Muscular System

Muscular System

The organ system consisting of skeletal, smooth, and cardiac muscles responsible for body movement, posture, heat production, and maintaining internal organ functions.

Skeletal muscle, smooth muscle, and cardiac muscle.

Three Types of Muscle

Skeletal Muscle

Voluntary, striated muscle attached to bones containing multinucleated cylindrical fibers.

Smooth Muscle

Involuntary, non-striated muscle with a single centrally-located nucleus found in blood vessels, gastrointestinal tract, urinary tract, uterus, respiratory passages, lymphatic vessels, spleen, and around hair follicles.

Cardiac Muscle

Involuntary, striated muscle found only in the heart, containing more mitochondria, intercalated discs, and a centrally-placed nucleus.

movement of the body, maintenance of posture, heat production, respiration, communication, constriction of organs and vessels, and contraction of the heart.

Functions of Muscular System

Movement of the Body

A function of the muscular system where standing, walking, and running are accomplished through contracting skeletal muscles.

Maintenance of Posture

A function of the muscular system where trunk muscles contract to allow standing and sitting erect.

Heat Production

A function of the muscular system where contracting muscles produce heat to maintain body temperature.

Respiration

A function of the muscular system where the diaphragm and intercostal muscles act as the two major muscles that help us breathe.

Communication

A function of the muscular system where writing, texting, speaking, making gestures, and facial expressions require muscle contraction.

Constriction of Organs and Vessels

A function of the muscular system where muscle action regulates blood flow and the movement of food through the gastrointestinal tract.

Contraction of the Heart

A function of the muscular system where the heart acts as a muscular pump to circulate blood.

Striated (contains striae under the microscope), voluntary, multinucleated cylindrical fibers, double-layered sarcolemma, alternating light (isotropic) and dark (anisotropic) bands, and contains myofilaments (actin and myosin).

Characteristics of Skeletal Muscle

Striated, contains more mitochondria, features intercalated discs, and has a centrally-placed nucleus.

Characteristics of Cardiac Muscle

Non-striated (whitish appearance), single centrally-located nucleus, located in the walls of blood vessels, gastrointestinal tract, urinary ducts, uterus, respiratory passages, lymphatic vessels, spleen, and around hair follicles of the skin.

Characteristics of Smooth Muscle

Intercalated Disc

Specialized microscopic junctions found between cardiac muscle cells that facilitate synchronized contraction.

Muscles are usually named by Latin terminologies based on their location, direction of fibers, action, size, number of heads, and points of attachment.

How Muscles Are Named

75% water, 20% protein, and 5% carbohydrates, lipids, inorganic salts, and extractives.

Chemical Composition of Muscle

electrical, chemical, structural, and mechanical.

Four Changes in Muscle Contraction

Electrical Change in Muscle Contraction

The release of nerve stimuli during muscle contraction.

Chemical Change in Muscle Contraction

The release of acetylcholine into the neuromuscular junction during muscle contraction.

Structural Change in Muscle Contraction

The shortening of muscle structure during muscle contraction.

Mechanical Change in Muscle Contraction

The execution of movement or contraction by the muscle.

Muscle Contraction Rule

The rule stating that when muscles contract or change in length, myofilaments do not shorten, but instead slide past each other.