Brain and Behaviour – Synaptic Transmission and Behaviour

These vocabulary flashcards cover the key terms and concepts from the lecture on neurons, synaptic transmission, action potentials, and classes of neurotransmitters.

Neuron

A specialized cell that forms the basic working unit of the nervous system (brain, spinal cord, peripheral ganglia) and consists of a soma, dendrites, and an axon.

Soma

The compact cell body of a neuron that contains the nucleus and integrates incoming signals.

Dendrite

Branch-like extensions of a neuron that receive synaptic inputs; branches thin with each division.

Axon

A long projection that carries action potentials away from the soma to other neurons or effectors.

Axon Hillock

Swollen region where the axon leaves the soma; the site where action potentials are initiated.

Afferent (Sensory) Neuron

Neuron that conveys information from tissues or organs into the CNS; converts external or internal stimuli into action potentials.

Efferent (Motor) Neuron

Neuron that transmits signals from the CNS to muscles or glands; features extensive dendrites and large axons.

Interneuron

Association neuron that connects other neurons within the CNS, linking sensory and motor pathways.

Synapse

The junction (synaptic gap) between two neurons where chemical or electrical signals are transmitted.

Synaptic Transmission (Neurotransmission)

The process by which an action potential triggers release of neurotransmitter across a synapse to communicate with another cell.

Action Potential (AP)

A rapid, transient electrical impulse that reaches about +40 mV and propagates along the axon when membrane depolarization crosses threshold (~-50 mV).

Resting Potential

The stable, negative electrical charge (≈-70 mV) inside a neuron relative to outside when the cell is inactive.

Depolarization

Positive shift in membrane potential caused by influx of cations (e.g., Na⁺) during the rising phase of an AP.

Hyperpolarization

Negative shift in membrane potential, moving farther from zero; can inhibit action-potential generation.

Voltage-Gated Ion Channel

Transmembrane protein that opens or closes in response to changes in membrane potential to allow specific ions through.

Ligand-Gated Ion Channel

Channel whose gate opens when a specific chemical (neurotransmitter) binds to the receptor portion.

Mechanically-Gated Ion Channel

Ion channel that opens in response to physical deformation, such as pressure or stretch.

Leak Channel

Ion channel that is always open, allowing passive ion movement to help set resting potential.

Cation

Positively charged ion (e.g., Na⁺, K⁺).

Anion

Negatively charged ion (e.g., Cl⁻, protein A⁻).

Refractory Period

Brief time after an action potential during which a neuron cannot fire another AP, limiting firing rate.

Excitatory Synapse (Type I)

Synapse in which the presynaptic action potential increases the probability of a postsynaptic AP; has large active zones and wide cleft.

Inhibitory Synapse (Type II)

Synapse in which the presynaptic action potential decreases the probability of a postsynaptic AP; has small active zones and narrow cleft.

Excitatory Post-Synaptic Potential (EPSP)

Depolarizing change in postsynaptic membrane potential whose reversal potential is more positive than AP threshold.

Inhibitory Post-Synaptic Potential (IPSP)

Hyperpolarizing change in postsynaptic membrane potential whose reversal potential is more negative than AP threshold.

Small-Molecule Neurotransmitter

Low-molecular-weight transmitter derived from diet, synthesized in axon terminals, and quickly replenished after release.

Peptide Neurotransmitter (Neuropeptide)

Larger transmitter synthesized on ribosomes, packaged in vesicles, slowly produced, and not rapidly replaced.

Acetylcholine (ACh)

Excitatory small-molecule neurotransmitter central to the parasympathetic system; involved in muscle activation, learning, arousal, and reward.

Serotonin (5-HT)

Excitatory small-molecule neurotransmitter from raphe nuclei that regulates mood, sleep, appetite, pain perception, and is implicated in depression and anxiety.

Endorphins

Endogenous opioid neuropeptides that inhibit pain transmission and produce euphoria; an inhibitory neuromodulator.

Gasotransmitter

Small gaseous signaling molecule (e.g., nitric oxide) synthesized on demand, freely diffusing across membranes rather than released from vesicles.

Nitric Oxide (NO)

A gasotransmitter that dilates blood vessels and acts as a neural messenger; produced as needed, not stored.