Sensory Systems Practice Questions

Q: A patient experiences sharp pain after touching a hot surface. Which sensory receptor is most likely responsible for detecting this painful stimulus?

Nociceptors. ***Nociceptors*** - **Nociceptors** are specialized sensory receptors (free nerve endings) that detect **noxious (painful)** stimuli, including extreme heat, cold, mechanical injury, or chemical irritants. - In this scenario, touching a **hot surface** activates **thermal nociceptors**, which transmit pain signals via A-delta fibers (sharp, fast pain) and C fibers (dull, slow pain). - Their activation leads to the sensation of **pain**, serving as a warning signal of potential or actual tissue damage. *Meissner corpuscles* - **Meissner corpuscles** are responsible for detecting **light touch** and **low-frequency vibrations** (30-50 Hz). - They are rapidly adapting mechanoreceptors located in the **dermal papillae** of glabrous (hairless) skin (e.g., fingertips, lips, palms). - They do not respond to painful or noxious stimuli. *Merkel cells* - **Merkel cells** (Merkel discs) are responsible for detecting **sustained pressure** and **fine texture** discrimination. - They are slowly adapting mechanoreceptors (Type I) found in the **basal epidermis**, particularly abundant in fingertips. - They provide detailed spatial information but do not detect pain. *Ruffini corpuscles* - **Ruffini corpuscles** (Ruffini endings) detect **skin stretch**, **sustained pressure**, and contribute to **proprioception**. - They are slowly adapting mechanoreceptors (Type II) located deep in the **dermis** and subcutaneous tissue. - They respond to mechanical deformation, not thermal or noxious stimuli.

Q: Which structure in the eye is responsible for the greatest amount of light refraction (focusing power)?

Cornea. ***Cornea*** - The **cornea** is the eye's outermost, transparent layer and provides approximately **two-thirds of the eye's total refractive power** (~43 diopters out of ~60 total). - It acts as a powerful **fixed lens** that performs the **majority of light bending** required to focus images on the retina. - While it cannot change shape, it is the **primary refractive element** of the eye. *Lens* - The **lens** is a transparent, biconvex structure that provides approximately **one-third of the eye's refractive power** (~15-17 diopters). - Its key function is **accommodation** - the ability to change shape to adjust focus for objects at different distances. - While crucial for **fine-tuning focus**, it contributes **less total refractive power** than the cornea. *Iris* - The **iris** is the colored part of the eye that controls the size of the **pupil**, regulating the **amount of light that enters the eye**. - It does not focus light onto the retina; its primary role is **light intensity control** and depth of field. *Sclera* - The **sclera** is the **white outer layer** of the eyeball, providing structural support and protection to the inner components. - It has **no role in focusing light**; its function is primarily structural and protective.

Q: Function of saccule is?

Linear acceleration. ***Linear acceleration*** - The **saccule** is one of the two **otolith organs** in the inner ear, responsible for detecting **linear acceleration** in the vertical plane. - Its sensory hair cells are embedded in a gelatinous membrane containing **otoliths (calcium carbonate crystals)**, which shift with linear movement and stimulate the hair cells. *Angular acceleration* - This function is primarily attributed to the **semicircular canals**, which detect **rotational movements** of the head. - The **crista ampullaris** within each canal responds to the flow of **endolymph** during angular motion. *Senses position of head* - While both the saccule and utricle contribute to sensing head position relative to gravity, the **utricle** is primarily responsible for detecting **horizontal linear acceleration** and static head tilt. - The saccule detects **vertical linear acceleration** and vertical head movements. *Rotational movement* - **Rotational movement** is detected by the **semicircular canals**, which are arranged in three planes to sense rotations in all directions. - The **cupula**, a gelatinous mass within the ampulla of each canal, is displaced by endolymph flow during rotation, stimulating hair cells.

Q: Transport of ascorbic acid to the lens is done by:

SVCT2 (Sodium-dependent Vitamin C Transporter 2). ***SVCT2 (Sodium-dependent Vitamin C Transporter 2)*** - **SVCT2** is the primary transporter responsible for the uptake and accumulation of **ascorbic acid (vitamin C)** in various tissues, including the lens. - This transporter uses a **sodium-dependent mechanism** to actively move vitamin C into cells, maintaining its high concentration essential for antioxidant protection in the lens. *Myoinositol* - **Myoinositol** is a sugar alcohol that plays a role in cellular signaling and is a component of cell membranes. - It is transported into cells by specific inositol transporters, but it is **not involved in ascorbic acid transport**. *Choline* - **Choline** is an essential nutrient involved in neurotransmitter synthesis (**acetylcholine**) and membrane structure. - It has its own dedicated transport systems and is **not involved in the transport of ascorbic acid**. *Taurine* - **Taurine** is an amino acid derivative found in high concentrations in the eye, where it plays roles in osmoregulation and antioxidant defense. - It is transported by **taurine transporters** and is **not responsible for ascorbic acid transport**.

Q: Threshold of hearing in a young normal adult is?

0 dB. **0 dB** - **0 dB** represents the **threshold of audibility** for a young, healthy adult at frequencies sensitive to human hearing. - It is a **reference level**, not an absence of sound, indicating the softest sound that can typically be perceived. *10 dB* - While a very soft sound, **10 dB** is still above the standard threshold for normal hearing. - Hearing sensitivity decreases with age and environmental exposure, so 10 dB may be a threshold for some individuals, but not the ideal normal. *20 dB* - **20 dB** is generally considered within the range of **normal conversational speech**, not the absolute threshold of hearing. - Sounds at this level are easily audible and do not indicate a hearing impairment in adults. *30 dB* - **30 dB** is clearly audible and significantly above the normal hearing threshold, often representing sounds like a very soft whisper. - If this were the threshold of hearing, it would suggest a **mild hearing loss**.

Q: What is the primary function of Merkel cells in the epidermis?

Touch. ***Touch*** - **Merkel cells** are specialized **neuroendocrine cells** located in the **stratum basale** of the epidermis. - They function as **mechanoreceptors** responsible for sensing **light touch** and **discriminative touch**. *Temperature* - **Thermoreception**, the sensation of temperature, is primarily mediated by **free nerve endings** in the skin, not Merkel cells. - These nerve endings detect changes in heat and cold through specific **TRP (transient receptor potential) channels**. *Pressure* - **Pressure sensation** is mainly detected by other mechanoreceptors such as **Pacinian corpuscles** (deep pressure, vibration) and **Ruffini endings** (stretch, sustained pressure). - Merkel cells contribute to fine touch, but not the primary sensation of deep pressure. *Proprioception* - **Proprioception** is the sense of the relative position of body parts and is crucial for motor control and balance. - This sense is primarily mediated by **proprioceptors** located in muscles (muscle spindles), tendons (Golgi tendon organs), and joints, not in the epidermis.

Q: Two point discrimination is mainly a function of which touch receptors?

Merkel's disc. ***Merkel's disc*** - Merkel's discs are **slowly adapting mechanoreceptors** located in the **basal epidermis** and are highly sensitive to sustained pressure and touch. - Their high density and small receptive fields, particularly in areas like fingertips, make them crucial for tasks requiring fine tactile discrimination, such as **two-point discrimination** and reading Braille. *Ruffini's end organ* - These are **slowly adapting mechanoreceptors** located deeper in the dermis and are primarily sensitive to **skin stretch** and sustained pressure. - Their larger receptive fields make them less suitable for fine spatial discrimination like two-point discrimination. *Paccinian corpuscle* - Pacinian corpuscles are **rapidly adapting mechanoreceptors** located deep in the dermis and subcutaneous tissue, sensitive to **vibration** and deep pressure. - Their large receptive fields and rapid adaptation make them excellent detectors of high-frequency stimuli, but not for spatial resolution. *Meissner's corpuscle* - Meissner's corpuscles are **rapidly adapting mechanoreceptors** located in the dermal papillae, just below the epidermis, and are sensitive to **light touch** and low-frequency vibration. - While important for light touch and grip control, their receptive fields are larger than Merkel's discs, making them less specialized for the fine spatial resolution needed for two-point discrimination.

Q: Parvocellular pathway for vision is concerned with?

Fine details of object. ***Fine details of object*** - The **parvocellular pathway** is responsible for processing **fine spatial details**, **color**, and **shape** information. - This pathway has a high spatial resolution and slower temporal response, making it ideal for detailed analysis of static objects. *Movements of object* - The **magnocellular pathway**, not the parvocellular pathway, is primarily concerned with detecting **motion** and fast changes in visual scenes. - The magnocellular pathway has a high temporal resolution and low spatial resolution, which is suitable for detecting movement. *Flickering features* - Similar to detecting movement, the processing of **flickering features** and rapid changes in luminance is predominantly handled by the **magnocellular pathway**. - This pathway is specialized for perceiving dynamic aspects of the visual environment. *Depth of vision* - While both major visual pathways contribute to depth perception, the processing of **depth of vision** often involves integration of information from both the parvocellular and magnocellular pathways, along with specialized cortical areas. - However, for fine-grained depth cues related to static objects, the parvocellular pathway plays a role but it is not its primary or exclusive function.

Q: A person with blue color vision deficiency is called?

Tritanopia. ***Tritanopia*** - This is a **rare form of blue-yellow color blindness** resulting from the **complete absence of functional blue cone photopigments** (S-cones). - People with tritanopia perceive the world in shades of red and green, with blue and yellow appearing washed out or gray. - This represents the **definitive form of blue color vision deficiency**, affecting approximately 1 in 10,000 individuals. - **Key clinical features**: Confusion between blue and green, violet appears as red, inability to distinguish yellow from pink or gray. *Tritanomaly* - This condition refers to a **mild form of blue-yellow color blindness**, where the blue cone photopigments are impaired but still present. - Individuals with tritanomaly have difficulty distinguishing shades of blue and yellow, and violet may appear pinkish. - This is a **partial blue deficiency** (anomalous trichromacy), less severe than tritanopia. *Deuteranomaly* - This is the most common type of **red-green** color vision deficiency, where the green cone photopigment is anomalous. - **Not a blue deficiency** - people with deuteranomaly have difficulty distinguishing between certain shades of red and green. *Deuteranopia* - This is a more severe form of **red-green** color blindness with complete absence of functional green cone photopigments. - **Not a blue deficiency** - individuals perceive only two primary colors (blue and yellow) and have significant difficulty with red-green discrimination.

Q: Horizontal acceleration with forward movement in the sagittal plane is detected by ?

Macula of Utricle. ***Macula of Utricle*** - The **utricle** is primarily responsible for detecting **horizontal linear acceleration**, such as forward/backward and side-to-side movements in the **sagittal and coronal planes**. - Its **macula** is oriented **horizontally**, making it the ideal structure for sensing horizontal acceleration with forward movement in the sagittal plane. - The utricle contains otoliths (calcium carbonate crystals) that shift with linear acceleration, stimulating hair cells that signal movement direction. *Macula of Saccule* - The **saccule** is primarily responsible for detecting **vertical linear acceleration** of the head, such as moving up and down in an elevator. - Its macula is oriented **vertically**, not horizontally, making it unsuitable for detecting horizontal forward movement. - While it may have minor secondary roles in certain head positions, it is NOT the primary detector for horizontal sagittal plane movement. *Lateral semicircular canal* - The **lateral semicircular canal** detects **rotational acceleration** primarily in the **horizontal plane**, such as turning the head from side to side (yaw rotation). - It does **not** detect linear acceleration like forward movement—only angular/rotational movements. *Posterior semicircular canal* - The **posterior semicircular canal** detects **rotational acceleration** when the head moves in the **sagittal plane**, like nodding (pitch rotation). - It works in conjunction with the anterior semicircular canal to detect head rotations, not linear acceleration.

Question 1

A patient experiences sharp pain after touching a hot surface. Which sensory receptor is most likely responsible for detecting this painful stimulus?

Accepted Answer

Nociceptors

Answer

Meissner corpuscles

Answer

Merkel cells

Answer

Ruffini corpuscles

Question 2

Which structure in the eye is responsible for the greatest amount of light refraction (focusing power)?

Accepted Answer

Cornea

Answer

Lens

Answer

Iris

Answer

Sclera

Question 3

Function of saccule is?

Accepted Answer

Linear acceleration

Answer

Angular acceleration

Answer

Senses position of head

Answer

Rotational movement

Question 4

Transport of ascorbic acid to the lens is done by:

Accepted Answer

SVCT2 (Sodium-dependent Vitamin C Transporter 2)

Answer

Myoinositol

Answer

Choline

Answer

Taurine

Question 5

Threshold of hearing in a young normal adult is?

Accepted Answer

0 dB

Answer

10 dB

Answer

20 dB

Answer

30 dB

Question 6

What is the primary function of Merkel cells in the epidermis?

Accepted Answer

Touch

Answer

Temperature

Answer

Pressure

Answer

Proprioception

Question 7

Two point discrimination is mainly a function of which touch receptors?

Accepted Answer

Merkel's disc

Answer

Ruffini's end organ

Answer

Paccinian corpuscle

Answer

Meissner's corpuscle

Question 8

Parvocellular pathway for vision is concerned with?

Accepted Answer

Fine details of object

Answer

Movements of object

Answer

Flickering features

Answer

Depth of vision

Question 9

A person with blue color vision deficiency is called?

Accepted Answer

Tritanopia

Answer

Tritanomaly

Answer

Deuteranomaly

Answer

Deuteranopia

Question 10

Horizontal acceleration with forward movement in the sagittal plane is detected by ?

Accepted Answer

Macula of Utricle

Answer

Macula of Saccule

Answer

Lateral semicircular canal

Answer

Posterior semicircular canal

Sensory Systems — MCQs

Sensory Systems — MCQs

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