Describe the events involved all the way to the brain when a person accidentally steps on a nail.

Answer and Explanation:

Pain receptors are stimulated in the skin generating an impulse. The impulse is conducted by the sensory neuron to the spinal cord. The neuron conveys the impulse to the CNS where it makes synaptic neuron connect with the motor neuron. The motor neuron conveys the impulse to the muscles of the leg. Contraction of the muscle results in withdrawal of the leg from the nail.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.