Muscle Actions & Antagonistic Pairs

These flashcards cover key definitions and examples of antagonistic muscle pairs and opposite muscle actions, including abduction/adduction, flexion/extension, pronation/supination, dorsiflexion/plantar flexion, elevation/depression, and more.

What does the term "antagonistic" mean in reference to muscle pairs?

It refers to two muscles that work in opposition—when one contracts, the other relaxes.

In an antagonistic pair, what happens when one muscle contracts?

The opposite muscle in the pair relaxes.

Define muscle contraction.

The tightening of a muscle, making it shorter and thicker, with an enlarged muscle belly.

Define muscle relaxation.

The return of a muscle to its original form, making it longer and thinner, with a non-enlarged belly.

During arm extension, which muscle contracts and which relaxes?

The triceps contracts and the biceps relaxes.

During arm flexion, which muscle contracts and which relaxes?

The biceps contracts and the triceps relaxes.

What movement describes a limb moving away from the midline of the body?

Abduction.

What movement describes a limb moving toward the midline of the body?

Adduction.

Which type of muscle moves a body part away from the midline?

An abductor muscle.

Which type of muscle moves a body part toward the midline?

An adductor muscle.

Define flexion.

Decreasing the angle between two bones by bending a limb at a joint.

Define extension.

Increasing the angle between two bones by straightening a limb at a joint.

Which muscle type bends a limb at a joint?

A flexor muscle.

Which muscle type straightens a limb at a joint?

An extensor muscle.

What is hyperextension?

Extreme or overextension of a limb or body part beyond its normal limit.

Define rotation in joint movement.

A circular movement around an axis, such as at the shoulder joint.

Define circumduction.

Circular movement at the far end of a limb.

Describe pronation of the forearm.

Turning the arm so the palm faces downward.

Describe supination of the forearm.

Turning the arm so the palm faces upward.

What is dorsiflexion?

Bending the foot upward at the ankle.

What is plantar flexion?

Bending the foot downward at the ankle.

Define elevation in muscular movement.

The act of raising or lifting a body part.

Define depression in muscular movement.

The act of lowering a body part.

Which facial muscle action raises the corners of the mouth into a smile?

Elevation by the levator anguli oris muscles.

Which facial muscle action lowers the corners of the mouth into a frown?

Depression by the depressor anguli oris muscles.