Question

Completely detail how action potentials are generated and propagated in the nervous system. Include in your answer each stage of the action potential and how it's taking place. Further include how signals are conveyed between neurons. How does myelin work, what does it do, what is it made of, what does it look like? Compare myelin differences between the central and peripheral sytems.

What are the different glial cells and what does each one do?
What does the Cerebral Spinal Fluid have to do with action potentials? What is CSF, what does it do, where is it being moved between?

Answer 1

Action potentials are electrical signals generated by changes in ion distribution across a neuron's membrane. They propagate along the neuron's axon, particularly jumping from node to node in myelinated fibers. Myelin sheaths in the CNS and PNS are produced by oligodendrocytes and Schwann cells respectively, accelerating signal transmission.

Step-by-step explanation:

Action potentials are generated and propagated in the nervous system through a series of stages. The resting potential is the state of a neuron when it is not activated, typically around -70mV due to the distribution of ions across its membrane. An action potential occurs when the neuron is stimulated past a certain threshold, leading to rapid changes in membrane potential. These changes are:

1. Depolarization: Sodium channels open, allowing Na+ to enter the cell, making the inside more positive.
2. Repolarization: Potassium channels open, K+ exits the cell, restoring negative charge inside.
3. Hyperpolarization: Membrane potential temporarily becomes more negative than resting potential.
4. Return to resting potential: Ion channels reset and the Na+/K+ pump restores the original ion distribution.

Action potentials propagate along the axon, jumping between nodes of Ranvier in myelinated neurons. Myelin sheaths, made of lipids and proteins, wrap around the axon to insulate and speed up signal transmission, appearing as white, segmented coverings. In the CNS, they are produced by oligodendrocytes, while in the PNS, Schwann cells are responsible. Glial cells such as astrocytes support neuron function, protect the CNS, and help form the blood-brain barrier. Cerebrospinal fluid (CSF), which surrounds the CNS, provides cushioning and buoyancy but does not directly influence action potentials. It is a clear, colorless liquid that circulates between the arachnoid and pia maters of the meninges.