prequiz 9

twitch

an entire muscle is given a single electrical stimulus of sufficient strength, it produces a single contraction

latent phase

time between the application of stimulus and beginning of contraction

contraction phase

muscle shortens according to the sliding filament theory

relaxation phase

the muscle returns to its initial resting length

all or none law

individual muscle cells contract fully or not at all, single muscle cell cannot partially contract

neuromuscular junction

the area of contact between the axon and the muscle fiber

multiple motor unit summation

increased force of contraction caused by the recruitment of additional motor unit, these additional muscle cells are stimulated to contract by increasing strength of stimulus

temporal summation

occurs when the frequency of stimulation is increased

threshold stimulus

the weakest stimulus that can initiate a contraction

subthreshold

a stimulus of less than threshold strength

tetanus

muscle does not have enough time to relax and the contractions summate, even higher frequency causes fusion of twitches to cause single sustained contracted

muscle fatigue

a decline in a muscles ability to maintain a constant level of force, or tension, after prolonged, repetitive stimulation

What is electromyography?

by placing electrodes on the skin, we can detect, record, and display the muscle fibers’ electrical activity during contraction

Will you use an electrode or transducer to record EMG?

electrode

What experiment will you perform using this technique?

subject will clench fist at different degrees then relax