Spinal Cord

The second important constituent of the central nervous system is the spinal cord. In fact, it is a bundle of axons covering full length of the body. Its primary function is to facilitate reflex movements. The animation given below demonstrates the mechanism of reflex action.

The sensory neuron carries the prick sensation from the painful stimulus. Through the association neurons this message is relayed to the motor neuron which in turn carries them to the muscles to cause the withdrawal reflex. Concurrently the message is conveyed to the brain. Our nervous system has three types of neurons— afferent neurons, efferent neurons and association neurons. Sensory neurons are also known as afferent neurons or receptor neurons. They carry impulses from sense organs to the brain. Motor neurons are also called efferent neurons. They carry the nerve impulse from the brain to muscles or glands. Association neurons are also called relay neuron or interneuron. They connect two neurons, thus facilitating smooth conduction of impulses.