Muscle Tissue Overview

Muscle Tissue

• Composed of specialized muscle tissues that contract and relax to create movement.
• Latin word "mus" means "mouse."
• Found throughout the body, under skin, within organs, and blood vessels.
• Muscle size and location influence body shape and movement.
• Functions: movement, shape, stabilize position, produce heat, maintain homeostasis.
• Characteristics:
  • Contractility: ability to shorten.
  • Excitability: capacity to respond to a stimulus (reflexes).
  • Extensibility: stretch beyond resting length and still contract.
  • Elasticity: recoil to resting length after stretching.
• Types:
  • Skeletal Muscle:
    • Strong, fast, voluntary contractions.
    • Striations, multiple nuclei, attached to skeleton.
  • Cardiac Muscle:
    • Strong, continuous, involuntary contractions.
    • Intercalated disks, single nuclei, heart walls.
  • Smooth Muscle:
    • Weak, slow, involuntary contractions.
    • No striations, single nuclei, walls of hollow organs.
  • Tendons: connect muscles to bones.

Anatomy of Skeletal Muscle

• Epimysium: connective tissue surrounding the entire muscle.
• Perimysium: connective tissue surrounding fascicles (bundles of muscle fibers).
• Endomysium: connective tissue surrounding individual muscle cells (fibers).
• Myofibrils: threadlike structures within muscle fibers containing contractile proteins.
  • Myosin: thick filaments, bind to ATP and actin. Myosin head is crucial for separation.
  • Actin: thin filaments, bound with troponin and tropomyosin. Troponin and tropomyosin cannot bind
  • Sarcomere: repeating unit of thick and thin filaments, basic contractile unit.
    • Z Line: actin attachment, sarcomere boundary.
    • M Line: myosin attachment.
    • A Band: Myosin and actin overlap.
    • H Zone and I Band: spaces that shorten during contraction.
• Sarcoplasm: muscle cell cytoplasm.
• Sarcoplasmic Reticulum: muscle cell's smooth endoplasmic reticulum.
• Sarcolemma: muscle cell membrane.

Sliding Filament Theory

• Z lines move closer.
• Mechanism by which sarcomeres shorten during contraction.

Posterior Muscle Group

• Trapezius
• Triceps brachii
• Latissimus dorsi
• Gluteus maximus
• Hamstrings (Biceps femoris, Semitendinosus, Semimembranosus)
• Gastrocnemius
• Soleus
• Erector spinae

Types of Motion

• Gliding: one flat bone slides over another.
• Angular: increase/decrease angle between bones
  • Flexion: decrease angle.
  • Extension: increase angle.
  • Hyperextension: excess extension.
  • Dorsiflexion (foot): lift the foot upward.
  • Plantarflexion (foot): point the foot downward.
  • Abduction: move limb away from body.
  • Adduction: move limb towards body.
  • Circumduction: limb moves in a circle.
• Rotation: turning around long axis.
  • Lateral: outwards
  • Medial: inwards
• Special:
  • Supination: radius rotates around ulna (palm faces up).
  • Pronation: radius rotates around ulna (palm faces down).
  • Inversion: sole of foot turns inward.

Explore the fascinating world of muscle tissue, including its composition, functions, and types. Learn about the unique characteristics of skeletal, cardiac, and smooth muscles that enable movement and maintain bodily functions. Understand how muscle structure influences body shape and motion.