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Neurological Disorders Lesson 2.2 - Differentiated

Neurological Disorders Lesson 2.2 - Differentiated. How do our neurons signal electrically?. Electrical Signal. Do Now:. Ethan needs to have a cavity filled. Before his doctor begins drilling, she gives him Novocain to prevent pain. How do you think Novocain works???

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Neurological Disorders Lesson 2.2 - Differentiated

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  1. Neurological DisordersLesson 2.2 - Differentiated How do our neurons signal electrically? Electrical Signal

  2. Do Now: • Ethan needs to have a cavity filled. Before his doctor begins drilling, she gives him Novocain to prevent pain. • How do you think Novocain works??? • Novocain stops our neurons from signaling electrically. • But how do our neurons signal electrically???

  3. Neurons Send Signals • Chemically via synapses • Electrically via axons Electrical Signal Electrical Signal Electrical Signal Chemical Signal Chemical Signal

  4. What is the Action Potential? • The action potential is how neurons send signals electricallydown their axons. • Neurons do this by using the potential energy stored in their membrane potentials. Electrical Signal

  5. First, what is electricity? • The flow of charged particles – also known as ions. • But, can ions just flow into the axon?? • No! Na+

  6. The Axon’s Ion Channels and Pumps • The axon has ion channels and pumps that act as doors through which ions enter and exit the axon. • These channels and pumps allow ONLY specific ions to flow or be pumped through them.

  7. The Axon’s Ion Channels and Pumps Voltage-gated sodium (Na+) channel Voltage-gated potassium (K+) channel Na+/K+Pump Pump Na+ out of and K+ into the axon. Allow Na+ to flow through. Allow K+ to flow through.

  8. But wait, what does “Voltage-gated” mean? • “Voltage-gated” – means that the channel opens at a specific voltage. • This means that the voltage of the membrane is like a key that opens the channel.

  9. The Axon’s Ion Channels and Pumps Voltage-gated Na+ channel Voltage-gated K+ channel Na+/K+Pump Open when the membrane potential is at +40 mV Open when the membrane potential is at -50 mV Keep this in mind for later…

  10. The Axon’s Membrane Potential • Refers to the potential energy stored at the membrane. • There is potential energy because there is a charge difference between the inside and the outside of the axon.

  11. The Axon’s Membrane Potential At rest Na+ Na+ Na+ Na+ Na+ More Na+ outside - More K+ inside K+ K+ K+ - More negatively charged proteins - -

  12. The Axon’s Membrane Potential At rest Na+ Na+ Na+ Na+ Na+ + + + + - - - - K+ K+ K+ - 70mV

  13. The Axon’s Membrane Potential At rest

  14. The Action Potential After stimulation Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ + + Does anyone remember the voltage at which the voltage-gated Na+ channels open? -50 mV - Threshold

  15. The Action Potential 0 mV Depolarization - 50 mV - 70 mV After stimulation

  16. The Action Potential After depolarization Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ Does anyone remember the voltage at which the voltage-gated K+ channels open? + 40 mV Does anyone remember the voltage at which the voltage-gated K+ channels open?

  17. The Action Potential After depolarization 40 mV 0 mV Depolarization Hyperpolarization - 50 mV - 70 mV

  18. The Action Potential After hyperpolarization Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ K+ K+ K+ K+ How does the axon return to its resting membrane potential with Na+ outside and K+ inside? Na+/K+Pump moves Na+ out and K+ into the axon. How does the axon return to its resting membrane potential with Na+ outside and K+ inside?

  19. The Action Potential After hyperpolarization 40 mV 0 mV Depolarization Hyperpolarization - 50 mV - 70 mV

  20. Modeling the Action Potentialalong the length of the axon Black-eye pea = Na+ ion Outside Inside Red toothpick = K+ion channel Black toothpick = Na+/K+ Pump Blue toothpick = Na+ ion channel Lima bean = K+ion

  21. The Action Potential along the Axon

  22. How does Novocain work? • Novocain inhibits the voltage-gated Na+ channels. No Signal PAIN • What happens if the voltage-gated Na+ channels can’t open? • The axon can’t send Action Potentials. • Meaning you can’t feel pain!

  23. Homework: The Stages of the Action Potential Write a summary of what is happening at each stage of the action potential. 3. 4. 2. 1. 5.

  24. The Stages of the Action Potential 3. The voltage-gated Na+ channel closes and the voltage-gated K+ channel opens. 2. The voltage-gated Na+ channel opens. Na+ enters the axon.Depolarization. 4. K+ ions leave the axon.Hyperpolarization. 1. The membrane is at rest. More Na+ is outside the cell. 5. The Na+/K+ pump restores the resting membrane potential by pumping Na+ out and K+ in.

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