The Action Potential
The Action Potential
An action potential is an all or none phenomenon where the axon receives enough of an input so that the voltage of the axon is roughly -55 mV. Once this threshold is reached, the neuron fires an action potential which propagates down the axon to the terminal buttons.
EPSP VS IPSP
An excitatory post synaptic potential (EPSP) is a signal that travels down the dendrite to the cell body of a neuron and brings the neuron close to the threshold of -55 mV. This means that this signal will likely cause the neuron to fire. An inhibitory post synaptic potential (IPSP) is responsible for inhibiting any further neurons from firing and brings the membrane potential away from the the threshold of -55 mV.
It is the addition of these EPSP and IPSP signals that determines if the neuron fires. If all the signals coming from all the dendrites of that neuron add up to -55 mv or lower, the neuron fires.
It is the addition of these EPSP and IPSP signals that determines if the neuron fires. If all the signals coming from all the dendrites of that neuron add up to -55 mv or lower, the neuron fires.
Resting Membrane Potential
When a neuron is at rest, there is a higher concentration of sodium (Na) ions on the outside of the cell and a higher concentration of potassium ions (K) on the inside of the cell. Because the inside of the cell also has many large negatively charged proteins, the resting membrane is measured to be at -70 mV.
Crash Course
This is a group of two brothers who have set their mission to make education fun and exciting. Their videos are encouraged to be used by teachers and provide in depth detail about many concepts including the action potential.
Saltatory Conduction
Imagine all of these sodium and potassium channels having to open all the way from the brain to your leg muscle in order to get it to move! That would take a long time, so how does everything happen so fast to allow someone to play soccer or run extremely fast?
Multiple Sclerosis - An Example
Multiple Sclerosis (MS) is an autoimmune disease that results in the Myelin Sheath or Schwann Cells that surround the axons of our neurons to degenerate. As a result, saltatory conduction cannot occur and the nerve signals are very slow. Some may have acute symptoms while others may have chronic symptoms like paralysis. There is no sure cure for MS, but research is constantly being done to make the quality of life better for these individuals. Your Schwann Cells are important. Without them we wouldn't be able to function the same way in our everyday lives.
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