Transmembrane Potential & Resting State
Living cells maintain a polarized plasma membrane characterized by an excess of these positive charges on the outside and negative charges inside.
What are positive charges (extracellular Na+ / ions)?
During this initial phase of an action potential, voltage-gated sodium channels open and Na+ ions rush into the cytosol, raising potential to +30 mV.
What is depolarization?
The specialized site where a neuron communicates with another cell in a strictly one-way direction.
What is a synapse?
The specific neurotransmitter released at all cholinergic synapses.
What is acetylcholine (ACh)?
Common neurotransmitter released by adrenergic synapses, playing important roles in the brain and autonomic nervous system.
What is norepinephrine (or noradrenaline)?
Measured in millivolts, this is the transmembrane potential of an undisturbed neuron at rest.
What is -70 mV?
This phase occurs as voltage-gated sodium channels close and voltage-gated potassium channels open, allowing K+ ions to move out of the cytosol.
What is repolarization?
The narrow extracellular space that separates the presynaptic membrane from the postsynaptic membrane.
What is the synaptic cleft?
The extracellular cation that enters the axon terminal through voltage-gated channels to trigger ACh vesicle exocytosis.
What is calcium (Ca2+)?
Three major CNS neurotransmitters explicitly listed alongside dopamine in the slides
What are GABA, serotonin, and dopamine?
Driven by ATP, this plasma membrane exchange pump maintains the resting potential by moving 3 Na+ out for every 2 K+ brought inside.
What is the sodium-potassium exchange pump?
Caused by potassium channels remaining open briefly past the resting potential, the membrane potential drops temporarily to around -90 mV during this state.
What is hyperpolarization?
Specific neuroeffector junction established between a motor neuron and a secretory gland cell.
What is a neuroglandular junction?
Chemically-gated sodium channels on the postsynaptic membrane that open when bound by ACh to produce depolarization.
What are ACh receptors?
Neural circuit mechanism that spreads stimulation from a single presynaptic neuron to multiple neurons or neuronal pools in the CNS.
What is divergence?
These passive membrane channels allow ions to go across the plasma membrane, with potassium channels playing a key role in resting potential
What are leak channels (or potassium leak channels)?
The timeframe following action potential initiation during which the axon membrane cannot respond to further stimulation
What is the refractory period?
Membrane-bound sacs inside the axon terminal that store chemical messengers prior to exocytosis.
What are synaptic vesicles?
The enzyme residing in the synaptic cleft that breaks down ACh to end postsynaptic membrane depolarization.
What is acetylcholinesterase (AChE)?
Neural circuit pattern where input from multiple presynaptic sources converges onto a single postsynaptic neuron
What is convergence?
The specific membrane potential value, typically around -60 mV, that must be reached to open voltage-gated sodium channels and trigger an action potential.
What is the threshold?
Fast mode of action potential propagation along a myelinated axon, where electrical impulses jump from node to node.
What is saltatory propagation?
General term for a synapse formed between a neuron and a non-neuronal target cell type.
What is a neuroeffector junction?
The initial event triggering calcium influx at a cholinergic synapse when an electrical impulse reaches the axon terminal
What is arrival of an action potential (or terminal depolarization)?
Two gaseous chemical messengers highlighted on the slides that function as unconventional neurotransmitters.
What are nitric oxide (NO) and carbon monoxide (CO)?