Muscle functions

Action

movement resulting from contraction of a muscle or group of muscles

Prime mover

muscle that causes the movement to occur

Agonist

muscle that contracts to cause an action

Antagonist

muscle that opposes the agonist, relaxes or lengthens as its agonist contracts

Synergist

muscle that assists the action of the agonist

Fixator

muscle that stabilizes the origin of the agonist

Origin

tendon attachment site to bone that does not move during its action

Insertion

tendon attachment site to bone that moves during its action

Frontalis

elevates eyebrows

Occipitalis

draws scalp posteriorly

Orbicularis oculi

closes eye (blinking or squinting)

Orbicularis oris

closes or purses lips (kissing or whistling muscle)

Zygomaticus major and minor

elevates corners of mouth (smiling muscle)

Risorius

draws corners of mouth laterally

Buccinator

compresses cheek (as in whistling), holds food between teeth during chewing

Medial pterygoid

elevates mandible (aids in grinding action of teeth)

Lateral pterygoid

protracts (anterior movement of) mandible (aids in grinding action of teeth)

Temporalis

elevates mandible

Masseter

elevates mandible

Sternocleidomastoid

bilateral contraction causes cervical flexion, unilateral contraction causes cervical rotation to opposite side

Platysma

depresses mandible

Scalenes

flexes and slightly rotates neck

Trapezius

superior portion elevates scapula, middle portion adducts scapula, inferior portion depresses scapula

Pectoralis minor

abducts scapula

Serratus anterior

abducts scapula

Rhomboids

adducts scapula

Levator scapulae

elevates scapula

External intercostals

inspiration

Internal intercostals

expiration

Diaphragm

inspiration

Supraspinatus

abducts humerus

Infraspinatus

laterally rotates humerus

Teres minor

laterally rotates humerus

Subscapularis

medially rotates humerus

Teres major

extends, medially rotates, and adducts humerus

Pectoralis major

adducts and medially rotates humerus

Deltoid

abducts humerus

Latissimus dorsi

extends, adducts, and medially rotates humerus

Erector spinae

extends vertebral column

Triceps brachii

forearm extension

Biceps brachii

forearm flexion and supination

Pronator teres

pronates forearm (palm down)

Supinator

supinates forearm (palm up)

Brachioradialis

forearm flexion

Brachialis

forearm flexion

Flexor carpi radialis

hand flexion at wrist

Extensor carpi radialis longus

hand extension at wrist

Rectus abdominus

trunk flexion

External obliques

trunk rotation and flexion unilaterally, trunk flexion bilaterally

Internal obliques

trunk rotation and flexion unilaterally, trunk flexion bilaterally

Transversus abdominis

compresses abdomen

Iliopsoas

flexes thigh

Gluteus maximus

extends thigh

Gluteus medius

abducts thigh

Tensor fascia latae

abducts thigh

Adductor magnus

adducts thigh

Adductor longus

adducts thigh

Gracilis

adducts thigh

Sartorius

flexes thigh and leg, laterally rotates thigh

Quadriceps group

rectus femoris, vastus lateralis, vastus medialis, vastus intermedius

Rectus femoris

leg extension and thigh flexion

Vastus lateralis

extends leg

Vastus medialis

extends leg

Vastus intermedius

extends leg

Hamstring group

biceps femoris, semitendinosus, semimembranosus: flexes leg, extends thigh

Tibialis anterior

foot dorsiflexion

Gastrocnemius

foot plantar flexion

Soleus

foot plantar flexion