The Sensory Nervous System Essay Example | Topics and Well Written Essays - 500 words

The Sensory Nervous System - Essay Example The basic unit of the entire nervous system is the neuron. The neurons themselves have three parts 1) the dendrite-which receive message impulses from other cells and transmits it to the cell body 2) the cell body 3) the axon-which transmits messages away from the cell body. There are three types of neurons namely sensory or afferent neurons, motor or efferent neurons and intermediate neurons. The sensory neurons are responsible for the transmission of messages from the various sensory receptors or organs in the human body, which receive the external stimulus, to the central nervous system. The intermediate or relay neurons are present only in the CNS. The motor neurons transmit the message impulses from the CNS to the corresponding effector organ which might be a muscle or a gland which responds to the received impulse. The plasma membrane of the neuron has an unequal distribution of electrical charges between its inner and the outer surfaces, i.e., positive on the inner membrane an d negative on the outer membrane. When a message impulse is to be transmitted the polarities reverse temporarily resulting in what is known as an action potential. This action potential which begins in one spot spreads to the adjacent membranes thereby transmitting the message across a neuron. While the action potential allows transmission within a neuron neurotransmitters allow the transmission of messages between different neurons through the synaptic cleft. The synapse is the space between two nerve cells. (Farabee, 1992). Depending on the type of external stimuli, various parts of the brain are targeted through various pathways through the spinal cord. For example the somatosensory system has three modalities. One particular modality being the discriminatory touch enables the human body to perceive shapes and sizes by touch alone. In this system sensory inputs are provided