The Nervous System :: Biology, Neurons, Axon

The peripheral nervous system consists of two separately functioning components: the sensory division and the motor division. The sensory division provides appropriate responses from sensory receptors to the central nervous system. Sensory neurons transmit reactive responses from the periphery to the central nervous system while the motor division conducts action potentials from effector organs such as muscles and glands. In contrast, motor neurons transmit action potentials from the central nervous system toward the periphery (Seeley et al., 2005). Neurons and their Electrical Activity The nervous system is composed of millions of nerve cells called neurons. Neurons are the parenchyma of the nervous system which performs every function of the nervous system from simple sensory functions to complex thinking and analysis. Neurons, upon receipt of stimuli, transmit responsive signals to other neurons or to effector organs. Clark (2005) observes that the anatomy of a neuron is composed of four main parts; the cell body, the dendrites, the axon, and the nerve fibers. Given the importance of each of the neuron components, it is important to discuss how each work separately and in tandem to achieve efficient and appropriate responses in the human body. Varying in diameter and containing a single nucleus, the cell body is the primary component of the neuron. The nucleus of the neuron provides information for protein synthesis and contains most of the organelles of the neuron. Seeley et al., (2005) write that the cell body contains large numbers of mitochondria because of its high metabolic function and also abundant rough endoplasmic reticulum’s which referred to as Nissl bodies. The dendrites of a neuron are cytoplasmic extensions that reach out from the cell body like arms and contain a full array of cellular organelles, such as mitochondria, chromatophilic substance, and ribosomes. The most important feature of a dendrite is its electrical activity. Dendrites receive information from other neurons and transmit them toward the cell body, then produce electrical impulses referred to as graded potentials. Graded potentials can have varying degrees of depolarization or hyperpolarization. These graded potentials arise in the dendrites or in the cell body as a result of various stimuli and are important in initiating action potentials in neurons. As the graded potential passes through a cell body, it may initiate an action potential at the base of another cytoplasmic projection which is the axon (Clark, 2005). An axon is a long cell process extending from the neuron cell body.