Muscular System

Muscular System

Lesson 1: Muscular System Overview

  • The muscular system contains over 600 muscles.
  • Functions of the muscular system:
    • Helps with body movement
    • Supports body posture
    • Produces heat and energy
    • Protects internal organs
    • Helps move blood, food, and waste products through the body
    • Opens and closes body openings

Lesson 1: Muscle Traits

  • All muscles have four common traits:
    • Excitability or Irritability: The ability to respond to stimuli.
    • Contractibility: The ability to shorten or contract.
    • Extensibility: The ability to be stretched.
    • Elasticity: The ability to return to its original length after being stretched.
  • Muscle tone: Refers to the ability of muscles to be slightly contracted at all times, even when not in use. It allows a person to be in a state of readiness to act.

Types of Muscles

  1. Cardiac:
    • Forms the walls of the heart.
    • Contracts to cause the heart to beat and circulate blood.
  2. Visceral (smooth):
    • Found in hollow organs, in the walls of blood vessels, and in the eyes.
    • Contracts to produce movement in these organs.
  3. Skeletal:
    • Attached to the bones.
    • Helps produce body movement.

Lesson 1: Types of Muscles - Voluntary vs. Involuntary

  • Involuntary Muscles
    • Cardiac and smooth muscles are involuntary, meaning they operate without conscious control.
  • Voluntary Muscles
    • Most skeletal muscles are voluntary, which means that a person can control their actions.

Microscopic Anatomy

  • Skeletal:
    • Under a microscope, skeletal muscles have alternating light and dark bands (striations).
  • Smooth:
    • Shows no cross stripes under microscopic magnification (non-striated).
  • Cardiac:
    • Like skeletal muscle cells, cardiac muscle cells are striated with narrow dark and light bands.
    • Cardiac muscle cells are narrower and much shorter than skeletal muscle cells.

Lesson 1: Attachment of Skeletal Muscles

  • Tendons: Connect muscles to bones.
  • Origin: The point where the muscle is attached to a less movable bone.
  • Insertion: The point where the muscle is attached to a more movable bone.
  • Fascia: A band or sheet of connective tissue that covers, supports, and separates muscles.

Lesson 1: Types of Body Movements

  • Types of body movements made by skeletal muscles include:
    • Flexion: Decreasing the angle between two bones.
    • Extension: Increasing the angle between two bones.
    • Abduction: Moving a limb away from the midline of the body.
    • Adduction: Moving a limb toward the midline of the body.
    • Rotation: Turning a bone around its longitudinal axis.
    • Circumduction: Circular movement of a limb or digit.
    • Supination and Pronation: Movements of the forearm that turn the palm forward (supination) or backward (pronation).
    • Dorsiflexion and Plantar flexion: Movements of the foot at the ankle, pointing the toes upward (dorsiflexion) or downward (plantar flexion).
    • Inversion and Eversion: Movements of the foot, turning the sole inward (inversion) or outward (eversion).
    • Protraction and Retraction: Anterior (protraction) or posterior (retraction) movement of a body part in the horizontal plane.

Lesson 2: Diseases and Disorders

Loss of Muscle Tone

  • Loss of muscle tone can result from serious illness.
  • Lack of muscle use can result in:
    • Atrophy: A reduction in size and strength of the muscle.
    • Contracture: A severe tightening of muscle resulting in permanent bending of a joint.

Diseases and Disorders of the Muscular System

  • Muscle Strain: Torn or stretched muscles or tendons.
  • Fibromyalgia: Refers to a group of muscle disorders with chronic pain in specific muscle sites.
  • Muscular Dystrophy: Refers to a group of inherited diseases in which the muscles gradually atrophy.