Basic Physiology of a Neuron and How it Fires
Describe the basic physiology of a neuron. Detail the manner by which neurons fire action potentials and how neurons communicate with one another across synapses. Outline the process of how an action petential occurs and hoe it propagates down an axon. Explain how chemical transmission occurs at synapses and how this allows neurons to activate of inhibit one another.
[Picture from "Answer to Neuron Structure"]
Neurons are the basic units of the brain. Above is a picture of a prototypical neuron with its parts labeled by number. The objects labeled by the number one are Dendrites. Dendrites conduct nerve impulses towards the nerve cell. The nucleus, which regulates activities
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Positive potassium ions then flow out and the neuron becomes negatively.After this, the neuron becomes hyperpolarized. More positive potassium ions flow out. This makes the voltage drop below -70 mv. When this occurs, the K+ gates close. Resting potential occurs after this at -70 mv (Andrews, Brains and Neurons) Messages travel from one neuron to another in a process that begins when an action potential travels down the axon, enters the terminal branches, spreads depolarization. Following this votage-gated Calcium channels are activated, calcium permeability increases and Ca influx results. Synaptic vesicles containing neurotransmitters now fuse with the neuron membrane becuase of increased intracellular calcium. Neurtrasmittitters are now released into synaptic clefts. It takes approximetly .3-3 seconds to diffuse. This deceleration is called the 'synaptic delay'. Depending on the nature of the receptor, either positive or negative ions will flow into the postsynaptic neuron. If the neurotransmitter gates a positive channel, sodium will flux and a excitatory postsynaptic potential occurs. And exitatory postsynaptic potential is a small depolarizing potential. If the neurotransmitter opens potassium or chlorine channels, the ions flow in or out (potassium out and chlorine in). This will cause an inhibitory postsynaptic potential. An inhibitory postsynaptic potential is a graded hyperpolarization. Reuptake of neurotransmitters by the presynaptic