PS1090 - neurophysiology neural signals and transmission

what is the cell membrane made of

phospholipids with hydrophilic heads and hydrophobic tails, plus embedded proteins for molecule passagew

what is membrane potential

the electrical difference across the cell membrane in living cells, measured in millivolts (mV)

what are excitable cells like neurons

cells where membrane potential changes with stimulation or inhibition, generating electrical currents

what is the resting membrane potential

-70 mV when the neuron is inactive; inside negative, outside positive (polarized state)

what is hyperpolarization

membrane potential becomes more negative than rest (-90 mV), inhibiting the neuron

what is depolarization

membrane potential becomes less negative, moving toward 0 mV (+40 mV) when stimulated

what is a diffusion gradient

movement of particles from high to low concentration until dynamic equilibrium

name the two key ions for neuron potential

sodium (Na+) and potassium (K+)

where is Na+ mostly concentrated, and what drives it

10x higher outside; diffusion drives it inward

where is K+ mostly concentrated, and what drives it

40x higher inside; diffusion drives it outward

what creates the electrical gradient

opposite charges attract ions (positive to negative inside)

what regulates ion movement

semi-permeable membrane with selective ion channels

why is resting potential -70 mV (closer to K+ equilibrium)

membrane more permeable to K+ than Na+ at rest

what maintains ion gradients long-term

sodium-potassium pump

where does an action potential start and how long does it last

starts at axon hillock; lasts ~2 milliseconds

what is the threshold for firing an action potential

-55 mV (all-or-nothing law)

describe the rising phase of action potential

Na+ channels open, Na+ rushes in, potential rises to +40 mV (overshoot)

describe the falling phase and undershoot

K+ channels open, K+ flows out to -90 mV (hyperpolarized undershoot)

what is saltatory conduction in myelinated axons

action potential jumps between Nodes of Ranvier for fast transmission

difference between myelinated and non-myelinated axons

myelinated: insulated, fast saltatory conduction (motor neurons); non-myelinated: slower continuous conduction (autonomic)