Lecture on Muscle and Nerve Cells

Key Characteristics of Muscle and Nerve Cells

• Muscle cells and nerve cells do not undergo mitosis.
• You are born with all the muscle cells you'll ever have.

Muscle Growth

• Muscle cells don't increase in number but in size.
• Weight training leads to hypertrophy:
  • Muscle fibers get bulkier.
  • Increase in actinomycin (proteins) content.
• Bodybuilders consume protein to increase actinomycin.

Atrophy vs. Hypertrophy

• Hypertrophy: Increase in muscle size without an increase in cell number.
• Atrophy: Decrease in muscle size due to disuse or disease.
• "Use it or lose it" principle applies to muscles and bones.

Muscle Contractions

• Types of contractions:
  • Isometric: Tension increases without muscle shortening (e.g., pushing against a wall).
  • Isotonic: Muscle shortens during contraction (e.g., lifting a dumbbell).

Muscle Mechanics

• Agonist and Antagonist:
  • Agonist contracts (e.g., biceps in a curl).
  • Antagonist relaxes (e.g., triceps in a curl).
• Synergists: Assist main muscles in performing movements.

Muscle Anatomy

• Origin: Attachment point that doesn't move.
• Insertion: Movable part of the skeletal system.
• Muscles have different fiber types:
  • Red Fibers: Slow twitch, rich in myoglobin, contract for long periods.
  • White Fibers: Fast twitch, less myoglobin, fatigue quickly.

Skeletal, Smooth, and Cardiac Muscle

• Differences in muscle types:
  • Skeletal Muscle: Focus in basic AMP studies.
  • Smooth Muscle: Contracts longer, less intensely.
  • Cardiac Muscle: More mitochondria, sensitive to calcium levels.

Calcium in Muscle Function

• Hypercalcemia: Excess calcium, can cause prolonged contractions.
• Hypocalcemia: Insufficient calcium, reduces ability to contract.
• Calcium levels are crucial for proper muscle function, especially in the heart.

Cardiac Muscle Characteristics

• Functional syncytium through gap junctions.
• Self-exciting and rhythmic contractions.
• Involuntary, all-or-none contraction mechanism.

These notes capture the essential points from the lecture, summarizing muscle cell behavior, muscle growth, types of muscle contractions, and characteristics of different muscle types.