Sample Test 2

A neuron is the basic structural and functional unit of a neural tissue. The anatomy of a neuron is related to its unidirectional function of transmitting an action potential (nerve impulse) down its axon. The process starts at the dendrites containing receptors that can, for the most part, either be stimulated electrically or chemically. Following the dendritic action, we form a true action potential at the axon hillock. The axon, which may or may not be myelinated, transmits the electrochemical signal towards the other end. An unmyelinated axon transmits slower than myelinated axons that are produced by the Schwann cells. The myelin, protein coating not only protects the axon but also increases the speed of conduction. Hence, myelinated axons are found in the white matter of the spinal cord. Next, within a myelinated axon, we find regions of unmyelination called Nodes of Ranvier. These regions act as trigger transmission sites due to large concentrations of sodium ion channels. Finally, the action potential migrates toward the axonal terminal and the synaptic end bulb where a new synaptic connection can be made with another neuron, muscle, or gland.

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