What is Summation Twitch and Tetanus

Tetanic contraction

from Latin: contrahere - to contract
Synonym: permanent contraction, electrotonus, tetanus

1 definition

As tetanic contraction In physiology, one describes the permanent shortening of a muscle cell or muscle tissue through rapidly successive action potentials or a permanent depolarization on the motor end plate.

2 classification

There are two types of tetanic contraction:

  • Incomplete tetanus: Several action potentials hit one after the other so that the contractions overlap (superposition). The individual twitches can still be registered, so the frequency of the muscle contractions corresponds to the stimulus frequency.
  • Complete tetanus: As a result of the high action potential frequencies, the muscle can no longer relax. As a result, there is a permanent contraction. The individual twitches can no longer be registered and the frequencies of the individual muscle contractions merge. The lowest stimulus rate at which a full tetanus occurs is called the fusion rate.

3 physiology

Arbitrary contractions of the skeletal muscles are usually superimposed single twitches. This allows a higher force to be generated.

The heart muscle cannot be tetanized due to the long refractory phase.