A neuron refers to a specialized cell of the nervous system that transmits sensory information in form of chemical and electrical signals across the body (Sircar 34). It can perform its function because it can be electrically exciting. A typical vertebrate neuron comprises three main parts that include a cell body or soma, dendrites, and an axon (Sircar 36). The cell body has several dendrites arising from its surface and a single axon at the terminal end. Dendrites comprise thin cellular structures that coalesce to form a complex structure known as a dendritic tree (Sircar 37). An axon refers to a cellular extension that transmits signals from the cell body to the dendrites. In invertebrates, the length of an axon could be a meter or longer depending on the species of the organism. A vertebrate’s neuron possesses a single axon. However, the axon branches several times along its length. Information transmission takes place from an axon of one neuron to a dendrite of another neuron through the aid of chemicals known as neurotransmitters (Sircar 41).
Synaptic transmission of an action potential occurs in four main steps. First, an action potential arrives at the surface of a synaptic knob and induces the release of a neurotransmitter that causes the movement of calcium ions into the synaptic knob (Saladin 73). The body produces and stores neurotransmitters in vesicles that are stimulated during signal transmission to release a specific neurotransmitter. Secondly, the neurotransmitter is released from the terminal into the synaptic cleft where it is recognized by receptors to transmit the signal successfully (Saladin 73). Receptors are specific. Specific receptors recognize specific neurotransmitters. A receptor can either amplify a signal or inhibit it depending on its nature. Thirdly, the neurotransmitter encounters the receptors of the postsynaptic cell. If it is recognized, it transmits the signal along the neuron. Fourthly, the neurotransmitter is inactivated to stop it from stimulating the postsynaptic cell after the signal has been transmitted. In addition, inactivation of the neurotransmitter enables receptor sites to receive another action potential by binding more neurotransmitter molecules (Saladin 74).
Glial cells refer to components of the nervous system that facilitate its proper functioning. Types of Glial cells include astrocytes, microglia, oligodendrocytes, and Schwann cells (Lopez 88). Each of these groups of cells performs a different function. Their functions include facilitating the repair of the nervous system and nourishing it. In addition, they foster the advancement of the nervous system and act as a metabolic center for neurons. Astrocytes constitute a part of the brain’s capillaries and their function is to determine which substances enter the brain and which substances are blocked from entering the brain by forming a blood-brain barrier (Lopez 88). Microglia cells are part of the central nervous system and their function is to get rid of cellular waste as well as protect the nervous system from attack by microorganisms (Lopez 89). Oligodendrocytes are components of the myelin sheath and their function is to insulate the central nervous system by covering the axons of neurons. Schwann cells are components of the peripheral nervous system and their function is to form a myelin sheath that insulates the nervous system (Lopez 91). Schwann cells and Oligodendrocytes also facilitate the conduction of signals through the neuron because myelinated nerves increase the speed of signal transmission.
Works Cited
Lopez, Brian. Glial Cell Function. New York: Gulf Professional Publishing, 2003. Print.
Saladin, Kenneth S. Nervous Tissue in Anatomy and Physiology: The Unity of Form and Function. New York: McGraw-Hill, 2001. Print.
Sircar, Sabyasachi. Principles of Medical Physiology. New York: Thiem Publishers, 2008. Print.