General Overview

Muscular Tissue

Tissues that are made up of muscular fibers or myocytes use up ATP to generate movement, insulation, and protection

Muscular Tissue: Myology

The scientific study of muscles.

Muscular Tissue: Three Types

• Skeletal muscle

• Cardiac muscle

• Smooth muscle.

Skeletal Muscle

Stratified, tubular fibers with multiple nuclei that move the bones of the skeleton

Skeletal Muscle: Function

Movement: Exert force on tendons to pull bones and generate movement

Stability: Maintain posture and body movement by stabilizing joints

Heat Production: Produce metabolic heat to maintain body temperature

Skeletal Muscle: Striated Appearance

Has alternating light and dark bands (striations) when viewed under a microscope.

Skeletal Muscle: Control

Primarily voluntary that are controlled by the somatic (voluntary) division of the nervous system.

Skeletal Muscle: Automatic Actions

Some actions occur subconsciously, such as breathing, maintaining posture, and stabilizing body positions.

Cardiac Muscle

Stratified, branched fibers with multiple nucleus that involuntary pumps blood to the heart

Cardiac Muscle: Striated Appearance

Has visible striations similar to skeletal muscle.

Cardiac Muscle: Location

Found only in the heart and forms most of the heart wall.

Cardiac Muscle: Control

Involuntary; heart contractions occur without conscious control

Cardiac Muscle: Autorhythmicity

The heart can generate its own rhythm and contractions through a natural pacemaker.

Cardiac Muscle: Heart Rate Regulation

Hormones and neurotransmitters can speed up or slow down the heart's natural pacemaker.

Cardiac Muscle: Cell Junction

• Desmosomes: Hold the fibers intact during vigorous contractions

• Gap Junction: Provides muscle action potentials a route throughout the heart

Smooth Muscle

Simple, spindle-shaped fibers with a centrally located nucleus that allow voluntary movement

Smooth Muscle: Function

• Digestive System: Performs peristalsis—a wave-like contraction that pushes food and waste through the stomach and intestines.

• Cardiovascular System: Constricts and dilates blood vessels to regulate blood pressure and distribute blood flow to tissues.

• Urinary System: Controls the flow of urine and aids in expelling it from the body.

• Reproductive System: Facilitates movements such as the propulsion of sperm and the strong contractions of the uterus during labor.

Smooth Muscle: Location

Found in the walls of hollow organs, blood vessels, airways, and attached to hair follicles in the skin.

Smooth Muscle: Appearance

Nonstriated (smooth-looking) because it lacks visible light and dark bands.

Smooth Muscle: Control

Usually involuntary and not under conscious control.

Cardiac & Smooth Muscle: Nervous System Division

Regulated by the autonomic (involuntary) division of the nervous system.

Cardiac & Smooth Muscle: Hormonal Regulation

Their activity can also be influenced by hormones released by endocrine glands.

Muscle Tissue Comparison: Skeletal Muscle

Striated, voluntary, attached mainly to bones, controlled by the somatic nervous system.

Muscle Function: Movement

Works with bones and joints to create movement

Muscle Function: Stabilizing Body Positions

Continuous muscle contractions maintain posture and stabilize joints

Muscle Function: Storing Substances

Smooth muscle sphincters temporarily store materials in hollow organs by preventing their outflow.

Muscle Function: Moving Substances

Muscles move substances throughout the body, including blood, food, bile, enzymes, gametes, urine, lymph, and venous blood.

Muscle Function: Assisting Circulation

Skeletal muscle contractions help move lymph through lymphatic vessels and aid the return of blood in veins to the heart.

Muscle Function: Generating Heat

Muscle contractions produce heat that helps maintain normal body temperature, known as termogenesis

Muscle Property: Electrical Excitability

The ability of muscle cells to respond to stimuli by producing electrical signals called action potentials

Electrical Excitability: Autorhythmic Signals

Electrical signals that originate within the muscle itself, such as the heart's natural pacemaker.

Electrical Excitability: Chemical Stimuli

Neurotransmitters, hormones, or local changes in pH that can trigger muscle action potentials.

Muscle Property: Contractility

The ability of muscle tissue to contract forcefully when stimulated to produce tension (force of contraction)

Contractility: Muscle Shortening

If muscle tension overcomes resistance, the muscle shortens and movement occurs.

Muscle Property: Extensibility

The ability of muscle tissue to stretch within limits without being damaged.

• Ex. Connective tissue within the muscle limits stretching and keeps the muscle within its safe contractile range.

Muscle Property: Elasticity

The ability of muscle tissue to return to its original length and shape after being stretched or contracted.

Muscle Properties: Memory Trick

Excite, Contract, Stretch, Snap Back = Electrical Excitability, Contractility, Extensibility, Elasticity.