Lecture Notes: Muscle Movement and Contraction

Introduction

• Analogy of Romance: Famous star-crossed lovers compared to protein strands in muscles.
• Key Proteins: Actin and Myosin are crucial for muscle movement.

Muscle Tissue Types

• Smooth Muscle Tissue:
  • Found in walls of visceral organs (e.g., stomach, airways).
  • Involuntary movement, pushing fluids/materials.
• Cardiac Muscle Tissue:
  • Striated, involuntary, pumps blood.
  • Found only in the heart.
• Skeletal Muscle Tissue:
  • Striated, mostly voluntary.
  • 640 skeletal muscles; attach to skeleton for movement.

Anatomy of Skeletal Muscle

• Muscle Structure:
  • Muscle fibers -> Fascicles -> Muscle organ (e.g., biceps brachii).
  • Each muscle is an organ with connective tissue, blood vessels, nerve fibers.
• Protective Sheaths:
  • Necessary for muscle protection and function.

Muscle Contraction Mechanics

• Basic Rules of Protein Function:
  1. Proteins change shape when binding occurs.
  2. Shape changes allow proteins to bind or unbind.
• Sarcomeres:
  • Segments within myofibrils containing actin and myosin.
  • Contraction involves actin and myosin interaction.

Sliding Filament Model

• Myofilaments:
  • Thin (Actin) and Thick (Myosin) filaments.
• Contraction Process:
  • Actin and Myosin interaction causes sarcomere contraction.
  • Involves ATP and calcium for binding and unbinding.

Muscle Contraction Detail

• Rest State:
  • Myosin heads are blocked by tropomyosin and troponin.
• Action Potential Trigger:
  • Initiated by brain signal via motor neurons.
  • Causes sodium influx, action potential propagation.
• Calcium's Role:
  • Calcium binds to troponin, removing tropomyosin barrier.
• ATP's Role:
  • Myosin uses ATP to bind and pull actin, causing contraction.
  • Release of ADP and phosphate allows cycle continuation.

Conclusion

• Repetitive Cycle:
  • Calcium pumps reset calcium levels for ongoing muscle activity.