Chapter 5 - Muscular System

Agonist

(Prime mover) A muscle or muscle group that causes the motion (elbow flexion agonist = biceps muscle)

Stabilizer

A muscle or muscle group that supports, or makes firm, a part and allows the agonist to work more efficiently. (abdominal muscles stabilize during push-up)

Antagonist

A muscle that performs the opposite motion of the agonist (elbow flexion antagonist = triceps muscle)

Synergist

A muscle that works with one or more other muscles to enhance a particular motion.

Assisting mover

Assist in providing a motion but not as effective as the prime mover (elbow flexion assisting mover = pronator teres muscle)

Total tension

Combination of passive and active tension

Active tension

Comes from the contractile units (releasing one end of a stretched rubber band)

Neutralizer

Contracts to prevent the unwanted motion of a muscle that can do two or more actions. (pronator teres contracts to counteract the supination of the biceps so elbow flexion can occur)

Triangular muscle

Flat and fan-shaped with fibers radiating from a narrow attachment at one end to a broad attachment at the other. (pectoralis major)

Rhomboidal muscle

Four-sided, flat, with broad attachments at each end. (Rhomboids)

Irritability

The ability to respond to a stimulus.

Insertion

The attachment of a muscle to a more movable bone that moves toward a more stable bone (origin). Tend to be more distal.

Origin

The attachment of a muscle to a stable bone. Tend to be closer to the trunk

Excursion

The distance from maximum elongation of a muscle to maximum shortening of a muscle. Muscle is capable of being shortened 1/2 of its normal resting length and can stretch twice as far as it can be shortened.

Tension

The force built up within a muscle. Can be passive or active.

Tenodesis (tendon action of a muscle

The functional use of passive insufficiency (wrist pronation - fingers extend/wrist supination - fingers flex)

Normal resting length

The length of a muscle when it is unstimulated.

Elasticity

The muscle's ability to recoil or return to normal resting length when the stretching or shortening force is removed.

Contractility

The muscle's ability to shorten or contract when it receives adequate stimulation.

Extensibility

The muscle's ability to stretch or lengthen when force is applied.

Active insufficiency

The point where a muscle cannot shorten any farther. Occurs to the agonist -the muscle that is contracting. (normal knee flexion vs. passive knee flexion)

Isotonic Contration

The resistance remains constant but the velocity varies.

Tone

The slight tension that is present in a muscle at all times

Isotonic Contraction

When a muscle contracts and the muscle length and joint angle changes. (Bicep curl with weight)

Isometric Contraction

When a muscle contracts producing force without changing the length of the muscle. The muscle is contracted but no joint muscle occurred. (hand pushing on wall)

Cocontraction

When the antagonist contracts at the same time as the agonist. Occurs when there is a need for accuracy.

Open kinetic chain

When the distal segment is free to move while the proximal segment can remain stationary (extending knee in sitting position without using the hip or ankle)

Reversal of muscle action

When the more movable end of a muscle becomes less movable (humerus toward forearm during pull-up)

Multipennate muscle

Oblique - Have many tendons with oblique fibers in between. Looks like two feathers together. (deltoid)

Unipennate muscle

Oblique - Look like one side of a feather. (tibialis posterior muscle of the ankle)

Bipennate muscle

Oblique - Looks like a common feather. (rectus femoris)

Muscle tissue properties

Irritability, contractility, extensibility, and elasticity.

Muscle name categories

Location, shape, action, number or heads or divisions, attachments (origin/insertion), direction of fibers, size of the muscle.

Strap muscle

Long and this with fibers running the entire length of the muscle. (sternocleidomastoid)

Oblique muscle

Muscle fibers arranged oblique to the muscle's long axis. Shorter but more numerous than parallel, tend to have greater strength potential but a smaller ROM.

Parallel muscle

Muscle fibers arranged parallel to the muscle's long axis. Longer with a greater range of motion potential.

Passive insuffiency

Occurs when a muscle cannot be elongated any farther without damage to its fibers. Occurs to the antagonist -the muscle that is relaxed and opposite the agonist. (hamstrings when bending over to touch toe: stretched over two joints at the same time- the hip and the knee)

Eccentric Contraction

Occurs when there is joint motion but the muscle appears to lengthen; the muscle attachments separate. Movement is usually with gravity. It is a deceleration activity. (pulling weight back down after bicep curl)

Concentric Contraction

Occurs when there is joint movement, the muscles shorten, and the muscle attachments move toward each other. Movement is usually against gravity. It is an acceleration activity. (Curling weight with bicep)

Isokinetic Contraction

Only done with special equipment. Resistance to the part varies, but the velocity, or speed, stays the same.

Gravity Eliminated Position

Putting a person in such a position that their exercise is NOT working against gravity.

Closed kinetic chain

Requires the distal segment is fixed and the proximal segments move (Sitting to standing: feet are fixed, cannot move knee without causing movement in hip and ankle when standing up)

Fusiform muscle

Shaped similar to a spindle. Wider in the middle and tapers at both ends. (biceps)

Passive tension

Stretching - involves the noncontractile units of a muscle. (stretching a rubber band)