A
subminimal stimulus or subthreshold stimulus is a stimulus that does not evoke
a response.
A threshold
stimulus is the minimum strength of stimulus that is just sufficient to evoke a
response.
A maximum
stimulus produces maximum response.
A
supramaximal stimulus is stronger than a maximal stimulus, but does not change
the magnitude of contraction after reaching a peak level.
Q.1 What is a motor unit?
- A single anterior horn cell (alpha motor neuron), its axon and all its branches, and all the muscle fibers innervated by this neuron is called a motor unit.
Q.2 What is all or none phenomenon?
- The all-or-none phenomenon refers to the relationship between the strength of a stimulus and the extent of response of a single unit of excitable tissue.
- The law states that under the same experimental conditions, a unit tissue responds to its maximum possible extent, (or does not respond at all, if the stimulus is subthreshold) whatever the strength of stimulus.