Membranes and Cell Excitation

Question 1

In a cell, what controls ion movement?

Answer 1

membrane

Question 2

Is K+ higher conc on intracellular or extracellular?

Answer 2

intracellular

Question 3

Is Na+ conc higher intracellular or extracellular?

Answer 3

extracellular

Question 4

What is the membrane potential (Em)?

Answer 4

• the voltage inside a cell

- negative due to excess of anions inside the cell

Question 5

What is the membrane potential in neurones?

Answer 5

-65mV (minus)

Question 6

What are essential for maintaining Em?

Answer 6

membrane proteins

Question 7

When maintaining Em what types of channels are used?

Answer 7

-non-gated (leak) channels

Question 8

What types of channels generate action potential?

Answer 8

voltage gated channels

Question 9

What type of channel generates Em changes at the synapse?

Answer 9

ligand

Question 10

What is membrane permeability dependent on?

Answer 10

the number of channels for a particular ion

Question 11

What factors effect the movement o ions?

Answer 11

• chemical gradient created by uneven ion distribution

- electrical force when ions are attracted or repelled by the voltage inside the cell

Question 12

When is an ion in equilibrium?

Answer 12

when the chemical and electrical forces are in balance

Question 13

What is Ek?

Answer 13

the voltage that the cell needs to be at for there to be no net movement of K+ ions

Question 14

What is the value for Ek?

Answer 14

-80mV

Question 15

What is the value for ENa

Answer 15

+62mV

Question 16

What is the ionic driving force?

Answer 16

the net force resulting from chemical and electrical influences

Question 17

When is the driving force for an ion >0?

Answer 17

whenever Em is different than the equilibrium potential of that ion

Question 18

At rest, what is Pk in terms of PNa

Answer 18

PK= 40xPNA

Question 19

How is the resting membrane potential maintained?

Answer 19

By a large driving force of Na+ coupled with a low permeability
-small driving force of K+ with a large permeability

Question 20

How does the sodium-potassium pump work?

Answer 20

• catalyses ATP breakdown
• exchanges internal Na+ for external K+
• against conc gradients (active transport)
• operate in background constantly
• not for controlling Em