Muscles Study Guide

Fascicle Arrangement

The organization of muscle fibers that affects a muscle's range of motion and power.

Parallel Muscles

Muscles with fascicles running parallel to the long axis, allowing for extensive range of motion but less power (e.g., sartorius).

Pennate Muscles

Muscles with fascicles attaching obliquely to a central tendon, providing greater power but limiting range of motion (e.g., rectus femoris).

Convergent Muscles

Muscles where fascicles converge from a broad area to a single tendon, offering versatility in movement (e.g., pectoralis major).

Circular Muscles

Muscles arranged in concentric rings, useful for closing openings (e.g., orbicularis oris).

Agonist

The primary muscle responsible for generating a specific movement (e.g., biceps brachii for elbow flexion).

Antagonist

The muscle that opposes the movement of the agonist (e.g., triceps brachii for elbow extension).

Synergist

A muscle that assists the agonist by providing additional force or reducing unwanted movement (e.g., brachialis).

Fixator

A muscle that stabilizes the origin of the agonist, enabling it to function more effectively (e.g., shoulder girdle muscles).

Axial Muscles

Muscles located on the head, neck, and trunk.

Appendicular Muscles

Muscles associated with the limbs.

Occipitofrontalis

A muscle with two bellies; frontal raises eyebrows, occipital pulls scalp backward.

Orbicularis Oculi

A muscle that closes the eye (blinking, squinting).

Orbicularis Oris

A muscle that closes and protrudes the lips (kissing muscle).

Levator Labii Superioris

A muscle that elevates the upper lip (smiling).

Zygomaticus

Muscles that elevate the corners of the mouth (smiling).

Depressor Anguli Oris

A muscle that lowers the corners of the mouth (frowning).

Temporalis

A muscle that elevates and retracts the mandible (chewing).

Masseter

A muscle that elevates the mandible (chewing).

Sternocleidomastoid

A muscle that flexes the neck and rotates the head.

Trapezius

A muscle that elevates, retracts, and rotates the scapula.

External Intercostals

Muscles that elevate ribs during inhalation.

Internal Intercostals

Muscles that depress ribs during forced exhalation.

Pectoralis Major

A muscle that adducts and medially rotates the arm.

Diaphragm

The prime mover for inhalation, contracts to enlarge the thoracic cavity.

Rectus Abdominis

A muscle that flexes the vertebral column.

External Obliques

Muscles that flex and rotate the vertebral column.

Rhomboideus Major

A muscle that retracts and elevates the scapula.

Infraspinatus

A muscle that laterally rotates the arm.

Deltoid

A muscle that abducts the arm.

Biceps Brachii

A muscle that flexes the elbow and supinates the forearm.

Triceps Brachii

A muscle that extends the elbow.

Gluteus Maximus

A muscle that extends and laterally rotates the thigh.

Sartorius

A muscle that flexes, abducts, and laterally rotates the thigh.

Biceps Femoris

A muscle that extends the thigh and flexes the knee.

Tibialis Anterior

A muscle that dorsiflexes and inverts the foot.

Gastrocnemius

A muscle that plantarflexes the foot and flexes the knee.

Calcaneal Tendon

Connects the gastrocnemius and soleus to the heel bone, aiding in plantarflexion.