Membrane Potentials Notes

The resting membrane potential depends on differences in ______ concentration and permeability.

ion

________ is a measure of the amount of difference in electrical charge between two points, called the potential difference.

Voltage

Chemically-gated (________ -gated) channels open when the correct chemical binds to the channel.

ligand

Mechanically-gated channels open when the channel is ____________ bent or stretched.

physically

Voltage-gated channels open in response to a change in membrane ____________.

potential

When ion channels _______, ions are able to diffuse through the channels to the other side.

open

When ion channels _______, ion pumps use ATP to put the ions back where they were before the channels opened.

close

The difference in electrical charge across the cell membrane is called the resting membrane potential (approximately -70 mV). At this point, the cell is _____________.

polarized

Resting membrane potential exists only across the membrane. Overall, fluids inside and outside of the cell are electrically neutral. Resting membrane potential occurs due to differences in ____________ of intracellular and extracellular fluids.

ion concentration

The inside of the cell has a ________ concentration of sodium ions (Na+) and ________ concentration of potassium ions (K+) than the extracellular fluid.

lower; higher

Because of K+ leaking out along the membrane, there are more cations () on the outside and more anions () on the inside of the cell.

Na+; K+

Pumps spend ATP to move Na+ to the ________ and K+ to the ________ of the cell.

outside; inside

__________ use changes in membrane potential as communication signals.

Neurons

Changes in membrane potential can produce either _________ potentials, usually incoming signals that travel short distances within the cell, or _________ potentials, long-distance signals that travel to the end of the neuron’s axon.

graded; action

__________polarization increases the probability of producing nerve impulses.

Depolarization

__________polarization decreases the probability of producing nerve impulses.

Hyperpolarization

Action potentials can only occur when a critical minimum or _______________ of depolarization is reached.

threshold

Higher-stimulus intensity is coded in the increased _______________ of action potentials, not greater magnitude of an action potential.

frequency

1. _____________ state All voltage-gated Na+ and K+ channels are closed. The axon plasma membrane is at resting membrane potential.

Resting

2. _____________ phase When membrane potential of axon reaches threshold, the Na+ channel activation gates open.

Depolarization

3. _____________ phase begins Na+ channel inactivation gates close and K+ channels open.

Repolarization

4. _____________ continues to _________________ K+ outflow continues, eventually restoring resting membrane potential.

Hyperpolarization; restore

The relationship among current, voltage, and resistance can be described by __________ law.

Ohm's

__________ channels open in response to changes in voltage across the membrane.

Voltage-gated

__________ channels open in response to mechanical forces, such as stretch or pressure.

Mechanically-gated

__________ channels open when a specific molecule binds to them.

Chemically-gated (Ligand-gated)

Resting membrane potential is primarily established by the differential distribution of __________ ions inside and outside of the cell.

potassium (K+) and sodium (Na+)