Apedia

A-Level Biology OCR A

Myelinated Axon Unmyelinated Transmission Bc Sodium Ions Depolarisation

Myelinated axons transmit action potentials much faster and more energy-efficiently than unmyelinated ones because the impulse jumps between nodes (saltatory conduction), reducing the number of times ion channels open and the need for extensive repolarization.

Myelinated axons transmit action potentials much faster and more energy-efficiently than unmyelinated ones because the impulse jumps between nodes (saltatory conduction), reducing the number of times ion channels open and the need for extensive repolarization.

Front Describe and explain how the transmission of an action potential along a myelinated axon is different to transmission along an unmyelinated one.
Back Myelinated vs unmyelinated conduction:
  • In myelinated - depolarisation of axon membrane only occurs at nodes of Ranvier bc that is only region where sodium ions can pass through protein channels in membrane, as result the AP 'jumps' from node to node
  • In unmyelinated - there is a wave of depolarisation along the whole length of the axon membane bc sodium ions can pass through throughout entire length of axon
  • Myelinated conduction is much faster than unmyelinated - every time channels opena dn ions move in it takes time so reducing number of places this happens speeds up AP transmission
  • Myelinated conduction is also more energy efficient bc repolarisation uses ATP in sodium pump, reducing amount of repolarisation means less energy used

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