Neurophysiology of Neurons and Synapses

Flashcards for reviewing key concepts in neurophysiology, specifically focusing on neuronal function, synaptic transmission, and the characteristics of action potentials.

Sodium-Potassium Pump (Na+/K+ Pump)

An active transport pump that uses ATP to transport 3 Na+ ions outside the cell and 2 K+ ions inside, maintaining the electrochemical gradient.

Resting Membrane Potential (RMP)

The electrical potential difference across the membrane of a neuron when it is not actively sending signals, typically around -70 mV.

Action Potential

A rapid change in membrane potential that occurs when the charge at a location reaches a threshold of -55 mV, leading to depolarization followed by repolarization.

Excitatory Postsynaptic Potential (EPSP)

A postsynaptic potential that makes the neuron more likely to fire an action potential, typically caused by the influx of Na+ ions.

Inhibitory Postsynaptic Potential (IPSP)

A postsynaptic potential that makes the neuron less likely to fire an action potential, often generated by the influx of Cl- or efflux of K+.

Summation

The process of adding together postsynaptic potentials (both EPSPs and IPSPs) to determine if the neuron will initiate an action potential.

Continuous Conduction

The propagation of action potentials in unmyelinated neurons where the action potential travels continuously along the axon.

Saltatory Conduction

The rapid conduction of action potentials along myelinated axons, where the action potentials appear to jump from node to node.

Absolute Refractory Period

A period during which a second action potential cannot be initiated, because the Na+ channels are inactive after being opened.

Relative Refractory Period

A period immediately following the absolute refractory period when a second action potential can occur, but only with a stronger-than-normal stimulus.

Neurotransmitter Receptor Types

Receptors that vary in influence based on whether they are ionotropic or metabotropic; ionotropic receptors directly mediate ion flow, while metabotropic receptors act indirectly through signaling pathways.

Synaptic Cleft

The small gap between presynaptic and postsynaptic neurons where neurotransmitter release and reception occur.

Divergent Circuit

A neural circuit in which impulses from a single source stimulate multiple postsynaptic neurons, allowing for amplification of signals.

Convergent Circuit

A neural circuit where impulses from multiple sources converge on a single postsynaptic neuron, providing finer control of responses.

Neuropeptides

A type of neurotransmitter composed of short chains of amino acids, often acting as modulators in synaptic transmission.

Ligand-Gated Channel

A channel that opens or closes in response to a specific chemical signal (ligand), such as a neurotransmitter binding to it.

Voltage-Gated Channel

A channel that opens or closes in response to changes in membrane potential.

Calcium Ion (Ca2+)

An important ion that enters the synaptic bulb through voltage-gated channels, triggering the release of neurotransmitters from synaptic vesicles.

Threshold

The critical level to which a membrane potential must be depolarized to initiate an action potential, typically around -55 mV.