(3) Ion Channel Receptors (Ligand-Gated Ion Channels)

Ion channel receptors

involved in rapid synaptic signaling, often between neurons or between neurons & muscle cells

Ion channel receptor response

opens or closes

Purpose of opening/closing ion channels

allows specific ions to move across the plasma membrane, changing the membrane potential

Effect of Ca²⁺ or Na⁺ influx on membrane potential

depolarization, making the inside of the cell less negative, which can trigger an action potential

Effect of Cl⁻ influx on membrane potential

hyperpolarization, making the inside of the cell more negative, inhibiting action potential

Acetylcholine

ligand at the neuromuscular junction

Neurotransmitter

ligand such as dopamine or serotonin

Gamma-aminobutyric acid (GABA)

ligand opening Cl⁻ channels, causing inhibition

Glutamate

major excitatory neurotransmitter in the brain

Inositol triphosphate (IP₃)

opens Ca²⁺ channels on intracellular membranes

Physical stimuli as ligands

sensory systems (light, sound, pressure) can open ion channels indirectly

Primary outcome of ion channel receptor binding

electrical impulse or change in excitability