Kines Lec 2, Muscles

Irritability

Ability to respond to a stimulus

Contractibility

Ability of a muscle to contract against some resistance

Extensibility

Ability of a muscle to extend beyond its normal length

Elasticity

Ability of a muscle to return to its resting length after it has been stretched

Epimysium Tissue

Surrounds whole muscle

Perimysium Tissue

Surrounds bundle of fibers (fasciculus)

Endomysium Tissue

Surrounds individual muscle fibers

Myofibrils

Made of sarcomeres, contractible unit of cell

Sarcoplasm

Cytoplasm of muscle cell

Sarcoplasmic Reticulum

Found in Sarcoplasm, series of channels that store calcium in muscle

Transverse Tubules

Channels that run through fiber, transmit electrical impulses

Slow twitch muscles

Type 1, oxidative, aerobic

Type IIa muscle fiber

Fast twitch, anerobic, oxidative/glycolytic

Type IIx

Fast twitch, anerobic, glycolytic, (most explosive)

Parallel muscle fiber

Fibers run length of muscle and are parallel to each other

Pennate muscle fibers

Fibers run diagonally in relation to tendons, typically shorter in length

Intrinsic muscle

Muscle actions don’t extend beyond area that muscle belongs to

Extrinsic

Muscles originate in an area outside of area that it acts on

Innervation

Particular portion of the nervous system that provides a stimulus for muscle actions

Amplitude

Difference in muscle fiber length from minimum to maximum lengthening

Origin of muscle

Least movable point of attachment, typically most proximal

Insertion of muscle

Most mobile point of attachment, typically most distal

Isometric contraction

Tension occurs without change in length of joint angle

Isotonic muscle contraction

Tension causes joint angle to change

Concentric

Shortening of muscle - working against gravity, harder (bicep curl)

Eccentric

Lengthening of muscle, working with gravity, easier (sitting in a squat)

Agonist muscle

Major source of movement

Antagonist muscle

Opposite of agonist, relaxes to allow joint to move

Stabilizer muscles

Fixates a joint or area to allow for movement of another

Synergist muscle

Assists agonist muscle in preventing unwanted actions

Proprioceptors

Receptors found in skin, muscles, joints, tendons that respond to stretch, contraction and tension

Stretch reflex

If muscle is stretched too rapidly, CNS sends a signal to contract muscle

Golgi Tendon Organs (GTO)

Located in tendons to sense tension + contraction, when GTO threshold is reached, it signals to CNS to tell muscle to relax

Action potentials

Electrical signals from CNS that tell muscles to contract

Subthreshold stimulus

Stimulus isn’t big enough

Threshold stimulus

Stimulus is big enough, action potential is created

Maximal stimulus

Stimulus is large enough to make all motor units fire