If we were to give the worm a stimulus pulse with a very low

If we were to give the worm a stimulus pulse with a very low voltage (slightly above threshold) but a long duration could we get the same response with a higher voltage but a shorter duration? (Explain your response remembering that we are NOT stimulating a single neuron.)

Solution

The nervous system of small worms and humans are fundamentally different from each other. Whereas the vertebrate/human nervous system shows all-or-none mode of function, the invertebrate nervous system does not follow this rule for impulse transmission. According to the all-or-none rule, if a stimulus of intensity strongh enough to cross the threshold is applied, it will produce a full reaction in the neuron just like a stimulus of very high intensity. However, this does not hold good for the invertebrate nervous system.

For the primitive type of nervous systems, the strength/intensity and duration of stimulus plays critical role in transmission of information. The longer the time of stimulus application, the more extended response is made by the organism.

Thus, if a worm is stimulated with a pulse of very low voltage, it will produce a different response from the one when a higher voltage is applied for shorter duration. This will be dependent upon the intensity and duration of the impulse on the neuron of the worm. Owing to functional simplicity of nervous system of worms, a stimulus with very low voltage for extended time will be more damaging in nature as compared to a stimulus of higher voltage but shorter duration.