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