How does myelin sheath speed up action potential propagation along myelinated peripheral nerves? (Hard)
Answer and explanation
Correct answer: C. Saltatory conduction where action potentials jump between nodes of Ranvier
- Step 1: Myelin acts as an electrical insulator with high resistance and low capacitance, preventing ion leakage along internodes. Step 2. Voltage-gated Na+ channels are clustered exclusively at unmyelinated nodes of Ranvier, allowing action potentials to leap from node to node (saltatory conduction) up to 120 m/s. Answer: Saltatory conduction where action potentials jump between nodes of Ranvier. Why not the others: Continuous slow conduction occurs in unmyelinated C-fibers (~1 m/s); myelin blocks ion leakage; nerve impulses are electrical and chemical, not acoustic.
Practise more Medical Optics, Electrophysiology and Clinical Radiation.
Free questions with an explanation for every one, and full timed Medical College Admission Test (Bangladesh) mock tests.
More Medical Optics, Electrophysiology and Clinical Radiation questions
- Which anatomical structure of the human eye provides the greatest portion (approximately 70% or 40-44 Diopters) of total refractive power?
- What vision defect occurs when the eyeball is too long or the cornea too curved, focusing parallel light rays in front of the retina?
- Which type of corrective ophthalmic lens is prescribed to correct Myopia (Short-sightedness)?
- Which vision defect is corrected using a Convex (converging) ophthalmic lens?
- What age-related refractive condition involves gradual progressive loss of crystalline lens elasticity and near accommodation?
- Which type of corrective lens is prescribed to neutralize the asymmetric corneal curvature of Astigmatism?