The rheobase is a measure of the excitability of the membrane potential. In neuroscience, rheobase is the minimum amplitude of current of an infinite duration (in the practical sense about 300 milliseconds) that allows to reach the threshold of depolarization of cell membranes, such as an action potential or the contraction of a muscle. [1] In Greek, the root rhe means “stream or river”, and basi means “soil or foundation”: the rheobase is therefore the minimum current that produces a potential for muscle action or contraction. The force-duration curve was first discovered by G. This is the time it takes for a dynamic force stimulus to excite the nerve and produce muscle contraction. Below this value, no muscle contraction takes place. [1] Nerve excitability studies have revealed a number of biophysical differences between human sensory and motor axons. [6] Although the diameters and conduction velocities of the most excitable motor and sensory fibers are similar, sensory fibers have significantly longer force-duration-time constants. [11] As a result, sensory nerves have a longer force-duration-time constant and a lower rheobase than motor nerves. [7] The rheobase is best understood in the context of the force-duration relationship (Fig. 1). [2] The ease with which a membrane can be stimulated depends on two variables: the strength of the stimulus and the length of time the stimulus is applied.
[3] These variables are inversely related: as the strength of the applied current increases, the time it takes to stimulate the membrane (and vice versa) to maintain a constant effect. [3] Mathematically, the rheobase is half of the current that must be applied during the duration of chronaxia, which is a time-force constant equal to the time that causes a response when the nerve is stimulated with a double rheobasic force. [3] In 1901, G. Weiss proposed another linear equation using a continuous Q-load curve. The electric charge Q can be calculated with the following equation: In clinical settings, the function of internodium can only be studied by excitability studies (see measurement). Experimental observations using threshold measurements to assess the excitability of myelinated nerve fibers have shown that the function of regenerated internodes actually remains consistently abnormal, with regenerated motor axons exhibiting high rheobase and decreased chronaxia – changes consistent with abnormal active membrane properties. [10] These studies also showed that the activity-dependent conduction block in myelination is due to hyperpolarization, as well as abnormally high Na+ currents and increased availability of fast K+ rectifiers. [10] Here are the results on changes in nerve excitability and therefore the constant strength-duration-time observed in several of the most common nervous diseases. His equation to determine the current I: In addition to the current duration, it is not possible to find the exact value of rheobase in a real cell.