Resting Membrane Potential Part B

Resting membrane potential

the membrane potential of a resting cell

Graded Potential

temporary localized change in resting potential

Graded potential can be caused by

stimulus

Action potential

electrical impulse

Action potential is produced by

graded potential

propagation of an action potential

propagates along surface of axon to synapse

Extracellular Fluid

has higher concentration of Na+ than ICF balanced chiefly by chloride ions (Cl-)

Intra Cellular Fluid

has higher concentration of K+ than ECF, balanced by negatively charged proteins

Plasma membrane polarization

refers to the difference in charge across the plasma membrane, resulting from the distribution of ions, primarily Na+ and K+.

In plasma membrane the external outside is

positive charged

The inside surface of the Plasma Membrane is

negative

Opposite charges attracted to each other

But when opposite charges are separated, the system has potential energy or potential (voltage)

In cells opposite charges are separated by the Plasma Membrane thus generating a potnetial energy named called

Membrane Potential

a measure of potential energy generated by separated charges. Measured between two points in volts (V) or millivolts (mV)

Voltage

In neurons and muscles (that are excitable) at rest this voltage is named

Membrane Resting Potential

-70 mV

How many mV in Membrane Resting Potential in Neurons

gives relationships of voltage current, resistance

Ohm’s law

Ohm’s law formula current

V= I X R

Current is directly proportional to

Voltage

IONS across the membrane

In a cell current is generated by the movement of

Sodium channels are

membrane proteins that allow rapid and selective flow of Na+ ions across the cell membrane, generating electrical signals in nuerons

Potassium K+ channels

membrane proteins that allow rapid an selective flow of K+ ions across the cell membrane, generating electrical signals in neurons

When K+ Leak Channels are present

K+ move out of the cell

When Na+ Leak Channels are present Na+

move inside of the cell

Ions move down their chemical concentration’s gradients

from higher concentration to lower concentration along electrical gradients toward opposite electrical charge

Plasma membrane is more permeable to K+

The permeability of Na+ and K+ across the membrane are different. K+ is more permeable because there are more potassium leak channels.

How many Na+ and K+ move out and inside the cell

3Na+ out of the cell and 2K inside the cell

The purpose of Na and K pump

maintains concentration gradient across the membrane so that the Membrane Resting Potential is maintained.

Ions are moved from high concentrations to low concentration

against their concentration gradient

Membrane Potentials is neurons is named

Membrane Resting Potential.

Membrane Resting Potential is maintained by two different types of

the sodium-potassium pump (pumps 3Na+ outside the cell 2K+ inside the cell) and the sodium potassium leak channels

electrical current and voltage changes across membrane

In a cell ion flow (Na+, K+, Cl-, Ca+2) creates an

True or False K+ ions are more abundant in the ICF

True K+ more abundant in the ICF

True or False Na+ ions are more abundant in the in the ICF

False Na+ ions more abundant in the ICF

True or False Na+/K+ pumps Na and K ions against their concentration gradient

True Na/K pump ions do go against their concentration gradient

True or False the Na+/K+ pumps 3 Na+ inside the cell and 2 K+ outside the cell

False 3Na+ outside the cell and 2K+ inside the cell

Cl- ions are more abundant in the ICF True or False

False Cl- more abundant in the ECF

Na+ and Cl- are more abundant in the

extracellular fluid

K+ ions are more abundant in the

ICF

Protain anion unable to follow

K+ through the membrane

Ions move along their

chemical concentration gradients) from higher concentration gradients to lower concentration), and electrical gradients toward the opposite electrical charge.

Membrane Resting Potentials

(membrane potentials in excitable cells)

The two different types of Membrane Resting Potentials ion Channels

1.) The Sodium Potassium Pump

2.) Sodium Potassium Leak Channels

What serves as selective membrane ion channels

Large proteins

Two Types of ion channels

Leakage (non-gated) and Gated)

which are always open

Leakage (non-gated) channels

channels in which part of the protein changes shape to open/close the channel.

Gated

Open only with binding of a specific chemical

Chemically gated (ligand-gated)

What is an Example of Chemically gated

Neurotransmitters

Voltage-gated

Open and close in response to changes in membrane potential

Open and close in response to physical deformation of receptors, as in sensory receptors. In Meissner corpuscles

Mechanically gated

Chemically gated ion channel

Open in response to binding of the appropriate neurotransmitter

Voltage-gated ion channel

Open in response to changes in membrane potential

When gated channels are open

ions diffuse quickly

Chemical concentration gradients

higher to lower concentration

Along electrical gradients toward

opposite electrical charge

When Na+ gated channels open

Less negative than the MRP

Acetylcholine

is a neurotransmitter that binds to Na+ channels

When Acetylcholine binds to acetylcholine receptors

potential becomes less negative than membrane resting potential

When K+ gated channels open the potential becomes

more negative membrane resting potential

When Cl- gated channels open the potential becomes

more negative than the resting membrane potential

GABA binds to Chorine receptors that will open causing

Hyperpolarization

Moves toward zero and above

Depolarization

Depolarization inside of membrane becomes

less negative than resting membrane potential

Depolarization is caused by

Na+ moving inside

Inside of membrane becomes more negative than resting membrane potential

Hyperpolarization

K+ moving out of the cells or Cl- moving inside the cell

Hyperpolarization is caused buy

The resting Membrane Potential is maintained by

leak channels and Na/K pumps

The opening of gated channels alters

The Membrane Potentials

Depolarization

The membrane potential moves toward 0 mV. the inside becoming less negative (more positive)

Hyperpolarization

The membrane potential increase, the inside becoming more negative

Ion Flow has

Na+, K+, Cl-, Ca+2

Ion flow creates

electrical current and voltage changes across membrane

Current is directly proportional to

Voltage

Once sodium gated ion channel opens, depolarization spreads from one area of membrane threw next because

Na+ inside the cells nearby

because current is lost through the leaky plasma membrane the voltage declines with distance from the stimulus (voltage is decremental). Consequently, graded potentials are short-distance signals.

Membrane potential decays with distance

Chemically gated (ligand-gated)

open only with binding of a specific chemical example: (neurotransmitter)

Open and close in response to changes in membrane potential

Voltage-gated channels

Open and close in response to physical deformation of receptors, as in sensory receptors

Mechanically gated channels

have one gate and two states

Voltage-gated K+ channels

at the resting state so no K+ exits the cell through them

Closed

after a delay allowing K+ to exit the cell

Opened by Depolarization

have two gates (activation gate and inactivation gate) and alternate between three different states

Voltage-gated Na+ channels

Closed State

Activation gate is closed Inactivation channel is open at the resting state, so no Na+ enters the cell through them

Open State

Both gates are open by depolarization, allowing Na+ to enter the cell

Inactivated State

inactivation gates are blocked Soon after they open. Na+ cannot enter

Membrane Resting Potentials (membrane potential in excitable cells)

of a cell at rest is around -70mV

Resting state

All gated Na+ and K+ channels are closed

In resting state only leakage channels for

Na+ K+ are open

Na/K is active

Depolarization

voltage gated Na+ channels open, allowing Na+ entry

Depolarization

Voltage gated Na+ channels open

Depolarizing local currents

open voltage-gated Na+ channels and Na+ rushes into the cell

Na+ activation and inactivation gates

open

Na+ influx causes more depolarization which opens more

Na+ channels

The results ICF is less negative

positive feedback causes opening of all Na+ channels

At threshold (-55 to -50 mV), positive feedback causes of all Na+ channels

The results of a threshold at (-55 to 50 mV)

large action potential spike

membrane polarity jumps to +30 mV

Repolarization

voltage gated channels Na+ channels are inactivating. Voltage gated K+ channels open, K+ to exit

Na+ channel inactivation the gates are

closed

Membrane permiabilty to Na+

declines to resting state

AP spike stops rising