New Recording 33

Overview of Joint Movements and Muscle Actions

• Understanding the types and terminology of joint movements is essential for studying muscle function.

• Focus will be on: flexion, extension, abduction, adduction, rotation, pronation, and supination.

Flexion and Extension

• Flexion of the Elbow: Bending of the elbow joint, primarily performed by the biceps brachii muscle, which is innervated by the musculocutaneous nerve and C5, C6 nerve roots.

  • Synergist: Brachialis

  • Antagonist: Triceps

• Flexion of the Shoulder: Raising arms above the head; starts from the anatomical position.

• Flexion of the Knee: Bending the knee joint.

• Extension of the Elbow and Knee: Straightening out the joint, opposite action to flexion.

  • Example: Kicking a leg straight is akin to extending the knee.

• Flexion of the Hip: Bringing the knee up towards the chest.

• Cervical Spine Flexion: Looking down or tucking chin towards the chest, decreases the angle of the neck.

Abduction and Adduction

• Abduction: Movement of limbs away from the body, starting from anatomical position.

• Adduction: Movement of limbs towards the body.

  • Key muscles include the adductor longus and adductor magnus for leg movements.

• Circumduction: A circular movement, not merely rotation; involves moving limbs in circular fashion.

Special Movements of the Foot and Ankle

• Dorsiflexion: Lifting the foot upwards at the ankle.

• Plantar Flexion: Pressing down into the ground, akin to walking on the balls of the feet.

  • Key illustration: Visualize stepping on a gas pedal as plantar flexion.

Supination and Pronation

• Supination: Turning the palms up.

• Pronation: Turning the palms down, often causing the radius and ulna to crisscross.

  • Importance in injury prevention: Falling in a prone position can lead to distal radius fractures.

Muscle Nerve Interaction

• Muscle activation involves the nervous system, though nerves do not directly contact muscle fibers; there is a synaptic gap.

• Sodium Ion Role: Sodium rushing in triggers muscle contraction via neuromuscular junctions.

• Calcium Release: Sarcoplasmic reticulum releases calcium, enabling muscle contraction by interacting with muscle fibers.

• Energy Dynamics: Muscle cells have limited ATP reserves (4-6 seconds worth); however, they can produce 32 ATP per glucose molecule through efficient aerobic respiration.

Conclusion

• Review concepts and prepare for practical applications and recognition of muscle actions in movement scenarios.