Neural Conduction

Vocabulary flashcards covering key concepts in Neural Conduction: membrane potentials, action potentials, dendritic function, synaptic transmission, neurotransmitters, and pharmacology.

Membrane potential

The difference in electrical charge between the inside and outside of a neuron.

Resting membrane potential

Approximately -70 millivolts; maintained by unequal ion distribution across the membrane (Na+ and Cl- outside; K+ and proteins inside).

Intracellular electrode

A microelectrode inserted into a neuron to measure its membrane potential.

Extracellular electrode

An electrode outside the neuron used to measure membrane potential.

Ion channels

Protein pores in the membrane that allow ions to pass, determining permeability.

Sodium-Potassium Pump

Active transporter moving 3 Na+ out and 2 K+ in; contributes to the resting potential.

Postsynaptic Potentials (PSPs)

Changes in membrane potential caused by neurotransmitter action at postsynaptic membranes.

Excitatory Postsynaptic Potential (EPSP)

Depolarizing PSP that increases the likelihood of neuron firing.

Inhibitory Postsynaptic Potential (IPSP)

Hyperpolarizing PSP that decreases the likelihood of neuron firing.

Graded potential

Amplitude proportional to the strength of the input.

Decremental conduction

PSPs weaken as they spread from their site of generation.

Rapid transmission (PSPs)

PSPs are transmitted rapidly along the membrane.

Threshold of excitation

Approximately -65 mV; the level at which an action potential is triggered.

Action Potential (AP)

Brief reversal of membrane potential from about -70 mV to +50 mV in ~1 ms.

Axon hillock

Region where action potentials are initiated.

All-or-none

APs occur fully or not at all; not graded.

Integration

Summing inputs from multiple synapses to determine firing.

Spatial summation

PSPs from multiple synapses arrive almost synchronously to influence firing.

Temporal summation

PSPs produced in rapid succession from one synapse summate.

Saltatory conduction

Fast conduction in myelinated axons where APs jump between nodes of Ranvier.

Nodes of Ranvier

Gaps in the myelin sheath where voltage-gated Na+ channels are concentrated.

Myelin

Insulating sheath around axons; increases conduction speed by reducing ion flow; produced by oligodendroglia (CNS) and Schwann cells (PNS).

Dendritic spines

Small buds on dendrites where many synapses occur.

Dendritic compartmentalization

Dendritic signals may be confined to specific parts of the dendritic tree.

Synapse

Junction where a neuron communicates with another cell; includes various types such as axosomatic, axodendritic, axoaxonic, dendrodendritic, and dendroaxonic.

Axosomatic synapse

Synapse onto the soma (cell body) of a neuron.

Axodendritic synapse

Synapse onto a dendrite.

Axoaxonic synapse

Synapse onto another axon; involved in presynaptic modulation.

Dendrodendritic synapse

Synapse between dendrites; can be reciprocal.

Dendroaxonic synapse

Synapse between dendrite and axon.

Nondirected synapse

Neurotransmitter release is dispersed to a broad area rather than targeted to a single postsynaptic site.

Autoreceptors

Presynaptic receptors that respond to the neuron's own transmitter and provide negative feedback.

Coexistence

Presence of small-molecule and peptide transmitters in the same nerve terminal.

Vesicles

Vesicular structures that store neurotransmitters in the presynaptic terminal.

Exocytosis

Release of neurotransmitter by fusion of vesicles with the presynaptic membrane in response to Ca++ entry.

Neurotransmitter receptors

Postsynaptic proteins that bind neurotransmitters.

Ligand

Molecule that binds to a receptor.

Ionotropic receptor

Ligand-gated ion channel; produces brief, fast EPSPs/IPSPs.

Metabotropic receptor

G-protein-coupled receptor that affects ion channels or triggers second messengers.

G-protein

Protein that transduces signals from metabotropic receptors to ions or second messengers.

Secondary messengers

Intracellular signaling molecules (e.g., cAMP) that mediate longer-term effects.

Reuptake

Neurotransmitters are reabsorbed into the presynaptic neuron for recycling.

Degradation

Neurotransmitters are broken down by enzymes in the synapse.

Amino Acid Neurotransmitters

Fast-acting transmitters derived from amino acids; examples include glutamate, aspartate, glycine, and GABA.

Glutamate

Major excitatory amino acid neurotransmitter.

GABA

Major inhibitory amino acid neurotransmitter.

Glycine

Inhibitory amino acid neurotransmitter (primarily spinal cord).

Aspartate

Excitatory amino acid neurotransmitter.

Monoamine Neurotransmitters

Neurotransmitters derived from amino acids; include catecholamines and indolamines.

Dopamine

Catecholamine involved in reward and movement.

Norepinephrine

Catecholamine involved in arousal and attention.

Epenephrine

(Epinephrine) Catecholamine with peripheral roles; also central effects.

Serotonin

Indolamine neurotransmitter derived from tryptophan; mood regulation.

Acetylcholine (ACh)

Neurotransmitter at neuromuscular junctions and many CNS and ANS synapses; degraded by acetylcholinesterase.

Acetylcholinesterase (AChE)

Enzyme that deactivates acetylcholine in the synapse.

Nitric oxide (NO)

Soluble gas neurotransmitter; diffuses rapidly and has short-lived action.

Carbon monoxide (CO)

Soluble gas neurotransmitter with rapid, short-lived effects.

Neuropeptides

Peptides used as neurotransmitters; include endorphins; involved in analgesia and reward.

Endorphins

Opioid-like neuropeptides involved in analgesia and reward.

Agonists

Drugs that enhance or mimic transmitter effects.

Antagonists

Drugs that diminish transmitter effects.

Cocaine

Catecholamine agonist that blocks reuptake of dopamine and norepinephrine.

Valium (diazepam)

GABA agonist that increases GABA binding to its receptor.

Atropine

ACh antagonist that blocks muscarinic receptors.

Curare

ACh antagonist that blocks nicotinic receptors.