Taste and Smell — MCQs

10 questions

All of the following contains Bipolar neurons except

Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue

Among the following trigeminal nerve divisions, which one is involved in orbital apex syndrome?

A child presents with unilateral foul-smelling nasal discharge. What is the most likely cause?

Frey's syndrome is associated with-

Impulses generated in the taste buds of the tongue reach the cerebral cortex via the

The bitter taste of toxic substances prevents us from their consumption, which of the following elicits the bitterness?

Which taste sensation is the most sensitive (i.e., has the lowest stimulation threshold)?

Transection at mid-pons level with intact vagus results in:

Q10

All are effects of the parasympathetic system on the heart except?

Taste and Smell Indian Medical PG Practice Questions and MCQs

Question 1: All of the following contains Bipolar neurons except

A. Retina
B. Olfactory bulb
C. Olfactory epithelium
D. Dorsal root ganglion (Correct Answer)

Explanation: ***Dorsal root ganglion*** - Dorsal root ganglia predominantly contain **pseudounipolar neurons**, which have a single process that branches into peripheral and central axons [3]. - These neurons are responsible for transmitting **sensory information** from the periphery to the central nervous system. - **This is the correct answer** as it does NOT contain bipolar neurons. *Retina* - The retina contains **bipolar cells**, which are interneurons that transmit signals from photoreceptors to ganglion cells [2]. - These bipolar neurons are crucial for **visual signal processing** [2]. *Olfactory bulb* - The olfactory bulb contains several types of neurons including **periglomerular cells and some interneurons that are bipolar in nature**. - It receives input from olfactory receptor neurons and processes **olfactory information**. *Olfactory epithelium* - The olfactory epithelium contains **olfactory receptor neurons**, which are true bipolar neurons [1]. - These specialized neurons have one dendrite extending to the surface and one axon projecting to the olfactory bulb, making them classic examples of bipolar neurons [1]. - These neurons are responsible for detecting **odors** and transmitting signals to the olfactory bulb [1].

Question 2: Match the following: A) Glossopharyngeal nerve B) Spinal accessory nerve C) Facial nerve D) Mandibular nerve 1) Shrugging of shoulder 2) Touch sensation from the posterior one-third of the tongue 3) Chewing 4) Taste from the anterior two-thirds of the tongue

A. A-3 , B-1 , C-4 , D-2
B. A-2 , B-3 , C-4 , D-1
C. A-4 , B-1 , C-2 , D-3
D. A-2 , B-1 , C-4 , D-3 (Correct Answer)

Explanation: ***A-2 , B-1 , C-4 , D-3*** - **A) Glossopharyngeal nerve (CN IX)** is responsible for **general sensation and taste from the posterior one-third of the tongue** [1]. (2). - **B) Spinal Accessory nerve (CN XI)** innervates the **sternocleidomastoid** and **trapezius muscles**, which are involved in shrugging the shoulders (1). - **C) Facial nerve (CN VII)** carries **taste sensation from the anterior two-thirds of the tongue** [1] (4) via the chorda tympani. - **D) Mandibular nerve (V3)**, a branch of the trigeminal nerve, innervates the muscles of mastication, enabling **chewing** (3). *A-3 , B-1 , C-4 , D-2* - This option incorrectly associates the **glossopharyngeal nerve** with chewing, which is a function of the mandibular nerve (V3). - It also incorrectly associates the **mandibular nerve** with touch sensation from the posterior one-third of the tongue, which is a function of the glossopharyngeal nerve [1]. *A-2 , B-3 , C-4 , D-1* - This option incorrectly links the **spinal accessory nerve** with chewing; this nerve primarily controls shoulder and neck movements. - It also incorrectly assigns shrugging of the shoulder to the **mandibular nerve** instead of the spinal accessory nerve. *A-4 , B-1 , C-2 , D-3* - This choice incorrectly attributes **taste from the anterior two-thirds of the tongue** to the glossopharyngeal nerve, which supplies the posterior one-third [1]. - It also incorrectly links **touch sensation from the posterior one-third of the tongue** to the facial nerve, which is involved in taste from the anterior two-thirds [1].

Question 3: Among the following trigeminal nerve divisions, which one is involved in orbital apex syndrome?

A. Olfactory nerve
B. Mandibular division of trigeminal nerve
C. Maxillary division of trigeminal nerve
D. Ophthalmic division of trigeminal nerve (Correct Answer)

Explanation: ***Ophthalmic division of trigeminal nerve*** - Orbital apex syndrome involves deficits of nerves passing through the **superior orbital fissure** and **optic canal**, which includes the ophthalmic division of the trigeminal nerve (CN V1). - Involvement of CN V1 leads to **sensory loss** in the forehead, upper eyelid, and side of the nose. *Olfactory nerve* - The **olfactory nerve (CN I)** is responsible for the sense of smell and does not pass through the orbital apex. - Its involvement would manifest as **anosmia**, which is not a characteristic feature of orbital apex syndrome. *Maxillary division of trigeminal nerve* - The **maxillary division (CN V2)** exits the skull through the **foramen rotundum** and innervates the midface. - It is generally **not involved** in orbital apex syndrome, as its anatomical course is distinct from the structures within the orbital apex. *Mandibular division of trigeminal nerve* - The **mandibular division (CN V3)** exits the skull through the **foramen ovale** and innervates the lower face and muscles of mastication. - Its involvement is **not associated** with orbital apex syndrome, as it is anatomically distant from the orbital apex.

Question 4: A child presents with unilateral foul-smelling nasal discharge. What is the most likely cause?

A. Acute sinusitis
B. Allergic rhinitis
C. Choanal atresia
D. Nasal foreign body (Correct Answer)

Explanation: ***Nasal foreign body*** - A **unilateral, foul-smelling nasal discharge** in a child is highly suggestive of a nasal foreign body, as it irritates the mucosa causing inflammation and bacterial growth. - Children often insert small objects into their nostrils, leading to these characteristic symptoms. *Acute sinusitis* - Acute sinusitis typically presents with **bilateral nasal discharge**, facial pain/pressure, and fever. - While discharge can be purulent and foul-smelling, it is usually **not unilateral** unless there's an underlying anatomical abnormality. *Allergic rhinitis* - Allergic rhinitis is characterized by **clear, watery bilateral nasal discharge**, sneezing, itching, and nasal congestion, often with seasonal triggers. - The discharge is **not typically unilateral or foul-smelling**. *Choanal atresia* - Choanal atresia is a congenital blockage of the nasal passage, usually causing **bilateral nasal obstruction and difficulty breathing**, particularly in neonates. - It would present from birth with **respiratory distress**, and discharge would likely be clear and mucous, not foul-smelling and unilateral.

Question 5: Frey's syndrome is associated with-

A. Motor fibres of facial nerve
B. Parasympathetic fibres of auriculo temporal nerve (Correct Answer)
C. Sympathetic fibres of auriculo temporal nerve
D. Parasympathetic fibres of trigeminal nerve

Explanation: ***Parasympathetic fibres of auriculo temporal nerve*** - **Frey's syndrome**, or **gustatory sweating**, occurs due to aberrant regeneration of damaged **auriculotemporal nerve fibers** after **parotid gland surgery** or trauma. - **Parasympathetic secretomotor fibers** that originally innervated the **parotid gland** mistakenly reinnervate overlying **sweat glands** and **blood vessels** of the skin. *Motor fibres of facial nerve* - **Motor fibers of the facial nerve** control **facial expression muscles** and are not directly involved in the pathogenesis of Frey's syndrome. - Damage to these fibers would result in **facial paralysis**, not gustatory sweating. *Sympathetic fibres of auriculo temporal nerve* - The **auriculotemporal nerve** contains **sensory fibers** to the temporal region and **parasympathetic secretomotor fibers** to the parotid gland, but its sympathetic fibers are primarily **vasomotor**. - **Sympathetic fibers** control vasoconstriction and eccrine sweating generally, but their aberrant regeneration is not the cause of Frey's syndrome. *Parasympathetic fibres of trigeminal nerve* - The **trigeminal nerve** is primarily **sensory** to the face and **motor** to the muscles of mastication; it does not directly innervate the parotid gland. - **Parasympathetic innervation** to the parotid gland is carried by the glossopharyngeal nerve via the otic ganglion, not the trigeminal nerve.

Question 6: Impulses generated in the taste buds of the tongue reach the cerebral cortex via the

A. Thalamus (Correct Answer)
B. Dorsal roots of the first cervical spinal nerve
C. Hypoglossal nerve
D. Lingual nerve

Explanation: ***Thalamus*** - The **thalamus** acts as a crucial relay station for almost all sensory information, including taste, before it reaches the **cerebral cortex** for conscious perception. - Taste signals from the cranial nerves (facial, glossopharyngeal, vagus) travel to the **nucleus of the solitary tract** in the brainstem, then to the **ventral posteromedial (VPM) nucleus of the thalamus**, and finally to the **gustatory cortex**. *Dorsal roots of the first cervical spinal nerve* - The dorsal roots of cervical spinal nerves are involved in transmitting **somatosensory information** (touch, pain, temperature, proprioception) from the neck and head region, not taste. - These nerves carry signals from the spinal cord to the brain, whereas taste pathways originate from cranial nerves in the head. *Hypoglossal nerve* - The **hypoglossal nerve (CN XII)** is primarily a **motor nerve** responsible for controlling the muscles of the tongue, essential for speech and swallowing. - It has no direct role in transmitting taste sensations to the cerebral cortex. *Lingual nerve* - The **lingual nerve** is a branch of the **trigeminal nerve (CN V)** and carries **general sensation** (touch, pain, temperature) from the anterior two-thirds of the tongue. - While it runs with the **chorda tympani** (a branch of the facial nerve that carries taste), the lingual nerve itself does not transmit taste signals to the brain.

Question 7: The bitter taste of toxic substances prevents us from their consumption, which of the following elicits the bitterness?

A. Aldehyde
B. Hydrogen ions
C. Alkaloids (Correct Answer)
D. Amino acids

Explanation: ***Alkaloids*** - **Alkaloids** are a large group of naturally occurring chemical compounds that are mostly produced by plants, often having marked physiological actions on humans and other animals. - Many alkaloids, such as **quinine** and **strychnine**, have a characteristic **bitter taste**, which serves as a natural defense mechanism for plants against herbivores. *Aldehyde* - **Aldehydes** are organic compounds characterized by a carbonyl group to which a hydrogen atom and an R-group are attached. - While some aldehydes may have strong or pungent odors, they do not typically elicit a **bitter taste** in the same way alkaloids do; some might be sweet or fruity. *Hydrogen ions* - **Hydrogen ions (H+)** are responsible for **acidity** and are detected as a **sour taste**. - The sensation of sourness is directly related to the concentration of hydrogen ions in a substance, not bitterness. *Amino acids* - **Amino acids** are the building blocks of proteins and can elicit various tastes depending on their specific structure. - Some amino acids are **sweet** (e.g., alanine, glycine), some are **umami** (e.g., glutamate), and some are **bitter** only in certain contexts or at high concentrations, but they are not the primary group defining a broad bitter taste like alkaloids.

Question 8: Which taste sensation is the most sensitive (i.e., has the lowest stimulation threshold)?

A. Sour
B. Sweet
C. Salty
D. Bitter (Correct Answer)

Explanation: ***Bitter*** - The sensation of **bitterness** serves as a protective mechanism, as many naturally occurring **toxins and poisons** are bitter. - Due to this crucial role, the **taste receptors for bitter compounds** are exceptionally sensitive, allowing detection at **very low concentrations** (threshold as low as 0.000008 M for quinine). - **Bitter taste has the lowest threshold** among all taste sensations, making it the most sensitive. *Sour* - **Sour taste** is typically triggered by **acids** (hydrogen ions) and is often associated with unripe or spoiled foods. - While important for detecting acidity, its **threshold is significantly higher** than that for bitter taste. *Sweet* - **Sweet taste** is primarily associated with **energy-rich compounds** like sugars, signaling a caloric source. - The sensitivity for sweet taste is **much lower than bitter**, with a threshold around 0.01 M for sucrose. *Salty* - **Salty taste** is primarily due to the presence of **sodium ions** and is essential for maintaining electrolyte balance. - The threshold for salty taste is **higher than bitter**, with moderate sensitivity at around 0.01 M for NaCl.

Question 9: Transection at mid-pons level with intact vagus results in:

A. Apneusis
B. Hyperventilation
C. Irregular shallow breathing
D. Deep and slow breathing (Correct Answer)

Explanation: ***Deep and slow breathing*** - A transection at the **mid-pons level** disconnects the **pneumotaxic center** from the medullary respiratory centers, while the **vagus nerves remain intact**. - Without the inhibitory input from the pneumotaxic center, inspirations become deep and prolonged due to the unopposed effect of the **apneustic center**, but the intact vagus still provides some inspiratory off-switch, preventing full apneusis. This leads to **deep and slow breathing**. *Apneusis* - **Apneusis**, characterized by prolonged inspiratory gasps, occurs when both the **pneumotaxic center and vagal afferents** (from lung stretch receptors) are non-functional or cut. - In this scenario, the vagus nerves are intact, providing an inspiratory off-switch that prevents the full development of apneusis. *Hyperventilation* - **Hyperventilation** typically results from metabolic acidosis, hypoxemia, or anxiety, leading to an increased rate and depth of breathing. - A mid-pons transection primarily affects the rhythm and duration of inspiration, not necessarily increasing the overall minute ventilation in a compensatory manner. *Irregular shallow breathing* - **Irregular shallow breathing** can be seen with damage to the **medullary respiratory centers** or severe respiratory muscle weakness. - The transection described primarily impacts the integration of pontine and medullary control, particularly the interaction between the apneustic and pneumotaxic centers, leading to deep and slow breaths, not shallow ones.

Question 10: All are effects of the parasympathetic system on the heart except?

A. Negative chronotropic
B. Negative dromotropic
C. All are seen
D. Negative inotropic (Correct Answer)

Explanation: ***Negative inotropic*** - While the parasympathetic system (via the **vagus nerve**) primarily affects the **sinoatrial (SA) and atrioventricular (AV) nodes** to decrease heart rate and conduction velocity, it has a **minimal direct effect on ventricular contractility** (inotropy) in humans. - The ventricles are less densely innervated by parasympathetic fibers compared to the atria, so acetylcholine's direct negative inotropic effect is **clinically insignificant** in a healthy heart. - This is the **EXCEPTION** - not a significant parasympathetic effect on the heart. *Negative chronotropic* - The parasympathetic system, primarily through **acetylcholine** acting on **muscarinic receptors** in the SA node, decreases the heart rate (chronotropy). - This slows the rate of spontaneous depolarization of pacemaker cells. - This **IS** a major parasympathetic effect. *Negative dromotropic* - Parasympathetic stimulation also slows the conduction velocity through the **AV node** (dromotropy). - This increases the PR interval on an ECG and can lead to various degrees of AV block in extreme cases. - This **IS** a major parasympathetic effect. *All are seen* - This option is incorrect because the **negative inotropic effect** is NOT a significant parasympathetic effect on the heart. - While negative chronotropic and negative dromotropic effects are prominent features of parasympathetic activity, the direct influence on ventricular contractility is minimal.

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