Synaptic Transmission and Neural Communication Flashcards

Vocabulary practice flashcards covering fundamental concepts in synaptic structure, neurotransmitters, receptor mechanisms, pharmacology, synaptic plasticity, and endocrine signaling.

Synapse

A specialized mechanism underlying neuronal communication, coined in 1897 by Charles Sherrington from the Greek word synapto meaning 'to clasp'.

Axodendritic synapse

A synapse in which an axon terminal from the presynaptic neuron communicates with a dendrite or dendritic spine of the postsynaptic cell.

Synaptic cleft

An exceedingly small gap (about $20\,nm$, or $20 \times 10^{-9}\,m$) between presynaptic and postsynaptic cells containing proteins that organize and maintain synaptic structure.

Postsynaptic density

A dark, fuzzy-looking area of the postsynaptic dendritic membrane facing the synaptic cleft that is rich in neurotransmitter receptors and anchoring proteins.

Axosomatic synapse

A type of synaptic connection between a presynaptic nerve terminal and a postsynaptic nerve cell body.

Axoaxonic synapse

A synaptic arrangement involving one axon synapsing directly on the axon terminal of another neuron, permitting direct alteration of neurotransmitter release.

Presynaptic inhibition

A reduction in neurotransmitter release from an axon terminal resulting from activity at an axoaxonic synapse.

Presynaptic facilitation

An enhancement of neurotransmitter release from an axon terminal resulting from activity at an axoaxonic synapse.

Neuromuscular junction

The specialized connection point between a neuron and a muscle cell that shares structural and functional similarities with a conventional synapse.

Volume transmission

Chemical communication characterized by the diffusion of neuromodulators or neurotransmitters away from the release site to influence distant cells.

Wiring transmission

Chemical communication characterized by tight cell-to-cell synaptic interactions.

Active zones

Specialized darkly-staining regions of the presynaptic terminal membrane near the postsynaptic cell where synaptic vesicle fusion and neurotransmitter release occur.

Readily releasable pool

The group of synaptic vesicles located directly at the active zones that are docked, primed, and ready for immediate neurotransmitter release upon calcium influx.

Synaptotagmin-1

A calcium-sensitive protein located in the synaptic vesicle membrane that rapidly triggers vesicle and terminal membrane fusion during exocytosis.

Clathrin-mediated endocytosis

A relatively slow, widely accepted vesicle retrieval mechanism occurring distant from the release site, requiring a protein coating called clathrin to form membrane invaginations.

Kiss-and-run model

A vesicle recycling mechanism where a synaptic vesicle briefly fuses with the nerve terminal membrane to open a temporary pore, releases its contents, and detaches intact without collapsing or requiring clathrin.

Retrograde messengers

Chemical substances, such as lipid and gaseous transmitters, that are released by the postsynaptic cell and travel backward across the synapse to signal the presynaptic cell.

Terminal autoreceptors

Autoreceptors located on axon terminals that, when activated by the released neurotransmitter, inhibit further neurotransmitter release from the presynaptic cell.

Somatodendritic autoreceptors

Autoreceptors located on the cell body (soma) or dendrites of a neuron that, when activated, slow the rate of cell firing and reduce overall neurotransmitter release.

Heteroreceptors

Receptors located on axon terminals that respond to different neurotransmitters released from adjacent neurons to enhance or reduce transmitter release.

Reuptake

The inactivation process in which a released neurotransmitter is transported out of the synaptic cleft back into the presynaptic axon terminal that released it.

Gut–brain axis

The bidirectional signaling communication network between the gastrointestinal tract (including the gut microbiome) and the central nervous system.

Ionotropic receptors

Fast-acting neurotransmitter receptors made of 4 or 5 protein subunits forming an intrinsic ion channel or pore that opens directly upon ligand binding.

Metabotropic receptors

Slower-acting, single-subunit neurotransmitter receptors with seven transmembrane domains that function by activating intracellular G proteins upon ligand binding.

Allosteric modulators

Molecules that bind to non-agonist binding sites (allosteric sites) on a receptor to positively or negatively modify the receptor's response to an agonist, having no direct effect on their own.

Protein kinases

Enzymes activated by second messengers that catalyze the addition of phosphate groups (\text{–PO}_4^{2-}) to substrate proteins to alter their functioning.

Phosphodiesterases (PDEs)

Enzymes responsible for the inactivation and breakdown of cyclic second messengers such as cyclic AMP (cAMP) and cyclic GMP (cGMP).

Tyrosine kinase receptors

Single-pass cell membrane receptors that mediate neurotrophic factor actions by phosphorylating each other on tyrosine residues upon ligand-induced dimerization.

Synaptic plasticity

The capacity of synapses to undergo functional changes in transmission strength or structural changes such as the growth or loss of dendritic spines and terminals.

Chromaffin cells

Specialized cells in the adrenal medulla that secrete the monoamine hormones epinephrine and norepinephrine into the bloodstream during stress responses.

Magnocellular neurons

Unusually large neurosecretory cells in the paraventricular and supraoptic nuclei of the hypothalamus that synthesize vasopressin or oxytocin for release from the posterior pituitary.

Social cognition

The processing of social cues (including attention, emotion, motivation, learning, and memory) to determine appropriate behavioral responses to conspecifics.