Muscular System + Movement (10/23)

Skeletal Muscle

Voluntary muscle tissue responsible for moving the skeleton.

Smooth Muscle

Involuntary muscle tissue that produces movement in digestive organs and other internal structures.

Cardiac Muscle

Involuntary muscle tissue that forms the walls of the heart.

What are the four primary functions of muscular tissue?

Producing body movements, stabilizing body positions, storing and moving substances, and generating heat.

Electrical Excitability

The property of muscle tissue to respond to stimuli by producing electrical action potentials.

Contractility

The ability of muscle tissue to contract forcefully when stimulated.

Extensibility

The ability of muscle tissue to stretch without being damaged.

Elasticity

The ability of muscle tissue to return to its original length and shape after contraction or extension.

Epimysium

The connective tissue layer that wraps around an entire skeletal muscle.

Perimysium

The connective tissue that surrounds groups of 10 to 100 muscle fibers called fascicles.

Endomysium

The connective tissue that surrounds individual muscle fibers.

Tendon

A cord of dense regular connective tissue that attaches skeletal muscle to bone.

Somatic Motor Neurons

Nerve cells that stimulate skeletal muscles to contract.

Sarcolemma

The plasma membrane of a muscle cell.

Sarcoplasm

The cytoplasm of a muscle cell, containing glycogen for ATP production and oxygen-binding myoglobin.

Sarcomere

The functional unit of a myofibril, located between two Z-discs.

Thin Filaments

Myofilaments composed primarily of the protein actin.

Thick Filaments

Myofilaments composed primarily of the protein myosin.

What happens to the length of actin and myosin filaments during the sliding filament mechanism?

Neither actin nor myosin changes length; thin filaments simply slide past thick filaments.

What event causes the detachment of myosin heads from actin during muscle contraction?

The attachment of an ATP molecule to the myosin head.

Gliding Movements

Flat bone surfaces move back and forth and side-to-side relative to each other.

Flexion

An angular movement that decreases the angle between articulating bones.

Extension

An angular movement that increases the angle between articulating bones.

Abduction

The movement of a bone away from the midline of the body.

Adduction

The movement of a bone toward the midline of the body.

Muscle Fiber

A single cylindrical skeletal muscle cell.

Fascicle

A bundle of 10 to 100 muscle fibers wrapped in perimysium.

Myofibril

Contractile thread-like structures that extend the entire length of a muscle fiber.

Myofilament

Smaller protein filaments (thick and thin filaments) within a myofibril involved in contraction.

Rotation

A movement in which a bone revolves around its own longitudinal axis.

Circumduction

Movement of the distal end of a body part in a circle.

Supination

Movement of the forearm that turns the palm anteriorly.

Pronation

Movement of the forearm that turns the palm posteriorly.

Dorsiflexion

Bending of the foot at the ankle in the direction of the superior surface.

Plantarflexion

Bending of the foot at the ankle in the direction of the sole.

Hyperextension

Over-extension of a body part such as the head, wrist, arm, or leg.

Lateral Flexion

Bending the head sideways.

Lateral Rotation

Rotating a body part away from the midline.

Medial Rotation

Rotating a body part toward the midline.

Inversion

Turning the ankle so that the sole is medial.

Eversion

Turning the ankle so that the sole is lateral.

Protraction

Jutting the mandible out.

Retraction

Bringing the mandible to its natural underbite position.

Elevation

Lifting a body part upward, such as the scapula and mouth.

Depression

Dropping a body part downward, such as the scapula and mouth.

Opposition

Touching the thumb to any other finger on the same hand.