Neuron information carried by? 

Electrical signals

Chemical signals 

Electrical signals are changes in what?

ion selectivity of resting channels (normally open)

concentration gradients of permeant ions 

cations 

determine resting membrane potential.

normally open.

not influenced by membraned potential 

normally closed

function is to generate electical signals 

Ex = (RT/zF) ln [x]o/[x]i

Ex = (Gas constant x temp / ion valence x farada constant) ln(extracellular concentration / intracellular concentration)

The Goldman Equation

Lecture 13 notes. too hard to type 

ion selectivity of resting channels

concentration gradients of permeant ions 

K+ leak channels

HCN channels

Inward rectifying K+ channels

 low threshold Ca²⁺ channels

Na/K pump

GABA receptors 

3 Na out

2 K in 

sub-threshold depolarization voltage signal increase or decreases in amplitude from its initiation site?

1. membrane resistance - resting channels make the cell leaky

2. membrane capacitance - capacity of the membrane to store changes

3. intracellular axial resistance along axons dendrites  - increases with the length and decreases with the diameter

measure of efficiency of passive spread of the voltage change along a process

equal to the distance where voltage change has decreased to 37% 

 Delta V(x) - Delta V_oe^-x/lamda

influences spatial summation

contributes to propagation of the action potential 

membrane resistance

axial resistance

diameter of a process 

a greater conducting property

leads to a signal that will spread further 

ahead of the action potential generates an action potential - the whole propagation thing

behind has large k influx for repolarization and Na channels are inactive 

How do passive electrical properties effect AP propagation? 

Membrane capacitance - larger leads to more charge deposited and slower AP propagation

Axial resistance - lower leads to rapid AP propagation

membrane Resistance - greater leads to rapid AP propagation 

1. increase diameter of axon - reducing axial resistance

2. myelation of axon - increases effective membrane resistance and reduces membrane capacitance 

periphery by Schwann cells

CNS by oligodendrocytes 

concentrated Na channels - generate large inward Na current

spread longitudinally along the fibre

accumulate to change the charge on the membrane surface

flow out through the membrane resistance 

slow down AP conduction

produce sever disturbances in motor and sensory function 

propagates in dendrites. large enough synaptic potentials trigger dendritic AP that propagate toward soma.

Ap initiated at trigger zone propagate along axon and towards axon terminals.