Muscle Tissue

Overview of Muscle Tissue

Chapter 10

  • Types of Muscle Tissue:

    • Skeletal Muscle: Voluntary, striated, moves bones.

    • Cardiac Muscle: Involuntary, striated, found in the heart.

    • Smooth Muscle: Involuntary, non-striated, in hollow organs.

Functions of Muscle Tissue

  • Produces movement.

  • Stabilizes body positions.

  • Supports soft tissues.

  • Moves substances internally.

  • Generates heat.

  • Stores nutrients.

Properties of Muscle Tissue

  • Excitability: Response to stimulus.

  • Contractility: Ability to contract forcefully.

  • Extensibility: Can stretch without damage.

  • Elasticity: Returns to original length.

Skeletal Muscle Connective Tissue Components

  • Fascia: Surrounds muscles.

  • Epimysium: Outermost layer.

  • Perimysium: Surrounds bundles of fascicles.

  • Endomysium: Surrounds individual fibers.

  • Tendon: Attaches muscle to bone.

  • Aponeurosis: Broad, flattened tendon.

Nerve and Blood Supply of Skeletal Muscle

  • Somatic motor neurons stimulate muscle contraction.

  • Muscle fibers closely contact capillaries.

Microscopic Anatomy of Skeletal Muscle

  • Skeletal muscle fibers number established prenatally.

  • Growth through hypertrophy, stimulated by hormones like testosterone.

Skeletal Muscle Terminology

  • Sarcolemma: Muscle cell membrane.

  • T-tubules: Conducts action potentials.

  • Sarcoplasma: Cytoplasm of muscle fiber.

  • Myofibrils: Structures responsible for contraction.

  • Sarcoplasmic Reticulum (SR): Stores calcium.

Muscle Contraction Mechanism

  • Sliding Filament Model: Myosin heads pull thin filaments towards the sarcomere center, shortening the muscle.

  • Contraction Cycle: Involves calcium binding to troponin, ATP hydrolysis, and cross-bridges formation and detachment.

Muscle Tension Control

  • Types of Contraction:

    • Isotonic: Muscle changes length at constant tension.

    • Isometric: Muscle length remains unchanged under tension.

Muscle Metabolism

  • ATP produced via:

    • Creatine Phosphate (15 seconds).

    • Anaerobic Respiration (30-40 seconds, producing lactic acid if oxygen is low).

    • Aerobic Respiration (for longer durations, yielding 36 ATP per glucose).

Muscle Fatigue and Recovery

  • Caused by depletion of ATP, creatine phosphate, and accumulation of lactic acid.

  • Oxygen Debt: Heavy breathing post-exercise restores oxygen levels and ATP/creatine phosphate synthesis.

Types of Skeletal Muscle Fibers

  • Slow Oxidative Fibers (SO): Endurance, high myoglobin.

  • Fast Oxidative-Glycolytic Fibers (FOG): Moderate endurance, intermediate recruitment.

  • Fast Glycolytic Fibers (FG): Quick fatigue, low myoglobin, high intensity movements.

Cardiac Muscle Tissue Features

  • Connected by intercalated discs for synchronized contraction.

  • Relies predominantly on aerobic respiration.

Smooth Muscle Tissue Characteristics

  • Non-striated, involuntary, slow contractions.

  • Primarily regulated by the autonomic nervous system and hormones.