antagonistic muscle

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Related to Antagonist (muscle): fixator muscle, stabilizer muscle

muscle

 [mus´'l]
a bundle of long slender cells (muscle fibers) that have the power to contract and hence to produce movement. Muscles are responsible for locomotion and play an important part in performing vital body functions. They also protect the contents of the abdomen against injury and help support the body. See appendix 3-4 and see color plates.

Muscle fibers range in length from a few hundred thousandths of a centimeter to several centimeters. They also vary in shape, and in color from white to deep red. Each fiber receives its own nerve impulses, so that fine and varied motions are possible. Each has its small stored supply of glycogen, which it uses as fuel for energy. Muscles, especially the heart, also use free fatty acids as fuel. At the signal of an impulse traveling down the nerve, the muscle fiber changes chemical energy into mechanical energy, and the result is muscle contraction.

Some muscles are attached to bones by tendons. Others are attached to other muscles, or to skin (producing the smile, the wink, and other facial expressions, for example). All or part of the walls of hollow internal organs, such as the heart, stomach, intestines, and blood vessels, are composed of muscles. The last stages of swallowing and of peristalsis are actually series of contractions by the muscles in the walls of the organs involved.
Types of Muscle. There are three types of muscle: involuntary, voluntary, and cardiac, composed respectively of smooth, striated, and mixed smooth and striated tissue.
Types and structure of muscle. From Dorland's, 2000.


Involuntary muscles are those not under the control of the conscious part of the brain; they respond to the nerve impulses of the autonomic nervous system. They include the countless short-fibered, or smooth, muscles of the internal organs and power the digestive tract, the pupils of the eyes, and all other involuntary mechanisms.

Voluntary muscles are those controlled by the conscious part of the brain, and are striated. These are the skeletal muscles that enable the body to move, and there are more than 600 of them in the human body. Their fibers are grouped together in sheaths of muscle cells. Groups of fibers are bundled together into fascicles, surrounded by a tough sheet of connective tissue to form a muscle group such as the biceps. Unlike the involuntary muscles, which can remain in a state of contraction for long periods without tiring and are capable of sustained rhythmic contractions, the voluntary muscles are readily subject to fatigue.

Cardiac muscles (the muscles of the heart) are the third kind; they are involuntary and consist of striated fibers different from those of voluntary muscle. The contraction and relaxation of cardiac muscle continues at a rhythmic pace until death unless the muscle is injured in some way.
Voluntary muscles extend from one bone to another, cause movements by contraction, and work on the principle of leverage. For every direct action made by a muscle, an antagonistic muscle can cause an opposite movement. To flex the arm, the biceps contracts and the triceps relaxes; to extend the arm, the triceps contracts and the biceps relaxes.
(See also heart.)
Physiology of Muscles. No muscle stays completely relaxed, and as long as a person is conscious, it remains slightly contracted. This condition is called tonus, or tone. It keeps the bones in place and enables a posture to be maintained. It allows a person to remain standing, sitting up straight, kneeling, or in any other natural position. Muscles also have elasticity. They are capable of being stretched and of performing reflex actions. This is made possible by the motor and sensory nerves which serve the muscles.

Muscles enable the body to perform different types of movement. Those that bend a limb at a joint, raising a thigh or bending an elbow, are called flexors. Those that straighten a limb are called extensors. Others, the abductors, make possible movement away from the midline of the body, whereas the adductors permit movement toward the midline. Muscles always act in opposing groups. In bending an elbow or flexing a muscle, for example, the biceps (flexor) contracts and the triceps (extensor) relaxes. The reverse happens in straightening the elbow.

A muscle that has contracted many times, and has exhausted its stores of glycogen and other substances, and accumulated too much lactic acid, becomes unable to contract further and suffers from fatigue. In prolonged exhausting work, fat in the muscles can also be used for energy, and as a consequence the muscles become leaner.
agonistic muscle one opposed in action by another muscle, the antagonistic muscle. Called also agonist.
antagonistic muscle one that counteracts the action of another (the agonistic muscle). Called also antagonist.
appendicular muscle one of the muscles of a limb.
articular muscle one that has one end attached to the capsule of a joint.
auricular m's
1. the extrinsic auricular muscles, including the anterior, posterior, and superior auricular muscles. See appendix 3-4.
2. the intrinsic auricular muscles that extend from one part of the auricle to another, including the helicis major, helicis minor, tragicus, antitragicus, transverse auricular, and oblique auricular muscles. See appendix 3-4.
cruciate muscle a muscle in which the fiber bundles are arranged in the shape of an X.
cutaneous muscle striated muscle that inserts into the skin.
deltoid muscle the muscular cap of the shoulder, often used as a site for an intramuscular injection. See appendix 3-4.
extraocular m's the six voluntary muscles that move the eyeball: superior, inferior, middle, and lateral recti, and superior and inferior oblique muscles. See appendix 3-4.
extrinsic muscle one that originates in another part than that of its insertion, as those originating outside the eye, which move the eyeball.
fixation m's (fixator m's) accessory muscles that serve to steady a part.
gluteal m's three muscles, the greatest, middle, and least, that extend, abduct, and rotate the thigh. See appendix 3-4.
hamstring m's the muscles of the back of the thigh, including the biceps femoris, semitendinosus, and semimembranosus. See appendix 3-4.
intraocular m's the intrinsic muscles of the eyeball. See appendix 3-4.
intrinsic muscle one whose origin and insertion are both in the same part or organ, as those entirely within the eye.
multipennate muscle a muscle in which the fiber bundles converge to several tendons.
palatine m's the intrinsic and extrinsic muscles that act upon the soft palate.
pectoral m's four muscles of the chest; See appendix 3-4.
quadrate muscle a square-shaped muscle; see appendix 3-4.
quadriceps muscle a name applied collectively to four muscles of the thigh; see anatomic Table of Muscles in the Appendices.
scalene m's four muscles of the upper thorax that raise the first two ribs, aiding in respiration. See appendix 3-4.
skeletal m's striated muscles that are attached to bones and typically cross at least one joint.
sphincter muscle a ringlike muscle that closes a natural orifice; called also sphincter.
synergic m's (synergistic m's) those that assist one another in action.
thenar m's the abductor and flexor muscles of the thumb. See appendix 3-4.
triangular muscle a muscle that is triangular in shape.
yoked m's those that normally act simultaneously and equally, as in moving the eyes.
Antagonistic muscleclick for a larger image
Fig. 38 Antagonistic muscle . Antagonistic muscles in the arm, biceps and triceps.

antagonistic muscle

any muscle which acts in opposition to another, e.g. a contractor to a relaxor or vice versa.

muscle

an organ composed of bundles of fibers that has the power to contract and hence to produce movement. Muscles are responsible for locomotion and help support the body, generate heat and perform a number of other functions. They are of two varieties: striated (or striped, voluntary or skeletal), which makes up most of the meat of a carcass, and smooth (unstriated), which includes all the involuntary muscle of the viscera, heart and blood vessels.
Skeletal muscle fibers range in length from a few millimeters to many centimeters. They also vary in color from white to deep red. Each muscle fiber receives its own nerve impulses, which trigger fine and varied motions. At the signal of an impulse traveling down the nerve, the muscle fiber changes chemical energy into mechanical energy, and the result is muscle contraction. At least two major types of muscle fiber have been identified by histochemical techniques: type I (red) fibers, which have a slow contraction; and type II (white) fibers, which have a fast contraction.
Some muscles are attached to bones by tendons. Others are attached to other muscles, and to skin, producing, for example, the skin twitch, the eye blink and hair erection. Parts of the walls of hollow internal organs, such as the heart, stomach and intestines and also blood vessels, are composed of muscles. See also muscular. For a complete list of named muscles see Table 13.

agonistic muscle
prime mover; a muscle opposed in action by another muscle, called the antagonist.
antagonistic muscle
one that counteracts the action of another muscle (the agonist).
appendicular muscle
one of the muscles of a limb.
arrector pili muscle
small, smooth muscle attached to the bulb of the hair which causes erection of the hair and compression of the attending sebaceous gland when it contracts.
arterial muscle
part of the tunica media; smooth muscle fibers arranged in a circular pattern around the lumen.
articular muscle
one that has one end attached to the capsule of a joint.
axial muscle
1. muscles derived from the somites in the embryo.
2. the muscles around the vertebral column.
muscle biopsy
sample of living muscle obtained by excision or punch.
cardiac muscle
striated involuntary muscle with branched fibers and containing modified fibers which act as cardiac conducting cells.
congenital muscle defects
may be environmental, e.g. nutritional muscular dystrophy, or inherited, e.g. splayleg of piglets.
congenital type II muscle fiber hypertrophy
occurs in the hip joint musculature in German shepherd dogs but there is no detectable abnormality of gait.
cutaneous muscle
striated muscle that inserts into the skin.
double muscle
see myofiber hyperplasia.
esophageal muscle
the tunica muscularis of the esophagus in most domestic animals is mostly striated; in pigs, horses and cats there are small segments of smooth muscle; in birds the entire tunic is smooth muscle.
extraocular m's
the six or seven voluntary muscles that move the eyeball: dorsal, ventral, medial and lateral recti, dorsal and ventral oblique, and retractor bulbi muscles.
extrinsic muscle
one that originates in another part than that of its insertion, e.g. those originating outside the eye, which move the eyeball.
fast-twitch skeletal muscle
two of the three types of skeletal muscle are pale in color and fast-twitch—type IIa (fast-twitch oxidative-glycolytic), type IIb (fast-twitch glycolytic). Type IIa fibers are fatigue-resistant, type IIb fatigue easily.
muscle fiber
see muscle (above).
fixation m's, fixator m's
accessory muscles that serve to steady a part.
hamstring m's
the biceps, semimembranosus and semitendinosus muscles. See also hamstring.
intraocular m's
the intrinsic muscles of the eyeball.
intrinsic muscle
one whose origin and insertion are both in the same part or organ, such as those entirely within the eye.
involuntary muscle
see smooth muscle (below).
iridial muscle
layers of circular (sphincter) and radial (dilator) muscles. See also iris.
jaw muscle
see Table 13.1H muscles of mastication.
laryngeal muscle
see Table 13.1E muscles of the larynx.
limb muscle
see Table 13.3, 13.4 muscles of the fore- and hindlimbs.
masseter muscle
the principal muscle of mastication. See also Table 13.1H.
mylohyoid muscle
see Table 13.1D muscles of the hyoid apparatus.
muscle neoplasms
of striated muscle—rhabdomyoma, rhabdomyosarcoma; of plain muscle—leiomyoma, leiomyosarcoma.
muscle nonstriated
see smooth muscle (below).
orbicular muscle
one that encircles a body opening, e.g. the eye or mouth.
muscle-paralyzing drugs
drugs which produce neuromuscular blockade, used as muscle relaxants during surgical procedures. Include d-tubocurarine, alcuronium chloride, pancuronium, vecuronium, atracurium besylate, succinylcholine.
red muscle
type 1 fibers predominate with slow contraction cycles and aerobic metabolism.
muscle rupture
the muscle may have torn away from its insertion, in which case the tendon will be slack, or it may be a complete or partial separation of the belly of the muscle, when the muscle will be swollen and hard. Structural and conformational changes may result, e.g. in rupture of the gastrocnemius muscle, and the hernias caused by rupture of the ventral abdominal muscles or the diaphragm.
skeletal m's
striated muscles that are attached to bones and typically cross at least one joint. Called also voluntary or striated muscles.
slow-twitch skeletal muscle
type 1 skeletal muscle fibers are bright red and contain large amounts of myoglobin; not easily fatigued.
smooth muscle
plain or involuntary muscle which powers the internal organs and is controlled by the autonomic nervous system; slow contracting cycles and fatigue resistant. Two types listed, visceral and vascular.
sphincter muscle
a ringlike muscle that closes a natural orifice; called also sphincter.
muscle spindle
sensory end-organ attached to the perimysial connective tissue of the muscle.
muscle strain
soreness and stiffness in a muscle due to overexertion or contusion, especially in muscles that have not been conditioned for hard use; some of the muscle fibers may actually tear.
striated muscle
see skeletal muscles (above).
synergic m's
those that assist one another in action.
temporal muscle
a significant muscle of mastication. See also Table 13.1H.
muscle-tendon junction
the union between connective tissue investing muscles and anchoring connective tissue.
type I muscle fiber
see slow-twitch skeletal muscle (above).
type II muscle fiber
see fast-twitch skeletal muscle (above).
type II muscle fiber deficiency
a relative deficiency of type II muscle fibers, with a predominance of type I fibers. An inherited defect in Labrador retrievers. Clinical signs include stunted growth, and muscle weakness and abnormal gait, which subside with rest, from an early age.
voluntary muscle
see skeletal muscle (above).
white muscle
consist of type II fibers; fast contraction fibers and aerobic metabolism are characteristic.
yoked m's
those that normally act simultaneously and equally, as in moving the eyes.