PNB exam 2

Coulomb's Law

Opposite electrical charges attract each other, while like charges repel each other.

Electrical Gradient

A difference in electrical charge that influences the movement of ions.

Resting Membrane Potential

The membrane voltage of a cell at rest, largely maintained through K+ leak-channel activity.

Ion Permeability

The ability of a particular ion to cross a cell membrane.

Ion Flux

Movement of ions across the cell membrane.

Influx

Movement of an ion into a cell.

Efflux

Movement of an ion out of a cell.

Ion Channel

A protein pore in the cell membrane that allows selected ions to pass through.

Leak Channel

An ion channel that contributes to ion permeability at rest.

Voltage-Gated Channel

An ion channel that opens or closes in response to changes in membrane potential.

Ligand-Gated Channel

An ion channel controlled by the binding of a chemical substance.

Equilibrium Potential (Ex)

The membrane potential at which the diffusional and electrical forces on an ion balance, producing zero net ion movement.

Nernst Potential

The voltage an individual ion would produce if the membrane were permeable only to that ion.

Reversal Potential

The membrane voltage at which the net flux of a particular ion changes direction.

Nernst Equation

Equation that determines an ion's equilibrium potential using its concentrations, charge, and temperature.

Potassium Equilibrium Potential (EK)

−93 mV

Sodium Equilibrium Potential (ENa)

+61

Chloride Equilibrium Potential (ECl)

−75 mV

Calcium Equilibrium Potential (ECa)

+132 mV

Na+/K+ Pump

A membrane pump that uses energy to maintain the concentration gradients of sodium and potassium.

Depolarization

A change in membrane potential that makes it more positive.

Repolarization

A return of membrane potential toward its resting value.

Hyperpolarization

A change in membrane potential that makes it more negative.

Goldman-Hodgkin-Katz Equation

Predicts membrane potential based on the concentrations and relative permeabilities of multiple ions.

Relative Permeability (Px)

The permeability of an ion compared with other ions, determining its influence on membrane voltage.

Steady State

An unchanging state maintained through continuous input and output.

Net Ionic Current

The combined electrical current produced by the movement of all permeant ions.

Single-Ion Case

A membrane condition where one ion is permeant, causing Vm to approach that ion's equilibrium potential.

Multiple-Ion Case

A membrane condition where several permeant ions collectively determine Vm.

Neuron

A nerve cell capable of initiating and conducting electrical activity throughout the body.

Neuroglia

Cells that support neurons.

Dendrites

Neuronal structures that receive incoming signals, often as graded potentials.

Cell Body (Soma)

Region of the neuron that integrates multiple incoming signals through summation.

Axon

Neuronal structure that carries output signals in the form of action potentials.

Axon Hillock

Region near the beginning of the axon that contributes to initiating action potentials.

Axon Initial Segment (AIS)

Region containing a high density of voltage-gated sodium channels that help trigger action potentials.

AnkyrinG

Protein identified in the slides as anchoring voltage-gated sodium channels at the axon initial segment.

Graded Potential (GP)

A passive change in membrane potential with variable amplitude, duration, and sign that decreases with distance.

Electrotonic Potential

Another term used for a passive graded potential that spreads along the membrane.

Action Potential (AP)

A self-regenerating, all-or-none electrical event with a relatively fixed amplitude and duration.

Threshold

The membrane voltage at which sufficient activation of voltage-gated sodium channels triggers an action potential.

Subthreshold Potential

A membrane potential change that does not reach the level needed to initiate an action potential.

Suprathreshold Stimulus

A stimulus sufficient to bring the membrane to threshold and initiate an action potential.

All-or-None Principle

Once threshold is reached, a complete action potential occurs rather than a partial one.

Action Potential Upstroke

The rapid depolarizing phase driven primarily by sodium influx.

Action Potential Downstroke

The repolarizing phase driven primarily by potassium efflux.

After-Hyperpolarization (AHP)

The period after an action potential when continued potassium efflux makes Vm more negative than resting potential.

Voltage-Gated Na+ Channel

Channel that activates rapidly with depolarization, allows sodium influx, and subsequently becomes inactivated.

Voltage-Gated K+ Channel

Channel that activates more slowly with depolarization and contributes to repolarization through potassium efflux.

Channel Activation

Opening of a voltage-gated channel in response to depolarization.

Channel Deactivation

Closing of a voltage-gated channel as the membrane repolarizes or hyperpolarizes.

Channel Inactivation

Blocking of an activated voltage-gated sodium channel, preventing ion flow until recovery.

Na+ Activation Gate

The fast gate that opens during depolarization and closes during repolarization.

Na+ Inactivation Gate

The slower gate that blocks sodium-channel activity during sustained depolarization and unblocks during recovery.

Action Potential Propagation

Movement of an action potential along an axon through sequential activation of neighboring membrane regions.

Local Circuit Current

Electrical current spreading from an active axon region to an adjacent region, helping initiate another action potential.

Refractory Period

Time following an action potential when a membrane region is resistant to generating another action potential.

Absolute Refractory Period

Period when another action potential cannot be initiated because sodium channels are inactivated.

Relative Refractory Period

Period when a stronger stimulus is required to initiate another action potential.

Myelin Sheath

Multiple concentric wrappings of glial membrane around an axon that increase conduction speed.

Node of Ranvier

Gap between myelinated regions where action potentials are regenerated.

Saltatory Conduction

Rapid conduction in myelinated axons as action potentials effectively jump from node to node.

Oligodendrocyte

Glial cell that produces myelin in the central nervous system.

Schwann Cell

Glial cell that produces myelin in the peripheral nervous system.

Unmyelinated Axon

An axon in which successive membrane segments must undergo the action-potential cycle during propagation.

Myelinated Axon

An axon in which myelin allows action potentials to be regenerated at nodes rather than continuously along every membrane segment.

Synapse

A point of communication between neurons or between a neuron and an effector cell.

Electrical Synapse

A synapse that transmits electrical signals directly between cells through gap junctions.

Chemical Synapse

A synapse where neurotransmitters are released into a synaptic cleft and bind to receptors on another cell.

Gap Junction

A direct channel connection between adjacent cells that allows electrical coupling.

Connexon

A channel structure involved in forming gap-junction connections.

Presynaptic Neuron

The neuron that sends a signal to another cell.

Postsynaptic Cell

The cell that receives a signal from a presynaptic neuron.

Axon Terminal

The end of an axon where neurotransmitters are released.

Synaptic Cleft

The narrow space separating presynaptic and postsynaptic membranes.

Synaptic Vesicle

A membrane-bound structure that stores neurotransmitters before release.

Neurotransmitter (NT)

A chemical messenger released by neurons that binds to receptors on target cells.

Voltage-Gated Ca2+ Channel

Channel that opens in response to presynaptic depolarization and allows calcium influx.

Exocytosis

Release of vesicle contents when the vesicle membrane fuses with the cell membrane.

Endocytosis

Process by which membrane is taken back into a cell to form vesicles.

Vesicle Trafficking

Movement of synaptic vesicles within the presynaptic terminal.

Vesicle Tethering

Initial association of a vesicle with proteins near its target membrane.

Vesicle Docking

Positioning a synaptic vesicle at the presynaptic membrane before release.

Vesicle Priming

Preparing a docked vesicle for calcium-triggered fusion.

SNARE Proteins

Proteins involved in bringing vesicle and plasma membranes together for fusion.

Synaptotagmin

The calcium-sensing protein that triggers synaptic vesicle fusion.

Clathrin

Protein that forms a coat during vesicle recycling by endocytosis.

Dynamin

Protein involved in pinching off vesicles during endocytosis.

Vesicle Recycling

Recovery and reuse of synaptic vesicle membrane following neurotransmitter release.

Synaptic Delay

Brief delay between a presynaptic action potential and the postsynaptic response at a chemical synapse.

Postsynaptic Receptor

A receptor that binds neurotransmitter and produces a response in the receiving cell.

Ionotropic Receptor

A ligand-gated ion channel that directly opens when a neurotransmitter binds.

Metabotropic Receptor

A receptor that activates intracellular signaling pathways, such as G-protein pathways, to produce its effects.

G-Protein-Coupled Receptor (GPCR)

A receptor that activates G proteins and intracellular signaling following ligand binding.

Second Messenger Pathway

An intracellular signaling pathway activated by a receptor that alters cellular activity.

Excitatory Postsynaptic Potential (EPSP)

A depolarizing postsynaptic graded potential that makes an action potential more likely.

Inhibitory Postsynaptic Potential (IPSP)

An inhibitory postsynaptic potential that decreases the likelihood of an action potential, often through hyperpolarization.

Spatial Summation

Addition of postsynaptic potentials arriving from different locations at approximately the same time.

Temporal Summation

Addition of postsynaptic potentials arriving at different times, often from the same location.

Synaptic Integration

Combining excitatory and inhibitory inputs to determine whether threshold is reached.