NEM 10V Lecture Notes - Lecture 55: Threshold Potential, Resting Potential, Membrane Potential

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6 May 2018
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Nematology
Peripheral Nervous System:
A neuron is a cell that communicates with other cells via a combination of electrical and
chemical signaling.
Neurons consist of dendrites, a cell body, and an axon
Dendrites are branched extensions that receive information from other cells.
They receive incoming messages.
Axons conduct impulses away from the cell body.
The difference in charges across a membrane causes a membrane potential.
When a neuron is not being stimulated, its membrane potential is classified as resting
potential.
A higher concentration of sodium ions outside the cell membrane maintains the
membrane potential.
An action potential is a brief reversal of the electrical gradient across the plasma
membrane
A stimulus from another neuron shifts the membrane potential.
Threshold potential is a stimulus large enough to cause the shift. Sodium flows into the
cell, down its concentration gradient.
The membrane now has a net negative charge outside of the cell.
Gated potassium channels then open and allow potassium to diffuse outward to restore
the net negative charge outside of the plasma membrane.
Some of the sodium that diffused into the cell moves to an adjacent area along the axon,
moving the action potential along the axon.
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Document Summary

Axons conduct impulses away from the cell body: the difference in charges across a membrane causes a membrane potential. Threshold potential is a stimulus large enough to cause the shift. An action potential is an all or nothing response. The action potential moves in only one direction along the axon. Action potentials cannot jump from the end of an axon to the next cell"s dendrite: a chemical synapse exists as a communication point between neurons, vesicles in the axon end contain neurotransmitters (chemical signals). Action potentials cause the vesicles to release the neurotransmitter by fusing membranes with the plasma membrane: the post-synaptic cell has receptors for the neurotransmitter. Acetylcholine is a common neurotransmitter: neurotransmitters must be broken down quickly after exerting their effects. The enzyme acetylcholinesterase breaks down acetylcholine: pain is the body"s early warning system that protects you from dangers around you, and from yourself, pain detectors are specialized nerve cells called nociceptors.

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