Lecture Notes: Introduction to Muscles and Movement

Overview

• The human body has over 600 muscles.
• The lecture focuses on 15 common superficial muscles.
• Key concepts include understanding muscle antagonistic pairs, movement terms, muscle origins and insertions, and types of muscle contractions.

Key Movement Terms

1. Flexion

   • Decreasing the angle of a joint.
   • E.g., contracting the bicep to bend the elbow.

2. Extension

   • Increasing the angle of a joint.
   • E.g., extending the elbow.

3. Rotation

   • Turning a joint, usually specified with a direction (medially or laterally).

4. Abduction

   • Movement away from the midline of the body.
   • Think "abducted" by aliens, moving away.

5. Adduction

   • Movement towards the midline of the body.
   • Think "add" back to the torso.

Understanding Muscle Attachments

• Origin: The bone that does not move during muscle contraction.
• Insertion: The bone that does move.
• Example: Biceps brachii connects from the scapula (origin) to the radius (insertion).

Types of Muscle Contractions

1. Isometric Contractions

   • Muscle contracts but no movement occurs (same length).

2. Isotonic Contractions

   • Muscle contracts and movement occurs (same force).

Muscle Groups and Functions

Arm Muscles

• Biceps Brachii

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

• Triceps Brachii

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

Shoulder Muscles

• Deltoids

  • Abduct the arm.
  • Origin: Clavicle and Sternum; Insertion: Humerus.

• Pectoralis Major

  • Rotates shoulder anteriorly.
  • Antagonist: Latissimus Dorsi.

• Latissimus Dorsi

  • Rotates shoulder posteriorly.
  • Origin: Lumbar spine and ribs; Insertion: Humerus.

• Trapezius

  • Moves and rotates scapula.
  • Origin: Thoracic and cervical spine; Insertion: Clavicle and scapula.

Torso Muscles

• Rectus Abdominis

  • Bends the spine (flexion).
  • Origin: Pelvis; Insertion: Costal cartilage.

• External Abdominal Obliques

  • Similar action to rectus abdominis, allows bending to the side.

Hip and Leg Muscles

• Gluteus Maximus

  • Extends the hip joint.
  • Origin: Pelvis; Insertion: Femur.
  • Antagonist: Iliopsoas (internal muscle).

• Biceps Femoris (Hamstrings)

  • Flexes the knee.
  • Origin: Pelvis and femur; Insertion: Tibia and fibula.

• Quadriceps

  • Extend the knee.
  • Composed of Rectus Femoris, Vastus Lateralis, Vastus Medialis, and Vastus Intermedius.

• Sartorius

  • Rotates the knee laterally.

Ankle Muscles

• Gastrocnemius

  • Causes plantar flexion of the ankle.
  • Origin: Femur; Insertion: Calcaneus.

• Tibialis Anterior

  • Causes dorsiflexion of the ankle.
  • Origin: Tibia; Insertion: Tarsal bones.

Summary

• The lecture covered the main muscles and their functions, focusing on their roles as antagonists and their effects on joint movement.
• Emphasis on understanding muscle origins, insertions, and types of contractions.

Learning Check

• Identify muscle locations and their actions on a diagram.
• Key focus on muscle movement and function rather than origins and insertions alone.