Neurology III – Synaptic Activity & Information Processing

Vocabulary flashcards covering key terms from Chapter 12 Neurology III: synaptic mechanisms, neurotransmitters, drugs/toxins, clinical condition myasthenia gravis, and principles of neuronal information processing.

Synaptic activity

The process by which a nerve impulse reaching an axon terminal leads to neurotransmitter release and communication with the postsynaptic cell.

Resting potential

The stable, negative membrane voltage of a neuron (≈ –70 mV) when it is not transmitting a signal.

Local potential

A small, graded change in membrane voltage that occurs in a neuron’s dendrites or soma and can summate to reach threshold.

Action potential

An all-or-nothing, self-propagating electrical impulse that travels along an axon once threshold is reached.

Voltage-gated Na⁺ and K⁺ channels

Membrane proteins that open or close in response to voltage changes to initiate and propagate action potentials.

Voltage-gated Ca²⁺ channels

Channels at axon terminals that open during an action potential; Ca²⁺ influx triggers neurotransmitter exocytosis.

Excitatory neurotransmitter

Chemical messenger that depolarizes the postsynaptic membrane, increasing the chance of an action potential.

Inhibitory neurotransmitter

Chemical messenger that hyperpolarizes the postsynaptic membrane, decreasing the chance of an action potential.

Cholinergic synapse

A synapse that uses acetylcholine (ACh) as its neurotransmitter, common at neuromuscular junctions and neuron-neuron synapses.

Acetylcholine esterase (AChE)

Enzyme in the synaptic cleft that breaks down acetylcholine to terminate the signal.

Norepinephrine

Neurotransmitter that typically excites cardiac muscle and some neurons.

Dopamine

Neurotransmitter associated with mood elevation and reward pathways.

Serotonin

Neurotransmitter involved in mood regulation, sleep, and many other functions.

GABA (gamma-aminobutyric acid)

Major inhibitory neurotransmitter in the CNS.

Anesthetics

Drugs that depress axolemma sensitivity, reducing neuron excitability.

Botulinum toxin

Toxin that blocks the release of ACh, leading to flaccid paralysis.

Nicotine

Drug that stimulates receptors on the postsynaptic membrane, mimicking ACh effects.

Myasthenia gravis

Autoimmune disorder where antibodies block ACh receptors, causing fluctuating muscle weakness; treated with AChE inhibitors and immunosuppressants.

Postsynaptic potential

The combined excitatory and inhibitory inputs on a neuron that determine its response.

Trigger zone

Region (axon hillock/initial segment) where local potentials summate; must reach –55 mV to fire an action potential.

Threshold voltage (≈ –55 mV)

Membrane potential that must be reached at the trigger zone to initiate an action potential.

Frequency coding

Method by which the CNS interprets stimulus intensity based on the rate (frequency) of action potentials.

Refractory period

Time after an action potential when a neuron cannot fire (absolute) or requires a stronger stimulus (relative) until repolarization is complete.