Physiology, MBBS Second Year. This chapter is split into 9 topics and has
343 practice questions. The topics covered are listed below, followed by
10 free sample questions from the chapter.
Relative taste indices (table-based questions)35 questions
Taste and smell: integrated and clinical questions25 questions
Sample questions: The Chemical Senses: Taste and Smell
10 sample questions with the correct answer and an explanation. Try to answer each one before reading the explanation.
Q1. At low concentration, a taste bud typically:
A. Responds only to bitter substances
B. Responds mostly to one primary taste stimulus(correct answer)
C. Does not respond at all
D. Responds to all primary tastes equally
Answer: B.At low concentration a taste bud responds mostly to one primary taste stimulus, whereas at high concentration it responds to two or more primary tastes and additional stimuli — reducing specificity for strong stimuli.
Q2. Which sequence correctly describes GPCR-mediated taste transduction?
A. Depolarization → receptor binding → second messenger cascade
B. Neurotransmitter release → receptor binding → depolarization
C. Ion entry → GPCR activation → hyperpolarization
Answer: D.For sweet, bitter and umami, taste substance binding activates a GPCR, triggering a second messenger cascade that depolarizes the taste cell, generating a receptor potential and releasing neurotransmitter to excite the afferent nerve.
Q3. Which ganglion is associated with the taste fibres of the facial nerve?
A. The nodose ganglion
B. The geniculate ganglion(correct answer)
C. The petrosal ganglion
D. The spiral ganglion
Answer: B.Taste fibres of the facial nerve (VII) pass through the geniculate ganglion; those of the glossopharyngeal (IX) pass through the petrosal ganglion and those of the vagus (X) through the nodose ganglion.
Q4. A patient loses taste from the anterior two-thirds of the tongue, posterior tongue and pharynx. Where is the lesion likely located?
A. Beyond the convergence point — e.g., the nucleus of the tractus solitarius or higher(correct answer)
B. The chorda tympani only
C. The olfactory bulb
D. The glossopharyngeal nerve only
Answer: A.Because the three taste nerves converge on the nucleus of the tractus solitarius, loss of taste from all regions points to a lesion at or beyond this convergence point rather than a single peripheral nerve.
Q5. Compared with taste receptor cells, olfactory receptor cells are unusual because they:
A. Are true neurons derived from the CNS that can regenerate(correct answer)
B. Are located in the tongue
C. Contain no cilia
D. Are epithelial cells replaced every 10 days
Answer: A.Olfactory receptor cells are unusual: they are true bipolar neurons derived from the CNS, and they can regenerate (unlike most CNS neurons) — contrasting with the epithelial taste cells replaced about every 10 days.
Q6. The olfactory amplification mechanism means that:
A. The signal attenuates rapidly
B. One odorant molecule activates multiple G-proteins, each activating several adenylyl cyclase molecules, greatly increasing cAMP(correct answer)
C. One odorant molecule activates exactly one sodium channel
D. cAMP decreases with stimulation
Answer: B.Even minute concentrations of odorant produce a cascading amplification: one odorant molecule activates multiple G-proteins, each activating several adenylyl cyclase molecules, so cAMP rises greatly and opens many sodium channels.
Q7. Which sequence correctly describes the olfactory pathway from the nose?
A. Odorant → olfactory bulb → cilia
B. Odorant → taste buds → brain
C. Odorant → thalamus → cilia
D. Odorant in mucus → cilia receptors → G-protein/adenylyl cyclase/cAMP → Na+ influx → action potential → olfactory bulb(correct answer)
Answer: D.Odorant dissolving in mucus binds cilia receptors, activating a G-protein/adenylyl cyclase/cAMP cascade that opens sodium channels; Na+ influx generates action potentials transmitted to the olfactory bulb.
Q8. Assertion: Only minute amounts of an odorant are needed for detection. Reason: Each odorant molecule triggers a cascading amplification via G-proteins and cAMP.
A. Both are true, but the Reason does not explain the Assertion
B. Assertion is true but Reason is false
C. Assertion is false but Reason is true
D. Both Assertion and Reason are true, and the Reason correctly explains the Assertion(correct answer)
Answer: D.Because one odorant molecule activates many G-proteins and each activates several adenylyl cyclase molecules, cAMP rises sharply, opening many sodium channels — enabling detection of extremely low odorant concentrations.
Q9. Which statement about olfactory pathways is TRUE?
A. They are entirely thalamic
B. They have no limbic connections
C. They terminate in the cerebellum
D. They include both primitive limbic-linked and newer thalamocortical components(correct answer)
Answer: D.Olfactory pathways comprise primitive (medial, limbic-linked), less-old (lateral, amygdalar) and newer (thalamo-orbitofrontal) components serving reflexive/emotional and conscious functions respectively.
Q10. A patient cannot consciously identify odours but shows normal emotional responses to them. Which pathway is likely intact?
A. The primitive/limbic olfactory pathway, with the newer thalamic pathway impaired(correct answer)
B. The newer thalamic pathway only
C. The optic pathway
D. The auditory pathway
Answer: A.Dissociation between conscious odour identification (newer thalamo-orbitofrontal pathway) and emotional responses (primitive limbic pathway) indicates preservation of the primitive pathway with impairment of the newer one.