wwww

100 vocabulary flashcards covering key terms related to neuronal physiology from the lecture notes.

Excitable cells

Cells capable of undergoing transient, rapid changes in their membrane potentials.

Polarization

Separation of charges across the plasma membrane.

Depolarization

Membrane potential becomes less negative (more positive) during excitation.

Repolarization

Membrane returns toward the resting potential after depolarization.

Hyperpolarization

Membrane becomes more negative than the resting potential.

Resting potential

Steady-state membrane potential when the cell is not firing (about -70 mV in neurons).

Graded potentials

Local changes in membrane potential that vary in magnitude with stimulus.

Local current flow

Passive spread of electrical current from the active site to adjacent areas.

Length constant (λ)

Distance over which a graded potential decays to 63% of its original value; λ = sqrt(Rm/Ri).

Ohm's law in neurons

Relationship among current, resistance, and voltage; ΔV = ΔI × R (or V = IR).

Passive spread

Spread of graded potentials by electrotonic conduction without active regeneration.

Postsynaptic potentials

Graded potentials produced in the postsynaptic neuron.

Receptor potentials

Graded potentials generated in sensory receptor cells.

End-plate potentials

Graded potentials at neuromuscular junctions.

Pacemaker potentials

Rhythmic potentials in pacemaker cells.

Slow-wave potentials

Slow, rhythmic potentials in certain tissues.

Action potentials

Brief, rapid, large changes in membrane potential that propagate without decrement.

All-or-none principle

AP occurs fully or not at all once the threshold is reached.

Nondecremental conduction

AP maintains its amplitude as it propagates.

Threshold potential

Membrane potential that triggers an action potential (about -50 to -55 mV).

Voltage-gated ion channels

Channels that open/close in response to membrane potential changes.

Na+ channels

Voltage-gated channels that allow Na+ entry; have activation and inactivation gates.

Activation gate (Na+ channel)

Gate that opens to allow Na+ influx when depolarized.

Inactivation gate (Na+ channel)

Gate that blocks Na+ channels after activation (ball-and-chain).

K+ channels

Voltage-gated channels that allow K+ efflux to repolarize the cell.

Delaved-rectifier potassium channel

Voltage-gated K+ channel that opens after a delay to aid repolarization.

Leak channels

Always-open channels contributing to the resting conductance.

Chemically gated channels

Channels opened by neurotransmitter binding.

Voltage-gated calcium channels

Channels opened by depolarization to allow Ca2+ influx; blocked by Verapamil and conotoxins.

Mechanically gated channels

Channels opened by mechanical stimuli (stretch, pressure).

Patch clamp

Technique that seals a patch of membrane to measure or control currents.

Microelectrodes

Electrodes inserted into a neuron to measure local potentials.

Voltage clamp

Technique that holds membrane potential constant to study ionic currents.

Electrotonic conduction

Passive spread of voltage without active regeneration.

Inward Na+ current

Na+ entry during depolarization contributing to excitation.

Sodium influx

Movement of Na+ into the cell during depolarization.

Sodium channel states

Closed, open, and inactivated states of Na+ channels.

Activation gate (definition)

Part of the Na+ channel that opens during depolarization.

Inactivation gate (definition)

Part of the Na+ channel that blocks the channel after activation.

Membrane potential

Electrical potential difference across the cell membrane.

Extracellular fluid (ECF)

Fluid outside the cell.

Intracellular fluid (ICF)

Fluid inside the cell.

Na+/K+-ATPase pump

ATPase that pumps Na+ out and K+ in to maintain gradients.

Axonal propagation

Transmission of the action potential along the axon.

Electrical synapses

Direct electrical signaling via gap junctions between neurons.

Chemical synapses

Neurotransmitter-mediated signaling across the synaptic cleft.

Gap junctions

Protein channels allowing direct ion flow between cells.

Synapses and integration

How multiple synaptic inputs are integrated to decide firing.

Tetrodotoxin (TTX)

Toxin that blocks voltage-gated Na+ channels from outside the cell.

TEA (tetraethylammonium)

Blocker of some voltage-gated K+ channels from inside the cell.

Verapamil

Calcium channel blocker.

Cone snail toxins (conotoxins)

Block voltage-gated calcium channels.

Sodium influx blockers

Agents that prevent Na+ entry into the cell (e.g., TTX).

K+ channel blockers

Agents that block K+ channels (e.g., TEA).

Activation gate (Na+ channel)

Gating element that opens to permit Na+ entry.

Inactivation gate (Na+ channel)

Gating element that blocks Na+ after activation.

Sodium channel reset

Na+ channels return to closed but capable of opening after AP.

Na+/K+ pump role

Maintains Na+ and K+ gradients essential for resting state.

Threshold crossing

Membrane potential reaching threshold to trigger AP.

Peak potential

AP apex, typically around +30 to +40 mV.

Depolarization to threshold

Progression of potential toward the threshold during excitation.

Repolarization to resting

Return of membrane potential to resting level after AP.

Afterhyperpolarization

Hyperpolarization following an action potential.

Positive feedback in AP

Na+ influx promotes further depolarization via more Na+ channel opening.

Decremental spread

Graded potentials decrease in amplitude with distance.

Conductors and insulators

Materials with low (conductors) or high (insulators) resistance to current.

Membrane conductance (G)

Ease of current flow across the membrane; inverse of resistance.

Membrane resistance (Rm)

Resistance of the cell membrane to ion flow.

Internal resistance (Ri)

Resistance within the cytoplasm.

Ohm's law form (V=I×R)

Fundamental relation between voltage, current, and resistance.

Current (I)

Flow of electrical charges.

Passive current flow

Current that flows without active regeneration of signal.

Active vs inactive areas in graded potential

Active depolarized region and surrounding inactive areas that receive current.

Current leak

Leakage across the membrane that reduces signal strength.

AP sequence

Depolarization, threshold, peak, repolarization, hyperpolarization.

Threshold potential range

Approximately -50 to -55 mV for many neurons.

Na+ channel reset mechanics

After AP, Na+ channels return to closed, activatable state.

Sodium channel closed state

Na+ channel neither open nor inactivated; ready to activate.

Potassium channel open state

K+ channel open during repolarization to exit K+.

Toxins and Na+ channels

TTX blocks Na+ channels; prevents Na+ influx.

Inactivation mechanism

Ball-and-chain closing Na+ channel after activation.

Calcium channels and toxins

Verapamil/conotoxins block voltage-gated Ca2+ channels.

Patch clamp vs voltage clamp

Patch clamp measures currents from a membrane patch; voltage clamp holds membrane potential.

Mechanically gated channel examples

Channels opened by mechanical deformation (e.g., touch receptors).

Chemically gated channel examples

Channels opened by neurotransmitters (e.g., acetylcholine receptors).

Resting potential value

Typical baseline membrane potential around -70 mV.

Graded potentials examples

Postsynaptic potentials, receptor potentials, end-plate potentials, pacemaker potentials, slow-wave potentials.

Postsynaptic potentials

Graded potentials in the postsynaptic neuron due to neurotransmitter binding.

End-plate potentials (muscle)

Graded potentials at the neuromuscular junction.

Pacemaker potentials

Rhythmic automatic depolarizations in pacemaker cells.

Slow-wave potentials

Slow rhythmic oscillations in certain tissues.

Axonal propagation speed

Speed at which the AP travels along the axon.

Length constant vs velocity

Larger λ generally indicates faster signal propagation.

External agents affecting channels

Drugs/toxins that block or modulate ion channels.

Ion movement and membrane potential

Potentials arise from selective ion movement through channels.

Electrotonic conduction vs action potential

Electrotonic conduction is passive spread; AP is regeneratively propagated.

Patch clamp measurement of currents

Using a patch clamp to record ionic currents across membrane.

Microelectrode measurement of potentials

Using microelectrodes to record local membrane potentials.

Membrane potential changes due to ion channels

Ion channel opening/closing causes changes in membrane potential.

Na+/K+-ATPase pump maintains gradients

Active pump sustaining Na+ and K+ gradients essential for resting state.