Unit 5 Lecture 34

Question 1

Two types of bioelectricity

Answer 1

• Resting membrane potential

- action potential

Question 2

Resting membrane potential charge

Answer 2

Negative

Question 3

Action potential charge

Answer 3

positive

Question 4

Define resting membrane potential

Answer 4

The charge difference across the cell membrane when the cell is at rest

*it’s the normal charge for all cells

Question 5

What are the two parameters of resting membrane potential

Answer 5

1. Transmembrane Ion Gradients (Na+ and K+)

2. Membrane permeability to those ions

Question 6

What ions have higher concentration inside resting membranes?

Answer 6

[K+] and [A-]

• A- = negatively charged protein and phosphate

Question 7

What ions have higher concentrations outside resting membranes?

Answer 7

[Na+] and [Cl-]

Question 8

What ion gradients are found in all cells?

Answer 8

1. K+ ‘leak’ channels

2. Sodium Potassium Pump (Na, K -ATPase)

Question 9

Describe a K+ leak channel

Answer 9

K+ leaves the membrane (down concentration gradient) -> inside negative resting membrane potential

Question 10

Describe the Sodium Potassium Pump

Answer 10

3 Na+ goes out and 2 K+ comes in

Steady-state ion gradient

Question 11

What are two kinds of forces that push and pull on K+?

Answer 11

Chemical and electrical

Question 12

Describe chemical force

Answer 12

• For K+ gradient

- PUSHES K+ out

Question 13

Describe electrical force

Answer 13

• For inside negative

- PULLS K+ in

Question 14

What happens with forces in typical cells?

Answer 14

Chemical and electrical K+ forces are nearly in balance

Question 15

Why aren’t K+ forces in full balance?

Answer 15

K+ comes in with pump and leaves with leak channel

Na goes out w/ pump and does not come in

Question 16

Why is a partial balance important?

Answer 16

K+ gradient results in a NEGATIVE electrical potential INSIDE cell

Question 17

How is electrical potential measured?

Answer 17

Volts

Question 18

What “state” is the resting membrane in?

Answer 18

Polarized state

Question 19

Define polarized membrane state

Answer 19

State at REST

When Na+ goes out and K+ comes in (Sodium Potassium Pump)

Question 20

What is the typical electrical potential difference for polarized membrane states?

Answer 20

-.05 to -.1 volts

or

-50 to -100 mV

Question 21

Define permeability

Answer 21

The state of a membrane that allows it to let things pass through it

*opens channels for that ion

Question 22

What happens to the membrane potential of a cell if the permeability increases for Na+

Answer 22

Depolarization

• Na+ channels open letting (+) Na into the cell so it gets less negative

Question 23

What happens to the membrane potential of a cell if the permeability increases for K+

Answer 23

Hyperpolarization

• More K+ wants to leave the cell making the cell more negative

Question 24

What allows cells to generate electrical signals?

Answer 24

The regulation of channel-mediated ion permeability

Question 25

How do you manipulate membrane potentials?

Answer 25

1. Maintain stable Na+ and K+ gradients (w/ pump)

2. Vary ion channel activity

Question 26

How can you vary ion channel activity?

Answer 26

1. W/ membrane proteins
2. ‘open’ or ‘close’ channels
3. some channels are routinely open

Question 27

What types of channels have their ‘open states’ regulated?

Answer 27

1. Chemically (ligand)
   gated channels
2. Mechanically gated channels
3. Voltage gated channels

Question 28

Describe chemically (ligand) gated channels

Answer 28

Open when a molecule (ACh) binds to the membrane protein

Question 29

Describe mechanically gated channels

Answer 29

Open when membrane is stretched

Question 30

Describe voltage gated channels

Answer 30

Open when the membrane potential is depolarized (gets less negative)