Muscle Movements, Types, and Names Pg. 175 - 181 October 5, 2012

5 Golden Rules of Skeletal Muscle Activity All muscles cross at least one joint. Typically, the bulk of the muscle lies PROXIMAL to the joint crossed. All muscles have at least two attachments: the origin and the insertion. Muscles can only pull; they never push. During contractions, the muscle insertion moves toward the origin.

Muscle Movement We have about 600 skeletal muscles All skeletal muscles have at least two attachment points Origin: immovable or less moveable bone Insertion: moveable bone The insertion ALWAYS moves TOWARD the origin

Types of Body Movements Flexion: decreases the angle of the joint and brings two bones closer together Typical of hinge joints and common in ball-and-socket joints Extension: opposite of flexion – it increases the angle of the joint, and thus the distance between two bones Straightening the knee or elbow Extension greater than 180˚ is called hyperextension Leaning your head/torso back to where your chin points to the ceiling

Rotation: movement of a bone around its longitudinal axis Common of ball-and-socket joints Describes the movement of the atlas around the axis (shaking your head no)

Abduction: moving a limb away from the midline of the body Also includes fanning the fingers or toes to spread them apart Adduction: opposite of abduction; moves a limb toward the body midline

Circumduction: combination of flexion, extension, abduction, and adduction Commonly seen in ball-and-socket joints Proximal end is stationary, distal end moves in a circle The entire limb outlines a cone

Special Movements Dorsiflexion: lifting the foot so that its superior surface approaches the shin (standing on your heels) Similar to extending the hand at the wrist Plantar flexion: depressing the foot (pointing the toes) Similar to flexion of the hand

Inversion: turn your sole medially (towards the other foot) Eversion: turn your sole laterally (away from the other foot)

Supination: SOUP! The palm faces up like you’re holding a bowl of soup Radius and ulna are parallel Pronation: palm faces down towards the ground Radius and ulna form an X shape

Opposition: thumb can touch the tips of every other finger on the same hand

Types of Muscles Prime mover: has the most responsibility for movement Antagonists: oppose or reverse a movement When a prime mover is active, the antagonist is relaxed and stretched Antagonists can have the chance to be prime movers Synergists: help prime movers by producing the same movement or reduce undesirable movemetns Fixators: specialized synergists; hold a bone still or stabilize the origin of a prime mover so all tension can be used to move the insertion bone

Naming Skeletal Muscles Direction of the muscle fibers: rectus means all muscle fibers are straight whereas oblique means muscle fibers are slanted Relative size of the muscle: maximus vs. minimus Location of the muscle: temporalis and frontalis are on top of the temporal and frontal skull bones Number of origins: biceps, triceps, quadriceps Location of the muscle’s origin and insertion: sternocleidomastoid – origin on the sternum, origin on the clavicle, and insertion is the mastoid process Shape of the muscle: deltoid means “triangular” Action of the muscle: flexor, extensor, adductor