Sensory Systems Practice Questions

Q: Which of the following stimulates the macula?

All of the above. The **maculae** are the sensory receptors located within the **otolith organs** (the Utricle and Saccule) of the inner ear. They are specifically designed to detect changes in static equilibrium and linear movement. ### **Explanation of the Correct Answer** The correct answer is **D (All of the above)** because the macula functions through the displacement of **otoconia** (calcium carbonate crystals) embedded in a gelatinous membrane. 1. **Gravity (Option A):** In a static position, gravity pulls on the otoconia, providing the brain with information about the head's orientation relative to the vertical axis. 2. **Head Position Change (Option B):** Tilting the head changes the angle of gravitational pull on the macula, causing the otolithic membrane to shift and stimulate hair cells. 3. **Linear Acceleration (Option C):** The inertia of the otoconia causes them to lag behind during horizontal (utricle) or vertical (saccule) movement, stimulating the hair cells. ### **Clinical Pearls & High-Yield Facts for NEET-PG** * **Utricle vs. Saccule:** The Utricle detects **horizontal** linear acceleration (e.g., a car moving forward), while the Saccule detects **vertical** linear acceleration (e.g., riding an elevator). * **Striola:** This is the central curved ridge in the macula. Hair cells are arranged in opposite directions on either side of the striola. * **BPPV Connection:** Benign Paroxysmal Positional Vertigo occurs when otoconia from the **utricular macula** become displaced into the semicircular canals (most commonly the posterior canal). * **Angular Acceleration:** Remember that **Angular (rotational) acceleration** is sensed by the **Crista Ampullaris** in the Semicircular Canals, NOT the macula. This is a common distractor in NEET-PG questions.

Q: Impulses generated in the taste buds of the tongue reach the cerebral cortex via which structure?

Thalamus. **Explanation:** The correct answer is **Thalamus**. In the sensory pathway for gustation (taste), the thalamus acts as the essential relay station before information reaches the primary gustatory cortex. **The Pathway:** 1. **First-order neurons:** Taste impulses from the tongue are carried by the Facial (CN VII), Glossopharyngeal (CN IX), and Vagus (CN X) nerves. 2. **Second-order neurons:** These fibers synapse in the **Nucleus Tractus Solitarius (NTS)** in the medulla. Axons from the NTS ascend via the central tegmental tract. 3. **Third-order neurons:** These are located in the **Ventral Posteromedial (VPM) nucleus of the Thalamus**. From here, impulses are projected to the gustatory cortex (Insula and frontal operculum). **Why other options are incorrect:** * **Internal capsule:** While taste fibers pass through the posterior limb of the internal capsule to reach the cortex, it is a white matter tract (conduit), not the relay structure where the synapse occurs. * **Cervical spinal nerve:** These carry general somatic sensation from the neck and back of the head, not special visceral afferents like taste. * **Trigeminal nerve:** This nerve carries general sensations (touch, pain, temperature) from the anterior 2/3rd of the tongue via the lingual nerve, but it does not carry taste impulses. **High-Yield NEET-PG Pearls:** * **VPM Nucleus:** Remember the mnemonic **"VPM = Very Polar Mouth"** (relays sensory/taste from the face/mouth). In contrast, the **VPL** relays sensations from the **L**imbs/body. * **Ageusia:** Loss of taste sensation. * **NTS:** Known as the "sensory nucleus" for all visceral afferents (Taste, Baroreceptors, Chemoreceptors).

Q: In near vision, what change occurs in the eye?

The depth of focus increases.. To understand the changes in the eye during near vision, we must look at the **Near Reflex triad**: Accommodation, Convergence, and Miosis. ### **Why the correct answer is right:** **B. The depth of focus increases:** During near vision, the pupils constrict (**Miosis**). A smaller pupil acts like a pinhole camera, reducing the size of the blur circles on the retina. This physical phenomenon increases the **depth of focus** (the range over which an object can be moved without appearing out of focus), allowing for sharper vision of near objects. ### **Why the other options are wrong:** * **A. The power of the lens decreases:** Incorrect. During accommodation, the ciliary muscle contracts, causing the lens to become more spherical (convex). This **increases** the refractive power of the lens to focus divergent rays from near objects onto the retina. * **C. The lateral recti contract:** Incorrect. To maintain single binocular vision at a near point, the eyes must turn inward. This requires the contraction of both **medial recti** (Convergence), not the lateral recti. * **D. The zonular tension increases:** Incorrect. When the ciliary muscle contracts for near vision, it moves forward and inward, which **relaxes the suspensory ligaments (zonules)**. This relaxation allows the elastic lens capsule to bulge and increase its curvature. ### **High-Yield Clinical Pearls for NEET-PG:** * **Accommodation Mechanism (Helmholtz Theory):** Ciliary muscle contraction → Zonular relaxation → Increased lens curvature (mostly anterior) → Increased dioptric power. * **Presbyopia:** A physiological loss of accommodation due to age-related decrease in lens elasticity and ciliary muscle efficiency. * **Argyll Robertson Pupil:** A classic neuro-ophthalmic condition where the **Light Reflex is lost but the Accommodation Reflex is present** (Prostitute's Pupil), often seen in neurosyphilis.

Q: Which body part is represented superiorly and medially within the postcentral gyrus?

Lower limb. ### Explanation The **postcentral gyrus** of the parietal lobe houses the **Primary Somatosensory Cortex (Brodmann areas 3, 1, and 2)**. The spatial distribution of body parts in this area follows a specific pattern known as the **Sensory Homunculus**. **1. Why the Lower Limb is Correct:** The sensory homunculus is an "upside-down" representation of the body. The **lower limb (leg and foot)** and the **perineum** are represented on the **medial surface** of the hemisphere and the most **superior (dorsal)** aspect of the postcentral gyrus. These areas are supplied by the **Anterior Cerebral Artery (ACA)**. **2. Analysis of Incorrect Options:** * **A. Upper Limb:** The hand and arm are represented on the **superolateral** aspect of the postcentral gyrus. The hand, particularly the thumb and fingers, occupies a disproportionately large area due to high receptor density. * **C. Abdomen:** The trunk and abdomen are located on the upper part of the **lateral surface**, inferior to the lower limb representation but superior to the upper limb. * **D. Genitalia:** While genitalia are also represented medially, they are located most inferiorly on the medial wall, often below the representation of the toes. In the context of "superior and medial," the lower limb is the primary landmark. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Blood Supply:** A stroke involving the **Anterior Cerebral Artery (ACA)** leads to sensory and motor deficits primarily in the **contralateral lower limb**. In contrast, a **Middle Cerebral Artery (MCA)** stroke affects the face and upper limb. * **Disproportionate Representation:** The size of the cortical area is not proportional to the size of the body part, but to the **density of sensory receptors** (e.g., the lips and hands have the largest representation). * **Sequence (Medial to Lateral):** Toes → Foot → Leg → Hip → Trunk → Upper Limb → Face → Intra-abdominal.

Q: A person with defective blue color appreciation is called?

Tritanomalous. ### Explanation The question tests the nomenclature of color vision deficiencies based on the **Trichromatic Theory**. Human color vision relies on three photopigments (cones): Erythrolabe (Red/Long-wave), Chlorolabe (Green/Medium-wave), and Cyanolabe (Blue/Short-wave). **Why Tritanomalous is correct:** The suffix **"-anomalous"** refers to a deficiency or "weakness" in a specific color pigment (trichromacy is preserved, but one pigment is altered). The prefix **"Trit-"** refers to the third pigment, which is **Blue**. Therefore, a person with **Tritanomalous** vision has a defective appreciation of blue light due to an altered spectral sensitivity of the blue cones. **Analysis of Incorrect Options:** * **Deuteranomalous (A):** This refers to a "green weakness." It is the most common type of color vision deficiency. * **Deuteranopia (B):** The suffix **"-anopia"** indicates a complete absence of a pigment. Deuteranopia is the total absence of green-sensitive cones ("green blindness"). * **Tritanopia (C):** This is the total absence of blue-sensitive cones ("blue blindness"). While it involves the blue spectrum, the question specifies "defective appreciation" (weakness) rather than total absence. **NEET-PG High-Yield Pearls:** 1. **Inheritance:** Most color blindness (Red-Green) is **X-linked recessive**. However, **Tritan** defects (Blue-Yellow) are rare and typically **Autosomal Dominant** (encoded on Chromosome 7). 2. **Kollner’s Rule:** * Outer retinal diseases/macular degeneration usually cause **Blue-Yellow** defects. * Optic nerve diseases (except Glaucoma) usually cause **Red-Green** defects. 3. **Screening:** **Ishihara Charts** are the most common screening tool but are primarily designed to detect Red-Green defects, not Blue-Yellow. 4. **Gold Standard:** The **Nagel Anomaloscope** is the definitive test to differentiate between dichromacy and anomalous trichromacy.

Q: What is the function of utricle and saccule?

Linear acceleration. ***Linear acceleration***- The **utricle** and **saccule** are the two **otolithic organs** of the inner ear responsible for detecting mechanical forces related to **linear motion** (acceleration, deceleration) and the pull of gravity.- The **utricle** senses horizontal linear acceleration (e.g., walking), while the **saccule** senses vertical linear acceleration (e.g., riding an elevator).*Hearing high-frequency sounds*- Sound detection (hearing) is carried out by the **cochlea** and its associated structures, primarily the hair cells in the **Organ of Corti**.- High frequencies stimulate hair cells located near the **base** of the **basilar membrane** but this is unrelated to the vestibular functions of the utricle and saccule.*Angular acceleration*- Rotational movements of the head, or **angular acceleration**, are detected solely by the three **semicircular canals**.- The canals use the movement of endolymph to displace the **cupula** within the **ampullae**, stimulating the enclosed hair cells.*Hearing low-frequency sounds*- The **cochlea** is the auditory apparatus; the utricle and saccule are part of the **vestibular system** responsible for balance and spatial orientation.- Low frequencies primarily stimulate hair cells located near the **apex** of the **basilar membrane** (apex is furthest from the oval window).

Q: Which of the following area of visual cortex is related to color vision?

V8. ***V8*** - **V8** is a specific area within the human **visual cortex** that has been implicated in **color perception**. - Damage to this area can lead to **cerebral achromatopsia**, a condition where individuals lose the ability to perceive colors. *V1* - **V1**, also known as the **primary visual cortex**, processes basic visual information such as orientation, spatial frequency, and color. - While it processes color information, it is not considered the primary or most specialized area for **color vision** compared to V8. *V2* - **V2** receives input from V1 and is involved in processing more complex visual features, including **form, depth, and color**. - It plays a role in color processing but is less specialized for this function than V8. *V3* - **V3** is primarily involved in processing **dynamic form** and motion, with some contribution to complex visual features. - It is not extensively associated with **color perception** as its main function.

Question 1

Which of the following stimulates the macula?

Accepted Answer

All of the above

Answer

Gravity

Answer

Head position change

Answer

Linear acceleration

Question 2

Somatosensory area I has the largest representation for which body part?

Accepted Answer

Arm

Answer

Leg

Answer

Back

Answer

Head

Question 3

Stereoanesthesia is due to a lesion of which of the following?

Accepted Answer

Cerebral cortex

Answer

Nucleus Gracilis

Answer

Nucleus cuneatus

Answer

Spinothalamic tract

Question 4

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

Accepted Answer

Thalamus

Answer

Internal capsule

Answer

Cervical spinal nerve

Answer

Trigeminal nerve

Question 5

In near vision, what change occurs in the eye?

Accepted Answer

The depth of focus increases.

Answer

The power of the lens decreases.

Answer

The lateral recti contract.

Answer

The zonular tension increases.

Question 6

Which body part is represented superiorly and medially within the postcentral gyrus?

Accepted Answer

Lower limb

Answer

Upper limb

Answer

Abdomen

Answer

Genitalia

Question 7

A person with defective blue color appreciation is called?

Accepted Answer

Tritanomalous

Answer

Deuteranomalous

Answer

Deuteranopia

Answer

Tritanopia

Question 8

Bilateral destruction of the auditory cortex in humans causes what type of hearing impairment?

Accepted Answer

Deficiency in the interpretation of sounds

Answer

Almost total deafness

Answer

Hearing defect for higher frequency sounds

Answer

Inability for the orientation of sounds

Question 9

What is the function of utricle and saccule?

Accepted Answer

Linear acceleration

Answer

Hearing high-frequency sounds

Answer

Hearing low-frequency sounds

Answer

Angular acceleration

Question 10

Which of the following area of visual cortex is related to color vision?

Accepted Answer

V8

Answer

V1

Answer

V2

Answer

V3

Sensory Systems — MCQs

Sensory Systems — MCQs

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