Question 1

The time constant describes

Accepted Answer

A)  The time course, when injecting a constant current, of changing from one steady-state
voltage to another 
B)  The time it takes for the action potential to be regenerated 
C)  The time it takes for the action potential to propagate a characteristic distance 
D)  The delay of the action potential at the nodes of Ranvier 
E)  The decay of the action potential with time between the nodes of Ranvier 
A)  The time course, when injecting a constant current, of changing from one steady-state
voltage to another 
B)  The time it takes for the action potential to be regenerated 
C)  The time it takes for the action potential to propagate a characteristic distance 
D)  The delay of the action potential at the nodes of Ranvier 
E)  The decay of the action potential with time between the nodes of Ranvier A

Question 2

The specific capacitance of a bare membrane is about

Accepted Answer

A)  1 pF cm -2 
B)  1 nF cm -2 
C)  1 µ F cm -2 
D)  1 mF cm -2 
E)  1 F cm -2 
A)  1 pF cm -2 
B)  1 nF cm -2 
C)  1 µ F cm -2 
D)  1 mF cm -2 
E)  1 F cm -2 C

Question 3

The time constant is given as

Accepted Answer

A)  T = Rm Cm 
B)  T =  $ \rho $i d / A 
C)  T =k $\epsilon$0 A/ $ \delta $ 
D)  T = = $ \sqrt{ } $ (Rma/2$\rho$i) 
E)  T = Q /V 
A)  T = Rm Cm 
B)  T =  $ \rho $i d / A 
C)  T =k $\epsilon$0 A/ $ \delta $ 
D)  T = = $ \sqrt{ } $ (Rma/2$\rho$i) 
E)  T = Q /V A

Question 4

Saltatory conduction refers to

Accepted Answer

A)  Decreased resistance of internal solutions due to electrolytes 
B)  Jumping of the action potentials from nerve to nerve 
C)  Jumping of the current from node to node 
D)  Rapid conduction in myelinated fibers 
E)  Both A and C are correct 
A)  Decreased resistance of internal solutions due to electrolytes 
B)  Jumping of the action potentials from nerve to nerve 
C)  Jumping of the current from node to node 
D)  Rapid conduction in myelinated fibers 
E)  Both A and C are correct

Question 5

he space constant or length constant is given as

Accepted Answer

A)  $\lambda$ = Rm Cm 
B)  $\lambda$ = $ \rho $i d / A 
C)  $\lambda$ = k $\epsilon$0 A/ $ \delta $ 
D)  $\lambda$ = $ \sqrt{ } $ (Rma/2$\rho$i) 
E)  $\lambda$ = QN 
A)  $\lambda$ = Rm Cm 
B)  $\lambda$ = $ \rho $i d / A 
C)  $\lambda$ = k $\epsilon$0 A/ $ \delta $ 
D)  $\lambda$ = $ \sqrt{ } $ (Rma/2$\rho$i) 
E)  $\lambda$ = QN

Question 6

Myelin does all of the following EXCEPT

Accepted Answer

A)  It increases the transmem brane resistance by insulating the axon interior from the exterior 
B)  It reduces the capacitance of the membrane by increasing its thickness 
C)  It reduces the time constant 
D)  It increases the space or length constant 
E)  It increases conduction velocity 
A)  It increases the transmem brane resistance by insulating the axon interior from the exterior 
B)  It reduces the capacitance of the membrane by increasing its thickness 
C)  It reduces the time constant 
D)  It increases the space or length constant 
E)  It increases conduction velocity

Question 7

The conduction velocity is increased by

Accepted Answer

A)  Shortening the time at which a remote patch of membrane is excited to threshold 
B)  Increasing capacitance by insulating membranes 
C)  Increasing axial resistance to current flow 
D)  Decreasing transmembrane resistances 
E)  None of the above 
A)  Shortening the time at which a remote patch of membrane is excited to threshold 
B)  Increasing capacitance by insulating membranes 
C)  Increasing axial resistance to current flow 
D)  Decreasing transmembrane resistances 
E)  None of the above

Question 8

An action potential begins at a special place, the axon hillock, adjacent to the soma of a motor neuron. You record an action potential 30 cm away on an efferent nerve. The action potential measured far away from the soma

Accepted Answer

A)  Is much smaller than the action potential near the soma because it decays with distance. 
B)  Is smaller, but not much, because the decay with distance is prevented by myelination 
C)  Is larger than the one at the soma because it is amplified at each new area of membrane 
D)  Is the same size as the action potential near the soma because it is regenerated anew along the axon 
E)  Is the same size as the action potential near the soma because there is no decay of potentials in axons 
A)  Is much smaller than the action potential near the soma because it decays with distance. 
B)  Is smaller, but not much, because the decay with distance is prevented by myelination 
C)  Is larger than the one at the soma because it is amplified at each new area of membrane 
D)  Is the same size as the action potential near the soma because it is regenerated anew along the axon 
E)  Is the same size as the action potential near the soma because there is no decay of potentials in axons

Question 9

The "specific capacitance" is the

Accepted Answer

A)  Capacitance per unit length 
B)  Capacitance per unit volume 
C)  Capacitance per unit time 
D)  Capacitance per unit area 
E)  Capacitance per unit charge 
A)  Capacitance per unit length 
B)  Capacitance per unit volume 
C)  Capacitance per unit time 
D)  Capacitance per unit area 
E)  Capacitance per unit charge

Question 10

W e inject a slightly depolarizing current into an axon at x = 0 cm continuously monitor the potential at x = 5 cm away. At steady state, the resting membrane potential is -70 mV. At the point of injection,the potential is -60 m V and at x = 5 cm away it is -66.3 mV. W hat is the space constant?

Accepted Answer

A)  2.5 cm 
B)  5.0 cm 
C)  10.0 cm 
D)  15.0 cm 
E)  20.0 cm 
A)  2.5 cm 
B)  5.0 cm 
C)  10.0 cm 
D)  15.0 cm 
E)  20.0 cm

Question 11

In a myelinated nerve, all of the following are true EXCEPT

Accepted Answer

A)  Na+ enters the axon and K+ leaves the axon during the action potential 
B)  The Na,K-ATPase continually re-establishes the Na+ and K+ gradients 
C)  Na+ influx occurs mainly at the nodes of Ranvier 
D)  The Na+ flux in a single action potential significantly changes axoplasmic [Na+] (> 5%) 
E)  None of the above 
A)  Na+ enters the axon and K+ leaves the axon during the action potential 
B)  The Na,K-ATPase continually re-establishes the Na+ and K+ gradients 
C)  Na+ influx occurs mainly at the nodes of Ranvier 
D)  The Na+ flux in a single action potential significantly changes axoplasmic [Na+] (> 5%) 
E)  None of the above

Question 12

Myelin increases conduction velocity because it

Accepted Answer

A)  Decreases Rm and increases Cm 
B)  Increases Rm and increases Cm 
C)  Increases Rm and decreases Cm 
D)  Decreases Rm and decreases Cm 
E)  Myelin does not do this 
A)  Decreases Rm and increases Cm 
B)  Increases Rm and increases Cm 
C)  Increases Rm and decreases Cm 
D)  Decreases Rm and decreases Cm 
E)  Myelin does not do this

Question 13

To determine the length constant, or space constant, you can inject current (without activating an action potential) and plot (Vr is the resting membrane potential; electrotonus is the steady-state voltage)

Accepted Answer

A)  Ln (V - Vr) vs x during conditions of electrotonus 
B)  Ln (V - Vr) vs t during conditions of electrotonus 
C)  Ln (V - Vr) vs t during the rise phase or decline phase of electrotonus 
D)  Ln (V - Vr) vs t only during the decline phase of electrotonus 
E)  Ln (V - Vr) vs t only during the rise phase of electrotonus 
A)  Ln (V - Vr) vs x during conditions of electrotonus 
B)  Ln (V - Vr) vs t during conditions of electrotonus 
C)  Ln (V - Vr) vs t during the rise phase or decline phase of electrotonus 
D)  Ln (V - Vr) vs t only during the decline phase of electrotonus 
E)  Ln (V - Vr) vs t only during the rise phase of electrotonus

Question 14

Decreasing the capacitance of the axon mem brane means

Accepted Answer

A)  It takes fewer charges to effect a given change in the membrane potential difference
across the membrane 
B)  For the same am ount of charges, the membrane potential changes less 
C)  It takes m ore axial current to depolarize the next patch of m em brane to threshold 
D)  It takes m ore axial voltage to depolarize the next patch of m em brane to threshold 
E)  For the same voltage change, more current is required 
A)  It takes fewer charges to effect a given change in the membrane potential difference
across the membrane 
B)  For the same am ount of charges, the membrane potential changes less 
C)  It takes m ore axial current to depolarize the next patch of m em brane to threshold 
D)  It takes m ore axial voltage to depolarize the next patch of m em brane to threshold 
E)  For the same voltage change, more current is required

Question 15

Myelin

Accepted Answer

A)  Decreases the capacitance of the axon membrane mainly by increasing the separation
between the inside and outside 
B)  Decreases the capacitance of the axon mem brane m ainly by increasing the dielectric constant
within the membrane 
C)  Decreases the capacitance of the axon mem brane m ainly by decreasing the dielectric
constant within the membrane 
D)  Increases the capacitance of the axon mem brane mainly by increasing the separation
between the inside and the outside 
E)  Increases the capacitance of the axon mem brane mainly by increasing the surface area 
A)  Decreases the capacitance of the axon membrane mainly by increasing the separation
between the inside and outside 
B)  Decreases the capacitance of the axon mem brane m ainly by increasing the dielectric constant
within the membrane 
C)  Decreases the capacitance of the axon mem brane m ainly by decreasing the dielectric
constant within the membrane 
D)  Increases the capacitance of the axon mem brane mainly by increasing the separation
between the inside and the outside 
E)  Increases the capacitance of the axon mem brane mainly by increasing the surface area

Question 16

Increasing Rm by myelination

Accepted Answer

A)  Decreases the time constant 
B)  Is proportional to the thickness of the myelin 
C)  Is inversely proportional to the thickness of the myelin 
D)  Increases proportionally with the cross-sectional area of the axon 
E)  Is inversely proportional to the cross-sectional area of the axon. 
A)  Decreases the time constant 
B)  Is proportional to the thickness of the myelin 
C)  Is inversely proportional to the thickness of the myelin 
D)  Increases proportionally with the cross-sectional area of the axon 
E)  Is inversely proportional to the cross-sectional area of the axon.

Question 17

The conduction velocity is fastest in

Accepted Answer

A)  Small diameter myelinated axons 
B)  Small diameter unmyelinated axons 
C)  Small diameter axons with large internodal distances 
D)  Large diameter myelinated axons 
E)  Large diameter unmyelinated axons 
A)  Small diameter myelinated axons 
B)  Small diameter unmyelinated axons 
C)  Small diameter axons with large internodal distances 
D)  Large diameter myelinated axons 
E)  Large diameter unmyelinated axons

Question 18

The axial resistance

Accepted Answer

A)  Depends inversely on the specific resistance of the cytoplasm 
B)  Depends inversely on the cross-sectional area of the cytoplasm 
C)  Depends directly on the electrolyte composition 
D)  Is decreased by myelination 
E)  Is increased by myelination 
A)  Depends inversely on the specific resistance of the cytoplasm 
B)  Depends inversely on the cross-sectional area of the cytoplasm 
C)  Depends directly on the electrolyte composition 
D)  Is decreased by myelination 
E)  Is increased by myelination

Question 19

The delay between an action potential in a soma and its appearance 30 cm down the efferent axon is 5 ms. The conduction velocity is

Accepted Answer

A)  6 mm s-1 
B)  6 cm s-1 
C)  150 cm s-1 
D)  15 m s-1 
E)  60 m s-1 
A)  6 mm s-1 
B)  6 cm s-1 
C)  150 cm s-1 
D)  15 m s-1 
E)  60 m s-1

Exam 19: Propagation of the Action Potential

The time constant describes

The specific capacitance of a bare membrane is about

The time constant is given as

Saltatory conduction refers to

he space constant or length constant is given as

Myelin does all of the following EXCEPT

The conduction velocity is increased by

An action potential begins at a special place, the axon hillock, adjacent to the soma of a motor neuron. You record an action potential 30 cm away on an efferent nerve. The action potential measured far away from the soma

The "specific capacitance" is the

W e inject a slightly depolarizing current into an axon at x = 0 cm continuously monitor the potential at x = 5 cm away. At steady state, the resting membrane potential is -70 mV. At the point of injection,the potential is -60 m V and at x = 5 cm away it is -66.3 mV. W hat is the space constant?

In a myelinated nerve, all of the following are true EXCEPT

Myelin increases conduction velocity because it

To determine the length constant, or space constant, you can inject current (without activating an action potential) and plot (Vr is the resting membrane potential; electrotonus is the steady-state voltage)

Decreasing the capacitance of the axon mem brane means

Myelin

Increasing Rm by myelination

The conduction velocity is fastest in

The axial resistance

The delay between an action potential in a soma and its appearance 30 cm down the efferent axon is 5 ms. The conduction velocity is

Physical Foundations Ii: Electrical Force Potential Capacitance and Current

Chemical Foundations I: Chemical Energy and Intermolecular Forces

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Increasing R_m by myelination