Body Movements

• Definition: Refers to the various ways the body can move, facilitated by muscles and joints.

• Types:

  • Flexion: Decreasing the angle between two body parts.

  • Opposition: Moving the thumb across the palm to touch the fingertips.

  • Rotation: Turning a body part around its axis.

• Example: A left turn involves rotation of the body to face in a different direction.

Types of Muscle Cells

• Skeletal Muscle Cells: Striated, voluntary muscle found attached to bones. Responsible for movement.

• Cardiac Muscle Cells: Striated, involuntary muscle found in the heart. Responsible for pumping blood.

• Smooth Muscle Cells: Non-striated, involuntary muscle found in walls of hollow organs. Controls slow, sustained contractions.

Muscle Layers

• Epimysium: Connective tissue surrounding the entire muscle.

• Perimysium: Connective tissue surrounding bundles (fascicles) of muscle fibers.

• Endomysium: Thin layer of connective tissue that surrounds individual muscle fibers.

Muscle Cell Structure

• Myofibrils: Long, thread-like structures that run parallel to the muscle fiber. Composed of sarcomeres, the functional unit of muscle contraction.

• Myosin: Thick filament protein involved in muscle contraction.

  • Role: Interacts with actin filaments to cause muscle contraction.

• Actin: Thin filament protein that works alongside myosin during contraction.

• Sarcoplasmic Reticulum: Organelle that stores calcium, crucial for muscle contraction initiation.

Muscle Contraction

• Sliding Filament Theory: Describes how myosin and actin filaments slide past each other to shorten the length of the muscle fiber, thus causing contraction.

• ATP Regeneration: Muscle contraction requires energy, derived from ATP.

  • Processes:

    • Aerobic Respiration: Occurs in the presence of oxygen, producing more ATP.

    • Anaerobic Respiration: Occurs without oxygen, leading to the production of lactic acid as a byproduct.

Important Concepts to Remember

• Muscle contractions can be voluntary (skeletal) or involuntary (smooth and cardiac).

• Key neurotransmitters play roles in muscle contraction, such as acetylcholine.

• Understanding the various muscle cell types and their functions is imperative for grasping muscle physiology and movement dynamics.