1. Neurones An overview of the speed of nervous impulses WAL: All Most What is the refractory period? What is its role in separating one impulse from the next? Starter – Match-up Some What factors affect the speed of conductance of an action potential? What is meant by the all-or- nothing principle?

2. Today we are covering from the specification: Pages 171-173 of your textbook

3. Factors Affecting the Speed of an AP 1.Myelin sheath – electrical insulator – the AP jumps from one Node of Ranvier to another = SALTATORY CONDUCTION. –Myelinated = 90ms -1 –Unmyelinated = 30ms -1

4. Factors Affecting the Speed of an AP 2.Diameter of the axon – greater diameter = faster conductance (due to less leakage).

5. Factors Affecting the Speed of an AP 3.Temperature – higher temp = faster nerve impulse (rate of diffusion is faster, enzyme activity is faster e.g. ATPase.

6. Understanding checkpoint! An overview of the speed of nervous impulses WAL: All Explain to your partner the three factors that affect the speed. Marks 3 for use of key words 3 for explaining with examples What factors affect the speed of conductance of an action potential?

7. The Refractory Period There is a time after depolarisation where no new AP can start – called the refractory period. –Time is needed to restore the proteins of voltage sensitive ion channels to their original resting conditions. –Na+ channels cannot be opened, as it can’t be depolarised again. WHY? –AP travel in one direction only. –Produces discrete impulses. –Limits the frequency of impulses.

8. Understanding checkpoint! An overview of the speed of nervous impulses WAL: Most Draw a picture on the mini white boards to explain. What is the refractory period? What is its role in separating one impulse from the next?

9. AP – All or nothing AP only happens if the stimulus reaches a threshold value. –Stimulus is strong enough to cause an AP –It is an ‘all or nothing event’ because once it starts, it travels to the synapse. AP is always the same size An AP is the same size all the way along the axon. The transmission of the AP along the axon is the nerve impulse.

10. How do we detect the size of a stimulus? The number of impulses in a given time – the larger the stimulus, the more impulses generated. By having neurones with different threshold values – the brain interprets the number and type of neurones and therby determines its size.

11. Nerve conductance test http://www.youtube.com/watch?v=xTHiqR 45T8Y&feature=youtu.behttp://www.youtube.com/watch?v=xTHiqR 45T8Y&feature=youtu.be 1. How fast do you think a nerve impulse can travel along a motor nerve in m/s? 2. Do you know of any conditions that affect the nerves? 3. Do you think temperature can affect the impulse speed?

12. Task: 1.AQA A2 Biology pg 173 Q1-5 2.Fill-in A3 nerves mind map (except synapse part )

13. Neurones An overview of the speed of nervous impulses WAL: All Most What is the refractory period? What is its role in separating one impulse from the next? Some What factors affect the speed of conductance of an action potential? What is meant by the all-or- nothing principle? 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?