Chapter 4

Question 1

Electrical potential/charge

Answer 1

: the ability to do work with stored electrical energy. Requires a difference in the concentration of electrons between two points.

Question 2

Volts

Answer 2

The units of measurement for electrical potential/charge.

Question 3

Current

Answer 3

The flow of electrons from an area of high concentration to an area of low concentration through a conductor

Question 4

Insulator

Answer 4

A substance whose electrochemical properties make it a bad medium for the movement of electrons

Question 5

Conductor

Answer 5

A substance whose electrochemical properties make it a good medium for the movement of electrons

Question 6

Who stuck charged metal on frog legs?

Answer 6

Luigi Galvani

Question 7

What is the resting membrane potential charge?

Answer 7

Between -65mV (excess of negative charge on the inside of cell membrane)

Question 8

Who measured nerve conduction velocity?

Answer 8

Herman von Helmholtz measured nerve conduction velocity as ~30 meters/second

Question 9

What are the ion concentrations at resting membrane potential?

Answer 9

Na+: High outside the cell, low inside Cl-: High outside the cell, low inside K+: High inside the cell, low outside Proteins (A-): High inside the cell, low outside

Question 10

What is necessary to achieve the gradients required for resting membrane potential?

Answer 10

• Proteins (A-) stuck inside the cell - Open K+ Channels “leak channels” - Closed Na+ Channels (don’t need them to have potential, but if you have them, they need to be closed to have a resting membrane potential) - Na+/K+ pump to maintain the imbalance

Question 11

Hyperpolarization

Answer 11

Moving the membrane potential more negative than the resting membrane potential.

Question 12

Depolarization

Answer 12

Moving the action potential more positive than the resting membrane potential. In action potentials, it’s dominated by the rapid influx of sodium (Na) through voltage-gated sodium channels.

Question 13

Action potential

Answer 13

A transient reversal of a membrane potential is an action potential (a change in voltage across time)

Question 14

What makes an action potential begin?

Answer 14

The axon hillock decides whether to fire or not. The axon hillock going from -65mV to -40 mV (threshold) makes the action potential begin.

Question 15

Repolarization

Answer 15

In action potentials, dominated by the delayed potassium efflux from the cell while sodium channels close.

Question 16

absolute refractory period

Answer 16

no new action potentials can be fired.

Question 17

relative refractory period

Answer 17

action potentials are possible, but harder to trigger.

Question 18

What makes pores open in the membrane?

Answer 18

pores are opening due to the cation amino acids present in the pore, it is a passive process.

Question 19

Where are voltage gated Na+ channels found in the cell?

Answer 19

The voltage gated channels for Na+ are ONLY found in the axon - they are not found in the dendrite and the soma.

Question 20

Big picture of action potentials

Answer 20

.

Question 21

What happens to voltage-gated Na+ channels after an axon potential

Answer 21

Na+ channels are blocked by their ball-and-chain shortly after they open, they do not open until they reach resting potential again.

Question 22

How do Na+ K+ pumps work?

Answer 22

They pump out three Na+ for two K+