Sensory Systems — MCQs

Sensory Systems Indian Medical PG Practice Questions and MCQs

Question 421: Function of saccule is?

A. Linear acceleration (Correct Answer)
B. Angular acceleration
C. Senses position of head
D. Rotational movement

Explanation: ***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.

Question 422: What is the primary function of Merkel cells in the epidermis?

A. Touch (Correct Answer)
B. Temperature
C. Pressure
D. Proprioception

Explanation: ***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.

Question 423: Parvocellular pathway for vision is concerned with?

A. Fine details of object (Correct Answer)
B. Movements of object
C. Flickering features
D. Depth of vision

Explanation: ***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.

Question 424: Two point discrimination is mainly a function of which touch receptors?

A. Merkel's disc (Correct Answer)
B. Ruffini's end organ
C. Paccinian corpuscle
D. Meissner's corpuscle

Explanation: ***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.

Question 425: Weber Fechner law is related to?

A. Phantom limb
B. Force of contraction in heart
C. Cortical plasticity
D. Relationship between intensity of stimulus and sensation felt (Correct Answer)

Explanation: ***Relationship between intensity of stimulus and sensation felt*** - The **Weber-Fechner law** describes a psychophysical relationship stating that the **magnitude of psychological sensation** to a stimulus is logarithmically proportional to the **physical intensity of the stimulus**. - This means that as the stimulus intensity increases, a larger change in physical intensity is needed to produce a noticeable change in sensation. *Phantom limb* - **Phantom limb phenomenon** is the sensation that an amputated or missing limb is still attached to the body and moving appropriately with other body parts. - This is primarily related to **cortical remapping** and **neuropathic pain**, not directly governed by the Weber-Fechner law. *Force of contraction in heart* - The **force of contraction in the heart** is primarily governed by factors such as **Frank-Starling mechanism** (preload), contractility, and afterload. - This physiological process is not directly explained by the Weber-Fechner law, which applies to psychophysical perception. *Cortical plasticity* - **Cortical plasticity** refers to the brain's ability to **reorganize both its structure and function** in response to experience, learning, or injury. - While related to sensation and perception, the Weber-Fechner law is a specific psychophysical principle, not a general concept of brain adaptability.

Question 426: Umami taste is evoked by?

A. Glucose
B. Glutamic acid (Correct Answer)
C. Quinine
D. Sodium chloride

Explanation: ***Glutamic acid*** - Umami is known as the **fifth basic taste** alongside sweet, sour, salty, and bitter. - It is primarily elicited by **L-glutamate**, an amino acid found in many protein-rich foods and fermented products. *Glucose* - **Glucose** is a simple sugar and is responsible for the **sweet taste**. - It does not directly evoke the umami sensation. *Quinine* - **Quinine** is a compound known for its intense **bitter taste**. - It is often used as a reference substance for bitterness perception studies. *Sodium chloride* - **Sodium chloride**, commonly known as table salt, is responsible for the **salty taste**. - It plays no direct role in eliciting the umami taste sensation.

Question 427: Which motor protein is primarily involved in the function of the organ of Corti in the inner ear?

A. Kinesin
B. Dynein
C. Myosin (Correct Answer)
D. Actin

Explanation: ***Myosin*** - **Myosin** is crucial for the **mechanotransduction** process in the hair cells of the organ of Corti, specifically the **outer hair cells**. - It facilitates **electromotility**, allowing outer hair cells to change length in response to sound, amplifying vibrations and enhancing hearing sensitivity. *Kinesin* - **Kinesin** is primarily involved in **anterograde axonal transport** of vesicles and organelles along **microtubules** in neurons. - While present in various cell types, its main role is not directly in the sound transduction mechanism of the organ of Corti. *Actin* - **Actin** is a fundamental component of the **cytoskeleton** and forms the core of the stereocilia in hair cells. - Although essential for the structural integrity and mechanical properties of stereocilia, **actin itself is not a motor protein**; rather, it interacts with motor proteins like myosin. *Dynein* - **Dynein** is primarily responsible for **retrograde axonal transport** along microtubules and the movement of **cilia and flagella**. - It plays a role in cellular transport, but not directly in the active sound amplification or mechanotransduction within the organ of Corti.

Question 428: Which sense organ is primarily associated with an efferent nerve supply?

A. Golgi tendon organ
B. Organ of Corti (Correct Answer)
C. Retina
D. Taste bud

Explanation: ***Organ of Corti*** - The **organ of Corti** receives efferent innervation via the **olivocochlear bundle**, which modulates the sensitivity of outer hair cells. - This efferent input helps to sharpen frequency tuning and protect the inner ear from excessive noise. *Golgi tendon organ* - The **Golgi tendon organ** is a **proprioceptor** that senses muscle tension and is supplied by afferent (sensory) fibers, not efferent. - Its primary role is to provide feedback on muscle force to the central nervous system. *Retina* - The retina is primarily a **sensory organ** containing photoreceptors that transmit visual information through afferent pathways to the brain. - While there are some interneurons, its main nerve supply is **afferent** for visual processing. *Taste bud* - Taste buds are **chemoreceptors** that detect taste stimuli and transmit signals via afferent nerve fibers to the brain. - They are not characterized by a prominent efferent nerve supply controlling their primary sensory function.

Question 429: Which Brodmann's areas are primarily associated with somatosensory perception?

A. 1, 2, 3 (Correct Answer)
B. 4, 6
C. 44, 45
D. 41, 42

Explanation: ***1, 2, 3*** - **Brodmann areas 1, 2, and 3** comprise the **primary somatosensory cortex**, responsible for processing sensory input from the body, such as **touch, temperature, pain, and proprioception**. - These areas are located in the **postcentral gyrus** of the parietal lobe. *4, 6* - **Brodmann area 4** is the **primary motor cortex**, critical for executing voluntary movements. - **Brodmann area 6** is the **premotor and supplementary motor cortex**, involved in planning and coordinating movements. *44, 45* - **Brodmann areas 44 and 45** constitute **Broca's area**, which is primarily involved in **speech production and language processing**. - Damage to this area can result in expressive aphasia. *41, 42* - **Brodmann areas 41 and 42** are the **primary auditory cortex**, responsible for processing auditory information and sound perception. - They are located in the temporal lobe.

Question 430: What is the intensity in decibel of normal conversation in humans?

A. 30dB
B. 60dB (Correct Answer)
C. 90dB
D. 150dB

Explanation: ***60dB*** - The sound intensity of **normal human conversation** is typically around **60 decibels (dB)**. - This level is considered **moderate** and is comfortably audible without causing discomfort or hearing damage. *30dB* - A sound intensity of **30dB** is characteristic of a **quiet whisper** or a **soft rustle of leaves**. - This level is much **quieter** than a normal conversation and would require closer proximity to be clearly heard. *90dB* - **90dB** represents a significantly **louder sound**, comparable to that of a **lawnmower** or a **heavy truck** passing by. - Prolonged exposure to sounds at this intensity can start to cause **hearing damage**. *150dB* - **150dB** is an **extremely loud** and potentially **painful** sound level, similar to a **jet engine at takeoff** or a **firecracker** exploding nearby. - Exposure to sounds this intense can cause **immediate and permanent hearing loss**.

Practice by Chapter

General Sensory Physiology

Practice Questions

Somatosensation

Practice Questions

Pain Physiology

Practice Questions

Vision and Optics

Practice Questions

Retinal Physiology

Practice Questions

Visual Pathways and Processing

Practice Questions

Auditory System

Practice Questions

Vestibular System

Practice Questions

Taste and Smell

Practice Questions

Sensory Integration

Practice Questions

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