Do Now: 1. What is 1 of the characteristics of nerve signals that you defined from the “dominos” lab? 2. What is the role of the axon? 3. What creates electrical signals? 4. What creates chemical signals?

What is the Action Potential? How neurons send signals __________down their axons. Neurons do this by using their __________ __________. What does electricity mean?

So, what is a Membrane Potential? Membrane potentials come from the ______of the ______cell membrane. When neurons are _____sending a signal, their cell membrane is _____________!

So, what is makes a cell membrane negative? _______! ___________ions (Cl-) sit in the cell membrane and make it ____________. They will ______move Outside Inside Outside

To create an action potential, we have to let ions move! Can ions just flow into the cell? We need ____ __________! How do we open ion channels at the synapse? Do you think all ion channels open that way?

Voltage-Gated Ion Channels They only open up when the cell membrane changes __________!

Two ions are responsible for nerve signaling: ___________(Na+) has ______concentration (more of it) ___________the cell when there is ___signal. _____________(K+) has _____concentration ______the cell when there is ___signal.

Neuron before signal looks like this! Sodium ions are mostly ____________! Potassium ions are mostly ____________! Outside Cl- Cl- Cl- Cl- Cl- Cl- Cl- Inside Cl- Cl- Cl- Cl- Cl- Cl- Cl- Outside

Ion mostly inside cell Ion mostly outside cell Charge inside cell Charge outside cell Signal?

+70 (membrane potential) Charge +50 -70 Time

So, we need to send a signal. What happens? The __________________will open up __________channels at the synapse! This will then make __________sodium channels open up nearby What do you think is happening to the charge of the cell?

Sodium turns ____an action potential Needs a ________change in charge!

Neuron when ___________looks like this! Sodium ions are mostly __________! Potassium ions are mostly _____________! K+ Outside Cl- Cl- Cl- Cl- Cl- Na+ Cl- Cl- Na+ K+ K+ K+ K+ K+ Na+ Na+ Inside K+ Na+ K+ K+ Na+ Na+ Na+ Na+ Na+ Cl- Cl- Cl- Na+ Cl- Cl- Cl- Cl- Outside K+

+70 (membrane potential) Charge +50 -70 Time

Ion mostly inside cell Ion mostly outside cell Charge inside cell Charge outside cell Signal? K+ Na+ Negative Positive No

Potassium turns ______an action potential Needs a _____change in charge!

Neuron when _______signaling looks like this! Sodium ions are mostly __________! Potassium ions are mostly ____________! K+ K+ K+ K+ K+ Outside Cl- Cl- Cl- Cl- Cl- Na+ Cl- Cl- Na+ Na+ Na+ Na+ Inside Na+ Na+ Na+ Na+ Na+ Cl- Cl- Cl- Na+ Cl- Cl- Cl- Cl- Outside K+ K+ K+ K+ K+

+70 (membrane potential) Charge +50 -70 Time

Ion mostly inside cell Ion mostly outside cell Charge inside cell Charge outside cell Signal? K+ Na+ Negative Positive No None Yes

We need to go back to where we started. Now we need to reset! We need to go back to where we started. Which ion should be outside the cell? Which ion should be inside the cell?

The sodium-potassium pump resets it. It uses energy to exchange ______________for ___________to bring it back to the starting position.

+70 (membrane potential) Charge +50 -70 Time

Ion mostly inside cell Ion mostly outside cell Charge inside cell Charge outside cell Signal? K+ Na+ Negative Positive No None Yes