Muscle Types

Overview

• Three types of muscle: Skeletal, Cardiac, and Smooth.
• Identification based on structure and function.

Skeletal Muscle

• Function: Moves the skeleton; considered voluntary muscles.
  • Example: Biceps, abdominals.
  • Exception: Reflex actions (e.g., withdrawal from heat, patella tendon reflex).
• Features:
  • Striated appearance due to actin, myosin, and accessory proteins.
  • Consistent thickness.
  • Multi-nucleated; nuclei are elongated along muscle fibers.
• Structure: Composed of muscle fibers.

Cardiac Muscle

• Function: Involuntary muscles controlling heart contraction.
• Features:
  • Striated like skeletal muscle.
  • Single, round nucleus per cell.
  • Presence of intercalated discs.
    • Important for heart function; allow ion flow.
    • Facilitate synchronized contraction of heart muscle cells.
  • Cells may look branched; inconsistent width.

Smooth Muscle

• Function: Involuntary muscle, not under conscious control.
• Features:
  • Not striated unlike skeletal and cardiac muscles.
  • Contains motor proteins for contraction.
  • Single nucleus per cell.
  • Looks different in texture compared to connective tissue.
  • Identification: Lacks striations, appears smooth under a microscope.

Key Identifiers

• Skeletal Muscle: Voluntary, striated, multi-nucleated.
• Cardiac Muscle: Involuntary, striated, intercalated discs, single nucleus.
• Smooth Muscle: Involuntary, non-striated, smooth texture.