NEUR30002 Neurophysiology: Neurons and Circuits Review

A comprehensive set of vocabulary flashcards covering the NEUR30002 Neurophysiology course, spanning cellular components, membrane potentials, circuits, and disease models.

Oligodendrocyte

A type of glial cell that forms the myelin sheath around multiple axons in the Central Nervous System (CNS).

Microglia

Modified immune cells in the CNS that act as scavengers for scavenger debris and pathogens.

Astrocyte

A glial cell that provides support for the CNS, helps form the blood-brain barrier, and regulates blood flow.

Ependymal cells

Cells in the CNS that create the blood-brain barrier and serve as a source of neurogenesis.

Radial glia

A type of glia involved in the developmental scaffolding of the nervous system.

Chemical phenotype

The classification of a neuron based on the production and release of a specific chemical/neurotransmitter, often with the suffix 'ergic'.

Functional phenotype

The classification of a neuron based on the action being stimulated for, such as motor or excitatory.

Axon hillock

The specialized region of the cell body where the axon originates and information is often integrated.

Synapse

The communication pathway or junction between neurons.

Axo-somatic synapse

A synapse where the axon of one neuron connects directly to the soma (cell body) of another, allowing for faster transmission.

Myelin sheath

A specialized property enclosing a neuron in a sheath to facilitate electrical conduction.

Spatial buffering

The continuous flow of $K^+$ between astrocytes through gap junctions to avoid ion poisoning.

Connexon

A channel component in gap junctions consisting of 6 connexin proteins.

Gliotransmitters

Chemical transmitters such as glutamate or $ATP$ released by astrocytes to communicate with other cells.

Neurovascular unit

A functional relationship where increased neural activity results in increased blood flow to that area.

Mosso (1880-90s)

Researcher who discovered that brain volume changes with brain activity in humans.

Roy and Sherrington

Researchers who demonstrated that stimulated brain metabolic activity increases brain volume in animals.

Ingvar and Lassen

Researchers who found that brain activity increases cerebral blood flow restricted to specifically active areas.

Blood-brain barrier (BBB)

A highly regulated protective barrier ensuring the blood system does not have direct access to the brain.

Tight junctions

Structures between endothelial cells in the brain that prevent leakages of molecules.

Tripartite synapse

A three-part synapse where astrocytic foot processes contact both pre- and post-synaptic areas.

Afferent fibers

Nerve fibers that carry sensory information into the spinal cord.

Efferent fibers

Nerve fibers that carry motor information out to initiate a response.

Excitatory synapse

A synapse where an increase in pre-synaptic stimulus leads to increased activity in the output neuron.

Inhibitory synapse

A synapse where an increase in pre-synaptic stimulus leads to decreased activity in the output neuron.

Convergent neural circuit

A complex circuit where multiple neuronal inputs lead onto a single neuron.

Divergent neural circuit

A complex circuit where one neuronal input leads onto multiple neurons.

Feedforward inhibition circuit

A circuit where a pre-synaptic neuron has multiple inputs onto a following neuron (one excitatory and one inhibitory) to control over-stimulation.

Disinhibition circuit

A complex neural circuit characterized by a double negative inhibition of a neuron.

Resting membrane potential (RMP)

The difference in ions between the intracellular fluid and extracellular fluid when a neuron is excitable but at rest.

Depolarize

A shift in membrane potential toward $0\,mV$.

Hyperpolarize

A shift in membrane potential further away from $0\,mV$.

Current ($I$)

The movement of charge, measured in amps.

Conductance ($G$)

The ability of charge to move in a particular substance, measured in siemens.

Resistance ($R$)

The opposition to the flow of charge, measured in ohms, where $G = \frac{1}{R}$.

Polar molecules

Molecules like water ($H_2O$) that attract both $Cl^-$ and $Na^+$ to separate salt in solution.

Ion Transporters

Proteins that use energy to move ions against their concentration gradient, creating ion gradients.

Ion Exchangers

Proteins that use energy stored in ion concentration gradients to transport other ions.

$Na^+/K^+$ pump

An ATPase pump that moves sodium out and potassium in, consuming approximately $70\%$ of brain energy.

Alpha subunit

The part of the ATPase pump where the $ATP$ binding site is located on the inside of the cell.

Beta subunit

The part of the ATPase pump that regulates the activity of the $Na^+/K^+$ ATPase.

Voltage-gated channels

Ion channels that open at a respective membrane voltage, crucial for action potentials.

Ligand-gated channels

Ion channels that open when a specific ligand binds to an ionotropic receptor.

Mechanically gated channels

Ion channels that are sensor-regulated to detect physical factors or certain ions.

Ion Selectivity

The property of a channel that requires an ion to be the correct size and arrangement to pass through.

Kv2.1

A potassium channel that stays open until the injected current stops.

Kv4.1

A potassium channel that opens upon depolarization but immediately closes again.

Equilibrium

The point at which concentration and electrical gradients balance so there is no net ion movement.

Nernst equation

An equation describing the membrane potential based on standard conditions for a single ion permeability.

Goldman equation

An equation describing the effect of membrane potential based on multiple ion permeabilities and concentrations.

Chemical synapse

The majority type of synapse where an $AP$ triggers neurotransmitter release into a synaptic cleft.

Electrical synapse

A synapse where gap junctions allow direct ion movement between neurons.

Glutamate

The principle fast excitatory neurotransmitter used in the brain.

AMPA receptor

A non-selective cation channel that allows equal passage of sodium and potassium in response to glutamate.

NMDA receptor

A selective channel that requires both glutamate binding and depolarization to remove the $Mg^{2+}$ block.

Glutaminase

The enzyme that converts glutamine into glutamate.

Glutamine synthetase

The enzyme in glial cells that converts excess glutamate into glutamine for recycling.

EAAT

Excitatory amino acid transporters responsible for removing glutamate from the synaptic cleft.

VGLUT

Receptors responsible for packaging glutamate into vesicles.

Nicotinic receptor

An ionotropic acetylcholine receptor, often important for somatic movements.

Muscarinic receptor

A metabotropic or G-protein coupled acetylcholine receptor.

Choline acetyltransferase

The enzyme that converts Acetyl CoA and choline into acetylcholine.

Acetylcholinesterase

The enzyme that breaks down excess acetylcholine into acetate and choline in the cleft.

GABA

The major fast inhibitory neurotransmitter system in the brain.

$GABA_A$ receptor

An ionotropic GABA receptor containing $2\alpha$, $2\beta$, and $1\gamma$ subunits.

$GABA_B$ receptor

A metabotropic GABA receptor.

VIATT

The transporter responsible for packaging GABA into synaptic vesicles.

GAT

The transporter that rapidly clears GABA from the synaptic cleft into glia or pre-synaptic terminals.

Glycine

An inhibitory neurotransmitter synthesized from serine.

Reverse potential

The point of no net movement of ions, also known as the equilibrium potential.

Channelrhodopsins

Light-responsive proteins, such as $ChR2$ which reacts to blue light, allowing the passage of $H^+$, $Na^+$, $K^+$, and $Ca^{2+}$.

Heterotrimeric GPCRs

G-protein coupled receptors consisting of a trimeric G protein that activates intracellular signaling.

Monomeric GPCRs

GPCRs like Ras that exist in an active ($GTP$-bound) or inactive ($GDP$-bound) state.

$$G\alpha_s$$

A G-protein associated with noradrenaline that increases protein phosphorylation.

$$G\alpha_q$$

A G-protein associated with mGluR that increases protein phosphorylation and activates calcium binding proteins.

$$G\alpha_i$$

A G-protein associated with dopamine that decreases protein phosphorylation.

$$IP_3$$

A secondary messenger that binds to receptors on the ER to cause the release of calcium.

DAG

A secondary messenger that remains in the membrane to activate protein kinase C ($PKC$).

Catecholamines

A family of molecules derived from tyrosine, including dopamine and noradrenaline.

Locus coeruleus

The brain region where noradrenaline is synthesized before spreading across the brain.

VMAT

Vesicular monoamine transporter responsible for packaging monoamines into vesicles.

Monoamine oxidase (MAO)

An enzyme responsible for the breakdown of monoamines, often blocked by antidepressants.

DAT

The dopamine transporter responsible for reuptake of dopamine.

NET

The transporter responsible for the reuptake of noradrenaline or adrenaline.

Graded potential

A potential that does not have a threshold level and decreases with distance from the stimulation site.

Action potential

An all-or-nothing depolarizing event reaching threshold that is propagated along the entire membrane surface.

Absolute refractory period

The phase during the rising and falling of an $AP$ when it is impossible to fire another action potential.

Relative refractory period

The phase from the return to $RMP$ where a new $AP$ can be fired depending on the speed of recovery.

Saltatory conduction

The process by which an action potential jumps between nodes of Ranvier in myelinated neurons.

Axon initial segment (AIS)

The region between the hillock and axon where action potentials are generated.

Ankyrin-G

A protein essential for the organization of the axonal cytoskeleton and clustering of voltage-gated channels.

Nav1.6

A sodium channel isoform located at the nodes of Ranvier known for rapid activation and inactivation.

EPSP

Excitatory postsynaptic potential, which causes depolarization.

IPSP

Inhibitory postsynaptic potential, which causes hyperpolarization.

Temporal summation

The addition of postsynaptic voltages over a short period of time.

Spatial summation

The addition of postsynaptic voltages across different points in space.

Tetrodotoxin (TTX)

A voltage-gated sodium channel blocker that prevents action potentials.

Tetraethylammonium (TEA)

A voltage-gated potassium channel blocker that keeps cells depolarized.

White matter

Brain regions consisting of densely packed axon fiber tracts and myelin.

Grey matter

Brain regions where neuron cell bodies are primarily located.