Lecture 15/ Neuro I

1 2 3 4 5 6 7

This creates a concentration gradientfor K+ and Na+ and an electrical charge gradient.

2. K+ channels
K⁺channels are the most common type of open channel in the plasma membrane on neurons. This allows K⁺to leak outdown its concentration gradient, making the inside of cell even more negativethan the outside, until the electrical gradient is strong enough to balance the concentration gradient.

3. Na+ channels
There is also a small tendency of Na⁺ions to leak into the cell, decreasing the charge difference.

The combined action of these 3 transport proteins creates a membrane potential in resting neurons of about -70 meV.

C. Action potential
An action potentialis a rapid change in membrane potential of an excitable cell caused by the movement of ions across the membrane.

1. The players
a. Ions
i. K⁺ii. Na⁺iii. Cl^-The 3 ions that can move into and out of neurons are Cl^-, Na⁺and K⁺.

Q. What happens to membrane potential if Na+ and K+ move? - If K+ moves out, membrane potential becomes more negative,it hyperpolarizes

48.6

- If Na+ moves in, membrane potential becomes less negative, it depolarizes

The change in membrane potential is proportional to the flux of ions, until it reaches a threshold value. At this point positive feedback kicks in resulting in a greater depolarization known as theaction potential.

What makes an action potential explosive is that the channels that allow the ions to flow only open in response to a stimulus. A stimulus causes a small change in the membrane potential. As we saw earlier, some of the ion channels in the membrane are voltage-gated. They are open or closed


		This creates a concentration gradientfor K+ and Na+ and an electrical charge gradient. 2. K+ channels K⁺channels are the most common type of open channel in the plasma membrane on neurons. This allows K⁺to leak outdown its concentration gradient, making the inside of cell even more negativethan the outside, until the electrical gradient is strong enough to balance the concentration gradient. 3. Na+ channels There is also a small tendency of Na⁺ions to leak into the cell, decreasing the charge difference. The combined action of these 3 transport proteins creates a membrane potential in resting neurons of about -70 meV. C. Action potential An action potentialis a rapid change in membrane potential of an excitable cell caused by the movement of ions across the membrane.
		1. The players a. Ions i. K⁺ii. Na⁺iii. Cl^-The 3 ions that can move into and out of neurons are Cl^-, Na⁺and K⁺. Q. What happens to membrane potential if Na+ and K+ move? - If K+ moves out, membrane potential becomes more negative,it hyperpolarizes
				48.6
		- If Na+ moves in, membrane potential becomes less negative, it depolarizes The change in membrane potential is proportional to the flux of ions, until it reaches a threshold value. At this point positive feedback kicks in resulting in a greater depolarization known as theaction potential. What makes an action potential explosive is that the channels that allow the ions to flow only open in response to a stimulus. A stimulus causes a small change in the membrane potential. As we saw earlier, some of the ion channels in the membrane are voltage-gated. They are open or closed