gated ions in channel neurons Flashcards
What do ion channels allow in a cell membrane?
Ion channels allow specific ions to pass across the membrane, enabling facilitated diffusion, moving ions from higher to lower concentrations.
What are gated ion channels?
Gated ion channels can open and close, regulating the flow of ions across the membrane, allowing the diffusion process to be switched on and off.
Where are voltage-gated sodium (Na+) and potassium (K+) channels found?
Voltage-gated Na+ and K+ channels are located along nerve fibers in neurons and are involved in transmitting nerve impulses.
How do voltage-gated Na+ and K+ channels work during a nerve impulse?
Voltage changes across the membrane open Na+ channels, allowing Na+ to diffuse in, and once the membrane reaches +40mV, K+ channels open, allowing K+ to diffuse out, restoring the membrane potential.
What happens to the voltage at the membrane during the action potential?
When the membrane voltage rises above -50mV, Na+ channels open, causing further depolarization. At +40mV, K+ channels open, leading to repolarization.
What is the gating mechanism of voltage-gated ion channels?
The gating mechanism involves reversible conformational changes in subunits of the ion channels. In the open state, ions can pass; in the closed state, no ions can pass.
How does the K+ channel ensure specificity for K+ ions?
K+ channels have a narrow pore that allows K+ ions to pass by temporarily bonding with amino acids, while Na+ ions are too small to bind properly, so they can’t pass through.
Why can’t Na+ ions pass through K+ channels?
Na+ ions are too small to shed their hydration shell, preventing them from fitting through the narrow pore of the K+ channel, which is designed for K+ ions.
What are nicotinic acetylcholine receptors?
Nicotinic acetylcholine receptors are found in synapses and bind acetylcholine. They have 5 transmembrane subunits and open a pore when acetylcholine binds, allowing cations (including Na+) to pass.
What happens when acetylcholine binds to its receptor?
Acetylcholine binding causes a conformational change in the receptor, opening a pore that allows Na+ to diffuse into the postsynaptic neuron, triggering the opening of voltage-gated Na+ channels.
How is the action of acetylcholine reversed?
After acetylcholine dissociates from the receptor, the conformational change reverses, closing the pore and halting ion movement.
