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Potential and transmission (Resting potential (Glia cell (K+ goes out…
Potential and transmission
Membrane
Ion channel
Types
Resting
open
Not influenced extrinsically
Maintaining resting potential
Gated
Closed at rest
Resting potential
Charge
Positive outside
Outside defined as 0
Negative inside
-70mV
Membrane potential
=Vin - Vout
Electronic potential
passive responses of the membrane
Hyperpolarization and small depolarization
changes in potental that don't lead to opening ion channels
Glia cell
-75 mV
K+ and A- inside
Na+ and Cl- outside
K+ goes out
More positive charge outside
K+ goes in
Equilibrium
K+ going out
by concentration gradient
K+ going in
by electrical potential
Nerst equation
#
equilibrium potential for any ion
balance between 2 forces that drive K+ in and out
#
diffusion
#
electrostatic pressure
distribution of electrical charge
Sodium potassium pump
3 Na+ go out, 2 K+ go in
Buildup of K+ inside
But goes out again through diffusion
Negative inside
K+ goes in again
equilibrium
consumes energy
-60 mV because that is the equilibrium of all ions together
Ions
Na+
sodium
Cl-
Chlorine
K+
Potassium
selective permeability
Types
Anions
negative
Cations
Positive
Action potential
Voltage gated Na+ channel
normally closed
Opens with depolarization
Depoleriztion
Threshold
Na+ channels open
Na+ goes in and opens even more channels
Na+ channels close
Gated K+ channel opens
K+ goes out
1 more item...
Refractory phases
absolute
Na+ open or unresponsive
No stimulus can elicit response
Relative
reduced sensitivity
only very strong stimulus goes through
K+ is still flowing out
hyperpolarization
Saltatory conduction
with myelin
prevents K+ leakage out
faster transduction
Synaptic transmission
effect determined by receptor
Channels
gated
Chemical, physical, electrical
non gated
Amloyd beta
too much calcium inside the cell
membrane is essential