Chapter 2 - Resting Membrane Potential Flashcards
In regards to signals, what can neurons do?
Can : receive signals (dendrites) Generate signals (axon hillock ) Conduct signals (axon)
Na+ is a …
Cation
Cl- is a…
Anion
What are the two types of ion channels?
PS : don’t forget the cation specificity
Cation channels : -non specific (any +)
-specific (only Na+, only Ca++,…)
The ion channels also differ in how they are gated. Explain
Leak channels : passive channels open all the time
Gated channels : active channels thy can be opened by certain changes (light, mechanical, …)
What and how gives rise to a resting potential?
- Leak channels are always open so give rise to the resting potential.
- The movement of charged particles across a membrane is what gives rise to a resting potential.
What are neural signals, or action potentials?
Neural signals consist of transient changes in this resting potential, which travel from the soma down the axon to the nerve terminal.
What are the two forces that govern the movement of particles across a permeable membrane?
1) diffusion : when there is a difference on concentration of a certain uncharged particle, the diffusion also force is going to push for equilibrium on both sides of the membrane.
2) the electric force : here we’re talking about charged particles —> opposite charges attract and like charges repel
Explain potential energy.
- opposite charges attract and require energy to be separated
- therefore spectated charges have potential energy as a result of the separation
- measure of potential energy = voltage
- voltage is always measured btw two points and is called the potential difference btw 2 points
What is the electrical current?
Movement of positively charged particles.
What is conductance?
Movement of ions through ion channels.
What is voltage?
Voltage is the electrical force exerted on a charged particle. It reflects the difference in charge between the anode and the cathode.
What is the current? And what is its unit?
Current is the motion of charged particles. Measured in Amperes (I)
What I the relation of voltage and current also known as Ohm’s law?
V=IR
What is the other formula for Ohm’s law?
I=gV
Where g is the conductance measured in Siemens and equal to 1/R.
In slide 23 how is equilibrium reached?
When electrical force pulling K+ back into the cell is equal to the chemical force driving K+ out of the cell, equilibrium is reached.
What is equilibrium potential?
The electrical potential difference that exactly balances an ionic concentration gradient.
What is the ionic driving force? What is the formula?
Ions are driven across the membrane at a rate proportional to the difference between the membrane potential (Vm) and the equilibrium potential
What does the Nernst equation calculate?
It calculates the equilibrium potential for an ion if the concentration difference across a membrane is known
What is the equilibrium potential for potassium?
E__K = -80mV
How does the driving force work (Vm>Ek, …)?
K flows out of cell when Vm>Ek
No net flow when Ek=Vm
K flows in when Vm
What happens when the membrane is permeable to more than one ion?
- Each ion will try to pull the membrane potential to its respective equilibrium potential.
- …so what’s going to determine the membrane’s potential is the permeability (or conductance) of the membrane to an ion.
At rest, to what is the membrane most permeable?
And to what is the resting membrane potential closest to??
1) most permeable to K+
2) is closer to Ek than E Na
What is the formula for the net ion flux across a membrane?
I (ion) = g (ion) . (Vm-E(ion))
Also known as permeability x driving force
Why is a neuron at rest constantly leaking out?
The permeability for K+ is high so potassium is leaking out ((( whereas the in force is weak.
What does the potassium/sodium pump do?
What does this pump require to function?
It pumps out 3Na+ and in 2K+
It requires ATP
How is extra cellular K+ removed?
Astrocytes use spatial buffering to remove the ions.
