Week 2: Nerve Excitability and Propagation

Question 1

The transmembrane potential of a resting cell.

Answer 1

Resting Potential

Question 2

A stimulus that produces temporary, localized changed in resting state.

Answer 2

Graded Potential

Question 3

An impulse that is propagated along the surface of the axon.

Answer 3

Action Potential

Question 4

Produces graded potentials in postsynaptic cells.

Answer 4

Synaptic Activity

Question 5

The integration of stimulus by the postsynaptic cell.

Answer 5

Information Processing

Question 6

This fluid has higher concentrations of Na+ and Cl-.

Answer 6

Extracellular Fluid

Question 7

This fluid has higher concentrations of K+ and negatively charged proteins.

Answer 7

Intracellular Fluid

Question 8

This means that ions have to move through membrane channels in order to pass from intracellular and extracellular fluid spaces.

Answer 8

Selective Permeability

Question 9

True or False?

Membrane permeability varies by ions.

Answer 9

True.

Question 10

True or False?
Both passive and active transport mechanisms at the level of the cell membrane ensure an equal charge exists across the cell membrane.

Answer 10

False.

Ensures an UNEQUAL charge exists across the cell membrane.

Question 11

Represent the imbalance in the number of particular ions across the cell membrane.

Answer 11

Chemical Gradients (Passive Force)

Question 12

Represent the imbalance of electrical charges across the cell membrane which is more negative inside the cell.

Answer 12

Electrical Gradients (Passive Force)

Question 13

Result from the combined chemical and electrical forces acting on a specific ion.

Answer 13

Electrochemical Gradients (Passive Force)

Question 14

There are ______ K+ inside the cell so the K+ wants to move _________.

Answer 14

More, out.

Question 15

There are ______ Na+ outside the cell so Na+ want to move ______.

Answer 15

More, in.

Question 16

A chemical gradient results in _____ movement driven by chemical ____________ differences between ECF and ICF.

Answer 16

Ion, concentration.

Question 17

Electrical differences are measured in __________.

Answer 17

Millivolts (mV)

Question 18

A typical neuron rests at ______.

Answer 18

-70 mV

Question 19

The membrane potential at which there is no net movement of a particular ion across the plasma membrane is called __________ ____________.

Answer 19

Equilibrium Potential

Question 20

K+ has an equilibrium potential of _______.

Answer 20

-90 mV

Question 21

Na+ has an equilibrium of _________.

Answer 21

+66 mV

Question 22

At normal resting potential, the cell must bail out ________ that leak in and recapture __________ that leaked out.

Answer 22

Sodium, potassium.

Question 23

The bailing of sodium and recapturing of potassium is done by what pump?

Answer 23

Sodium-Potassium Exchange Pump

Question 24

The Sodium-Potassium Exchange Pump is powered by ______, making it an active transport mechanism.

Answer 24

ATP

Question 25

The Sodium-Potassium Exchange Pump exchanges __ intracellular Na+ for __ intracellular K+.

Answer 25

3 Na+, 2 K+

Question 26

The Sodium-Potassium Exchange Pump involves a carrier protein called ____________.

Answer 26

Sodium-Potassium ATPase

Question 27

Also called leak channels; are always open but permeability can vary from moment to moment.

Answer 27

Passive Channels

Question 28

Also called gated channels; open or close in response to specific stimuli

Answer 28

Active Channels

Question 29

Gated channels that open or close when specific chemical bind to receptor sites on the channel.

Answer 29

Chemically Gated Channels

Question 30

Gated channels that open and close in response to changes in the transmembrane potential when the cell reaches threshold.

Answer 30

Electrically Gated Channels

Question 31

Gated channels that open and close in response to physical distortion (pressure) of the membrane surface.

Answer 31

Mechanically Gated Channels

Question 32

Graded potentials are also called ___________.

Answer 32

Local Potentials

Question 33

True or False? | Graded potentials are changes in the membrane potential that can spread far from the site of stimulation.

Answer 33

False. | Graded potentials CANNOT spread far.

Question 34

True or False? | Any stimulus that opens gated channels produces a graded potential.

Answer 34

True.

Question 35

``` Na+ are attracted to the __________ charges along the ___________ surface of the nerve cell membrane. A) positive, outer B) negative, inner C) positive, inner D) negative, outer ```

Answer 35

B) negative, inner

Question 36

``` Na+ influx shifts the membrane potential toward 0 mV also called ______________. A) hyperpolarization B) equilibrium C) depolarization D) polarization ```

Answer 36

C) depolarization

Question 37

True or False? | During graded potentials, the degree of depolarization decreases with distance away from the site of stimulation.

Answer 37

True.

Question 38

True or False? | Graded potentials always lead to an action potential.

Answer 38

False. | Graded potentials MAY OR MAY NOT lead to an action potential.

Question 39

When a stimulus is removed, normal membrane permeability is restored to resting levels, which is called ____________.

Answer 39

Repolarization.

Question 40

``` Graded potentials are usually brought about by _________ or ___________ gated channels. A) chemically, mechanically B) chemically, electrically C) electrically, mechanically D) active, passive ```

Answer 40

A) chemically, mechanically

Question 41

True or False? | Electrically gated ion channels are associated with action potentials.

Answer 41

True.

Question 42

-70mV toward -60 mV a graded _____________.

Answer 42

Depolarization

Question 43

-70 mV toward -90 mV a graded ______________.

Answer 43

Hyperpolarization

Question 44

Also called excitation; is any shift from resting membrane potential toward 0 mV.

Answer 44

Depolarization

Question 45

The process of restoring the normal resting potential after depolarization.

Answer 45

Repolarization

Question 46

The first step in generation of an action potential is the opening of voltage gated ________ _________.

Answer 46

Sodium channels

Question 47

Threshold is at _____ mV.

Answer 47

-60 mV

Question 48

True or False? | Once one voltage gated Na+ channels is opened, adjacent voltage gated Na+ channels open.

Answer 48

True.

Question 49

Arrange the steps of an action potential. _____ Around 30+ mV; Na + inactivation gate close; K+ activation gates open: K+ moves out; repolarization begins _____ The cell body is depolarized enough that it reaches threshold and voltage gated Na+ channels open _____ Na+ inactivation gate remains closed until threshold reached; K+ channels begin to close at -70 mV; a brief period of hyperpolarization occurs after _____ Na+ activation gates open; Na+ is driven down the electrochemical gradient; rapid depolarization results in a positive intracellular charge

Answer 49

Step 3 Step 1 Step 4 Step 2

Question 50

The period in which the plasma membrane does not respond normally to additional stimuli from the time an action potential begins until the normal resting membrane has stabilized.

Answer 50

Refractory Period

Question 51

This type of refractory period occurs when Na+ activation gates are open or Na+ inactivation gates are closed.

Answer 51

Absolute Refractory Period

Question 52

This type of refractory period occurs when Na+ channels regain their rest position up until resting membrane potential is achieved.

Answer 52

Relative Refractory Period

Question 53

True or False? Another action potential can occur in the relative refractory period only if the cell membrane is sufficiently hyperpolarized.

Answer 53

False. | Only if the cell membrane is sufficiently DEPOLARIZED.

Question 54

This type of propagation occurs along an unmyelinated axon resembling dominos; this is a slower type of propagation.

Answer 54

Continuous Propagation

Question 55

This type of propagation occurs along a myelinated axon resembling the game "Leap Frog"; this is a much faster type of propagation.

Answer 55

Saltatory Propagtaion

Question 56

``` Myelin greatly _______ propagation speed of action potentials. A) decreases B) inhibits C) deducts D) increases ```

Answer 56

D) increases

Question 57

``` The diameter of the axon affects the propagation speed, and the ________ the diameter, the lower the ________ to propagation. A) smaller, acceptance B) larger, resistance C) larger, acceptance D) smaller, resistance ```

Answer 57

B) larger, resistance

Question 58

These type of fibres are the largest diameter, myelinated fibres; action potential speeds up to 120 m/s (268 mph)

Answer 58

Type A Fibres

Question 59

These type of fibres are smaller in diameter, myelinated fibres; 18 m/s (40 mph).

Answer 59

Type B Fibres

Question 60

These type of fibres are smaller in diameter, unmyelinated fibres; 1 m/s (2mph)

Answer 60

Type C Fibres