Sensory Processing — MCQs
Sensory fibers from the taste buds in the back of the tongue and soft palate travel along:
Which tract is responsible for the loss of proprioception and fine touch?
Auditory pathway passes through -
Vibrations are detected by which types of receptors?
A female presents with loss of vision in the right halves of both eyes. Where is the lesion located in the optic pathway?
Sensations of pain from teeth and temperature are carried by
Which of the following is not true regarding Vestibular neuroma
A 30-year-old male regained consciousness 36 hours after an accident. It was then discovered that the patient is unable to create new memories. The probable site of lesion for this symptom is:
Alpha block on EEG is typically observed during which of the following activities?
Fine touch and rapidly adapting receptor is
Sensory Processing Indian Medical PG Practice Questions and MCQs
Question 1: Sensory fibers from the taste buds in the back of the tongue and soft palate travel along:
- A. Facial nerve
- B. Trigeminal nerve
- C. Vagus nerve
- D. Glossopharyngeal nerve (Correct Answer)
Explanation: ***Glossopharyngeal nerve*** - The **glossopharyngeal nerve** (cranial nerve IX) innervates the **posterior one-third of the tongue** for general sensation and taste, as well as the **palatoglossal arch** and **soft palate** [1]. - This nerve carries taste sensations from taste buds located in these regions to the brainstem [1]. *Trigeminal nerve* - The **trigeminal nerve** (cranial nerve V) is primarily responsible for **general sensation** from the face, oral cavity, and anterior two-thirds of the tongue, but it does **not** carry taste fibers. - It also provides motor innervation to the muscles of mastication. *Facial nerve* - The **facial nerve** (cranial nerve VII) carries taste sensation from the **anterior two-thirds of the tongue** via the chorda tympani, not the posterior tongue or soft palate. - It also controls the muscles of facial expression. *Vagus nerve* - The **vagus nerve** (cranial nerve X) plays a minor role in taste, primarily innervating taste buds in the **epiglottis** and **pharynx**, which are not specified in this question [1]. - Its main functions include parasympathetic innervation to many visceral organs.
Question 2: Which tract is responsible for the loss of proprioception and fine touch?
- A. Anterior spinothalamic tract
- B. Lateral spinothalamic tract
- C. Dorsal column (Correct Answer)
- D. Corticospinal tract
Explanation: ***Dorsal column*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting **fine touch**, **vibration**, and **proprioception** from the body to the cerebral cortex. - Damage to this tract (e.g., in **tabes dorsalis** or **vitamin B12 deficiency**) leads to a loss of these sensations. *Anterior spinothalamic tract* - This tract primarily conveys crude touch and pressure sensations. - While it carries tactile information, it does not transmit the fine discriminative touch or proprioception associated with the dorsal columns. *Lateral spinothalamic tract* - This pathway is responsible for transmitting **pain** and **temperature** sensations. - It does not play a role in proprioception or fine touch. *Corticospinal tract* - The **corticospinal tract** is a **motor pathway** responsible for voluntary movement. - It has no role in transmitting sensory information such as proprioception or fine touch.
Question 3: Auditory pathway passes through -
- A. Fornix
- B. Lateral geniculate body
- C. Medial geniculate body (Correct Answer)
- D. Reticular formation
Explanation: ***Medial geniculate body*** - The **medial geniculate body (MGB)** is the **thalamic relay nucleus** for the **auditory pathway** [1] - It receives input from the **inferior colliculus** and projects to the **primary auditory cortex** (Heschl's gyrus) in the temporal lobe [1], [3] - Essential for processing and relaying auditory information from the brainstem to the cortex *Fornix* - The **fornix** is a C-shaped white matter tract that is part of the **limbic system**, connecting the hippocampus to the mammillary bodies and septal nuclei [2] - It is primarily involved in **memory consolidation** and emotional processing, not auditory function - Not a component of the auditory pathway *Lateral geniculate body* - The **lateral geniculate body (LGB)** is the **thalamic relay nucleus** for the **visual pathway** - It receives input from the retina via the optic tract and projects to the primary visual cortex - Dedicated exclusively to visual processing, not auditory information *Reticular formation* - The **reticular formation** is a diffuse network of neurons in the brainstem involved in **arousal, consciousness, sleep-wake cycles**, and autonomic regulation [2] - While it can modulate attention to auditory stimuli through ascending reticular activating system (ARAS), it is not part of the **primary ascending auditory pathway** - The dedicated auditory pathway goes: cochlear nuclei → superior olivary complex → lateral lemniscus → inferior colliculus → medial geniculate body → auditory cortex [1], [3]
Question 4: Vibrations are detected by which types of receptors?
- A. Slowly adapting
- B. Rapidly adapting (Correct Answer)
- C. Non-adapting
- D. None of the above
Explanation: ***Rapidly adapting*** - **Rapidly adapting mechanoreceptors**, such as **Pacinian corpuscles** and **Meissner's corpuscles**, are highly sensitive to changes in pressure and movement. - They fire at the **onset and offset of a stimulus**, making them ideal for detecting vibrations, which are rhythmic changes in pressure. *Slowly adapting* - **Slowly adapting mechanoreceptors**, such as **Merkel cells** and **Ruffini endings**, are responsible for sustained pressure and touch. - They continue to fire as long as the stimulus is present, making them less suited for detecting transient vibratory stimuli. *Non-adapting* - The human body does not typically have **truly non-adapting** sensory receptors; most receptors show some form of adaptation to continuous stimuli. - This term is not standard in the classification of mechanoreceptors based on their adaptation rates. *None of the above* - This option is incorrect because rapidly adapting receptors are indeed responsible for detecting vibrations.
Question 5: A female presents with loss of vision in the right halves of both eyes. Where is the lesion located in the optic pathway?
- A. Left optic tract (Correct Answer)
- B. Optic radiation
- C. Optic chiasma
- D. Right optic tract
Explanation: Left optic tract - A lesion in the **left optic tract** causes **right homonymous hemianopsia**, meaning loss of vision in the right halves of both eyes [1]. - This is because the left optic tract carries visual information from the **nasal retina of the right eye** and the **temporal retina of the left eye**, both of which process the right visual field [1]. *Optic radiation* - A lesion in the optic radiation would also cause a **homonymous hemianopsia** but depending on the specific location within the radiation, it could result in a **quadrantanopia** (loss of a quarter visual field) rather than a complete hemianopsia. - The optic radiation projects from the **lateral geniculate nucleus** to the **visual cortex**, and damage here affects the post-chiasmatic visual pathway [1]. *Optic chiasma* - A lesion at the **optic chiasma** typically results in **bitemporal hemianopsia**, which is the loss of vision in the **temporal halves of both eyes** [1]. - This occurs because the **crossing nasal fibers** from both eyes, which carry information from the temporal visual fields, are affected [1]. *Right optic tract* - A lesion in the **right optic tract** would result in **left homonymous hemianopsia**, meaning loss of vision in the **left halves of both eyes** [1]. - This is due to the right optic tract carrying fibers from the **nasal retina of the left eye** and the **temporal retina of the right eye**, both of which process the left visual field [1].
Question 6: Sensations of pain from teeth and temperature are carried by
- A. Lateral spinothalamic tract (Correct Answer)
- B. Trigeminal nerve pathway
- C. Ventral spinothalamic tract
- D. Corticospinal tract
Explanation: ***Lateral spinothalamic tract*** - The **lateral spinothalamic tract** primarily carries sensations of **pain and temperature** from the body to the brain. - This pathway is crucial for transmitting these somatosensory modalities from the periphery, including dental structures, up the spinal cord to the **thalamus** and then to the cerebral cortex. *Trigeminal nerve pathway* - The **trigeminal nerve (CN V)** is responsible for sensory innervation of the face, including teeth, and jaw motor function. - While it transmits sensory information from the teeth, its central pathway eventually synapses with the **trigeminal lemniscus** which then projects to the thalamus, rather than directly being the spinothalamic tract itself. *Ventral spinothalamic tract* - The **ventral (anterior) spinothalamic tract** primarily carries sensations of **crude touch and pressure**. - It does not significantly contribute to the transmission of pain and temperature, which are the main sensations from teeth and temperature described. *Corticospinal tract* - The **corticospinal tract** is a major **motor pathway** that originates in the cerebral cortex and descends to the spinal cord. - It is responsible for **voluntary fine motor control** of the limbs and body, having no role in carrying sensory information like pain or temperature.
Question 7: Which of the following is not true regarding Vestibular neuroma
- A. Nystagmus
- B. High frequency sensorineural deafness
- C. Absence of caloric response
- D. Normal Corneal reflex (Correct Answer)
Explanation: ***Absence of caloric response*** - A **vestibular schwannoma** (acoustic neuroma) typically arises from the **vestibular nerve**, causing early impairment of **vestibular function**. - This often manifests as a **reduced or absent caloric response** in the affected ear, indicating damage to the peripheral vestibular system. *Normal Corneal reflex* - The **corneal reflex** tests the integrity of the **trigeminal nerve (CN V)** for the afferent limb and the **facial nerve (CN VII)** for the efferent limb. - While a large vestibular schwannoma can compress the trigeminal nerve and cause a diminished corneal reflex, early-stage tumors, or smaller tumors less commonly lead to this finding. *Nystagmus* - **Nystagmus** is an involuntary rhythmic eye movement and can be a sign of **vestibular dysfunction**, which is characteristic of a vestibular schwannoma. - It often presents as a **vestibular nystagmus**, which can be spontaneous or provoked, particularly in the early stages as the tumor affects balance pathways. *High frequency sensorineural deafness* - **Sensorineural hearing loss** is a classic and often the earliest symptom of a vestibular schwannoma, as the tumor compresses the **cochlear nerve**. - The hearing loss typically affects **higher frequencies** first and is progressive and unilateral.
Question 8: A 30-year-old male regained consciousness 36 hours after an accident. It was then discovered that the patient is unable to create new memories. The probable site of lesion for this symptom is:
- A. Hippocampus (Correct Answer)
- B. Amygdala
- C. Neocortex
- D. Hypothalamus
Explanation: ***Hippocampus*** - The **hippocampus** is a critical brain structure for the formation of **new declarative memories** (episodic and semantic memory). Damage to this area, often seen after trauma or anoxia, typically leads to **anterograde amnesia**. - The inability to create new memories (anterograde amnesia) is a classic symptom of **hippocampal damage**, as this region plays a vital role in memory consolidation from short-term to long-term memory. *Amygdala* - The **amygdala** is primarily involved in processing **emotions**, particularly fear, and plays a role in the formation and retrieval of **emotional memories**. - Damage to the amygdala would more likely result in deficits in emotional processing or the emotional component of memories, rather than a general inability to form new declarative memories. *Neocortex* - The **neocortex** is responsible for higher-level cognitive functions, including **long-term storage of memories**, language, perception, and voluntary movement. - While memories are ultimately stored in the neocortex, damage to this area would typically manifest as deficits in specific cognitive functions (e.g., aphasia, agnosia) or affect previously stored memories, rather than the initial formation of new memories. *Hypothalamus* - The **hypothalamus** is a key brain structure for regulating various **autonomic functions** and **hormone release**, including body temperature, hunger, thirst, and circadian rhythms. - While it has indirect connections to memory circuits, damage to the hypothalamus would primarily lead to disruptions in homeostatic processes, not specifically the inability to form new memories.
Question 9: Alpha block on EEG is typically observed during which of the following activities?
- A. Seizures
- B. Concentrating (Correct Answer)
- C. Sleep
- D. None of the options
Explanation: ***Concentrating*** - **Alpha rhythm** (8-13 Hz) is strongest in the **posterior regions** of the brain during quiet wakefulness with closed eyes. - When a person opens their eyes or engages in mental activity like concentrating, the alpha rhythm **attenuates or disappears**, a phenomenon known as alpha blocking or **alpha desynchronization**. *Sleep* - During sleep, the EEG activity changes from alpha to slower rhythms like **theta** (4-7 Hz) and **delta** (0.5-3 Hz), along with the appearance of sleep spindles and K-complexes. - **Alpha waves diminish** significantly or are entirely absent, substituted by these other waveforms. *Seizures* - Seizures are characterized by **abnormal, hypersynchronous neuronal activity**, which manifests on EEG as abrupt changes in frequency, amplitude, and morphology, such as **spikes and sharp waves**, or generalized spike-and-wave discharges. - While alpha rhythms might be present in the interictal period, the ictal phase shows distinct, abnormal activity, not normal alpha blocking. *None of the options* - This option is incorrect because alpha block is a well-described phenomenon associated with specific mental states. - **Concentrating** directly causes the attenuation of alpha rhythms.
Question 10: Fine touch and rapidly adapting receptor is
- A. Ruffini's nerve ending
- B. Pacinian corpuscle
- C. Meissners corpuscle (Correct Answer)
- D. Merkel's disc
Explanation: ***Meissners corpuscles*** - They are responsible for **discriminative touch** and ability to differentiate between two points close together. - These receptors are **rapidly adapting**, meaning they respond strongly to initial stimulation but quickly cease firing if the stimulus is constant. *Ruffini's nerve ending* - These are **slowly adapting receptors** sensitive to **stretch** and sustained pressure. - They provide information about **proprioception** and the shape of objects. *Pacinian corpuscle* - Pacinian corpuscles are **rapidly adapting mechanoreceptors** sensitive to **vibration** and deep pressure. - They have a large receptive field and are less involved in fine touch discrimination. *Merkel's disc* - Merkel's discs are **slowly adapting mechanoreceptors** responsible for sensing sustained touch and **pressure**. - They contribute to the perception of **texture** and edges, having a small receptive field.
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