Basics of Neurophysiology Flashcards
Lectures 3/4
Electrolyte
-fluid with a high concentration of ions
Ions
-atomic particles that have an imbalance in their number of protons and electrons
Which ion is most concentrated in the cell (intracellular)?
K+ (tends to want to flow outward)
Which ions are heavily weighted to flow INTO the cell?
Na+, Cl-, Ca2+
Electrical current
rate of flow of electric charge past a point/region
Current (in neurons)
-ions flow through specialized pores in the cellular membrane
Voltage
-electrical potential difference between two points/compartments
How is an electrical potential difference used/created in neurons?
Sodium/potassium pumps control the concentrations of ions on either side of the membrane (more K+ in, more Na+ out)
What is the membrane of a neuron made up of?
it’s a phospholipid bilayer
What is the phospholipid bilayer impermeable to?
water, ions, other molecules
How do ions move in/out of neuron?
transmembrane protein channels
What are the three states a transmembrane protein channel can be in?
OPEN, CLOSED, INACTIVATED
How do ligand-gated channels work?
-Open when they come in contact with a ligand (ion/compound)
-“lock and key”
What effect would glutamate have on the channels?
EXCITATORY- would allow sodium to rush in (make membrane more positive)
What effect would GABA have on the channels?
INHIBITORY- allow Cl- to rush in? (makes the membrane more negative)
How do thermally gated ion channels work?
They open in response to hot/cold stimulus
How do mechanically gated ion channels work?
They open in response to mechanical forces (pressure)
Electrostatic force (Coulomb’s Law)
The force between two ions is related to the distance between them and the product of their charges
Positive coulomb force
repulsion
Negative coulomb force
attraction
Molecular diffusion force
movement of particles down their concentration gradient until they are equally distributed throughout
Define: electrochemical equilibrium
When electrostatic force is equal and opposite to the force of chemical diffusion
Synonym for the inside of a cell
cytoplasm
What is the Nernst equation used for?
Calculating the voltage at equilibrium when the membrane is permeable to just one type of ion
What is the equilibrium potential of potassium?
Ek= -84mV
What is the equilibrium potential for sodium?
ENa= 67mV
What is the equilibrium potential for chloride?
ECl= -67mV
What is the equilibrium potentials for calcium?
ECa= 116mV
What the resting potential inside a neuron?
-65mV
What two factors determine the resting potential of a neuron?
1) primarily permeable to K+ (leak channels)
2) K+ is more concentrated inside vs out
What is the Goldman equation used for?
-calculating the resting membrane potential
How does an action potential begin?
Small amount of Na+ enters the cell (making it more positive), which leads to more Na+ channels opening
What happens simultaneously with the closing of Na+ channels?
K+ channels gradually (slowly) open
What is unique about the K+ channels
They are slow to open/close
The slow closure of K+ channels makes K+ more permeable than at rest, what does this lead to?
The voltage becomes more negative than at rest (hyperpolarization)
