Day 1 content

What does the separation of charges create?

It creates a voltage

What does voltage cause?

Causes the movement of charges across

What separates charges in a cell?

By the membrane of the cell

What does the separation of charges cause?

It creates a membrane potential, which is present in every single cell in the body

What does normal membrane potential (Vm) allow the cell to do?

For the cell to perform certain functions

What is resting membrane potential?

The membrane potential of a cell when it is not being stimulated or inhibited

What plays a big role in determining resting Vm?

The distribution of potassium because it has the greatest permeability at rest

What is the intracellular conc. of potassium at resting Vm?

~135 mEq/L

What is the extracellular conc. of potassium at resting Vm?

~ 5 mEq/L

What is the permeability of potassium channels at resting Vm?

~ 1.0

What is the intracellular conc. of sodium at resting Vm?

~ 15 mEq/L

What is the extracellular conc. of sodium at resting Vm?

~140 mEq/L

What is the permeability of sodium channels at resting Vm?

~ 0.05

What is the intracellular conc. of chloride at resting Vm?

~ 10 mEq/L

What is the extracellular conc. of chloride at resting Vm?

~ 100 mEq/L

What is the permeability of chloride channels at resting Vm?

~ 0.45

What does the average resting Vm in all cells range from?

from ~ 40 mv to ~90 mv

What’s the role of Na/K pumps in resting Vm ?

Is to create/maintain the gradients

What are the three changes that can happen in Vm?

• Depolarization

• Hyperpolarization

• Repolarization

What is depolarization?

The cell becomes stimulated/excited, resulting in the Vm becoming more positive

What is hyperpolarization?

The cell becomes inhibited, resulting in the Vm becoming more negative

What is repolarization?

Vm returns back towards resting after a change to it occurs

What happens when the intracellular conc. of sodium increases?

Hyper polarization occurs where:

1. The Na gradient decreases

2. Causing Na transport into the cell to decrease

3. which causes Na to get less “stuck” to the inner membrane

4. resulting in inner membrane becoming less positive and more negative

What happens when the intracellular conc. of potassium increases?

Hyperpolarization occurs where:

1. The K gradient increases

2. causing K transport out of the cell to increase

3. which causes K to get more “stuck” to the outer membrane

4. resulting in the outer membrane becoming more positive and the inner membrane more negative

What happens when the intracellular conc. of chloride decreases?

Depolarization occurs where:

1. The Cl gradient decreases

2. causing Cl transport into the cell to decrease

3. which causes Cl to get less “stuck” to the inner membrane

4. resulting in the inner membrane becoming less negative and more positive