What is meant by stimulus and reaction?
Stimulus is the change in the environment or environmental factors to to which the organism can respond or react. Theresponse shown by organisms towards or awaya stimulus is called reaction.
What is a neuron? Describe the structure of neuron with neat and clean figure.
A neuron or nerve cell is a highly specialized cell which acts as the structural and functional unit of nervous system.
A neuron basically consists of three parts, viz. cell body, axon and dendrites. The cell body contains large central nucleus surrounded by cytoplasm. The cytoplasm contains granules and neurofibrils along with mitochondria, endoplasmic reticulum, golgi complex, etc. Numerous short, thread like structure arises from the cell body (dendrites) which carries the impulses to nerve cell. One of dendrites grows very large which is called axon. It carries impulses, away from the cell.