Lecture on Muscles

Introduction

• The human body has over 600 muscles.
• Focus on 15 common superficial muscles controlling joints like the elbow and shoulder.
• Concepts covered include:
  • Antagonist muscle pairs
  • Movement terms (flexion, extension, etc.)
  • Muscle origins and insertions
  • Isometric and isotonic contractions

Key Movement Terms

• Flexion: Decreasing the angle of a joint (e.g., bending the elbow by contracting the bicep).
• Extension: Increasing the angle of a joint (e.g., straightening the elbow by contracting the tricep).
• Rotation: Turning a joint in a direction (medially or laterally).
• Abduction: Movement away from the midline (e.g., lifting arms sideways).
• Adduction: Movement towards the midline (e.g., returning arms to sides).

Muscle Attachments

• Origin: Bone that does not move during muscle contraction.
• Insertion: Bone that moves during muscle contraction.

Types of Muscle Contractions

• Isometric: Muscle contracts without movement (same length).
• Isotonic: Muscle contracts with movement (same force).

Muscles of Interest

Upper Body Muscles

• Biceps Brachii

  • Action: Flexes the elbow.
  • Origin: Scapula.
  • Insertion: Radius.
  • Antagonist: Triceps Brachii.

• Triceps Brachii

  • Action: Extends the elbow.
  • Origin: Humerus.
  • Insertion: Ulna.

• Deltoids

  • Action: Abducts the arm.
  • Origin: Clavicle and sternum.
  • Insertion: Humerus.

• Pectoralis Major

  • Action: Rotates shoulders anteriorly.
  • Antagonist: Latissimus Dorsi.

• Latissimus Dorsi

  • Action: Rotates shoulders posteriorly, aids in adduction of the arm.

• Trapezius

  • Action: Moves scapula; supports neck and upper back movement.

Core Muscles

• Rectus Abdominis

  • Action: Flexes spine (e.g., sit-ups).

• External Abdominal Obliques

  • Action: Aids in lateral flexion and rotation of the trunk.

Lower Body Muscles

• Gluteus Maximus

  • Action: Extends the hip joint.
  • Antagonist: Iliopsoas.

• Iliopsoas

  • Action: Flexes the hip joint.

• Biceps Femoris (Hamstrings)

  • Action: Flexes the knee.

• Quadriceps

  • Action: Extends the knee.
  • Components: Rectus Femoris, Vastus Lateralis, Vastus Medialis, Vastus Intermedius.

• Sartorius

  • Action: Rotates the knee laterally.
  • Note: Longest muscle in the body.

Ankle Muscles

• Gastrocnemius

  • Action: Plantar flexion of the foot.

• Tibialis Anterior

  • Action: Dorsiflexion of the foot.

Recap

• Reviewed the main muscles and their actions.
• Importance of understanding muscle function and contraction types.

Note: Understanding these concepts and muscle functions can aid in identifying muscles and their actions using diagrams.