15.1.6

Saltatory Conduction

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Transmission of Nerve Impulses

Factors that speed up the transmission of nerve impulses include:

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Myelination

  • Schwann cells wrap around the axon of neurones to create a myelin sheath.
  • The myelin sheath acts as an electrical insulator because it is impermeable to ions (Na+ and K+).
  • Depolarisation and action potentials cannot occur at the myelinated parts of the axon and can only occur in the gaps between (the nodes of Ranvier).
  • The nervous impulse jumps from one node to the next. This is called saltatory conduction.
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Temperature

  • An increase in temperature increases kinetic energy.
  • Ions move across the membrane more rapidly when they have more kinetic energy.
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Axon diameter

  • Giant axons are found in the giant squid and allow it to have a rapid escape response.
  • Greater axon diameter means there is a greater surface area for the movement of ions across the cell membrane.

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1Cell Structure

2Biological Molecules

3Enzymes

4Cell Membranes & Transport

5The Mitotic Cell Cycle

6Nucleic Acids & Protein Synthesis

7Transport in Plants

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12Energy & Respiration (A2 Only)

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15Control & Coordination (A2 Only)

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17Selection & Evolution (A2 Only)

18Classification & Conservation (A2 Only)

19Genetic Technology (A2 Only)

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