SL6 membrane potentials

What are the 3 types of membrane potentials

1. Resting membrane potential

2. Grades potential

3. Action potential

What part of the cell separates the positive cells outside from negative inside

Plasma membrane

What is the definition of resting membrane potential.

Potential difference across the plasma membrane at rest.

How is a cell charged in comparison to its outside.

Negatively charged

Resting membrane potential hold steady unless…

Changes in electrical current alter it.

Extra and intra cellular concentrations of major ions.

Intra

Na-145 Cl-100 K-5

Extra

Na-15 Cl-7 K-150

What’s the units

Mmol/liter

Resting membrane potential depends on what two factors

1. Difference in ion concentration between intracellular and extracellular environment.

2. Membrane permeability to ions

What is an ion leak channel

A channel that allows ion to leak through the membrane.

Always open

Ion-specific

Do ion leak channels require atp

No

Ion movement across the membrane is kept in balance by what and what

Concentration and electrical potential

Concentration: ions want to flow down their concentration gradient

Electrical: electrons want to flow towards the opposite charge

What is equilibrium potential

The membrane potential when concentration and electrical potential of an ion are equal and opposite in magnitude.

What is a gated ion channel

It is opened or closed depending on on the position of the environment

What are the 3 types of gated ion channels

1. Mechanical

2. Chemical/ligand

3. Voltage

What is the electrochemical gradient and ion flux

When there is no potential difference, equal number of pos and neg ions in each compartment. But then K+ channels open and the K+ travels across the channels and makes a potential difference. This is an electrochemical gradient. If the movement of K+ due to the concentration gradient is greater than the flux due to the membrane potential, K+ will continue to flow into compartment 1 and the potential difference will increase.

At rest a neuron has a high concentration of … intracellularly.

Potassium(K+)

What about extracellularly

High concentration of NA+ (sodium)

What establishes and maintains the concentration gradient between the NA and K

The NA+/K+-ATPase pump

More specific, How is the resting membrane potential maintained between NA and K with the pump.

K+ is highly permeable but has low electrochemical gradient

NA+ has low permeability but has high electrochemical gradient

What is a graded potential

A potential confined to a very small area, with a magnitude that can varry in change of potential

Named after their location example synaptic potential

What’s polarized

Potential difference exists

What’s depolarized

Potential becomes less negative

What’s Overshoot

Reversal of membrane potential polarity

What’s repolarizing

When a resting membrane potential returns to resting value

What’s hyper polarization

The potential difference is more negative than the resting level

Potential difference decreases with

Distance from initial site of depolarization

Summation can take place if…

Another stimulus arrives before the graded potential has diminished.

What is summation

It’s when a neuron adds multiple graded potentials together to cause the membrane potential to reach threshold

Graded potentials can … action potentials

Initiate

What’s an action potential

Large alteration in the membrane potential

How long does it last

1-4ms

What’s their variance in magnitude

None

What other characteristics do action potential have

They travel long distances, transient changes in membrane permeability allows propagation.

What’s a voltage gated ion channel

Ion specific channel

Closed when membrane is negative,

When does it open

During propagation of action potential

Which voltage gated channel opens first

Na channels then K

Initial depolarization to threshold is achieved by what…

3 types of graded potentials

1. Receptor potentials

2. Synaptic potentials

3. Pacemaker potentials

Receptor potential definition

Graded potential produced at peripheral endings of agreement neurons. In response to stimulus

What’s a synaptic potential

Produced In post synaptic neuron in response to release of meurotransmitters by presnyaptic neurons.

Action potential steps