Effectors are the muscles and glands, which are the exercising organs for doing action. Effectors are the organs, which bring “effects” in the environment. Effect leads to changes; we exercise our actions by our hands, legs, and muscles. Secretions from glands within the body at required time supply energies to such activities. The “effects” or changes, which are brought by our bodily effectors, are called “responses” or “performances”. Salivary glands, digestive glands, and sweat glands are a few examples of glands.

Nervous System connects all receptors with all effectors. It spreads over the entire body through nerves. A single nerve consists of a bundle of many individual neurons. Neurons in a nerve differ both in sizes of axon and diameter of axon.

There are chains of neural structures, which connect each receptor with each effectors. These connections are made by nerves and neurons inside. The neurons, which conduct impulses from the different sense organs to the brain, are called sensory neurons.

For example a neuron, which carries impulses from the ears to the brain, is an example of sensory neuron. Sensory neurons are called afferent neurons. Most sensory neurons extend from each sense organ to the central nervous system, which is composed of the brain and the spinal cord. The neurons that transmit nerve impulses from the brain to the motor organs (or effectors) are called motor or efferent neurons. The nerve impulses are carried by efferent neurons to the muscles or glands in order to contract, relax or to expand according to the responses made by the organism.