Muscle Anatomy and Physiology Quiz

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Questions and Answers

What is the primary function of muscles in the body?

Store energy for physical activity

Contract or shorten to facilitate movement (correct)

Initiate nerve signals for movement

Support the skeletal structure

Which layer of connective tissue covers the entire skeletal muscle?

Epimysium (correct)

Fascia

Perimysium

Endomysium

Which type of muscle is characterized by striated appearance and voluntary control?

Skeletal muscle (correct)

Cardiac muscle

Myofibrillar muscle

Smooth muscle

What component primarily composes thick filaments in muscle fibers?

Myosin Signup and view all the answers

What separates individual muscle fibers within the fascicle?

Endomysium Signup and view all the answers

Which of the following is NOT a category of skeletal muscle proteins?

Structural proteins Signup and view all the answers

Fascia serves which primary purpose within the muscular system?

Separate muscles from each other and from the skin Signup and view all the answers

Which protein is primarily involved in the regulatory function of muscle contraction?

Myosin Signup and view all the answers

What role do desmin and filamin play in muscle structure?

They connect myofibrils to the sarcolemma and stabilize muscle structure. Signup and view all the answers

Which component becomes active first in the transmission of a nerve impulse to muscle contraction?

Release of acetylcholine from the nerve. Signup and view all the answers

What primarily causes the muscle contractions to occur at the molecular level?

The sliding of actin filaments over myosin filaments. Signup and view all the answers

Which structure acts as a specialized plasma membrane in muscle cells?

Sarcolemma Signup and view all the answers

What is the primary role of troponin and tropomyosin in muscle contraction?

They regulate the interaction between actin and myosin. Signup and view all the answers

What initiates the sliding filament model of muscle contraction?

The formation of crossbridges between myosin and actin. Signup and view all the answers

Which cellular structure is primarily involved in storing calcium ions for muscle contraction?

Sarcoplasmic reticulum Signup and view all the answers

What occurs during the power stroke phase of muscle contraction?

Thick filaments pull thin filaments towards the center of the sarcomere. Signup and view all the answers

Study Notes

Muscular System Overview

Muscles are responsible for all types of body movement
They contract or shorten, acting as the body's machines
Three main types: skeletal, cardiac, and smooth muscle

Learning Outcomes

Describe the microscopic anatomy of skeletal muscle fibers
Define sarcomere
Describe muscle proteins

Organization of Skeletal Muscle

Muscle belly -> Fascicle -> Muscle fiber (muscle cell) -> Myofibrils -> Myofilaments -> Sarcomere
Myofibrils: Structures within muscle fibers
Myofilaments: Proteins that make up the sarcomere
Myosin: Thick filaments
Actin: Thin filaments
Sarcomere: The functional unit of a muscle fiber, responsible for striated appearance

Skeletal Muscle Fiber Structure

Cells are multinucleated (multiple nuclei)
Nuclei are located just beneath the membrane
Sarcolemma: Specialized plasma membrane of the muscle cell
Myofibrils: Bundles of myofilaments within the muscle cell
Dark band (A-band) and Light band (I-band) visible under microscopy

Muscle Protein Types

Myofibrillar proteins: Contractile, structural, and regulatory proteins—including myosin and actin
Sarcoplasmic proteins: Essential for connecting myofibrils to the sarcolemma and maintaining muscle structure (e.g., desmin and filamin)
Stromal proteins: The primary component of connective tissue in the muscle; includes collagen (important), elastin, laminin, fibronectin, and proteoglycans. Cells like fibroblasts, macrophages, lymphoid, mast, and eosinophils are also present.

Skeletal Muscle Coverings

Epimysium: Covers the entire muscle
Perimysium: Surrounds bundles of muscle fibers (fascicles)
Endomysium: Separates individual muscle fibers
Fascia: Layer of fibrous tissue separating muscles from each other and the skin

Skeletal Muscle Attachments

Epimysium blends into a connective tissue attachment (tendon)
Tendon: Cord-like structure that connects muscle to bone
Muscle attachments include bones, cartilages, and connective tissue coverings

Physiology of Muscle Contraction

Skeletal muscles must be stimulated by a motor neuron to contract
Motor neuron: Nerve cell that transmits signals to muscle cells
Neurotransmitters are released to stimulate muscle contraction (e.g. acetylcholine)

Sliding Filament Theory

Muscle contraction occurs due to the sliding of actin and myosin filaments.
Thin actin filaments slide over thick myosin filaments, shortening the sarcomere, and thus the muscle.
Requires ATP (energy) and calcium ions.
Steps of Muscle Contraction:
- Influx of calcium initiates cross-bridge formation (actin and myosin)
- Myosin heads change shape and pull on the actin filaments, sliding them towards the center of the sarcomere.
- ATP causes myosin heads to detach from actin.
- The cycle is repeated, causing continuous muscle shortening.

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Description

Test your knowledge on the functions, proteins, and structures of muscles in the human body. This quiz covers key concepts such as muscle types, connective tissue layers, and molecular mechanisms of muscle contraction. Perfect for students studying anatomy and physiology.