Membranes, Transport & Action Potentials Flashcards
(20 cards)
What is the resting membrane potential of most cells?
Around -70 mV.
What maintains the resting membrane potential?
Unequal distribution of ions and selective permeability of the membrane.
What is the role of the Na+/K+ pump?
Maintains ion gradients by pumping 3 Na+ out and 2 K+ in using ATP.
What is an ion channel?
A protein that allows specific ions to pass through the membrane.
What is the difference between ligand-gated and voltage-gated ion channels?
Ligand-gated open in response to chemicals; voltage-gated open due to membrane potential changes.
What is depolarization?
A rise in membrane potential toward a more positive value.
What is repolarization?
A return of membrane potential toward resting level.
What is hyperpolarization?
A drop below the resting potential after repolarization.
What ion is responsible for depolarization in neurons?
Sodium (Na+).
What ion is responsible for repolarization in neurons?
Potassium (K+).
What is the threshold potential?
The membrane potential required to initiate an action potential.
What is saltatory conduction?
Jumping of action potentials between nodes in myelinated axons.
What are nodes of Ranvier?
Gaps in myelin sheath where ion channels are concentrated.
What is continuous conduction?
Slow, stepwise conduction along unmyelinated fibers.
How do myelinated and unmyelinated axons differ in signal speed?
Myelinated axons conduct faster due to saltatory conduction.
What is the refractory period?
A period when a neuron cannot fire another action potential immediately.
What is passive transport?
Movement of substances without energy input (e.g., diffusion, osmosis).
What is facilitated diffusion?
Passive movement through a protein channel or carrier.
What is active transport?
Requires energy (ATP) to move substances against their gradient.
What is secondary active transport?
Uses the gradient created by active transport to drive another substance.
