Communication occurs within and between neurons in very specific ways that allow

Question

Communication occurs within and between neurons in very specific ways that allows the information to be held to the standard of independence of identical signals stated in the neural doctrine (The hypothesis that the brain is composed of separate cells that are distinct structurally, metabolically, and functionally). For example, sodium is used to depolarize the cell in both the dendrites and the axon, but the channels are gated by different mechanisms that confer unique, functional responses. Using the example just given, explain how you understand the neural doctrine and the necessity of create these different types of signals. How is this process replicated in neural circuits, where hundreds of neurons are making contacts and all signaling with action potentials?

Explanation / Answer

The central nervous system (CNS) is composed of two kinds of specialized cells: neurons and glia. The function of a neuron is to receive input "information" from other neurons, to process that information, then to send "information" as output to other neurons. Synapses are the connections between neurons through which "information" flows from one neuron to another. Glia (or glial cells) are the cells that provide support to the neurons. To achieve long distance, rapid communication, neurons have evolved special abilities for sending electrical signals (action potentials) along axons. This mechanism, called conduction, is how the cell body of a neuron communicates with its own terminals via the axon. Communication between neurons is achieved at synapses by the process of neurotransmission. Ions move across the membrane by ion channels that are able to open and close due to the presence of neurotransmitter. The influx and outflux of ions (through ion channels during neurotransmission) will be responsible to make the inside of the target neuron more positive (de-polarized). When this depolarization reaches a point of no return called a threshold, a large electrical signal is generated. This is called as the action potential. At electrical synapses, two neurons are physically connected to one another through gap junctions. Gap junctions permit changes in the electrical properties of one neuron to effect the other, and vice versa. So, the two neurons essentially behave as one. Chemical neurotransmission occurs at chemical synapses. In chemical neurotransmission, the presynaptic neuron and the postsynaptic neuron are separated by a small gap called as the synaptic cleft. The synaptic cleft creates a physical barrier for the electrical signal carried by one neuron to be transferred to another neuron.

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