Nervous-System-Based Insecticides

The nervous system is the command organ of the body. It continuously monitors variations in both the external and internal environments via sensory receptors, processes the information through vast networks of interneurons in the central nervous system (CNS), and transmits commands through its motorneurons to effector cells (e.g., muscles and glands) to respond appropriately. The electrically excitable nerve cells maintain an intracellular concentration of K⁺ that is high and Na⁺ that is low relative to the extracellular fluid through the energy-dependent pumping of these cations by Na⁺, K⁺-ATPase. This results in an inside negative resting membrane potential. Changes in membrane potential cause voltage-sensitive ion channels that are selective for Na⁺, K⁺, Ca²⁺, or CI^- to open and close, allowing rapid movement of their specific ions down their concentration gradients so that ionic currents pass into or out of the cell, causing cell depolarization (i.e., excitation) or hyperpolarization (i.e., inhibition), respectively. Neurons process and transmit information in the form of electrical signals (i.e., nerve impulses or action potentials) that are propagated along their axons as a product of the sequential opening and closing of Na⁺ and K⁺ channels.