Neuroscience - Action Potentials & Neurotransmitters

The principal excitatory neurotransmitter in the central nervous system (CNS). Acts on ionotropic receptors (AMPA, NMDA, Kainate) and metabotropic receptors (mGluRs).

The primary inhibitory neurotransmitter in the brain. ${\text{GABA}}_A$ receptors are ligand-gated ${\text{Cl}}^{-}$ channels (ionotropic); ${\text{GABA}}_B$ receptors are G-protein coupled (metabotropic) that open ${\text{K}}^{+}$ channels.

The electrical potential difference across a neuronal membrane at rest, typically around $-70\text{ mV}$. It is primarily established by ${\text{K}}^{+}$ leak channels and maintained by the ${\text{Na}}^{+}/{\text{K}}^{+}$ ATPase.

An electrogenic primary active transporter that pumps $3{\text{ Na}}^{+}$ ions out of the cell and $2{\text{ K}}^{+}$ ions into the cell per hydrolysed ATP molecule, maintaining the resting membrane gradient.

Calculates the equilibrium potential ($E_{\text{ion}}$) for a single membrane-permeable ion: $E_{\text{ion}}=\frac{RT}{zF}\ln \frac{[\text{Ion}{]}_{\text{outside}}}{[\text{Ion}{]}_{\text{inside}}}$. For ${\text{K}}^{+}$, this is approximately $-90\text{ mV}$; for ${\text{Na}}^{+}$, approximately $+60\text{ mV}$.

The critical membrane potential (typically around $-55\text{ mV}$) required to trigger an all-or-none action potential by opening voltage-gated ${\text{Na}}^{+}$ channels.

The rapid phase of the action potential where membrane potential shifts from negative toward positive (up to $+30\text{ mV}$), caused by a massive influx of ${\text{Na}}^{+}$ through voltage-gated ${\text{Na}}^{+}$ channels.

The return of the membrane potential toward resting state, caused by the inactivation of voltage-gated ${\text{Na}}^{+}$ channels and efflux of ${\text{K}}^{+}$ through slower-opening voltage-gated ${\text{K}}^{+}$ channels.