Question

Duration of a single muscle contraction is 200 mс, excitement is 5 mс. Determine the frequency of irritation that causes the formation of incomplete and complete tetanus

Answer 1

Answer:

Twitch and tetanus responses

Skeletal muscles respond to a single electric shock of sufficient magnitude by rapid, intense contractions called phasic contractions. If the ends of a frog sartorius muscle (at 0 °C) are fixed to prevent shortening, the tension increases for about 200 milliseconds and then begins to decrease, at first rather rapidly and then more slowly. More happens during this mechanical response to a single stimulation, called a twitch, than the tension record suggests

Explanation:

The mechanical response to repeated stimulation depends on the rate of the stimulation. Muscle, like other excitable tissues, has a period following its action potential during which the membrane will not respond to stimulation regardless of the strength. This absolute refractory period in the frog sartorius at 0 °C lasts about 10 milliseconds after stimulation. Therefore, a second pulse within that time span will not elicit any response. If, however, the pulses are 300 milliseconds apart, the muscle will be relaxing when the second pulse is given, and the tension will appear in waves in phase with the stimulation, causing an unfused tetanus. It is possible to stimulate the muscle at a frequency between these extremes so that the tension developed by the muscle remains constant. This latter type of contraction is called a fused tetanus, and the rate of stimulation that produces it is called the fusion frequency. The exact rate depends upon the particular muscle and the temperature.

Usually, the maximum tetanus