Ion Channels of the Nervous System Edoxie E

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Ion Channels of the Nervous System Edoxie E

ORGANISATION FOR THE PROHIBITION OF CHEMICAL WEAPONS Working Together for a World Free of Chemical Weapons Ion channels of the Nervous System Edoxie E. Allier-Gagneur and Jonathan E. Forman Nerve agents and neurotoxins (such as botulinum toxin and saxitoxin) affect life processes by Type of ion Mechanism disrupting chemical signalling between nerve cells (neurons). Neurological signalling processes channel involve ion channels. Those are proteins that enable the transport of ions ( specifically K+, Na+, Ca2+, Activated by the binding of a ligand. In the nervous system, Cl-) across cellular membranes. The direction of ion flow is driven by concentration gradients, with Ligand gated neurotransmitters such as acetylcholine or glutamate often the ions flowing from higher to lower concentration. serve as binding ligands. Depolarization Activated when the membrane potential exceeds or falls Extracellular fluid Voltage-gated + K+ channel K+ Na Na+ channel Repolarization behind a triggering threshold (see action potential chart). Extracellular fluid + + + K channel + Na Na+ channel Allows K ions to flow into the cell while at negative mem- K Inwardly-rectifying/ brane potential. This allows the cell to maintain the resting tandem pore domain + + potential state. Cytoplasm K Na + + Cytoplasm K+ Na - +30 mV Effect when Ion channels Ion Flow Blocked Overstimulated + No signaling. Constant excitation. Voltage-gated Inward Muscle: Paralysis Muscle: Contractions (depolarisation) 0 mV Action potential Ligand-gated Brain: Neurological Brain: Neurological Repolarisation The change in membrane Sodium Na shut-down shut-down potential occuring during No new signal sent. No signaling. Voltage-gated neuronal signaling, which is Outward Muscle: Paralysis Muscle: Paralysis Depolarisation associated with the action of + Brain: Neurological Brain: Neurological Ligand-gated (repolarisation) ion channels. shut-down shut-down Cell cannot achieve Membrane potential Processes that disrupt Inward resting potential. Potassium K Potassium Inwardly-rectifying/ the action of these - 55 mV (resting potential/ Muscle: Convulsions tandem pore domain channels only result hyperpolarisation) Brain: Neurological in blocking. - 70 mV shut-down Hyperpolarisation 2+ No signaling. Constant excitation. Voltage-gated Inward Muscle: Paralysis Muscle: Contractions (depolarisation) Brain: Neurological Brain: Neurological Time Ligand-gated Calcium Ca Calcium shut-down shut-down Resting potential Hyperpolarization Extracellular fluid - No signaling. Constant excitation. + + Energy powered Extracellular fluid K channel + + Na channel + Voltage-gated K Na K+ channel K+ Na Na+ channel Outward Muscle: Paralysis Muscle: Contractions (depolarisation) Brain: Neurological Brain: Neurological Ligand-gated Chloride Cl shut-down shut-down + Na+ @opcw Cytoplasm K + + - Cytoplasm K K Na+ - @opcw_st /opcwonline /opcwonline /company/opcw /opcw.

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