Muscle Physiology and Mechanics

Flashcards covering muscle structure, mechanics, contraction types, and related concepts from a lecture on muscle physiology.

Sarcomere

The basic contractile unit of muscle fiber.

Myofibril

A long, filamentous organelle found in muscle cells that has a repeating pattern of sacromeres.

Myofilaments

The structure containing the thick (myosin) and thin (actin) filaments.

Active Components of Muscle

The contractile elements of muscle tissue.

Passive Components of Muscle

The non-contractile, connective tissue elements of muscle.

Parallel Components (muscle)

Connective tissue that responds in the same manner as contractile components; shortens and lengthens with contraction.

Series Elastic Components

Connective tissue in series with contractile components that responds opposite that of contractile tissue; an example is the tendon.

Motor Unit

One alpha motor neuron and all the muscle fibers it innervates.

Recruitment

Firing motor units to create action potentials to specific muscle fibers.

Henneman's Size Principle

The principle stating motor units are recruited in order of size, from smallest to largest.

Concentric Contraction

Muscle shortening.

Isometric Contraction

Muscle contraction with no change in length.

Eccentric Contraction

Muscle lengthening.

Active Tension

Tension developed by contractile elements of muscle.

Passive Tension

Tension developed in the passive elastic components of muscle.

Length-Tension Curve

Illustrates the optimal alignment or length of sarcomeres for maximal isometric tension.

Active Insufficiency

The decrease in muscle tension production capability. Occurs when a full ROM is actively attempted simultaneously at all joints by a two- or multi-joint muscle due to the 'over-shortening' of the muscle .

Passive Insufficiency

When a muscle (usually an antagonist) demonstrates insufficient length to allow full ROM being attempted by the agonist(s). This involves passive or elastic elements reaching their elastic limit.

Tenodesis

The passive response of the wrist and hand to passive tension of the wrist/finger musculature when only the wrist extensors are active.

Force-Velocity Relationship

As the speed of the shortening contraction increases, tension decreases, and as the speed of lengthening increases, tension increases.

Fusiform Fibers

Muscle fibers with a line of action nearly parallel to the tendon and length of fiber. These muscles tend to be longer with more sarcomeres and are best for speed.

Pennate Fibers

Muscle fibers with a line of action at an angle to the tendon. These muscles are shorter, in general, than fusiform muscles and are best for strong force production.

Physiological Cross-Sectional Area (PCSA)

Area of the cross section of a muscle perpendicular to its fibers, generally at its largest point indicating the number of contractile proteins.

Agonist

Prime mover; the muscle responsible for producing the desired or specific movement at a joint.

Antagonist

Muscles directly opposite to the desired motion. These have the potential to oppose action but are usually inactive and passively elongate.

Co-contraction

When antagonist and agonist work or contract at the same time. May be desired, such as for stability or pathological.

Synergist

Muscles functioning in cooperation with an agonist to peform a desired motion.

Sarcopenia

The loss of muscle mass often associated with aging.

Electromyography (EMG)

Study of muscle function through inquiry of the electrical signal the muscle emulates.