Eccentric: Muscle elongates

Concentric: Muscle shortens

Action potential spreads via T-tubules, releasing calcium

Release of acetylcholine (ACh) causes sodium influx & depolarization

Synapse between neuron and muscle fiber

Z lines move closer

Zones of overlap widen

H and I bands narrow

Myofilaments: Thin (actin) and thick (myosin) filaments

Sarcoplasmic Reticulum (SR) stores/releases calcium

T-tubules transmit action potentials

Contain sarcolemma (cell membrane) and sarcoplasm (cytoplasm)

Large, multinucleate, and striated

Aponeurosis: Tendinous sheet

Tendon: Attaches muscles to bone

Endomysium: Surrounds individual muscle cells/fibers

Perimysium: Surrounds muscle fiber bundles (fascicles)

Epimysium: Outermost layer, surrounds muscle

Smooth Muscle: Involuntary, lines hollow organs

Cardiac Muscle: Involuntary, found in the heart

Skeletal Muscle: Voluntary, focus of this chapter

Chapter 12 will focus on the nervous system and its role in muscle control

Repetition and visualization key to mastering this complex subject

Understanding muscle fiber anatomy is crucial for grasping muscle function

Red Muscle (Slow Fibers): High endurance, more myoglobin

White Muscle (Fast Fibers): Quick contraction, low endurance

Fibrosis increases, recovery slows

Muscle fibers shrink, become less elastic

Muscle hypertrophy vs. atrophy

Intermediate Fibers: Have properties of both

Slow Fibers: Slow to contract, resist fatigue

Fast Fibers: Quick to contract, fatigue quickly

Oxygen debt occurs post-exercise

Muscle fibers store ATP and regenerate more during activity

ATP is primary energy source for contraction

Muscle tone maintains posture without movement

Elastic forces, opposing muscle groups, and gravity aid in relaxation

Isometric Contractions: Muscle length remains unchanged

Isotonic Contractions: Muscle changes length

ATP binds to myosin, re-cocks the head for repeated cycles

Power stroke pulls thin filaments towards center

Myosin heads bind to actin's active sites forming cross-bridges

Calcium binds to troponin, shifting tropomyosin, exposing active sites

Neuromuscular Junction (NMJ):

Action potentials trigger contractions

Thin filaments slide toward sarcomere center

During contraction:

I Bands: Contain Z lines and titan proteins

A Bands: Include M line, H band, and zone of overlap

Arrangement of thin and thick filaments creates striations

Smallest functional unit of muscle fiber

Myofibrils: Subdivisions within muscle cells responsible for contraction

Skeletal Muscle Fibers:

Collagen fibers from all layers converge to form:

Rich blood supply and nerves

Connective Tissue Layers:

Stores nutrients

Guards body entrances/exits, maintains temperature

Supports posture, body position, and soft tissues

Moves body by pulling on bones

Specialized for contraction

Three main types of muscle:

Repetition of content for better understanding

Focus on muscle tissue details

Looking Ahead

Summary and Review

Types of Muscle Fibers

Aging and Muscle Tissue

Muscle Performance

ATP and Muscle Metabolism

Muscle Relaxation

Types of Muscle Contractions

Cross-Bridge Cycle

Neuromuscular Junction and Action Potentials

Muscle Contraction: Sliding Filament Theory

Sarcomere Structure

Muscle Fiber Structure

Anatomy of Skeletal Muscle

Skeletal Muscle Overview

Introduction

Anatomy and Physiology Chapter 10: Muscle Tissue