Neuroscience and Cell Physiology: Membrane Potentials, Ion Channels, and Synaptic Transmission

Electric potential

Stored electrical charge difference.

Diffusion

Ions move from high → low concentration.

Concentration gradient

Difference in ion concentration across membrane.

Electrostatic gradient

Attraction/repulsion of charges.

Selective permeability

Membrane allows some ions through.

Equilibrium potential

Voltage balancing forces on one ion.

Nernst/Goldman equations

Calculate Eion and Vm.

Na⁺/K⁺ pump

Maintains gradients (3 Na⁺ out, 2 K⁺ in).

Ion channels

Control ion flow (leak, voltage, ligand, mechanical).

Depolarization/Hyperpolarization

Less negative / more negative.

Threshold

Voltage needed to trigger AP.

All-or-none

AP fires fully or not at all.

Rate law

Intensity = AP frequency.

Continuous vs. Saltatory conduction

Unmyelinated slow / Myelinated fast.

Optogenetics

Light-controlled ion channels.

Synapse terms

Presynaptic = sender, postsynaptic = receiver, cleft = gap.

Endocytosis/Exocytosis

Vesicle recycling/release.

PSP, EPSP, IPSP

Graded voltage changes.

AChE

Enzyme that breaks down acetylcholine.

NMJ / EPP / Myasthenia / Toxins

Muscle synapse, depolarization, disease, and blockade.

SNARE proteins

Mediate vesicle fusion.

Neural integration / Spatial / Temporal summation

Combining inputs to trigger AP.