Electrophysiology of Neurons (2)

Question 1

What is the structure of a typical neuron and what are each of them?

Answer 1

• neurosoma: control center
• axon hillock: mound on the neurosoma
• axoplasm: cytoplasm of axon
• dendrites: branches of neruosoma
• axon: transmits nerve impulses away form the cell body and toward other cells

Question 2

What is the electrical potential?

Answer 2

difference in the concentration of charged particles between one point and another

Question 3

What is an electrical current?

Answer 3

flow of charged particles from one point to another

under the right circumstances an electrical potential creates a current

Question 4

As long as there’s a potential (voltage), a battery is ____

Answer 4

polarized

Question 5

Living cells are ___

Answer 5

polarized

Question 6

Difference in charge on each side of the plasma membrane is due to:

Answer 6

1) permeability of membrane
2) action of sodium-potassium pump
3) negatively charged molecules

Question 7

What is the difference in charge called?

Answer 7

potential difference

Question 8

What is the resting potential energy?

Answer 8

Storage of energy for conduction of nerve signals (causes the cell membrane to be polarized [charged])

Question 9

What do channel proteins do?

Answer 9

allow solutes and water to pass through the membrane

Question 10

What do Ligand-Gated Channels respond to?

Answer 10

chemical messengers

Question 11

What do Voltage-Gated Channels respond to?

Answer 11

charge changes

Question 12

What do Mechanically-Gated Channels respond to?

Answer 12

physical stress on the cell

Question 13

The Resting Membrane Potential (RMP) results from the combined effect of three factors:

Answer 13

1. ions diffuse down their concentration gradient through the membrane (permeability)
2. action of Na+/K+ pumps
3. Electrical attraction of cations and anions to each other (negatively charged molecules inside the cell)

Question 14

What has the greatest influence on RMP?

Answer 14

potassium

Question 15

Cytoplasmic anions cannot escape due to ___

Answer 15

size (too big)

Question 16

Plasma is not very permeable to ___ as to ___

Answer 16

sodium

potassium

Question 17

Na+/K+ pump moved ___ out for every ___ brought in.

Answer 17

3 Na+

2 K+

Question 18

True or False

the sodium/potassium pump requires a lot of ATP

Answer 18

True

Question 19

sodium/potassium pumps use ___ of the energy requirement of the nervous system

Answer 19

70%

highest rates of ATP consumption

Question 20

Local Potentials Definition

Answer 20

changes in membrane potential of a neuron occurring at/near the part of the cell that is stimulated

Question 21

Entry of a positive ion makes the cell ___ ____

Answer 21

less negative

Question 22

depolarization definition

Answer 22

a change in membrane potential toward zero mV

Question 23

Local potential is a short range change in membrane ___

Answer 23

voltage

Question 24

What are the four properties of local potentials?

Answer 24

1. Graded (vary in magnitude with stimulus strength/duration
2. Decremental (get weaker the farther they spread from the point of stimulation)
3. Reversible (if stimulation ceases, the cell quickly returns to its normal resting position)
4. Either Exciting or Inhibitory (some neurotransmitters make the membrane potential more negative)

Question 25

Nerve signaling is controlled by ion channels. What are the types of ion channels?

Answer 25

1. Ligand-gated

2. Voltage-gated

Question 26

Ligand-gated channels defintion

Answer 26

membrane protein opens/closes when ligand binds

Question 27

Voltage-gated channels definition

Answer 27

opens/closes due to change in membrane potentials

Question 28

A dramatic change in membrane polarity produced by ___ ___ ion channels

Answer 28

voltage-gated

Question 29

What on a neuron cannot generate an action potential in the soma?

Answer 29

Neurosoma

Question 30

Where on a neuron are action potentials generated?

Answer 30

trigger zone

Question 31

What are the 8 steps in producing an action potential?

Answer 31

1) strong local potential produced (stimulus)
2) arrival of current at axon hillock depolarizes membrane
3) depolarization must reach a threshold (about -55 mV)
4) voltage-gated sodium channels to open quickly
5) membrane potential rises above 0 mV
6) slow potassium channels open – outflow repolarizes cell
7) potassium channel remain open for a time so that membrane is briefly hyper polarized (more negative than RMP)
8) RMP is restored – ion concentrations are now flipped: sodium intracellular and extracellular potasium

Question 32

What are the 3 characteristics of an action potential?

Answer 32

1) follow all or none
2) none decremental: does not get weaker with distance
3) irreversible: once started, goes to completion (cannot be stopped)

Question 33

What are the two phases of action potential- refractory period?

Answer 33

1) absolute refractory period (no stimulus of any strength will generate or tigger a new action potential; lasts as long as sodium gates are open, then inactivated)
2) relative refractory period (especially strong stimulus will trigger new action potential; potassium gates are still open and generally any effect of incoming sodium is opposed by the outgoing potassium; generally lasts until hyperpolarization ends)