Explain how the action potential is generated and is transmitted along the axon. Include information about the effect of myelin on the speed of transmission.

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  1. Explain how the action potential is generated and is transmitted along the axon. Include information about the effect of myelin on the speed of transmission.

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The brain and the spinal cord form the central nervous system (CNS). The CNS processes information using millions of nerve cells (or neurones). In order to understand their function and process, a description of the neurones and their environment seems necessary. This will lead to the second part which will cover the neurone’s actual action potential generation and transmission.

Neurones are constituted of an outer membrane, a cell body (or soma) and a nucleus. These characteristics are common to all body cells. Nevertheless, other fundamental features are needed in order to respond to environmental changes: the dendrites that surround the soma and receive nerve impulses. The axon, connected to the soma by the axon hillock, is composed of myelin and nodes of Ranvier, through which the impulses pass. Finally, the impulses reach the axon terminal, and through the synapse, get transmitted to the next neurone.

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The neurone’s resting membrane potential represents its stability, when not stimulated or firing. The cell’s charge is –70 mV, the cell is negatively charged whereas the outside is less. The membrane controlling ions moving in and out the cell through ion channels using ion pumps (sucking in or extruding the ions) creates a negative voltage due to unequal distribution of ions:        

  • The protein anions, which are too large to pass the semi-permeable axon’s membrane.
  • Sodium cations (Na+) are pumped out of the cell. The channels allowing the sodium back into the cell are shut during the resting membrane potential. ...

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