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Biophysics Quiz on Chapter 7, created by Y Y on 26/06/2019.

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Chapter 7

Question 1 of 22

1

Which of the following currents is responsible for the depolarization phase of the axonal action
potential?

Select one of the following:

  • a) inward sodium ion current;

  • b) inward potassium ion current;

  • c) outward calcium ion current.

Explanation

Question 2 of 22

1

Which of the following currents is responsible for the repolarization phase of the axonal action
potential?

Select one of the following:

  • a) inward sodium ion current;

  • b) inward calcium ion current;

  • c) outward potassium ion current.

Explanation

Question 3 of 22

1

Choose the correct statement:

Select one of the following:

  • a) action potentials propagate without attenuation (decrease) of amplitude and with relatives constant speed;

  • b) action potentials propagate with significant decrease of amplitude over the length of the membrane;

  • c) action potentials propagate with increase of the amplitude over the length of the membrane.

Explanation

Question 4 of 22

1

Which of the following factors affects the speed of propagation of axonal action potentials?

Select one of the following:

  • a) diameter and myelination;

  • b) only the diameter of the axon;

  • c) the length of the axon.

Explanation

Question 5 of 22

1

Sodium equilibrium potential (ENa+) for typical neurons is about:

Select one of the following:

  • a) +45 mV;

  • b) - 90 mV;

  • c) +95 mV.

Explanation

Question 6 of 22

1

The depolarization phase in typical neurons is due to:

Select one of the following:

  • a) Na+ ions;

  • b) Na+ and Ca2+ ions;

  • c) Ca2+ ions.

Explanation

Question 7 of 22

1

The equilibrium potential of which of the following ions is the closest to the membrane resting
potential?

Select one of the following:

  • a) Na+ ;

  • b) Ca2+;

  • c) K+

Explanation

Question 8 of 22

1

Treatment of tissue with tetrodotoxin (TTX) will result in:

Select one of the following:

  • a) change of the sodium equilibrium potential;

  • b) change in the extracellular sodium concentration;

  • c) inhibition of passive sodium transport.

Explanation

Question 9 of 22

1

Treatment of tissue with tetraethylammonium (TEA) will result in:

Select one of the following:

  • a) change of the potassium equilibrium potential;

  • b) inhibition of active potassium transport;

  • c) inhibition of passive potassium transport.

Explanation

Question 10 of 22

1

What makes the membrane resting potential so close to the potassium equilibrium potential?

Select one of the following:

  • a) leak potassium channels and low membrane permeability for other ions;

  • b) the much higher potassium concentration inside the cell compared to other ions;

  • c) the work of the sodium-potassium pump which balances the outward leak of potassium.

Explanation

Question 11 of 22

1

What is represented on the graph on the right?

Select one of the following:

  • a) the evolution of total membrane current during the course of the action potential;

  • b) the inward Na+ current during the course of the action potential;

  • c) the outward K + current during the course of the action potential.

Explanation

Question 12 of 22

1

For their experimental model Hodgkin and Huxley used the method of the:

Select one of the following:

  • a) generated voltage;

  • b) fixed voltage;

  • c) sinusoidal voltage.

Explanation

Question 13 of 22

1

The equation gNa = 1/RNa describes:

Select one of the following:

  • a) sodium membrane conductance;

  • b) sodium membrane current;

  • c) sodium membrane voltage.

Explanation

Question 14 of 22

1

Membrane conductance for Na+
and K
+
ions is not constant. It depends on:

Select one of the following:

  • a) the strength of the sub-threshold stimulus;

  • b) the state of the voltage-gated ion channels;

  • c) the state of the leak ion channels.

Explanation

Question 15 of 22

1

The depolarization phase of the axonal action potential is contributed to the:

Select one of the following:

  • a) inward Na+ current due to the electrogenic work of the sodium-potassium pump;

  • b) inward Na+ current due to the non-electrogenic work of the sodium-potassium pump;

  • c) inward Na+ current due to the activation of voltage-gated sodium channels.

Explanation

Question 16 of 22

1

The repolarization phase of the axonal action potential is contributed to:

Select one of the following:

  • a) the outward K + current due to potassium leak channels;

  • b) the outward K + current due to the activation of voltage-gated potassium channels;

  • c) the outward K + current due to the electrogenic work of the sodium-potassium pump.

Explanation

Question 17 of 22

1

What happens when the membrane potential in neurons becomes equal or greater than the
critical depolarisation threshold?

Select one of the following:

  • a) voltage gated Na+ channels become deactivated, and the membrane potential returns to its resting state;

  • b) voltage-gated Na+ channels do not respond to changes in the membrane potential reaching the critical threshold depolarization level;

  • c) voltage-gated Na+ channels open and action potential is initiated.

Explanation

Question 18 of 22

1

What kind of ion current flows across the axonal membrane during the repolarization phase of
the action potential?

Select one of the following:

  • a) negative Na+ current;

  • b) positive Na+ current;

  • c) positive K + current.

Explanation

Question 19 of 22

1

During the voltage clamp method, the voltage across the membrane is fixed and the current
passing through the membrane is measured:

Select one of the following:

  • a) directly, using sensitive voltmeter across the membrane;

  • b) indirectly, by the input current required to keep the voltage fixed;

  • c) current is not measured but calculated using Ohm’s law.

Explanation

Question 20 of 22

1

During the resting state of the axonal membrane the ratio of the ion permeabilities for potassium
and sodium is PK : PNa = 1 : 0.04. During the depolarization phase of the action potential this ratio
changes as follows:

Select one of the following:

  • a) PK : PNa = 1 : 0.0004;

  • b) PK : PNa = 1 : 20;

  • c) PK : PNa = 20 : 0.04.

Explanation

Question 21 of 22

1

A common property of “excitable" cells are:

Select one of the following:

  • a) the voltage-gated ion channels of the cellular membrane;

  • b) the Na+/K+ pumps of the cellular membrane;

  • c) the membrane specialisation for communication via neurotransmitters and hormones.

Explanation

Question 22 of 22

1

What type of ion current does not pass through membrane treated with 10-5 M of TEA
(tetraethylammonium)?

Select one of the following:

  • a) Na+ influx;

  • b) Na+ efflux;

  • c) K + efflux.

Explanation

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