part 1 lecture 15

Muscular System Overview

• Muscle Function

  • Muscles can only pull; they do not push.

  • Muscles pull the insertion towards the origin of the muscle.

Biceps Brachii

• Location:

  • Anterior (front) upper arm.

• Function:

  • Controls the lower arm (specifically the forearm) for flexion.

  • Origin at the shoulder; insertion on the ulna.

  • Pulling the ulna towards the shoulder results in flexion of the lower arm.

Triceps Brachii

• Location:

  • Posterior (back) lower arm.

• Function:

  • Origin is at the shoulder; insertion on the ulna.

  • Pulling the insertion towards the origin results in extension of the lower arm.

Key Definitions

• Flexion:

  • Decrease in the angle between two bones at a joint.

• Extension:

  • Increase in the angle between two bones at a joint.

• Abduction:

  • Movement of a limb away from the midline of the body.

• Adduction:

  • Movement of a limb towards the midline of the body.

• Rotation:

  • Movement in which a bone revolves around its own axis.

• Plantar Flexion:

  • Pointing the toes down.

• Dorsi Flexion:

  • Pointing the toes up.

• Hyperextension:

  • Extension beyond the normal range (e.g., bending the head backward beyond a neutral position).

Muscle Actions in the Legs

• Hamstrings:

  • Location: Posterior upper leg.

  • Action: Flexion of the lower leg.

• Quadriceps:

  • Location: Anterior upper leg.

  • Action: Extension of the lower leg.

Muscle Groups and Specifics

• Deltoid:

  • Location: Shoulder.

  • Action: Moves the arm.

• External Oblique:

  • Location: Side of abdomen.

  • Action: Flexion and rotation of the trunk.

• Diaphragm:

  • Location: Between chest and abdomen.

  • Action: Essential for breathing; contracts to inhale.

Guidelines for Muscle Study

• Focus on superficial muscles for actions.

• Establish muscle location and then deduce the function based on insertion and origin positions.

• Always articulate the action clearly using the correct anatomical terminology.

• Recognize that muscles often have antagonistic pairs, where one muscle will function to cause a movement while another will be responsible for the opposite movement.