Sensory Systems Practice Questions

Q: The image given below shows stapedial reflex. What does ' $X$ ' denote?

Superior olivary complex. ***Superior olivary complex*** - The image depicts the neural pathway for the **stapedial reflex**, where sound input from the cochlea is processed, and the signal travels to the superior olivary complex. - From the superior olivary complex (labeled 'X'), signals project to the **facial nerve nucleus**, which then innervates the **stapedius muscle** to contract and dampen sound. *Medial geniculate body* - The medial geniculate body is part of the **thalamus** and is involved in processing auditory information before it reaches the auditory cortex. - It is a more rostral structure in the auditory pathway and is not directly involved in the brainstem reflex arc of the stapedius reflex at the labeled point 'X'. *Superior colliculus* - The superior colliculus is primarily involved in **visual reflexes** and directing gaze towards salient stimuli. - Although it has some multimodal sensory integration, it is not a key relay in the auditory pathway for the stapedial reflex. *Lateral lemniscus* - The lateral lemniscus is an **ascending auditory pathway** in the brainstem, carrying information from the cochlear nuclei and superior olivary complex to higher centers like the inferior colliculus. - While it carries auditory signals, "X" represents a more specific processing center (superior olivary complex) that integrates bilateral auditory input and projects to motor nuclei for acoustic reflexes.

Q: What is correct about the composition of fluid in the area marked as X?

Na = 3 mEq/L, K = 150 mEq/L, Chloride = 125 mEq/L. ***Na = 3 mEq/L, K = 150 mEq/L, Chloride = 125 mEq/L*** - The area marked as X points to the **endolymph** within the scala media of the cochlea, which has a unique high **potassium concentration** (~150 mEq/L) and low **sodium concentration** (~3 mEq/L). - This composition is maintained by the **stria vascularis** and is essential for proper **hair cell function** and hearing transduction. - The high K⁺/low Na⁺ ratio creates the **endocochlear potential** (+80 mV) necessary for cochlear amplification. *Na = 150 mEq/L, K = 3 mEq/L, Chloride = 125 mEq/L* - This represents typical **extracellular fluid** or **perilymph** composition with high sodium and low potassium, which is the opposite of endolymph. - The **perilymph** is found in the scala vestibuli and scala tympani, not in the area marked as X (scala media). *Na = 152 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L* - The sodium level is too high and potassium too low to represent **endolymph**, which requires an extreme K⁺/Na⁺ gradient for proper cochlear function. - These intermediate values don't match any specific **cochlear fluid compartment** and would not support normal hearing. *Na = 50 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L* - Both sodium and potassium levels are insufficient to create the **electrochemical gradient** necessary for cochlear hair cell depolarization. - These values don't correspond to either **endolymph** or **perilymph** compositions found in the inner ear.

Q: What is correct about the composition of fluid in the area marked as $X$ ?

Na = 3 mEq/L, K = 150 mEq/L, Chloride = 125 mEq/L. ***Na = 3 mEq/L, K = 150 mEq/L, Chloride = 125 mEq/L*** - The area marked 'X' represents the **scala media** in the cochlear cross-section, which contains **endolymph**. - Endolymph has a unique ionic composition with **high potassium concentration** (150 mEq/L) and **low sodium concentration** (3 mEq/L), similar to intracellular fluid. *Na = 150 mEq/L, K = 3 mEq/L, Chloride = 125 mEq/L* - This composition represents **perilymph**, found in the **scala vestibuli** and **scala tympani**, not in the scala media. - Perilymph has high Na+ and low K+ concentrations, resembling **cerebrospinal fluid** and extracellular fluid. *Na = 150 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L* - The **potassium level of 30 mEq/L** is intermediate and doesn't match any physiological cochlear fluid composition. - This value is too high for perilymph (normally 3 mEq/L) and too low for endolymph (normally 150 mEq/L). *Na = 50 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L* - The **sodium concentration of 50 mEq/L** is abnormally low for any extracellular fluid compartment. - Neither the Na+ nor K+ values correspond to the known ionic gradients essential for **cochlear hair cell function**.

Q: Which of the following cells in the brain are responsible for handling information regarding ability to read the slide below? (Recent NEET Pattern 2016-17)

Parvocellular cells. ***Parvocellular cells*** - **Parvocellular cells** (P-cells) are responsible for processing detailed visual information, including **color**, **form**, and fine **texture**. Reading the Ishihara test requires the ability to distinguish specific colors and fine patterns. - They have **small receptive fields** and transmit information about high spatial resolution and chromatic detail, crucial for tasks such as reading and recognizing fine visual cues. *Magnocellular cells* - **Magnocellular cells** (M-cells) are primarily involved in detecting **motion** and processing **low-spatial frequency information**, such as global shape and location. - They have **large receptive fields** and are not primarily responsible for detailed color or pattern discrimination needed for reading. *Purkinje cells* - **Purkinje cells** are a type of large, extensively branched neuron located in the **cerebellar cortex**. - Their primary function is motor coordination, balance, and motor learning, not visual processing or reading. *Pyramidal cells* - **Pyramidal cells** are excitatory neurons found in the cerebral cortex and hippocampus, characterized by their pyramidal-shaped cell bodies. - While they are involved in complex cognitive functions, including parts of visual perception, they are not the specific cells in the primary visual pathway responsible for initial processing of fine details and color as required for reading this type of visual test.

Q: The image given below shows:

Dark adaptation curve. ***Dark adaptation curve*** - The image displays the change in **threshold luminance** over time, specifically showing two distinct phases of recovery of sensitivity: an initial rapid phase (cones) and a later, slower, more sensitive phase (rods). - This bimodal curve is characteristic of the **dark adaptation process**, where the eye adjusts from bright to dim light, increasing its sensitivity to light stimuli. *Visual evoked response* - A **visual evoked response (VER)** measures the electrical signals generated in the brain in response to visual stimuli. - VER graphs typically show amplitude and latency of brain activity, not a curve of threshold luminance over time. *Contrast sensitivity plot* - A **contrast sensitivity plot** illustrates the ability to distinguish between different levels of contrast at various spatial frequencies. - This is usually depicted as a curve showing contrast sensitivity as a function of spatial frequency, which is different from the time-dependent threshold luminance shown. *Electroretinography curve* - **Electroretinography (ERG)** measures the electrical responses of various retinal cell types to light stimuli. - An ERG curve typically shows a characteristic waveform with specific a-wave and b-wave components, representing photoreceptor and bipolar cell activity, which is not what is presented in the image.

Q: All are true about the recording shown except:

C wave is due to activation of optic nerve. ***C wave is due to activation of optic nerve*** - The **C wave** in an electroretinogram (ERG) primarily reflects the activity of the **retinal pigment epithelium (RPE)** and its interaction with the photoreceptors, not the optic nerve. - The optic nerve's activity (ganglion cell action potentials) is usually recorded as part of the **pattern ERG** or visual evoked potentials (VEPs), not directly as the C wave on a full-field ERG. *R1 is due to photochemical reactions in outer segment of rods and cones* - The early receptor potential (**ERP**), which includes R1 and R2 components, is indeed a very early electrical event generated by the **photochemical changes** in the outer segments of photoreceptors (rods and cones) upon light stimulation. - It occurs almost instantaneously after light absorption due to molecular changes in the photopigments. *A wave is due to photoreceptor activity* - The **A wave** (or a-wave) of the ERG represents the **hyperpolarization of photoreceptors** (rods and cones) in response to light. - It is typically a negative deflection and its amplitude reflects the number and function of the photoreceptors. *B wave is due to response of bipolar cells* - The **B wave** (or b-wave) is a positive deflection and is primarily generated by the activity of **on-bipolar cells** and Müller cells in the inner retina. - Its amplitude is often used to assess the function of these retinal layers.

Q: A woman suffered a sunburn while enjoying a vacation on the beach. Now, while taking a shower, the lukewarm water (40° C) touching her back caused her to feel pain. What types of receptors were activated by the lukewarm water, and why did she experience pain?

Thermal nociceptors & allodynia. ***Thermal nociceptors & allodynia*** - Sunburn causes tissue damage, leading to the sensitization of **thermal nociceptors** (e.g., TRPV1 channels), making them responsive to normally innocuous thermal stimuli. - **Allodynia** is the perception of pain from a stimulus that does not ordinarily cause pain, such as lukewarm water after a sunburn, due to increased sensitivity of the pain pathways. *Thermal nociceptors & nociceptive pain* - While thermal nociceptors are involved, **nociceptive pain** typically refers to pain caused by direct tissue damage from a noxious (harmful) stimulus. Here, the lukewarm water itself is not noxious. - The pain experienced from the lukewarm water is not due to a *new* noxious stimulus but rather an exaggerated response to a *non-noxious* one. *Innocuous thermal receptors and hyperalgesia* - **Innocuous thermal receptors** (e.g., TRPM8 for cold, TRPV3/TRPV4 for warmth) normally detect non-painful temperature changes, not pain from sunburn. - **Hyperalgesia** is an increased response to a stimulus that *is* normally painful, but applied at a lower intensity. The lukewarm water is not normally painful. *Innocuous thermal receptors and allodynia* - As mentioned, **innocuous thermal receptors** are not primarily responsible for pain transmission, even in a sensitized state, as they are not nociceptors. - While **allodynia** is an accurate description of the pain type, the primary receptors activated for the pain sensation are sensitized nociceptors, not innocuous thermal receptors.

Q: Select the correct option regarding the function of receptors:

Pacinian corpuscle - fast vibration. ***Pacinian corpuscle - fast vibration*** - **Pacinian corpuscles** are rapidly adapting mechanoreceptors that are highly sensitive to **vibrations** and **deep pressure**. - Their layered structure allows them to detect even slight deformations and transmit information about **rapid changes** in mechanical stimuli. *Merkel cells - slow vibration* - **Merkel cells** are slow-adapting mechanoreceptors primarily responsible for sensing **light touch**, **texture**, and sustained pressure. - They are not associated with the detection of vibrations, whether slow or fast. *Meissner's corpuscle - stretch* - **Meissner's corpuscles** are rapidly adapting mechanoreceptors that detect **light touch**, **low-frequency vibration**, and discriminatory touch. - **Stretch sensation** is primarily mediated by Ruffini corpuscles and muscle spindle organs. *Ruffini corpuscle - light touch* - **Ruffini corpuscles** are slow-adapting mechanoreceptors that respond to **sustained pressure**, skin **stretch**, and joint position. - **Light touch** is primarily detected by Merkel cells and Meissner's corpuscles.

Q: Sour taste is mediated by which of the following receptors?

OTOP1. ***OTOP1*** - The **OTOP1** receptor, an **otopetrin protein**, is responsible for detecting the **sour taste** sensation by mediating proton influx. - It functions as a **proton channel**, allowing hydrogen ions (H+) from acidic substances to enter taste receptor cells. *T1R1* - **T1R1** is a component of the **umami (savory) taste receptor**, forming a heterodimer with T1R3 to detect glutamate. - It does not directly detect sourness but is involved in the perception of amino acids. *T1R2* - **T1R2** is a component of the **sweet taste receptor**, forming a heterodimer with T1R3 to detect sugars. - This receptor is not involved in the transduction of sour taste. *T1R3* - **T1R3** is a common subunit that combines with **T1R1** for umami taste and with **T1R2** for sweet taste. - While essential for sweet and umami, it does not directly mediate the perception of sourness.

Q: Match the following receptors with their correct functions: Receptors: 1. Ruffini corpuscle 2. Merkel cells 3. Pacinian corpuscle 4. Meissner's corpuscle Functions: A. Vibration B. Sustained pressure C. Stretching D. Fine touch Select the option that correctly matches each receptor (1-4) with its function (A-D).

1C 2B 3A 4D. ***1C 2B 3A 4D*** - **Ruffini corpuscles** (1) detect **stretching** (C) of the skin. They are **slow-adapting Type II mechanoreceptors** located deep in the dermis, responding to sustained skin stretch and contributing to proprioception. - **Merkel cells** (2) detect **sustained pressure** (B) and fine texture discrimination. They are **slow-adapting Type I mechanoreceptors** with the highest spatial resolution, providing detailed information about touch. - **Pacinian corpuscles** (3) detect **vibration** (A), particularly high-frequency vibrations (200-300 Hz). They are **rapidly adapting receptors** with an onion-like lamellated structure located deep in the dermis and subcutaneous tissue. - **Meissner's corpuscles** (4) detect **fine touch** (D) and light pressure. They are **rapidly adapting receptors** located in dermal papillae of glabrous (hairless) skin, particularly abundant in fingertips and lips. *1C 2D 3B 4A* - Incorrectly assigns Merkel cells to fine touch (should be sustained pressure) and Pacinian corpuscles to sustained pressure (should be vibration). - Meissner's corpuscles are mismatched with vibration instead of fine touch. *1D 2C 3B 4A* - Incorrectly assigns Ruffini corpuscles to fine touch (should be stretching) and Merkel cells to stretching (should be sustained pressure). - Pacinian corpuscles are mismatched with sustained pressure (should be vibration). - Meissner's corpuscles are mismatched with vibration (should be fine touch). *1B 2A 3D 4C* - Completely incorrect matching: Ruffini to sustained pressure, Merkel to vibration, Pacinian to fine touch, and Meissner's to stretching. - Demonstrates fundamental misunderstanding of mechanoreceptor functions.

Question 1

The image given below shows stapedial reflex. What does ' $X$ ' denote?

Accepted Answer

Superior olivary complex

Answer

Medial geniculate body

Answer

Superior colliculus

Answer

Lateral lemniscus

Question 2

What is correct about the composition of fluid in the area marked as X?

Accepted Answer

Na = 3 mEq/L, K = 150 mEq/L, Chloride = 125 mEq/L

Answer

Na = 150 mEq/L, K = 3 mEq/L, Chloride = 125 mEq/L

Answer

Na = 152 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L

Answer

Na = 50 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L

Question 3

What is correct about the composition of fluid in the area marked as $X$ ?

Accepted Answer

Na = 3 mEq/L, K = 150 mEq/L, Chloride = 125 mEq/L

Answer

Na = 150 mEq/L, K = 3 mEq/L, Chloride = 125 mEq/L

Answer

Na = 50 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L

Answer

Na = 150 mEq/L, K = 30 mEq/L, Chloride = 125 mEq/L

Question 4

Which of the following cells in the brain are responsible for handling information regarding ability to read the slide below? (Recent NEET Pattern 2016-17)

Accepted Answer

Parvocellular cells

Answer

Magnocellular cells

Answer

Purkinje cells

Answer

Pyramidal cells

Question 5

The image given below shows:

Accepted Answer

Dark adaptation curve

Answer

Visual evoked response

Answer

Contrast sensitivity plot

Answer

Electroretinography curve

Question 6

All are true about the recording shown except:

Accepted Answer

C wave is due to activation of optic nerve

Answer

R1 is due to photochemical reactions in outer segment of rods and cones

Answer

A wave is due to photoreceptor activity

Answer

B wave is due to response of bipolar cells

Question 7

A woman suffered a sunburn while enjoying a vacation on the beach. Now, while taking a shower, the lukewarm water (40° C) touching her back caused her to feel pain. What types of receptors were activated by the lukewarm water, and why did she experience pain?

Accepted Answer

Thermal nociceptors & allodynia

Answer

Thermal nociceptors & nociceptive pain

Answer

Innocuous thermal receptors and hyperalgesia

Answer

Innocuous thermal receptors and allodynia

Question 8

Select the correct option regarding the function of receptors:

Accepted Answer

Pacinian corpuscle - fast vibration

Answer

Merkel cells - slow vibration

Answer

Meissner's corpuscle - stretch

Answer

Ruffini corpuscle - light touch

Question 9

Sour taste is mediated by which of the following receptors?

Accepted Answer

OTOP1

Answer

T1R1

Answer

T1R2

Answer

T1R3

Question 10

Match the following receptors with their correct functions:

Receptors:
1. Ruffini corpuscle
2. Merkel cells
3. Pacinian corpuscle
4. Meissner's corpuscle

Functions:
A. Vibration
B. Sustained pressure
C. Stretching
D. Fine touch

Select the option that correctly matches each receptor (1-4) with its function (A-D).

Accepted Answer

1C 2B 3A 4D

Answer

1C 2D 3B 4A

Answer

1D 2C 3B 4A

Answer

1B 2A 3D 4C

Sensory Systems — MCQs

Sensory Systems — MCQs

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