Muscle Tissue Types and Functions

Types of Muscle Tissue

• Smooth Muscle: Found in hollow organs, vessels, and respiratory passageways. Cells are tapered, have a single nucleus, and are non-striated. Involuntary muscle that contracts and relaxes slowly. Responsible for peristalsis.
• Cardiac Muscle: Found in the heart wall. Cells are branched, have a single nucleus, and are lightly striated. Involuntary and self-excitatory.
• Skeletal Muscle: Most are attached to bones and move the skeleton. Cells are long, cylindrical, have multiple nuclei, and are heavily striated. Voluntary muscle that contracts and relaxes rapidly. Works in pairs (antagonist).

Muscle Functions

• Movement of skeleton.
• Maintenance of posture.
• Generation of heat.

Structure of Muscles

• Surrounded by connective tissue:
  • Endomysium surrounds individual fibers.
  • Perimysium surrounds fascicles (bundles).
  • Epimysium surrounds the whole muscle.
• Individual cells within a muscle are called muscle fibers.

Neuromuscular Junction

• Point where a nerve fiber stimulates a muscle cell.
• Neurotransmitter: Acetylcholine (Ach) generates an action potential.
• Motor end plate: membrane of the muscle cell.

Muscle Fiber

• Myofibrils: Bundles of myofilaments that contract.
• Sarcomeres: Units within myofibrils.
• Myofilaments: Actin (thin, light filaments) and myosin (thick, dark filaments with projecting heads). When muscle fibers are stimulated to contract, myofilaments slide past one another, shortening the sarcomeres.

Muscle Contraction

• Sliding Filament Theory: Actin and myosin filaments slide past one another to shorten the muscle.
• Role of Calcium: Uncovers binding sites on actin, allowing cross-bridges to form between actin and myosin.

Energy Sources for Muscle Contraction

• ATP (Adenosine triphosphate): Provides energy for muscle contraction.
• Myoglobin: Stores oxygen within muscle cells.
• Glycogen: Stores glucose within muscle cells.
• Creatine Phosphate: Stores energy for quick bursts of muscle activity.

Oxygen Debt and Muscle Fatigue

• Oxygen Debt: Develops during strenuous exercise when oxygen supply is insufficient.
• Anaerobic Metabolism: Produces lactic acid, causing muscle fatigue.
• Recovery Oxygen Consumption: Removes lactic acid and replenishes energy-storing compounds.

Effects of Exercise

• Structural and functional changes in muscle cells.
• Vasodilation increases blood flow to muscle tissue.
• Strengthened heart.
• Improved breathing capacity.

Types of Muscle Contractions

• Tonus: A state of slight contraction.
• Isotonic Contractions: Muscle shortens and creates movement.
• Isometric Contractions: Muscle remains the same length but tension increases.
• Tetanus: Sustained muscle contraction.

Muscle Disorders

• Myasthenia Gravis: Autoimmune disease affecting neuromuscular junctions.
• Muscular Dystrophy: Group of inherited diseases that cause muscle weakness and degeneration.
• Fibromyalgia: Chronic condition causing widespread musculoskeletal pain and fatigue.
• Sprains and Strains: Injuries affecting ligaments and muscles, respectively.