Stimulus Suprathreshold

Stimuli are various influences that lead to the appearance of an excitation process in nerve centers and peripheral nerve fibers. Based on the nature of the changes caused, two types of stimuli are distinguished - constant and variable.

Non-constant stimuli are intermittent, so they are often caused by fluctuations in the frequency or amplitude of the stimulus at a constant value; this type of irritation is denoted by the letter ¨f¨¨, and a constant stimulating agent is simply denoted by the letter S. Irritation by constant impulses is also called biocurrent or physical current, and the perception of such impulses is denoted by the letter I.

Variable stimuli are caused by changes in the frequency, amplitude, or phase of signal oscillations, but tend to have some stability in these parameters over time. In electrophysiology, such stimuli are denoted by the letter V, and the main physical parameter of the signals, the change in which causes the effect, is called the variable strength parameter. An alternating signal of type V1 is a stimulus where the amplitude changes; a stimulus of type V2 is a stimulus with a changing frequency; a stimulus of type V3 is a signal with a changing phase of the stimulus. To determine the magnitude of the stimulus, the parameter P is used - intensity or dose. The intensity of the stimulus V becomes equal to its parameter P. At this measurement interval, the parameter Q either cannot be measured due to the absence of an analogue in nature or a signal receiver. The type of stimulus influences the strength of the response to it, and it usually takes longer to reach threshold. The body's reactions that occur after the cessation of external influence are characterized not only by their absolute value, but also by time parameters, for example, adaptation delay, latency, and the presence of a postparabital period.

**Suprathreshold stimuli** The value of the stimulus P, which exceeds its threshold value P0, is called a suprathreshold stimulus. In this case, P is greater than P0, but less than the critical Pk. What is important is the influence of only such stimuli on excitable structures such as nervous tissue, in particular nerve and muscle cells. At