Nervous system (electrophysiology)

Question 1

What are the ways a membrane potential can change due to ion movement?

Answer 1

Depolarize
Repolarize
Hyperpolarize

Question 2

What happens to the membrane potential when it depolarizes?

Answer 2

Membrane potential becomes more + than the resting membrane potetial and creates an electrical signal

Question 3

What happens to the membrane potential when it repolarizes?

Answer 3

The depolarized membrane returns to resting potential

Question 4

What happens to the membrane potetntial when is hyperpolarizes?

Answer 4

The membrane potential becomes less negative than the resting potential

Question 5

What is the function of ion channels?

Answer 5

Allow the cell to change its ion permeability by opening or closing existing channels on the membrane

Question 6

What are some examples of ion channels in the membrane?

Answer 6

K+ channels, Na+ channels, Ca2+ channels, Cl- channels

Question 7

What is the definition of conductance?

Answer 7

The ease in which ions flow through a channel

Question 8

How is a mechanical gate controlled (opened/closed)?

Answer 8

-deforms due to pressure

Question 9

How are chemically gated ion channels controlled?

Answer 9

-controlled by intracellular messenger molecules or extracellular ligands that bind to the channel protein

Question 10

How are voltage gated ion channels controlled?

Answer 10

-respond to changes in the cell’s membrane potential

-open and close when the electrical state of the cell changes
>opens at threshold voltage

Question 11

Voltage charges across the membrane can be classified into what 2 types of electrical signals?

Answer 11

Graded potentials and action potentials

Question 12

What are the characteristics of a graded potential?

Answer 12

• variable strength signals
• travel short distances and lose strength as they travel through the cell
• occurs through dendrites and cell body
• mechanically, chemically, o voltage gated channels involved
• what ions are involved; Na+, K+, Ca+

Question 13

Where do graded potentials occur?

Answer 13

-occurs through the dendrites and cell body

Question 14

What kind of gated channels are grade potentials involved in?

Answer 14

• mechanical
• chemical
• voltage

Question 15

What kind of signals do graded potentials produce? How far do they travel?

Answer 15

• variable strength signals

- travels over short distance and lose strength as they travel through the cell

Question 16

What are the characteristics of an Action potential?

Answer 16

• Very brief, large depolarizations
• travel long distances through a neuron, without losing strength
• occurs at axon hillock (trigger zone)
• All or Nothing

Question 17

What kind of signals does an action potential produce? How far does it travel?

Answer 17

• very brief, large depolarizations

- travel large distances without losing strength

Question 18

Where do action potentials occur?

Answer 18

-occur at the axon hillock (trigger zone)

Question 19

Why is an action potential considered an “ All -or-Nothing” response?

Answer 19

-Action potential occurs if a stimulus reaches threshold or does not occur at all (below threshold)

Question 20

What does not influence the amplitude of an action potential?

Answer 20

-the strength of a graded potential

Question 21

How is a action potential initiated?

Answer 21

-when a depolarizing graded potential is strong enough when it reaches an integrating center within a neuron

Question 22

Conduction of the action potential along the axon requires what types of ion channels to open/close to alter the membrane permeability (2)

Answer 22

• Voltage gated Na+ channels

- voltage gated K+ channels

Question 23

During the conduction of an Action potential, what channels help regulate the movement of ions?

Answer 23

Activation and inactivation gates

Question 24

9 steps to create an action potential

Answer 24

1) resting membrane potential
2) depolarizing stimulus
3) As the cell starts depolarizing, Voltage gated Na+ and K+ channels begin to open
4) Rapid entry of Na+ depolarizes the cell
5) As the membrane potential reaches threshold, Na+ channels close and slower K+ channels open
6) K+ moves from cell to extracellular
7) K+ channels remain open and additional K+ leaves cell, hyper polarizing it
8) Voltage- Gated K+ channels then close, less K+ leaks out of the cell
9) cell returns to resting ion permeability and resting membrane potential.

Question 25

Describe the ion movement during the depolarization phase of an action potential

Answer 25

• rapid entry of Na+

Question 26

What happens to the Na+ and K+ ion channels when the action potential reaches the threshold?

Answer 26

-Na+ channels close and slower K+ channels open

Question 27

Describe the ion movement during the repolarization phase of the action potential?

Answer 27

-K+ moves from the cell to the extracellular fluid

Question 28

What causes the cell to hyperpolarize?

Answer 28

• K+ channels remain open and additional K+ leaves the cell

- Voltage gate K+ channels eventually close and less K+ leaks out of the cell

Question 29

What happens during the refractory period?

Answer 29

-once an Action potential has begun, a 2nd action potential cannot be triggered during this time (1-2 mill sec), no matter how large the stimulus

Question 30

What is a subthreshold graded potential?

Answer 30

• starts above the threshold at its initiation point but decreases in strength as it travels through they cell body
• at trigger zone, its below threshold= does not initiate an action potential

Question 31

What is a Suprathreshold graded potential?

Answer 31

-A stronger stimulus that creates a graded potential that is still above threshold by the time it reaches the trigger zone=initiates action potential

Question 32

The refractory period is divided into what 2 periods

Answer 32

• Absolute refractory period

- Relative refractory period

Question 33

Describe the absolute refractory period?

Answer 33

• represents the time required for Na+ channel gates to reset to their resting positions
• ensures one way travel
• 2nd AP cannot occur before the first has finished

Question 34

Describe the relative refractory period?

Answer 34

• follows the absolute refractory period
• some but not all Na+ channel gates have reset to their original positions
• K+ channels are still open
• a STRONG stimulus may induce a 2nd action potential at this time

Question 35

Describe saltatory conduction

Answer 35

• the action potential transmits from node to node with myelinated axons
• can only perform an AP at a node of ranvier

Question 36

What factors can influence a faster action potential?

Answer 36

• large diameter of an axon

- myelinated axons (leak resistant); prevents ion flow of of the cytoplasm

Question 37

What determines the number of action potentials produced at the axon hillock?

Answer 37

• stimulus intensity
• weak stimulus releases little neurotransmitters
• strong stimulus causes more action potentials and releases more neurotransmitters

Question 38

What 3 chemical factors alter electrical activity?

Answer 38

1) Normokelemia
2) hyperkalemia
3) hypokelemia

Question 39

Describe Normokalemia

Answer 39

• blood K+ is in the normal range

Question 40

Describe hyperkalemia

Answer 40

• increase in blood K+ concentration
• depolarizes cell
• a stimulus that would normally be subthreshold can trigger an action potential

Question 41

Describe Hypokalemia

Answer 41

• decrease in blood K+ concentration
• hyperpolarizes cell
• a stimulus that would normally be above threshold would less likely be able to fire an action potential