Action Potential

ACTION POTENTIAL

Q. 1

During the Repolarisation phase of Action Potential of a Neuron, which among the following takes place?

 A Increased permeability to K+ ion
 B

Decreased permeability to K+ ion

 C Increased permeability to Ca2+ ion
 D

Increased permeability to Na+ ion

Q. 1

During the Repolarisation phase of Action Potential of a Neuron, which among the following takes place?

 A Increased permeability to K+ ion
 B

Decreased permeability to K+ ion

 C Increased permeability to Ca2+ ion
 D

Increased permeability to Na+ ion

Ans. A

Explanation:

Increased Permeability to K+ ion

REF: See previous question for explanation


Q. 2 Which of the following will be less during the overshoot of an action potential than during the resting state?
 A Membrane conductance for sodium
 B Membrane conductance for potassium 
 C Transference for sodium
 D Transference for potassium
Q. 2 Which of the following will be less during the overshoot of an action potential than during the resting state?
 A Membrane conductance for sodium
 B Membrane conductance for potassium 
 C Transference for sodium
 D Transference for potassium
Ans. D

Explanation:

During an  action potential,  the conductance for both sodium and potassium is higher than it is at rest.  However,  the  conductance  for  sodium  is higher than the conductance for potassium during the over shoots. Hence, the transference for potassium is less. Recall that transference is a measure of an ion’s relative conductance: 

TN.  = gN.lCgN. + gK) and TK = gK/(gN.  + gK)

Where T = transference and g = conductance.


Q. 3

Action potential is generated in excitable cells. All the following are excitable cells, except:

 A

Nerve cells

 B

Neuroglial cells

 C

Glands

 D

Muscle

Q. 3

Action potential is generated in excitable cells. All the following are excitable cells, except:

 A

Nerve cells

 B

Neuroglial cells

 C

Glands

 D

Muscle

Ans. B

Explanation:

The main difference between the nerve and the glial cells are the possession of axons and dendrites and the capacity to generate action potentials.

Ref: Choudary Physiology, 6th Edition, Pages 7, 19

 


Q. 4

Action potential is generated in excitable cells. These cells are:

 A

Nerves

 B

Muscle

 C

Glands

 D

All

Q. 4

Action potential is generated in excitable cells. These cells are:

 A

Nerves

 B

Muscle

 C

Glands

 D

All

Ans. C

Explanation:

A i.e. Nerves; B i.e. Muscle; C i.e. Glands

Action potential develops in excitable cells such as nerves (neurons), muscle (skeletal, smooth and cardiac), and other contractile tissues such as few glandsQ. Glial cells such as neuroglial cells do not generate action potential.


Q. 5

Action potential is:

 A

Decremental phenomenon

 B

Doesn’t obey all or none phenomenon

 C

K+ goes from ECF to ICF

 D

Threshold stimulus is required

Q. 5

Action potential is:

 A

Decremental phenomenon

 B

Doesn’t obey all or none phenomenon

 C

K+ goes from ECF to ICF

 D

Threshold stimulus is required

Ans. D

Explanation:

D i.e. Threshold stimulus is required


Q. 6

Intensity of sensory stimulation is directly related to:

 A

Duration of action potential (AP)

 B

Frequency of AP

 C

Amplitude of AP

 D

All of the above.

Q. 6

Intensity of sensory stimulation is directly related to:

 A

Duration of action potential (AP)

 B

Frequency of AP

 C

Amplitude of AP

 D

All of the above.

Ans. B

Explanation:

B i.e. Frequency of AP


Q. 7

Magnitude of action potential is mainly affected by:

September 2005

 A

Calcium ion

 B

Hydrogen ion

 C

Sodium ion

 D

Potassium ion

Q. 7

Magnitude of action potential is mainly affected by:

September 2005

 A

Calcium ion

 B

Hydrogen ion

 C

Sodium ion

 D

Potassium ion

Ans. C

Explanation:

Ans. C: Sodium ion


Q. 8

Size of action potential is decreased as a result of:

March 2010

 A

Lower extracellular sodium

 B

Raised extracellular calcium

 C

Lower extracellular calcium

 D

Raised extracellular sodium

Q. 8

Size of action potential is decreased as a result of:

March 2010

 A

Lower extracellular sodium

 B

Raised extracellular calcium

 C

Lower extracellular calcium

 D

Raised extracellular sodium

Ans. A

Explanation:

Ans. A: Lower extracellular sodium

Decreasing the external Na+ concentration decreases the size of the action potential but has little effect on the resting membrane potential. The lack of much effect on the resting membrane potential would be predicted, since the permeability of the membrane to Na+ at rest is relatively low.

Conversely, increasing the external K+ concentration decreases the resting membrane potential.

A decrease in extracellular Ca2+ concentration increases the excitability of nerve and muscle cells by decreasing the amount of depolarization necessary to initiate the changes in the Na+ and K+ conductance that produce the action potential. Conversely, an increase in extracellular Ca2+ concentration “stabilizes the membrane” by decreasing excitability



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