Action Potentials and Graded Potentials in Neurons

Action Potential

Rapid change in membrane potential for neuron signaling.

Graded Potential

Local changes in membrane potential, varying in size.

Resting Membrane Potential

Stable membrane voltage of -70 mV in neurons.

Equilibrium Potential

Membrane potential where ion concentrations are balanced.

Gated Ion Channels

Channels that open/close in response to stimuli.

Chemically Gated Channels

Open in response to specific chemical signals.

Voltage-Gated Channels

Open in response to changes in membrane voltage.

Mechanically Gated Channels

Open in response to mechanical deformation.

Depolarization

Decrease in membrane potential; Na+ enters cell.

Repolarization

Return to resting potential after depolarization.

Hyperpolarization

Increase in negativity of membrane potential; K+ exits.

Threshold

Minimum potential needed to trigger an action potential.

All-or-None Principle

Action potentials occur fully or not at all.

Refractory Periods

Time during which neuron cannot fire another action potential.

Saltatory Conduction

Action potential jumps between nodes of Ranvier.

Continuous Propagation

Unmyelinated neurons conduct action potentials continuously.

Temporal Summation

Repeated stimuli from same source add effects.

Spatial Summation

Simultaneous stimuli from different sources combine effects.

Na+/K+ ATPase

Pump that maintains ion gradients across the membrane.

Permeability

Ability of the membrane to allow ion passage.

Ion Concentration Gradient

Difference in ion concentration across the membrane.

Nodes of Ranvier

Gaps in myelin sheath for action potential regeneration.

Axon Hillock

Region where action potentials are initiated.

Myelin

Insulating layer that speeds up action potential propagation.

Voltage Gated Activity

Ion channel activity dependent on membrane voltage changes.

Post synaptic neuron

Neuron receiving signals from another neuron.

Subthreshold graded potential

Graded potential insufficient to trigger action potential.

Summation Signals

Combining multiple graded potentials for action potential.

Suprathreshold

Graded potentials exceeding threshold for action potential.

Graded potentials

Local changes in membrane potential.

Voltage-gated Na+ channels

Channels that open during depolarization phase.

Absolute refractory period

Period when no action potential can occur.

Relative refractory period

Period requiring stronger stimulus for action potential.

Positive feedback cycle

Initial stimulus enhances response, leading to action potential.

Saltatory propagation

Faster conduction in myelinated axons via nodes.

Continuous propagation

Slower conduction in unmyelinated axons.

Ion permeability

Changes in membrane permeability during action potential.

Graded potential summary

Local potentials that vary in size and duration.

Chemically gated channels

Channels opened by chemical ligands, causing depolarization.

Equilibrium potential of Na+

Membrane potential where Na+ influx equals efflux.

Equilibrium potential of K+

Membrane potential where K+ efflux equals influx.

Threshold potential

Typically around -55mV for action potential initiation.

Frequency coding

Rate of action potentials indicates stimulus intensity.

Membrane potential

Voltage difference across a neuron's membrane.

Local current

Current generated by ion movement during graded potential.

Sodium ion influx

Movement of Na+ into cell during depolarization.

Potassium ion efflux

Movement of K+ out of cell during repolarization.

Action potential components

Includes generation, propagation, and refractory periods.