Sensory Systems Practice Questions

Q: What is true about visceral pain?

It is poorly localized.. ### Explanation **Correct Answer: A. It is poorly localized.** Visceral pain originates from internal organs and is characterized by its diffuse nature. This occurs because the density of sensory receptors in the viscera is significantly lower than in the skin. Furthermore, visceral afferent fibers from different organs often converge onto the same second-order neurons in the spinal cord (multisegmental innervation), making it difficult for the cerebral cortex to pinpoint the exact site of origin. **Analysis of Incorrect Options:** * **B. It resembles "fast pain":** Visceral pain is typically described as "slow pain" (dull, aching, or burning). Fast pain is sharp, pricking, and localized, characteristic of cutaneous (skin) injury. * **C. It is mediated by B fibers:** Visceral pain is primarily mediated by **unmyelinated C fibers** (slow pain) and some small myelinated **A-delta fibers**. B fibers are preganglionic autonomic fibers and do not transmit pain. * **D. It shows relatively rapid adaptation:** Pain receptors (nociceptors) are **non-adapting** or very slowly adapting. This is a protective mechanism; if pain adapted quickly, the body would ignore ongoing tissue damage. **High-Yield Clinical Pearls for NEET-PG:** 1. **Referred Pain:** Because visceral and somatic nociceptors converge on the same dorsal horn neurons (Dermatomal Rule), visceral pain is often felt in a somatic structure (e.g., Kehr’s sign: splenic rupture causing left shoulder pain). 2. **Stimuli for Visceral Pain:** Unlike the skin, the viscera are insensitive to cutting or burning. The primary triggers are **distension** (stretch), **ischemia**, **inflammation**, and **smooth muscle spasm**. 3. **Autonomic Association:** Severe visceral pain is frequently accompanied by autonomic responses like nausea, vomiting, and changes in blood pressure.

Q: Angular movement is sensed by:

Semicircular canal. ### Explanation The vestibular apparatus in the inner ear is responsible for maintaining equilibrium and sensing motion. It is divided into two functional units: the **Semicircular Canals** and the **Otolith Organs**. **1. Why Semicircular Canals are correct:** The three semicircular canals (anterior, posterior, and lateral) are oriented at right angles to each other to sense motion in three-dimensional space. They contain **endolymph** and a sensory structure called the **crista ampullaris**. When the head undergoes **angular (rotational) acceleration**, the inertia of the endolymph causes it to push against the **cupula**, bending the hair cells and triggering neural impulses. **2. Why the other options are incorrect:** * **Cochlea:** This is the organ of hearing, not balance. It converts sound waves into electrical signals via the Organ of Corti. * **Saccule & Utricle:** These are known as the **Otolith Organs**. They contain **maculae** and sense **linear acceleration** and **static tilt** (gravity). Specifically, the Utricle senses horizontal linear acceleration (e.g., a moving car), while the Saccule senses vertical linear acceleration (e.g., an elevator). **High-Yield NEET-PG Pearls:** * **Sensory Receptor:** Crista Ampullaris (Semicircular canals) vs. Macula (Otolith organs). * **Medium:** Semicircular canals detect the *rate of change* of angular velocity, not constant velocity. * **Clinical Correlation:** Benign Paroxysmal Positional Vertigo (BPPV) most commonly involves displaced otoconia (from the utricle) entering the **posterior semicircular canal**. * **Caloric Reflex Test:** Used to test the horizontal semicircular canal (COWS: Cold Opposite, Warm Same).

Q: Which is the only sensory modality that does not reach the thalamus directly?

Olfaction. ### Explanation **Correct Answer: C. Olfaction** The **thalamus** is often referred to as the "Gateway to the Cerebral Cortex" because almost all sensory information is filtered and processed through its nuclei before reaching the primary sensory areas. **Olfaction (smell)** is the unique exception to this rule. **Why Olfaction is the correct answer:** Olfactory pathways are phylogenetically the oldest sensory system. The axons of the olfactory bulb (forming the olfactory tract) bypass the thalamus and project **directly** to the **primary olfactory cortex** (piriform cortex, amygdala, and entorhinal cortex) in the temporal lobe. While olfactory information eventually reaches the thalamus (specifically the Mediodorsal nucleus) for odor discrimination and integration, it does so only **after** reaching the cortex. **Why the other options are incorrect:** * **A. Proprioception:** Conscious proprioception travels via the Dorsal Column-Medial Lemniscus (DCML) pathway and synapses in the **Ventral Posterolateral (VPL)** nucleus of the thalamus. * **B. Taste:** Gustatory pathways from the tongue (via CN VII, IX, X) synapse in the Nucleus Tractus Solitarius (NTS) and then project to the **Ventral Posteromedial (VPM)** nucleus of the thalamus. * **C. Pain and Temperature:** These modalities travel via the Lateral Spinothalamic tract and synapse in the **VPL nucleus** of the thalamus before reaching the somatosensory cortex. **High-Yield Clinical Pearls for NEET-PG:** * **Thalamic Nuclei Mnemonic:** **VPL** (Ventral Posterolateral) = **L**imbs/Body; **VPM** (Ventral Posteromedial) = **M**akeup/Face & Mouth (Taste). * **Lateral Geniculate Body (LGB):** Relay center for **L**ight (Vision). * **Medial Geniculate Body (MGB):** Relay center for **M**usic (Hearing). * **Anosmia** (loss of smell) can be an early clinical sign of neurodegenerative diseases like Parkinson’s or Alzheimer’s.

Q: Obnoxious smell and olfactory hallucinations are typically seen in lesions of which brain lobe?

Temporal lobe. **Explanation:** The correct answer is **Temporal lobe**. **1. Why Temporal Lobe is Correct:** The primary olfactory cortex is located in the **uncus** and the **parahippocampal gyrus**, which are parts of the medial temporal lobe. Lesions in this area—most commonly due to temporal lobe epilepsy (complex partial seizures) or tumors—irritate the olfactory pathways. This irritation leads to **"uncinate fits,"** characterized by olfactory hallucinations. These hallucinations are typically **obnoxious** (cacosmia), involving unpleasant smells like burning rubber, rotten eggs, or chemicals. **2. Why Other Options are Incorrect:** * **Frontal Lobe:** While the orbitofrontal cortex is involved in the conscious perception and discrimination of odors, lesions here typically result in **anosmia** (loss of smell), especially in cases like Foster Kennedy Syndrome, rather than hallucinations. * **Parietal Lobe:** This lobe is primarily responsible for somatosensory processing (touch, pressure, pain) and spatial awareness. Lesions here cause sensory deficits or agnosia, not olfactory symptoms. * **Occipital Lobe:** This is the visual processing center. Lesions here result in visual field defects (e.g., homonymous hemianopia) or visual hallucinations, not olfactory ones. **3. High-Yield Clinical Pearls for NEET-PG:** * **Uncinate Fits:** A classic term for temporal lobe seizures presenting with foul-smelling hallucinations and a "dreamy state." * **Pathway Uniqueness:** Olfaction is the **only** sensory modality that reaches the cerebral cortex (temporal lobe) without first relaying in the thalamus. * **Entorhinal Cortex:** Located in the temporal lobe, it serves as the main interface between the hippocampus and the neocortex, playing a vital role in memory and odor association.

Q: Mydriasis is due to?

Contraction of radial muscles. **Explanation:** The size of the pupil is determined by the balance between two smooth muscles in the iris: the **sphincter pupillae** (circular muscle) and the **dilator pupillae** (radial muscle). **1. Why the correct answer is right:** **Mydriasis** refers to the dilation of the pupil. This occurs when the **radial muscles (dilator pupillae)** of the iris contract. These muscles are under **sympathetic control** (via alpha-1 adrenergic receptors). When they contract, they pull the inner edge of the iris outward, increasing the pupillary diameter to allow more light to enter the eye (the "fight or flight" response). **2. Why the incorrect options are wrong:** * **Relaxation of radial muscle:** This would lead to passive narrowing of the pupil, not dilation. * **Contraction of ciliary muscle:** The ciliary muscle controls the curvature of the lens for **accommodation**, not pupil size. Contraction of the ciliary muscle relaxes the suspensory ligaments, making the lens more globular for near vision. * **Relaxation of ciliary muscle:** This occurs during far vision to flatten the lens; it has no direct effect on pupillary diameter. **3. NEET-PG High-Yield Pearls:** * **Miosis (Pupillary Constriction):** Caused by the contraction of **circular muscles** (sphincter pupillae) via **parasympathetic** fibers (Cranial Nerve III). * **Nerve Supply:** Sympathetic supply for mydriasis originates from the **Ciliospinal center of Budge (C8-T2)**. * **Pharmacology Link:** * **Atropine** causes mydriasis by blocking parasympathetic action. * **Phenylephrine** causes mydriasis by stimulating alpha-1 receptors on radial muscles. * **Horner’s Syndrome:** Characterized by miosis due to loss of sympathetic supply to the radial muscles.

Q: Endolymph is secreted by which structure?

Stria vascularis. **Explanation:** The correct answer is **Stria vascularis**. **1. Why Stria Vascularis is Correct:** The stria vascularis is a highly vascularized layer of stratified epithelium located on the lateral wall of the **cochlear duct (scala media)**. It is the primary site for the production and secretion of **endolymph**. Unlike most extracellular fluids, endolymph is unique because it is rich in **Potassium (K+)** and low in Sodium (Na+), resembling intracellular fluid. The stria vascularis maintains this high positive potential (+80 mV, known as the endocochlear potential) which is essential for the transduction of sound by hair cells. **2. Why Other Options are Incorrect:** * **Basilar membrane:** This is a structural framework that supports the Organ of Corti. It vibrates in response to sound waves but has no secretory function. * **Cochlear duct:** While the endolymph is *contained* within the cochlear duct (scala media), the duct itself is a space. The specific structure within it that secretes the fluid is the stria vascularis. * **Hensen cells:** These are supportive cells located lateral to the outer hair cells in the Organ of Corti. They provide structural support but do not secrete endolymph. **3. High-Yield Clinical Pearls for NEET-PG:** * **Composition:** Endolymph (High K+, Low Na+); Perilymph (High Na+, Low K+ — similar to ECF/CSF). * **Absorption:** Endolymph is drained/absorbed by the **endolymphatic sac**. * **Meniere’s Disease:** Caused by the distension of the membranous labyrinth due to overproduction or decreased absorption of endolymph (**Endolymphatic Hydrops**), leading to vertigo, tinnitus, and sensorineural hearing loss. * **Blood Supply:** The stria vascularis is supplied by the **labyrinthine artery** (usually a branch of the AICA).

Question 1

Regarding color vision, which of the following statements is true?

Accepted Answer

It involves opponent color cells.

Answer

It is independent of the wavelength of light.

Answer

It depends on intensity discrimination.

Answer

It is minimal at the fixation point.

Question 2

What is true about visceral pain?

Accepted Answer

It is poorly localized.

Answer

It resembles "fast pain" produced by noxious stimulation of the skin.

Answer

It is mediated by B fibers in the dorsal root of the spinal nerve.

Answer

It shows relatively rapid adaptation.

Question 3

Angular movement is sensed by:

Accepted Answer

Semicircular canal

Answer

Cochlea

Answer

Saccule

Answer

Utricle

Question 4

Which is the only sensory modality that does not reach the thalamus directly?

Accepted Answer

Olfaction

Answer

Proprioception

Answer

Taste

Answer

Pain and temperature

Question 5

Obnoxious smell and olfactory hallucinations are typically seen in lesions of which brain lobe?

Accepted Answer

Temporal lobe

Answer

Frontal lobe

Answer

Parietal lobe

Answer

Occipital lobe

Question 6

Mydriasis is due to?

Accepted Answer

Contraction of radial muscles

Answer

Relaxation of ciliary muscle

Answer

Relaxation of radial muscle

Answer

Contraction of ciliary muscle

Question 7

Efferents from the cochlear nucleus arise for which of the following structures?

Accepted Answer

Superior olivary nucleus

Answer

Inferior colliculus

Answer

Medial geniculate body

Answer

Lateral lemniscus

Question 8

In pupillary reflex, which cranial nerves are tested?

Accepted Answer

Both 2nd and 3rd cranial nerves

Answer

2nd cranial nerve

Answer

3rd cranial nerve

Answer

4th cranial nerve

Question 9

Which of the following is the basis for referred pain?

Accepted Answer

Some visceral pain signals and pain signals from the skin provide convergent input to a common set of neurons in the dorsal horn

Answer

Visceral pain signals and pain signals from the skin synapse with separate populations of neurons in the dorsal horn

Answer

Visceral pain transmission and pain transmission from the skin are received by a common set of neurons in the thalamus

Answer

Visceral pain signals are rarely of sufficient magnitude to exceed the threshold of activation of dorsal horn neurons

Question 10

Endolymph is secreted by which structure?

Accepted Answer

Stria vascularis

Answer

Basilar membrane

Answer

Cochlear duct

Answer

Hensen cell

Sensory Systems — MCQs

Sensory Systems — MCQs

On this page

Practice by Chapter

Want unlimited practice?