Question

All or none law is associated with-
a. Muscle fibre
b. Neuron
c. Uriniferous tubule
d. Both A and B

Answer 1

Hint: It is a physiological reaction, which was introduced by Henry Pickering Bowditch. It was further described in skeletal muscle by Keith Lucas. It stated that the strength of a response is dependent upon the strength of the stimulus.

Complete answer:
All or none law states that the strength of the nerve or muscle fibre to generate a response is independent of the strength of the stimulus. When the stimulus goes beyond the threshold, a complete response is produced by the muscle fibre and nerve.
It was established by Henry Pickering Bowditch in 1871. This was first seen in heart muscle contraction.

A single nerve terminal innervates 2 or more muscle fibres. Hence the responses of either are not related to one another. This relationship is applicable for a muscle fibre in particular. In case of nervous tissue the unit is a neuron (nerve cell). In case of skeletal tissue a muscle fibre is the unit. In case of cardiac muscle, the entire auricle or ventricle acts as a unit.

When the stimuli is stronger it brings more muscles into its action resulting in tension in the muscles. This law is not applicable to the whole muscle bundle. It is applicable to a particular muscle fibre along the path.

Hence, the correct answer is option (B).

Note: All or none law was first seen in cardiac muscle undergoing contraction. It is a type of explosive reaction. When the stimulus goes beyond the threshold, a complete response is produced by the muscle fibre and nerve.