Twitch, Tetanus, Fatigue

isometric contraction

Muscle contracts but there is no movement, muscle stays the same length

wave summation

The situation in which contractions become stronger due to stimulation before complete relaxation occurs.

Tetanus

a sustained muscular contraction resulting from a rapid series of nerve impulses In incomplete (unfused) tetanus the muscle partially relaxes between the stimuli In complete (fused) tetanus, no relaxation is observed between the stimuli.

relaxation period

calcium ions are removed from the cytoplasm, cross bridges disappear, and the elastic components pull the sarcomere back to its original configuration.

latent period

excitation of the muscle fiber occurs and calcium ions are released from the sarcoplasmic reticulum into the cytoplasm of the cell

Motor (muscle) twitch

is the response of a muscle to a single stimulation. done in 3 phases

motor unit

A motor neuron and all of the muscle fibers it innervates

muscle fatigue

Inability of muscle to maintain its strength of contraction or tension; may be related to insufficient oxygen, depletion of glycogen, and/or lactic acid buildup NOT comparable to physiological fatigue

Motor twitch components

Latent Period Contraction Period Relaxation Period

refractory period

a period of inactivity after a neuron has fired only occurs in cardiac muscles

contraction period

cross bridges are formed between the thick and thin filaments and the sarcomere shortens

isotonic contraction

eccentric: (extend) muscle contracts and increases in length concentric: (flex) muscles contract and shorten

muscles with small motor units

muscles that exert fine control EX: fingers and eyes

Components of a motor unit

one motor neuron and all the muscle fibers it innervates

Treppe

the gradual increase in muscular contraction following rapidly repeated stimulation the "warm-up" phenomenon

muscles with large motor units

weight bearing muscles EX: thigh, hips