TheMuscular System

Muscles

Three types of muscle tissue

•Cardiac – found only in the heart.

Non-voluntary

•Smooth/visceral – found in all internal organs.

Non-voluntary

•Skeletal – associated with the skeletal system.

Voluntary

Cardiac MuscleCells are cylindrical and striated

Single large, centrally located nucleus

Branched and connected to each other via intercalated discs

Smooth Muscle

Cells are spindle shaped, non-striated

Single large, centrally located nucleus

Gap junctions are found between cells

Skeletal Muscle

Cells are very long, cylindrical and striated

Multinucleated, found towards periphery

Functions of Skeletal Muscle

Body Movement (Force)

Maintenance of posture

Production of body heat

Communication

Characteristic Properties of Muscle

• Conductivity: A muscle has the ability to conduct an action potential.

• Irritability: When stimulated, the muscle will react.• Contractility: A muscle can shorten or produce tension

between its ends.• Relaxation: A muscle can return to resting properties after

contraction.• Distensibility: A muscle can be stretched by a force outside of

the muscle itself. The muscle is not injured as long as it is not stretched past its physiological limits.

• Elasticity: The muscle will resist elongation and will return to its original position after passive or active elongation.

General TermsOrigin [head] – end of muscle attached to the bone that is stationary

Insertion – end of muscle attached to the bone that moves

Belly – largest portion between origin and insertion

Agonist – muscle causing an action when it contracts

Antagonist – muscle that works in opposition to agonist – move structure in opposite direction

Synergists – muscles that work together to move a structure