Myelination

• Myelinated neurones have Schwann cells that make myelin, which is a lipid insulating layer around the axon that wraps around the axon during development in embryos.
• Myelinated neurones have very little cytoplasm and are wrapped in spirals around the axon.
• Being myelinated helps by making the action potential travel faster, resulting in quicker nervous responses and less harm/damage caused.
• Saltatory conduction only happens in myelinated neurones, as the neurone is insulated ion exchange can only happen at the nodes of Ranvier.
• A node of Ranvier is a location where saltatory conduction can occur.
• Saltatory conduction is the process of signal jumping.
• When the impulse reaches the node of Ranvier, Na+ diffuse into the axon membrane and K+ are displaced down the axon because both are positively charged.
• The movement of K+ makes the next node more positive and depolarisation happens.
• Being myelinated is beneficial as it uses less ATP and exchanges fewer ions.
• Unmyelinated neurones are slower in terms of conducting impulses and are found in the peripheral nervous system, especially the visceral nervous system, and the grey matter of the nervous system.
• The speed of an action potential in myelinated neurones is 3-120m/s, while in unmyelinated neurones it is 1/2m/s.
• The speed of an action potential depends on the axon diameter, with larger axons enabling faster conduction.
• The speed of an action potential also depends on the number of synapses involved, with fewer synapses resulting in quicker communication.