Resting Membrane Potential

Question 1

What is an action potential?

Answer 1

A brief fluctuation in membrane potential caused by the rapid opening and closing of voltage gated ion channels

Also known as spike, nerve impulse, discharge

They sweep like a wave along axons to transfer information from one place to another

Question 2

What is the resting membrane potential?

Answer 2

The membrane maintained by a cell when it is not generating action potentials.

Question 3

What is a sodium-potassium pump

Answer 3

Is an enzyme that breaks down ATP in the presence of internal Na+. The chemical energy released by this reaction drives the pump, which exchanges internal Na+ for external K+.

Question 4

Define capacitance

Answer 4

Storage of electric charge

Question 5

The resting membrane potential of a neuron is close to the value of the equilibrium for what ion and why?

Answer 5

K+ because the resting membrane is highly permeable to K+ ions

Question 6

What does the Nernst equation calculate?

Answer 6

Calculates the exact value of the equilibrium potential for each ion in mV

Question 7

What does the Goldman equation calculate?

Answer 7

Resting membrane potential - takes into consideration the relative permeability of the membrane to different ions.

Question 8

Define:
1. Hydrophobic
2. Hydrophilic

Answer 8

1. Water loving ions and polar molecules. Substances with a net or uneven electrical charge
2. Water fearing compounds (e.g. oil). Atoms with non-polar covalent bonds (shared electrons are distributed evenly with no net electrical charge).

Question 9

How are proteins synthesised?

Answer 9

By ribosomes in neuronal cell body

Question 10

What is a subunit?

Answer 10

Each polypeptide bonded together to form a large molecule

Question 11

What factors determine how much current will flow?

Answer 11

Electrical potential (voltage) - the force exerted on an electrically charged particle (V)

Electrical conductance - the relative ability of an electrical charge to migrate from one point to another (g, measured in Siemens)

Question 12

State the order of ions interns of their ionic concentration inside the typical neuron, from highest to lowest.

Answer 12

K+ > Na+ > Ca++

Question 13

What is the resting membrane potential of a typical neuron?

Answer 13

-65 mV

Question 14

What is the difference between cations and anions? Examples?

Answer 14

Cations - ions with net positive charge
Na+
K+
Ca++

Anions - ions with a net negative charge
Cl-

Question 15

Define ion channels

Answer 15

Consisted of membrane spanning proteins that assemble to form a pore, that allows the passage of ions from one side of the membrane to the other

Question 16

Define ion selectivity

Answer 16

A property of the ion channels that are selectively permeable to some ions but not others.

Question 17

What is required to generate a steady electrical potential differences across a membrane?

Answer 17

1. Ionic concentration gradient
2. Selective ionic permeability

Question 18

What effect would an intravenous injection of isotonic (150mM) KCl have on the behaviour of neurons and why?

Answer 18

Extracellular [K+] would increase, therefore neuronal membranes would depolarise.

Question 19

The resting membrane potential of a typical neuron or muscle fibre is…?
A. Equal to Ek
B. Less negative than Ek
C. Equal to ENa
D. More negative than Ek
E. Approx halfway between Ek and ENa

Answer 19

B

Question 20

Define ‘gating’ in regards to ion channels

Answer 20

A property of many ion channels, making them open or closed in response to specific signals, such as membrane voltage or the presence of neurotransmitters.

Question 21

What are ion pumps?

Answer 21

Ion pumps are enzymes that use the energy released by the breakdown of ATP to transport certain ions across the membrane

Question 22

Define Ohm’s law

Answer 22

The relationship between electrical current (I), voltage (V) and conductance (g)

I = gV

Question 23

Define membrane potential

Answer 23

Is the voltage across the neuronal membrane at any moment (Vm)

Question 24

Define ionic driving force

Answer 24

The difference between the real membrane potential and the ionic equilibrium potential.

Question 25

Define the equilibrium potential

Answer 25

The electrical potential difference that exactly balances an ionic concentration gradient

Question 26

Why are proteins on the neuron membranes important?

Answer 26

1. To catalyse chemical reactions through enzymes
2. The cytoskeleton of proteins gives neurons it special shape
3. To provide receptors that are sensitive to neurotransmitters

Overall, allow for passage of ions and controls resting and action potentials