Muscle System

Muscle fiber

Muscle cell; contractile and excitable.

Sarcoplasmic Reticulum

The muscle cell's E.R.; Ca storage site (big role in contraction).

Myofibril

Bundles of interconnected filaments making up a fiber.

Endomysium

Connective tissue surrounding fiber.

Fascicle

Bundle of muscle fibers.

Perimysium

Connective tissue surrounding fascicle.

Epimysium

Connective tissue surrounding entire muscle.

Fascia

Most superficial connective tissue layer; continuous with epimysium and separates individual muscles.

Sarcomere

The functional unit of the muscle fiber composed of actin and myosin filaments.

Tendon

Muscle to bone (dense regular connective tissue).

Ligament

Bone to bone (dense regular connective tissue).

Origin

Fixed end of muscle, usually to bone.

Insertion

Flexible end, attached to bone via tendons.

Agonist

AKA Prime Mover; muscle responsible for movement.

Antagonist

Muscle opposing agonist.

Synergist

Helper of the agonist.

Sagittal Plane

Vertical plane dividing the body into right and left portions.

Coronal Plane

Vertical plane dividing the body into anterior and posterior portions.

Transverse Plane

Horizontal plane dividing the body into superior and inferior portions.

Medial

Toward the midline.

Lateral

Away from the midline.

Proximal

Toward the point of attachment.

Distal

Away from the point of attachment.

Abduction

Movement away from the midline.

Adduction

Movement toward the midline.

Flexion

Decreasing the angle of a joint.

Extension

Increasing the angle of a joint.

Supination

Palm anterior (facing up).

Pronation

Palm posterior (facing down).

Dorsiflexion

Bending the foot upward toward the shin.

Plantar flexion

Bending the foot downward (pointing toes).

Inversion

Turning the sole of the foot medially.

Eversion

Turning the sole of the foot laterally.

Frontalis

Elevates eyebrows.

Occipitalis

Retracts (extends) scalp posteriorly.

Buccinator

Compresses cheek for mastication.

Masseter

Elevates mandible (jaw flexion).

Zygomaticus

Elevates corners of mouth.

Orbicularis oculi

Closes eyelids.

Orbicularis oris

Closes and protrudes lips.

Platysma

Depresses mandible; tenses neck.

Sternocleidomastoid

Flexes neck; rotates head.

Trapezius

Elevates, retracts, and depresses scapula; extends neck.

Pectoralis major

Flexes, adducts, medially rotates arm.

Rectus abdominis

Flexes vertebral column.

Latissimus dorsi

Extends, adducts, medially rotates arm.

Deltoid

Abducts arm; flexes and extends.

Biceps brachii

Flexes elbow; supinates forearm.

Triceps brachii

Extends elbow; long head adducts.

Gluteus maximus

Hip extension; lateral rotation.

Quadriceps Group

Rectus Femoris, Vastus Lateralis, Intermedius, and Medialis; Hip Flexion and Knee Extension.

Hamstring Group

Biceps Femoris, Semitendinosus, Semimembranosus; Hip Extension and Knee Flexion.

Tibialis Anterior

Dorsiflexion and foot inversion.

Gastrocnemius

Plantar Flexion and Knee Flexion.

Skeletal Muscle

Attached to bones; voluntary; striated.

Smooth Muscle

Organs; involuntary; non-striated.

Cardiac Muscle

Heart; Involuntary; striated.

Fast Twitch

Muscle action that varies force by recruitment or frequency (e.g., Rat Tibialis Anterior).

Slow Twitch

Muscle fibers designed for endurance (e.g., Rat Soleus).