7. Resting & action potentials

Question 1

What is voltage? (Action potentials B&B)

Answer 1

The difference in charge between two points

Question 2

What is current? (Action potentials B&B)

Answer 2

The rate at which charge is flowing

Question 3

What are the four structures of a neuron? (Action potentials B&B)

Answer 3

• Dendrites
• Soma
• Axon
• Terminal boutons

Question 4

What is the purpose of the dendrite? (Action potentials B&B)

Answer 4

• Recipient of information from one neuron to the other

- Large receptive field

Question 5

What is the purpose of the soma? (Action potentials B&B)

Answer 5

Contains machinery that controls processing in the cell and integrates information

Question 6

What is the purpose of the axon? (Action potentials B&B)

Answer 6

Carries information from the soma to the terminal boutons

Question 7

What is the purpose of the terminal boutons? (Action potentials B&B)

Answer 7

• Found at the end of the axon

- Communication point to other neurons

Question 8

What are properties of the neuron important for? (Action potentials B&B)

Answer 8

Within neuron communication

Question 9

What is the membrane potential? (Action potentials B&B)

Answer 9

• Electrical charge across the membrane

- From an area of higher concentration to an area of lower concentration

Question 10

What is force of electrostatic pressure? (Action potentials B&B)

Answer 10

The idea that particle with the same forces repel and those with opposite attract

Question 11

What is the process of the equilibrium potential? (Action potentials B&B)

Answer 11

• P+ ions move across membrane via diffusion
• Increases electric potential across membrane
• Eventually, diffusion force = electrostatic force

Question 12

What does the resting membrane potential result from? (Action potentials B&B)

Answer 12

The separation of charge across the membrane

Question 13

What is the process of resting membrane potential? (Action potentials B&B)

Answer 13

• High Na+ outside membrane, high K+ inside the membrane
• At rest, more K+ channels open than Na+
• Na+ into the neuron, K+ out of the neuron

Question 14

What does the Nernst equation measure? (Action potentials B&B)

Answer 14

The equilibrium potential from any ion

Question 15

Why are sodium pumps needed? (Action potentials B&B)

Answer 15

Because the membrane is not permeable enough for sodium diffusion

Question 16

What do sodium pumps do? (Action potentials B&B)

Answer 16

Maintain the ionic concentration gradients (Na+ and K+) across the membrane

Question 17

Why is ATP broken down? (Action potentials B&B)

Answer 17

To release energy, used to force ions against their concentration gradient

Question 18

What is an action potential? (Action potentials B&B)

Answer 18

A nerve impulse that allows for communication within the neuron

Question 19

Where is an action potential generated? (Action potentials B&B)

Answer 19

At the axon hillock

Question 20

What is hyperpolarisation? (Action potentials B&B)

Answer 20

A change in a cells membrane potential, making it more negative, inhibiting action potentials

Question 21

What is the order of an action potential firing? (Action potentials B&B)

Answer 21

• Resting potential
• Depolarisation
• Peak action potential
• Repolarisation
• Hyperpolarisation
• Threshold of excitation

Question 22

What does an increase in the size of stimulation do to an action potential? (Action potentials B&B)

Answer 22

Increases the degree of depolarisation

Question 23

What do voltage-gated channels do? (Action potentials B&B)

Answer 23

Open when the membrane becomes depolarised

Question 24

What causes positive membrane potentials and what do they do? (Action potentials B&B)

Answer 24

• Very high degree of depolarisation

- Results in inactivation of Na+ channels

Question 25

What is the period of time known as, where the majority of sodium channels are inactive? (Action potentials B&B)

Answer 25

Refractory period

Question 26

What is the process of an action potential? (Action potentials B&B)

Answer 26

1) At rest, most channels are closed
2) Small depolarisation opens some Na+ channels
3) Na+ begins to diffuse in = further depolarisation
4) More Na+ channels open
5) More Na+ moves in
6) Few K+ channels open
7) Some K+ moves in
8) Na+ channels become deactivated (refractory period)
9) Remaining K+ channels open
10) K+ moves in
11) Membrane potential decreases (repolarisation)
12) K+ channels begin to close
13) Membrane potential drops below resting potential (hyperpolarisation)
14) Na+/K+ channels attempt to restore resting membrane potential