The Resting Potential Flashcards
(29 cards)
What is a membrane potential?
Electrical charge across the membrane
What is the membrane potential at rest?
-65/70 millivolts - inside is more negatively charged than the outside
What does a voltmeter measure?
The flow and strength of electrical voltage, records difference in electrical potential between two bodies
What cause there to be a membrane potential?
The movement of particles across a membrane due to two forces
What are the two forces which cause a membrane potential?
Diffusion
Electrostatic pressure
What is diffusion?
Molecules move from an area of high concentration to an area of low concentration -
What is electrostatic pressure?
If you placed an electrical charge by connecting it to a battery, you would have an electrical difference
particles with a similar charge repel, particles with an opposite charge attract
What is an equilibrium potential?
The balance between the chemical and electrical charges
when the diffusion force = electrostatic force (outward movement = inward movement)
What is important for the equilibrium potential?
The initial concentration difference
high concentration difference = large EP
very few ions need to move to achieve this
What are the steps of the EP?
Positive ions move across the membrane by diffusion force
As positive ions move there is an increase in electrical potential across the membrane - more positive on one side
Eventually, a point is reached when the diffusion force = electrostatic force - outward movement = inward movement
What do organic ions do?
Contribute to the relatively negative charge inside the neuron
What is there lots of inside a neuron?
Potassium K+
What is there lots of outside a neuron?
Sodium Na+
Chloride Cl-
What does the resting potential result from?
The separation of charge across the membrane
Why is the inside of the cell more negative compared to the outside?
Because there are way more sodium ions on the outside
The inside of the cell is more negative to the outside of the cell, what does this mean?
There is an electrostatic force pulling sodium in because it is more negative and diffusion is pulling it in as more sodium on the outside
The electrostatic force pulls potassium in but the diffusion pushes it out as more on inside. So they move out
Chloride - diffuse inwards, but the electrostatic force keeps it away
What is predicting the MP?
The electrostatic force and diffusion
What is the boss ion and why?
Potassium because at rest, there are 40x more K than Na channels open - this determines the membrane potential
More opportunity for potassium to go out than for sodium to come in
What are ion channels?
Passions in and out
Always open
Why is the resting membrane potential near the K+ equilibrium potential?
There is NA moving into the neuron and K moving out due to diffusion, but more K than NA can diffuse, so the membrane comes to rest near the K+ EP
What is the K+ equilibrium potential?
-85mV
How is the EP calculated?
Using the Nernst equation - can be influenced by body temperature
What would the EP be if it was only K+ ions or Na+ moving across the membrane?
K+ = -92mV Na+ = 62mV
What happens if there are more ions inside the cell than outside?
EP is positive
