Synapses

Flashcards covering key vocabulary related to synapses, action potential voltage gates, types of synapses, neurotransmitter release and reception, and neurotransmitter life cycle from the NEU 101 lecture.

Action Potential Voltage Gates

The sequence of opening and closing of voltage-gated sodium and potassium channels during an action potential: Sodium gates open (sodium in), Potassium gates open (potassium out), Sodium gates inactivate (sodium stops moving), Potassium gates close (potassium stops moving).

Axodendritic Synapse

A type of synapse where the axon of one neuron communicates with a dendrite of another neuron.

Axosomatic Synapse

A type of synapse where the axon of one neuron communicates with the soma (cell body) of another neuron.

Axoaxonic Synapse

A type of synapse where the axon of one neuron communicates with the axon of another neuron.

Exocytosis

The process by which synaptic vesicles fuse with the presynaptic membrane and release neurotransmitters into the synaptic cleft, typically triggered by calcium influx.

Ions vs. Neurotransmitters

Ions are single charged atoms (e.g., Na+, K+) that pass through ion channels, whereas neurotransmitters are larger molecules (more than one atom) that function as a unit and do not pass through ion channels themselves.

Glial Cell Removal

A mechanism for neurotransmitter removal from the synapse, where glial cells (like astrocytes) take up neurotransmitters, sometimes into the bloodstream.

Gap Junctions (Electrical Synapses)

Direct connections between the cytoplasm of two adjacent cells that allow ions and small molecules to pass directly, facilitating rapid electrical signal transmission.

Connexon

A protein channel that forms a gap junction, allowing direct communication between adjacent cells.

Chemical Synapse

A synapse where neurotransmitters are released from the presynaptic terminal into the synaptic cleft to bind to receptors on the postsynaptic membrane, transmitting a signal.

Synaptic Vesicles

Small sacs within the terminal buttons that contain neurotransmitters, ready for release into the synapse.

Calcium Dependent Exocytosis

The specific process where the influx of calcium ions into the presynaptic terminal triggers a chain reaction causing synaptic vesicles to fuse with the cell membrane and release their neurotransmitter contents.

Postsynaptic Density (PSD)

A protein-dense specialization within the postsynaptic membrane where receptors are embedded to receive neurotransmitter signals.

Voltage-Gated Ion Channels

Ion channels that open in response to changes in the cell's membrane potential, crucial for generating and propagating action potentials.

Mechanically-Gated Ion Channels

Ion channels that open in response to physical pressure or mechanical distortion of the cell membrane.

Ligand-Gated Ion Channels (Chemically-Gated Channels)

Ion channels that open when a specific ligand (such as a neurotransmitter) binds to a receptor site on the channel protein.

Ionotropic Receptor

A type of ligand-gated ion channel that directly opens an ion channel upon neurotransmitter binding, causing rapid EPSPs or IPSPs.

Metabotropic Receptors (G-Protein Coupled Receptors - GPCRs)

Receptors that, upon neurotransmitter binding, cause metabolic changes inside the cell via activation of G-proteins and subsequent second messenger cascades, leading to slower, longer-lasting effects.

G-Proteins

Intracellular proteins activated by metabotropic receptors, which then trigger second messengers to change intracellular activity.

Second Messengers

Intracellular molecules that relay signals from receptors on the cell surface to target molecules inside the cell, often initiated by metabotropic receptor activation (e.g., cAMP, IP3, DAG).

Intracellular Signalling Cascades

A series of biochemical reactions inside a cell, initiated by a signal (like neurotransmitter binding to a GPCR) that leads to a specific, often long-term, cellular response.

Autoreceptors

Metabotropic receptors often located on the axon of the presynaptic cell, which detect the neuron's own neurotransmitter release and typically regulate further neurotransmitter synthesis or release.

Neurotransmitter Reuptake

A mechanism for neurotransmitter removal from the synapse, where the neurotransmitter is drawn back into the presynaptic cell or sometimes glial cells and can be re-used.

Enzyme Degradation

A mechanism for neurotransmitter removal from the synapse, where specialized enzymes in the extracellular fluid break down the neurotransmitter.