Muscular System

Muscle Cells

Muscle cells are specialized cells responsible for body movement through contraction.

Three Main Parts of a Muscle Cell

Nuclei, sarcoplasm, and sarcolemma.

Nuclei

Contain the genetic material of muscle cells and control cellular functions.

Sarcoplasm

The cytoplasm of a muscle cell, which contains contractile proteins and other cellular components.

Sarcolemma

The plasma membrane that encloses the muscle fiber; it receives electrical signals from the nervous system and propagates them into the cell to trigger contraction.

Three Main Types of Muscle

Skeletal muscle, cardiac muscle, and smooth muscle.

Skeletal Muscle

Muscles attached to bones and responsible for voluntary movements such as walking.

Cardiac Muscle

Muscle found in the heart and responsible for generating the force that pumps blood.

Smooth Muscle

Muscle found in the walls of organs and blood vessels and responsible for involuntary movements such as peristalsis.

Skeletal Muscle

Located attached to bones; under voluntary control; multinucleated; striated; contains sarcomeres; contracts rapidly and powerfully; uses aerobic and anaerobic respiration; has no intercalated discs; regulated by motor neuron stimulation.

Smooth Muscle

Located in the walls of organs and blood vessels; under involuntary control; has a single nucleus; non-striated; lacks sarcomeres; contracts slowly and sustainably; primarily uses aerobic respiration; has no intercalated discs; regulated by hormones and the autonomic nervous system.

Cardiac Muscle

Located in the heart; under involuntary control; has a single nucleus; striated; contains sarcomeres; contracts rapidly and sustainably; uses aerobic respiration; has intercalated discs for coordinated beating; regulated by intrinsic pacemaker cells.

Skeletal Muscle Nuclei

Multinucleated.

Smooth Muscle and Cardiac Muscle Nuclei

Single nucleus.