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Eduncle posted an MCQ
October 18, 2019 • 23:57 pm 0 points
  • CSIR NET
  • Life Sciences

The conduction velocity of action potential in a myelinated nerve fibre was much greater than that of an unmyelinated fibre of

The conduction velocity of action potential in a myelinated nerve fibre was much greater than that of an unmyelinated fibre of the same diameter. The following statements were proposed to explain this observation. (A) The speed of conduction in a nerve fibre is determined by the plasma membrane resistance and axial resistance of axonal cytoplasm. (B) The electrical properties of myelinated and unmyelinated nerve fibres are not similar (C) The myelin sheath decreases the effective membrane resistance. (D) The magnitude of an electrotonic potential decreases more with distance along the axon in myelinated nerve fibres than that of unmyelinated fibres. (E) The voltage-gated Na+ channels are highly concentrated at the nodes of Ranvier. Choose one of the following combinations with both INCORRECT statements.

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    Eduncle Best Answer

    Both membrane and axonal resistance is required to calculate the speed of conductance. Statement A is true
    Myelin has both passive and active properties: it increases the axon's membrane resistance and decreases the membrane capacitance. Statement B is true and C is false
    The movement of sodium ions to depolarize the membrane can only occur at the Node of Ranvier, as the sodium voltage-gated channels are found only at the nodes of Ranvier. Statement E is correct

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