Treppe:
- It is the progressive increase in the force of contraction for the first two to three contractions when a muscle is stimulated repeatedly.
Clonus:
- With repeated maximal stimulation during the mid relaxation phase of the previous stimulus, the muscle relaxes but not completely.
Tetanus:
- It is a state of sustained contraction. The muscle remains in a state of tonic contraction without relaxation.
Q.1 What is tetanizing frequency?
- The “tetanizing” or “fusion” frequency is that rate of stimulation at which there is complete fusion of individual contractions to produce tetanus. In amphibian muscle and in “slow” muscle fibers, the tetanizing frequency is about 30/sec, while in mammalian muscle and in “fast” fibers, it is 60 or more stimuli per second.
Q.2 What is “treppe” or “staircase effect”?
- When a skeletal muscle is stimulated with a series of stimuli just below the tetanizing frequency, there is a progressive increase in the tension (force) developed during each twitch until, after a number of contractions, there is no further increase in tension.
- Treppe (German word for staircase) can also be demonstrated in cardiac muscle, which, however, cannot be tetanized due to its refractoriness during the contraction phase. Treppe should not be confused with summation of contractions and tetanus.