Describe the effect of myelination on the speed ofaction potential propagation, as well as other factorsthat affect the speed of action potential conduction.
Describe the effect of myelination on the speed of
action potential propagation, as well as other factors
that affect the speed of action potential conduction.
The change in the electrical potential across the cell membrane of a nerve cell is referred to as the action potential, by which the neuron sends information to the downstream neurons for communicating the information forward.
The speed of the conduction of an action potential depends upon three major factors:
- Myelination
- Temperature
- Axon diameter
The myelin sheath is a modified and extended layer of plasma membrane, which is wrapped around the axonal part of the neuron in a spiral arrangement. It is composed of fatty molecules and proteins. The Schwann cells in the PNS synthesize the myelin sheath, whereas the myelin sheath in the CNS is synthesized by the oligodendrocytes. Its function are: electrically insulate the neuron, prevent movement of ions across the neuron and increase the speed of conduction of nervous impulse.
Effect of myelination on the speed of action potential conduction: The myelin sheath increases the speed of action potential conduction as, there are certain places on the axon where the myelin sheath is not present, those spots are called the nodes of Ranvier, and the voltage-gated ion channels are only present here. Thus, the time taking process of generating the action potential only takes place here. Myelin sheath acting as an insulator does not allow the flow of current through it, thus the action potential flow by jumping from one node of Ranvier to the other node. this is called saltatory conduction. Thus, this the way by which myelin sheath increases the conduction speed of the action potential.
Effect of temperature on the speed of action potential conduction: At higher temperature, the speed of conduction of action potential is increased, because enzymes work efficiently at high temperatures. The Na+-K+ ATPase pump is also governed by enzymes, which function better at high temperatures.
Effect of axon diameter on the speed of action potential conduction: A larger diameter of axons increases the speed of conduction of the nerve impulse, as in case of large diameter axon, there is more space for the ions to flow and there is no resistance. The ions will also not bounce back, thus conduction speed increases.
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