Resting Membrane Potential + Graded Potentials

What is the resting membrane potential (RMP) in neurons

and what is it caused by

-70mV

(inside of membrane is negatively charged vs outside)

difference in ionic makeup of extracellular fluid and intracellular fluid

plasma membrane is more permeable to some ions than others

Differences in ionic makeup of resting neuron cell

Outside - more Na+ → positive

Inside - more K+ and negatively charged proteins (A-/ anions)

Differential Membrane Permeability

membrane is more permeable to some ions than others

more K+ channels than Na+ channels so K+ leaves easily making inside negative

What do Changes in membrane potential do

acts as signals used to receive or send information

What are the 2 types of signals

Graded potential and action potential

Graded potential → what is it and how does it spread

shortlived local signals (dendrites) → signal decrease as it travels (decremental)

spread as local currents

Action potentials → what is it and how does it spread

long distance signals (axons) → signal is constant

Steps from neurons through graded potential and actional potential

Other neurons release neurotransmitters which binds to receptor → creates graded potential (very short lived because it only needs to go from dendrite to cell body to axon hillock) → if enough graded potential at axon hillock → fire action potential down axon (very long)

Depolarization → what signal + what does it do for the threshold

Graded potential

membrane potential decreases (towards 0) → inside becomes less negative

ex: -70 → -55

excites → easier to send action potential

towards threshold

Hyperpolarization → what signal + what does it do for the threshold

Graded potential

Membrane potential becomes more negative than resting (inside becomes even more negative ) → ex: -70 → -80

inhibits → makes firing action potential less likely

away from threshold

Threshold

minimum membrane potential needed to fire action potential

What are the two types of graded potential

Excitatory postsynaptic potential and inhibitory postsynaptic potential

Excitatory postsynaptic potential (EPSP)

depolarizes membrane → moves membrane towards from threshold → makes firing action potential more likely

inhibitory postsynaptic potential (IPSP)

hyperpolarizes membrane → moves membrane away from threshold → makes firing action potential less likely