Special Senses and Sensory Receptors MCQs

Physiology · 23 free questions with answers & explanations.

1. A 70-year-old patient with pure-tone audiometry showing bilateral high-frequency hearing loss with preserved speech discrimination represents which type of hearing loss?
2. Phototransduction in rod photoreceptors involves a G-protein cascade. In darkness, what is the state of the rod cell and how does light change it?
3. Phototransduction in rod photoreceptors involves a signal amplification cascade. When light activates rhodopsin, the G-protein (transducin) activates phosphodiesterase (PDE), which hydrolyses cGMP. The fall in cGMP causes closure of CNG channels. Which electrophysiological consequence immediately follows CNG channel closure in the outer segment?
4. The phototransduction cascade in rod photoreceptors involves G protein signalling. Which effector enzyme is activated by transducin (Gt), and what is the downstream effect on the dark current?
5. Phototransduction in rod photoreceptors involves closure of cGMP-gated channels upon light exposure. Which G-protein mediates the signal from activated rhodopsin to phosphodiesterase 6 (PDE6)?
6. Phototransduction in rod photoreceptors involves a G-protein cascade. In the dark, cGMP-gated channels maintain a 'dark current.' When light is absorbed by rhodopsin, the sequence of events that closes these channels is:
7. In phototransduction by rod photoreceptors, light isomerizes 11-cis-retinal to all-trans-retinal, activating rhodopsin → transducin (Gt) → phosphodiesterase (PDE6) cascade. PDE6 hydrolyzes cGMP, closing CNG channels and hyperpolarizing the rod. Recovery of the dark current requires resynthesis of cGMP. Which enzyme is responsible for cGMP resynthesis and what stimulates it during recovery?
8. The type II hair cells in the vestibular system differ from type I hair cells in their afferent innervation pattern. Type II hair cells have bouton (en passant) endings while type I are surrounded by calyx endings. The efferent innervation by olivovestibular fibers has what net effect on vestibular type I hair cell transmission?
9. Phototransduction in rod photoreceptors involves a cGMP-gated ion channel. In the dark state, high cGMP keeps the channel open and the cell is relatively depolarized (-40 mV). The molecular mechanism by which light absorption closes these channels is:
10. The hair cells of the cochlear organ of Corti transduce sound-induced basilar membrane vibration into electrical signals. Mechanotransduction depends on tip links connecting adjacent stereocilia. What ion predominantly enters through the tip-link-gated channels during stereocilia deflection toward the tallest row?
11. The phototransduction cascade in rod photoreceptors involves a series of steps following photon absorption. The correct sequence after rhodopsin activation is:
12. Phototransduction in rod photoreceptors involves a G-protein cascade. In the dark, rods maintain a 'dark current.' The molecular mechanism maintaining the dark current is:
13. The generator potential in a Pacinian corpuscle, a rapidly-adapting mechanoreceptor, adapts quickly because:
14. Dark adaptation of the eye enables vision at extremely low light intensities. The prolonged time course of complete dark adaptation (approximately 30-40 minutes) is primarily determined by:
15. A patient with Meniere's disease has episodic vertigo, tinnitus, and low-frequency sensorineural hearing loss. The pathophysiology involves endolymphatic hydrops. Which ion transport abnormality underlies endolymph accumulation?
16. A patient with a vestibular schwannoma has progressive unilateral hearing loss with poor speech discrimination disproportionate to the pure-tone thresholds, positive SISI (short increment sensitivity index), negative tone decay test (no significant fatigue), and absent stapedial reflexes. Which of these findings specifically indicates RETROCOCHLEAR (nerve/central) rather than cochlear pathology?
17. In the auditory system, the tonotopic organization of the basilar membrane means that high-frequency sounds cause maximal vibration at the base and low frequencies at the apex. Which property of the basilar membrane explains this frequency gradient?
18. In phototransduction, when a photon is absorbed by rhodopsin in a rod photoreceptor, the cell hyperpolarises rather than depolarises. Which sequence of events explains this paradoxical hyperpolarisation?
19. In the semicircular canals, the cupula deflects in response to angular acceleration. Deflection of hair cells in the horizontal (lateral) canal towards the kinocilium causes:
20. In the cochlea, high-frequency sounds are encoded at the BASE and low-frequency sounds at the APEX. This tonotopic organization is determined by which property of the basilar membrane?
21. The dark current in photoreceptors (rods) is maintained in the dark by which mechanism, and what happens when light strikes the photoreceptor?
22. In phototransduction, the 'dark current' maintains photoreceptors in a slightly depolarised state in the absence of light. Which ion channel and second messenger are responsible for maintaining this dark current?
23. In the cochlea, the travelling wave from base to apex reaches its peak displacement at a location that depends on sound frequency. For a high-frequency sound (e.g., 8000 Hz), the peak basilar membrane displacement occurs at the: