The part of the human ear that converts the pressure variations associated with audible sound waves to electrical signals is
- A.auditory nerve
- B.cochlea
- C.eardrum
- D.eustachian tube
Correct answer
Explanation
The correct answer is B, cochlea. The cochlea of the inner ear changes the pressure variations of sound into electrical (nerve) signals, which the auditory nerve then carries to the brain.
Sound waves first make the eardrum vibrate. The three tiny bones of the middle ear, the malleus, incus and stapes, pass these vibrations on and strengthen them. The stapes pushes on the oval window of the snail-shaped cochlea, which is filled with fluid. Waves in this fluid bend the hair cells lining the organ of Corti, and the hair cells turn that movement into electrical impulses. Different parts of the cochlea respond to different pitches.
A is wrong: the auditory nerve only carries the signals to the brain; it does not create them. C is wrong: the eardrum turns sound into mechanical vibrations, not electrical signals. D is wrong: the eustachian tube links the middle ear to the throat and balances air pressure on both sides of the eardrum.
Exam tip: eardrum vibrates, ossicles amplify, cochlea converts to nerve signals, auditory nerve carries them to the brain.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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