resting potential Flashcards
Neuron communication
- conduct info using electrical signals called action potentials
flow of ions
- ions flow in and out of the membrane in waves
- not like free electrons flowing down
Potential
possibility to do something
- caused by separation of electrical charges across the membrane
electrical potential
difference in electrical charge
- voltage
Neuron at rest
- has no inputs
- the ions are not evenly distrubuted across the membrane
- inside is more negative
main ions at play
- Na+
- K+
- Cl-
- Ca2+
Ions inside the cell
- k+ is more prevalen inside
- also anions present
ions outside the cell
- Cl-
- Na+
- Ca2+
How does the RMp state arise?
because of the semi permeable membrane
what makes up the mebrane
- phospholipid bilayer
- polar hydrophilic heads
- nonpolar hydrophobic tails
Semi permeable membrane
- only small, uncharged lipid soluble molecules can pass
- charged ions cant cross without the use of pores or pumps because of their size and hydration
Channels
- proteins make up channels that are very selective to certain ions
- thay can be gated and open and close
selecting ions in channels
- select based on charge (+/-)
- based on size (diameter of hydration)
main ingredient of fluid (in and out)
- polar water
- covalent bonds
factor affecting RMP
- diffusional force
- electrical force
diffusional force
- ions flow from area of high concentration to low concentration
- acts until they are balanced
Electrical force
- ions of similar charges repel, and opposite attract
- depends on resistance
1 mV
= 0.001 V
- voltage (read by voltmeter)
Equilibrium potential
reached when the diffusional and electrical forces are equal and opposite
- net movement across membrane will cease
generating electrical potential
- ionic concentration gradient
- selective permeability
Nernst equation
- calculated equilibirum of one ion
- need to know concentration in and out
E of RMP
-65 mV
E of Na+
+58 mV
E of K+
- 80mV
E of Ca2+
+123 mV
E of Cl-
- 65 mV
why does K contribute the most
- there is a lot in the neuron
- some channels are always open
- diffuses out until voltage balance concentration
- k has 40:1 more channels
- it leaks
Goldman equation
- extension of nerst
- caluculates eq of all ions acting together
goldman depends on what
- permeability of ion
- concentration of ions
Forces on K+
concentration pushes outward
- electrical psuhes inward
- wants to get to -80 but concentrational wins
forces on Na+
- diffusion and electrical push it inwards
Ion pumps
- leakage woul reduce concentration gradient if it werent for pumps
- they use 70% of the brain ATP
- not a pore
- always going
Sodium potassium pump
- bring in 2 K+
- takes out 3 Na+
Important considerations
- very small changes in concentration of an ion can cause large changes in RMP
- this happens on the surfaces of the membranes (edges)
Astrocytes and K+
- diffuse it over a large area
- regulate external concntration
- store it
- remove it through pumps and channels
- a little change in it could really mess things up
- BBB
