Nerve Tissue Physiology – Quick Review

Vocabulary flashcards summarizing essential terms, structures, and processes involved in neuronal electrical activity, signal conduction, synaptic transmission, neurotransmitters, neural integration, and related neurological disorders.

Electrophysiology

Study of cellular mechanisms that produce electrical potentials and currents.

Electrical Potential

Difference in concentration of charged particles between two points.

Electrophysiology

Study of cellular mechanisms that produce electrical potentials and currents.

Electrical Potential

Difference in concentration of charged particles between two points.

Electrical Current

Flow of charged particles (ions) from one point to another.

Resting Membrane Potential (RMP)

Baseline charge difference across a cell membrane (≈ –70 mV in neurons).

Polarized Cell

Cell whose interior is more negative than its exterior.

Na⁺/K⁺ Pump

Membrane transport protein that expels 3 Na⁺ and imports 2 K⁺ per ATP to maintain RMP.

Local Potential

Small, graded change in membrane voltage near the site of stimulation.

Depolarization

Shift of membrane potential toward 0 mV (inside becomes less negative).

Hyperpolarization

Shift of membrane potential to a more negative value than RMP.

Graded (Potential)

Property where voltage change varies with stimulus strength.

Decremental

Voltage change that decreases in magnitude with distance traveled.

Reversible (Potential)

Membrane potential returns to RMP when stimulus ceases.

Action Potential (Spike)

Rapid, self-propagating change in membrane polarity via voltage-gated channels.

Threshold

Critical voltage (≈ –55 mV) needed to trigger an action potential.

All-or-None Law

APs occur at full strength if threshold is reached, or not at all.

Refractory Period

Time after an AP when a membrane is resistant to new stimulation.

Absolute Refractory Period

Phase when no stimulus can elicit another AP.

Relative Refractory Period

Phase when only a strong stimulus can trigger a new AP.

Unmyelinated Conduction

Continuous propagation of APs along entire axon membrane.

Saltatory Conduction

Rapid signal conduction in myelinated fibers where impulses “jump” between nodes.

Nodes of Ranvier

Gaps in myelin sheath rich in voltage-gated ion channels.

Synapse

Junction where a neuron communicates with another cell.

Presynaptic Neuron

Neuron that releases neurotransmitter at a synapse.

Postsynaptic Neuron

Neuron that receives and responds to neurotransmitter.

Electrical Synapse

Gap-junction connection allowing direct ion flow and rapid, bidirectional signaling.

Chemical Synapse

Site where neurotransmitters carry signals across a synaptic cleft.

Neurotransmitter

Chemical messenger released by neurons to alter another cell’s physiology.

Acetylcholine (ACh)

Neurotransmitter involved in muscle activation, attention, and learning.

Amino Acid Neurotransmitters

Simple amino acids acting as transmitters; e.g., glutamate, GABA, glycine.

Monoamines

Neurotransmitters synthesized from amino acids; include dopamine, NE, epinephrine, serotonin, histamine.

Neuropeptides

Chains of 2–40 amino acids that function as neurotransmitters or neuromodulators.

Excitatory Postsynaptic Potential (EPSP)

Depolarizing graded potential that moves membrane toward threshold.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarizing graded potential that moves membrane farther from threshold.

Summation

Addition of EPSPs and IPSPs to determine neuronal output.

Temporal Summation

Rapid, successive EPSPs from one synapse that build to threshold.

Spatial Summation

EPSPs from multiple synapses combine to reach threshold.

Second Messenger

Intracellular molecule (e.g., cAMP) that relays signals from membrane receptors.

cAMP

Cyclic AMP; common second messenger activated by G-protein-coupled receptors.

GABA

Major inhibitory neurotransmitter that opens Cl⁻ channels to hyperpolarize neurons.

Glutamate

Primary excitatory neurotransmitter in the CNS, crucial for learning and memory.

Dopamine

Monoamine associated with reward, motivation, and motor control.

Norepinephrine (NE)

Monoamine involved in arousal, attention, and adrenergic synapses.

Serotonin

Monoamine that regulates mood, sleep, and appetite.

Endorphins

Neuropeptides that reduce pain and induce euphoria.

Acetylcholinesterase (AChE)

Enzyme that degrades acetylcholine in the synaptic cleft.

Monoamine Oxidase (MAO)

Enzyme that degrades monoamine neurotransmitters after reuptake.

Synaptic Plasticity

Ability of synapses to change their strength over time.

Synaptic Potentiation

Long-lasting increase in synaptic efficiency after repeated activity.

Alzheimer Disease

Neurodegenerative disorder marked by β-amyloid plaques and memory loss.

Parkinson Disease

Motor disorder due to degeneration of dopamine-releasing neurons in basal nuclei.

Amphetamine

Drug that increases release and blocks reuptake of NE and dopamine, producing euphoria and alertness.

Alcohol (Ethanol)

Substance that enhances GABA effects, inhibits glutamate receptors, and elevates dopamine, causing sedation and incoordination.