Set 1 — CH 6 Key Terms: Muscle Structure and Function

creatine

A substance in muscle cells that stores energy for contraction

glycogen

A complex sugar that is stored for energy in muscles and in the liver

isometric

Pertaining to a muscle action in which the muscle tenses but does not shorten (literally: same measurement)

isotonic

Pertaining to a muscle action in which the muscle shortens to accomplish movement (literally: same tone)

lactate

An organic compound that accumulates in muscle cells functioning without enough oxygen (anaerobically), as in times of great physical exertion

motor unit

A single motor neuron and all of the muscle cells that its branches stimulate

myoglobin

A protein similar to hemoglobin that stores oxygen in muscle cells

acetylcholine (ACH)

A neurotransmitter that stimulates contraction of skeletal muscles

actin

One of the two contractile proteins in muscle cells; the other is myosin

agonist

A muscle that carries out a given movement (from Greek agon meaning "contest," "struggle")

antagonist

The muscle that opposes an agonist; it must relax when the agonist contracts

cardiac muscle

Involuntary muscle that makes up the heart wall

fascia

The fibrous sheath of connective tissue that covers a muscle; called deep fascia to differentiate it from the superficial fascia that underlies the skin (root: fasci/o) (plural: fasciae)

fascicle

A small bundle, as of muscle or nerve fibers

insertion

In a given movement, the point where a muscle is attached to a moving part of the skeleton

muscle

An organ that produces movement by contracting; also the tissue that composes such organs (roots: my/o, muscul/o)

myosin

One of the two contractile proteins in muscle cells; the other is actin

neuromuscular junction (NMJ)

The point of contact, or synapse, between a branch of a motor neuron and a muscle cell

origin

In a given movement, the point where a muscle is attached to a stable part of the skeleton

prime mover

The main muscle involved in a given movement

skeletal muscle

Voluntary muscle that moves the skeleton and maintains posture

smooth muscle

Involuntary muscle that makes up the wall of hollow organs, vessels, and ducts; visceral muscle

synergist

A muscle that assists a prime mover to produce a given movement

tendon

A fibrous band of connective tissue that attaches a muscle to a bone (roots: ten/o, tendin/o)

tonus

A state of steady, partial muscle contraction that maintains firmness; muscle tone (root: ton/o)