Sensory Systems Practice Questions

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: 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: 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: 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: Umami taste is evoked by?

Glutamic acid. ***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.

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

Myosin. ***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.

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

Organ of Corti. ***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.

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

1, 2, 3. ***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.

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

60dB. ***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**.

Question 1

Function of saccule is?

Accepted Answer

Linear acceleration

Answer

Angular acceleration

Answer

Senses position of head

Answer

Rotational movement

Question 2

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

Accepted Answer

Touch

Answer

Temperature

Answer

Pressure

Answer

Proprioception

Question 3

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 4

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 5

Weber Fechner law is related to?

Accepted Answer

Relationship between intensity of stimulus and sensation felt

Answer

Phantom limb

Answer

Force of contraction in heart

Answer

Cortical plasticity

Question 6

Umami taste is evoked by?

Accepted Answer

Glutamic acid

Answer

Glucose

Answer

Quinine

Answer

Sodium chloride

Question 7

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

Accepted Answer

Myosin

Answer

Kinesin

Answer

Dynein

Answer

Actin

Question 8

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

Accepted Answer

Organ of Corti

Answer

Golgi tendon organ

Answer

Retina

Answer

Taste bud

Question 9

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

Accepted Answer

1, 2, 3

Answer

4, 6

Answer

44, 45

Answer

41, 42

Question 10

What is the intensity in decibel of normal conversation in humans?

Accepted Answer

60dB

Answer

30dB

Answer

90dB

Answer

150dB

Sensory Systems — MCQs

Sensory Systems — MCQs

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