aerobic metabolism, anaerobic metabolism (lactic acid).

Contraction Regulation

All-or-nothing principle: Muscle fibers either contract fully or not at all.
Twitch contraction: A single contraction-relaxation cycle.
Motor units: Motor neuron and all the muscle fibers it supplies (fine vs. gross control).

Other Important Information

Important muscles of the head and neck, abdomen, thoracic limbs, pelvic limbs, and respiration.
Muscles of respiration: The main muscles responsible for breathing.
Muscle types in the iris, lens, and airways
Cardiac muscle cells and their unique properties.
Intercalated discs: Intercellular junctions connecting heart muscle cells

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Description

Dive into the intricacies of the muscular system, which plays a critical role in movement, posture, and heat generation. This quiz covers types of muscle tissues, skeletal muscle structure, and the unique attributes of each muscle cell type. Test your knowledge on how these components work together to facilitate bodily functions.