Module 15 - Resting membrane potential

polarized membrane

Charge difference from the 2 sides of membrane

Ions on inside vs outside of cell membrane

Outside - Chloride, sodium, Calcium
Inside - Phosphate, Protein, Potassium

Anion vs Cation

Cat - Pos ion
An - Neg ion

Electrical force

A separation of opposite electrical charge causing them to attract together

Membrane potential

Also known as potential difference
Separation of charge

Resting condition of axons voltage

-70 milivolt
Sign dictates which one is MORE (- is more inside + is more outside)
number is volt

Resting membrane potential

Voltage difference over the cell membrane when the cell is not active

Even though there are same amount of total ions in out and in, how come there is a electrical difference?

The electrical difference right next to the membrane

How is the concentration gradient maintained

With the sodium potassium pump, using ATP to move 3 Na out and 2 K in the cell

Steps with Na/K pump

3 Na and 1 ATP attach to pump
Pump opens out
Na goes out, 2 K bind in
Inorganic phosphate leaves, pump moves back to original shape
K goes into cell
Always running

Leak (non gated) channels

Always open
Allows ions to constantly move with concentration gradient
Each leak channel is specific to a certain ion

Gated ion channels

Open and close
Have gates that close
We can control when to open
3 types - ligand, mechanical, voltage gated channel

What are the 2 ion channels

Gated and leak ion channels

Ligand gated channel

A chemical signal binds to channel and opens gate
Specific to each “ligand” (chemical)
Mostly found on dendrite and cell body of motor neurons

Voltage gated channel

Opens when a change in membrane potential is detected
Found primarily in axons plasma membrane/presynaptic terminal (Mostly potassium and sodium, a little calcium)

What affects membrane permiability

Number of open channels
Size of ions
Type of leak channel
Number of gated channels

Are there more potassium or sodium leak channels

Lots of potassium

What happens when lots of potassium move out the cell

Negative protein ions go closer to the cell membrane
Potassium’s are moving back in

When is resting membrane potential reached

When the potassium’s moving in and out are the same. For every one out, one is in.
The amount of potassium is NOT the same on both sides. Only movement is the same

Which gradient is strongest

Concentration gradient

Mechanical gated channels

Responds to mechanical vibration
Physically opening gates
Operated by gating springs that attached to another cell
Found in dendrites of sensory neurons