5 4 3 2 1 go can you

5, 4, 3, 2, 1 go… can you talk about nerves for 60 seconds mentioning as many as the key words as possible? 2 Axon Na+ Action potential Depolarised Sodiumpotassium pump Cell body Nodes of Ranvier Schwann cell 3 K+ Polarised Active transport Repolarisation Voltage-gated channel Diffusion Myelin

Neurones WAL: An overview of the passage of neurones Some Most All How does an action potential pass along a myelinated axon? How does an action potential pass along an unmyelinated axon? Starter – 5, 4, 3, 2, 1 ……. . go!

Today we are covering from the specification: Pages 168 -170 of your textbook

Passage of Action potential Once it has been created, an action potential ‘moves’ rapidly along the axon. The size of the action potential remains the same from one end of the axon to the other. The movement is the reversal of electrical charge at different point along the axon membrane.

Passage of Action potential As one region of the axon produces an action potential and becomes depolarised, it acts as a stimulus for the depolarisation of the next region of the axon. Action potentials are regenerated along each small region of the axon membrane. In the meantime, the previous region of the membrane returns to its resting potential, that is it undergoes repolarisation.

Unmyelinated neurone 1) Resting potential axon is polarised (overall concentration of positive ions is greater on the outside compared with the inside) 2) Stimulus causes a sudden influx of Na+ and axon becomes depolarised (reversal of charge) 3) Localised electrical circuits established by the influx of Na+ cause the opening of Na-voltage channels a little further along the axon. This causes depolarisation in this region of the axon.

Unmyelinated neurone 4) Behind the depolarisation, the Na voltage-gated channels close and the K ones open. K+ move out of the axon. 5) Depolarisation (action potential) is propagated in the same way further along the neurone. 6) The outward movement of the K+ has continued to the extent that the axon membrane behind the action potential has returned to its original state (repolarised)

Unmyelinated neurone 7) Repolarisation of the neurone allows Na+ to be actively transported out returning to resting potential

Task • Do word loop

Myelinated neurone Fatty sheath of myelin around the axon acts as an electrical insulator, preventing action potentials forming. At intervals of 1 -3 mm there are breaks in this myelin insulation, called nodes of Ranvier. Action potentials can occur at these points.

Myelinated neurone Localised circuits arise between adjacent nodes of Ranvier and the action potential effectively jumps from one node to the next – salutatory conduction As a result, an action potential passes along a myelinated neurone faster than an unmyelinated neurone.

Task • Fill in mind map

Coordination & the Nervous system

Coordination & the Nervous system

Neurones WAL: An overview of the passage of neurones Some Most All How does an action potential pass along a myelinated axon? How does an action potential pass along an unmyelinated axon? Plenary– 1) Taboo 2) Refections: What did you learn? What do you want to find out? How might you find this out? What skills did you use?