What is the falling phase of an action potential?
Falling Phase: First, the voltage-gated sodium channels inactivate. Second, the voltage-gated potassium channels open (the delayed-rectifier potassium channels). The driving force pushes potassium out of the cell, causing the membrane potential to become negative again.
What happens to the resting membrane potential of MV when potassium channels close?
The membrane is hyperpolarized at the end of the AP because voltage-gated potassium channels have increased the permeability to K+. As they close, the membrane returns to the resting potential, which is set by permeability through the “leak” channels.
What factors affect resting membrane potential?
The resting membrane potential is determined mainly by two factors:
- the differences in ion concentration of the intracellular and extracellular fluids and.
- the relative permeabilities of the plasma membrane to different ion species.
What is responsible for resting membrane potential?
The resting membrane potential (RMP) is due to changes in membrane permeability for potassium, sodium, calcium, and chloride, which results from the movement of these ions across it. Once the membrane is polarized, it acquires a voltage, which is the difference of potentials between intra and extracellular spaces.
How does the Na +- K+ pump generate a membrane potential?
The Na+/K+ Pump creates a concentration gradient by moving 3 Na+ out of the cell and 2 K+ into the cell. In other words, Na+ is being pumped (and K+ in) against their concentration gradients. Because this pump is moving ions against their concentration gradients it requires energy in the form of ATP.
What determines membrane permeability?
Permeability. The permeability of a membrane is the rate of passive diffusion of molecules through the membrane. These molecules are known as permeant molecules. Permeability depends mainly on the electric charge and polarity of the molecule and to a lesser extent the molar mass of the molecule.
What changes membrane permeability?
Overview. The action potential, the primary electrical signal generated by nerve cells, reflects changes in membrane permeability to specific ions. Both permeabilities are voltage-dependent, increasing as the membrane potential depolarizes.
What causes membrane permeability change?
The reasons should be self-evident: larger molecules simply cannot fit between the lipid molecules to make their way through. Higher concentrations of cholesterol, by filling in gaps between phospholipid tails, decreases permeability even for small molecules that can normally pass through the membrane easily.
What components of a cell membrane can be disrupted by heat?
Both integral and peripheral proteins in the membrane can also be damaged by high temperatures and, if extremely high, heat might cause these proteins to break down, or denature.
What type of material can slip through the cell membrane?
Lipid-soluble material can easily slip through the hydrophobic lipid core of the membrane. Substances such as the fat-soluble vitamins A, D, E, and K readily pass through the plasma membranes in the digestive tract and other tissues.