Anatomy: Ch. 6 Vocabulary Terms

Skeletal Muscle

Muscle composed of cylindrical, multinucleated cells with obvious striations, these muscles are attached to bone, and are voluntary muscles.

Smooth Muscle

Muscle composed of spindle-shaped, unstriped (non-striated) muscles cells, uni-nucleated, and involuntary

Cardiac Muscle

Specialized muscle of the heart. Is uni-nucleated, involuntary, has intercalated disks, and is elongated cylindrical fibers that branch.

Endomysium

Thin connective tissue surrounding each muscle cell or fiber.

Perimysium

The connective tissue enveloping bundles of muscle fibers.

Epimysium

The sheath of fibrous connective tissue surrounding a muscle.

Origin

This is where a muscle is attached to the immovable or less movable bone.

Insertion

The movable attachment of a muscle as opposed to the origin.

Tendon

Skeletal muscles are often attached to bone by these cordlike structures.

Voluntary

Muscle under control of the will; (ex: skeletal muscle).

Involuntary

Muscle not under the control of the will; usually consists of smooth muscle tissue and cardiac muscles.

Antagonistic

Muscles that act in opposition to an agonist or prime mover.

Muscle

Is the contractile tissue of animals, responsible for movement (3 types). Has the ability to contract.

Muscle fiber

Is a muscle cell, an individual component of a skeletal muscle. Each fiber contains 4-20 myofibrils.

Myofibril

Contractile organelles found in the cytoplasm of muscle cells. These are made up of sarcomeres.

Sarcomeres

Is the basic unit of a muscle's cross-striated myofibril (cylindrical organelles found within muscle cells). These are multi-protein complexes composed of different filament systems.

Myofilaments

Filaments composing the myofibrils. Two types: Actin and myosin

Actin

These are the thin filaments in a myofibril

Myosin

These are the thick filaments in a myofibril

Sliding Filament Model

A proposed mechanism of muscle contraction in which the actin and myosin filaments of striated muscle slide over each other to shorten the length of the muscle fibers (see sarcomere). The actin slide over the myosin.

Acetylcholine

A neurotransmitter that stimulates a skeletal muscle to contract.

Tropomyosin

An actin-binding protein that regulates actin mechanics, in muscle contractions.

Troponin

Is found at regular intervals along the actin filament, it binds both tropomyosin and actin molecules. Calcium ions bind to it.

Sarcoplasmic Reticulum

A specialized network of membranes in skeletal muscle that functions in the storage of calcium.

Synaptic Cleft

The gap between the motor neuron and the muscle fiber it supplies at the neuromuscular junction.

Lactic Acid

The product of anaerobic metabolism, especially in the muscle

Isotonic contractions

Having a uniform tension, of the same tone, muscle shortens and movement occurs.

Isometric contractions

Movement against an immoveable object; muscles don't shorten, (same length).

Atrophy

A wasting away of muscle.

Hypertrophy

An increasing in size of muscle.

Motor Unit

A motor neuron and all the muscle cells it supplies.

Motor Neuron

Neurons that carry impulses toward muscle fibers.

Tetanus

A smooth sustained muscle contraction

Tonus

Is a condition in which a muscle is kept partially contracted over a period of time, (muscle tone).

Anaerobic

Without oxygen.

Aerobic

With oxygen.

Hamstrings

Refers to one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee.

Quadriceps

The large muscle at the front of the thigh, which is divided into four distinct portions and acts to extend the leg.

Prime Mover

The muscle that has the major responsibility for causing a particular movement.

Sarcolemma

Cell (plasma) membrane of the muscle fiber.