Physiology Lab this week began with pithing and dissecting Lithobates pipiens (Northern Leopard Frogs) to remove the gastrocnemius. After removing the gastrocnemius (the muscle of the lower leg) we attached it alternating current and measured the contract time, relaxation time, latency and amplitude of the skeletal muscle.
The second half of the lab measured summation and tetany. Summation is the process in which small motor units are contracted and recruit larger units as a stronger contraction is needed.
When there is an increase in frequency of motor unit stimulus, the muscle fibers no longer has
enough time to remove all of the calcium from the muscle fiber, thus, the muscle does not fully relax between stimuli and there is a summation of muscle activity. If the frequency of the muscle enervation is short enough, it will result in a sustained muscle contraction called tetanus. Tetanus may be sustained until there is no longer available ATP to hydrolyze and the muscle fatigues.
About 40% of the total body mass of a human is skeletal muscle. Skeletal muscle is intimately associated with the skeletal system and, combined, these muscles and bones are responsible for supporting and moving the body.
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