1. Part Two: Sending an Impulse

2. 16. What do the sodium channels do?
Open up and allow a flood of sodium ions to flow in

3. 17. As sodium channels open, the cytoplasm…
Goes from negative to positive

4. 18. The threshold…
Depolarization
Is reached when sodium levels have raised the voltage of the cytoplasm to about -55mV.
At this point a chain reaction of depolarization occurs.

5. 19. And then…..
A wave of depolarization moves down the axon

6. FACILITATED DIFFUSION,
BY THE WAY, THIS IS NOW
FACILITATED DIFFUSION,
WHICH IS GOING WITH THE GRADIENT SO DOES NOT REQUIRE ENERGY
19 continued…
Facilitated by sodium channels

7. 20. At full depolarization, the voltage is at…

8. Myelinated neuron wins
21. Who is faster?
Myelinated neuron wins

9. 21. continued…
Notice that both the sensory and motor neurons are myelinated
But the interneuron is NOT

10. 21. continued…
Unmyelinated axon conduction velocities range from about 0.5 to 10 m/s, myelinated axons can conduct at velocities up to 150 m/s.

11. Here’s an actual race!

12. 22. Why does an impulse travel faster on a myelinated neuron?
Action potentials travel faster when they jump from node to node rather than going through the entire axon.
Can you think of an analogy?

13. 23. This movement is called…
Saltatory movement

14. LOOK AT MY PRECIOUS NODES
24. Who am I?
LOOK AT MY PRECIOUS NODES
Louis-Antoine Ranvier, the discoverer of the nodes between the Schwann cells

15. 25. Order of operations: Resting Stimulus Threshold Depolarization
Repolarization
Hyperpolarization
Resting

16. 26. The voltage at hyperpolarization…

17. 27. What new ion enters at the terminus?

18. 28. The little vesicles at the synaptic end bulb contain…

19. 28 continued… Examples of neurotransmitters include: What are the most famous two?

20. 29. The three destinations of an impulse are…

21. 30. The little gap at the synapse is called the…
SYNAPTIC CLEFT

22. 30. continued… Actually, you should know all these:3. 2. 4. 1. 5. 6.

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