Sensory Systems Practice Questions

Q: Fine touch and rapidly adapting receptor is

Meissners corpuscle. ***Meissners corpuscles*** - They are responsible for **discriminative touch** and ability to differentiate between two points close together. - These receptors are **rapidly adapting**, meaning they respond strongly to initial stimulation but quickly cease firing if the stimulus is constant. *Ruffini's nerve ending* - These are **slowly adapting receptors** sensitive to **stretch** and sustained pressure. - They provide information about **proprioception** and the shape of objects. *Pacinian corpuscle* - Pacinian corpuscles are **rapidly adapting mechanoreceptors** sensitive to **vibration** and deep pressure. - They have a large receptive field and are less involved in fine touch discrimination. *Merkel's disc* - Merkel's discs are **slowly adapting mechanoreceptors** responsible for sensing sustained touch and **pressure**. - They contribute to the perception of **texture** and edges, having a small receptive field.

Q: Stapedial reflex is mediated by-

VII and VIII nerves. ***VII and VIII nerves*** - The **afferent limb** of the stapedial reflex arc is carried by the **vestibulocochlear nerve (CN VIII)**, which detects the loud sound. - The **efferent limb** of the reflex, which causes contraction of the stapedius muscle, is mediated by the **facial nerve (CN VII)**. *V and VIII nerves* - The **trigeminal nerve (CN V)** is involved in sensation from the face and muscles of mastication, not directly in the stapedial reflex. - While **CN VIII** correctly represents the afferent pathway, **CN V** is not the efferent pathway for this reflex. *V and VII nerves* - This combination incorrectly identifies **CN V** as the afferent pathway for sound detection. - **CN VII** is correctly identified as the efferent pathway, but **CN V** is not involved in the sensory input for the stapedial reflex. *VII and VI nerves* - This option incorrectly identifies the **abducens nerve (CN VI)**, which controls the lateral rectus muscle of the eye, as part of the stapedial reflex. - Although **CN VII** is correctly identified as the efferent pathway, the afferent pathway (CN VIII) is missing and replaced by an irrelevant nerve (CN VI).

Q: Motor protein in organ of Corti -

Myosin. **Myosin** - **Myosin I** and **Myosin VIIa** are key motor proteins found in the **hair cells** of the organ of Corti. - They play crucial roles in **stereocilia bundle stiffness** and the **adaptation** process of mechanotransduction, which is essential for hearing. *Kinesin* - **Kinesin** is primarily involved in **anterograde axonal transport** of vesicles and organelles along microtubules in neurons. - It is not the primary motor protein responsible for the unique mechanical properties of hair cells in the organ of Corti. *Albumin* - **Albumin** is a major **plasma protein** primarily involved in maintaining **osmotic pressure** and transporting various substances in the bloodstream. - It is not a motor protein and does not have a direct role in the mechanical function of the organ of Corti. *Dynein* - **Dynein** is a microtubule-associated motor protein responsible for **retrograde axonal transport** and the movement of cilia and flagella. - While important for intracellular transport in many cells, it is not the primary motor protein driving the mechanical processes within the hair cells of the organ of Corti.

Q: A 50-year-old woman who is a known diabetic and hypertensive has developed vesicular eruption on the trunk in T6 dermatome. The dermatologist confirmed it as Herpes Zoster. She is complaining of severe pain and increased sensitivity to touch. Which of the following receptors sense sustained pressure?

Ruffini corpuscles. ***Ruffini corpuscles*** - **Ruffini corpuscles** are slow-adapting mechanoreceptors located deep in the dermis and subcutaneous tissue. - They are responsible for sensing **sustained pressure**, skin stretch, and contribute to the perception of object slippage and grasp. *Pacinian corpuscle* - **Pacinian corpuscles** are rapidly adapting receptors that detect **vibration** and **deep pressure**. - They are not primarily involved in sensing sustained pressure due to their rapid adaptation. *Merkel cells* - **Merkel cells** are slow-adapting mechanoreceptors found in the basal epidermis. - They are crucial for sensing **light touch**, **texture**, and **two-point discrimination**, but not deep or sustained pressure. *Meissner's corpuscles* - **Meissner's corpuscles** are rapidly adapting mechanoreceptors located in the dermal papillae. - They are specialized for detecting **light touch** and **low-frequency vibration**, particularly important for discriminative touch.

Q: The only neurons in retina showing action potentials are

Ganglion cells. ***Ganglion cells*** - **Ganglion cells are the only retinal neurons that generate action potentials** to transmit visual information to the brain via the optic nerve. - All other retinal neurons produce graded potentials, which are local changes in membrane potential that do not propagate over long distances. *Bipolar cells* - **Bipolar cells operate via graded potentials**, not action potentials. - They receive input from photoreceptors and horizontal cells, and transmit signals to ganglion cells and amacrine cells. *Amacrine cells* - **Amacrine cells primarily use graded potentials** to modulate the activity of bipolar and ganglion cells. - They are involved in complex processing within the inner plexiform layer of the retina. *Rods and cones* - **Rods and cones (photoreceptors) respond to light with graded potentials** (hyperpolarization). - They are responsible for transducing light into electrical signals, but they do not generate action potentials.

Q: Function of Merkel's cells is:

Tactile sensation. ***Tactile sensation*** - **Merkel cells** are specialized epidermal cells located in the **stratum basale** that function as **mechanoreceptors**. - They are crucial for **light touch** and the discrimination of shapes and textures, making them essential for tactile sensation. *Chemoreceptor* - **Chemoreceptors** detect changes in chemical concentrations, such as taste, smell, or blood gas levels. - Merkel cells are not involved in chemical sensing; their primary role is in perceiving mechanical stimuli. *Proprioception* - **Proprioception** refers to the sense of the relative position of one's own body parts and the strength of effort being used in movement (body position sense). - This function is primarily mediated by receptors in muscles, tendons, and joints, not Merkel cells in the skin. *Temperature sensation* - **Temperature sensation** (thermoreception) is mediated by specialized thermoreceptors such as cold receptors (responding to temperatures below skin temperature) and warm receptors (responding to temperatures above skin temperature). - Merkel cells are mechanoreceptors that respond to mechanical deformation, not thermal stimuli, and do not play a role in temperature detection.

Q: The blobs of the visual cortex are associated with:

Color processing. ***Color processing*** - **Blobs** are cytochrome oxidase-rich regions within the **primary visual cortex (V1)**, specifically located in layers II and III. - They are primarily involved in the processing of **color information**, exhibiting selectivity for different wavelengths of light. *Ocular dominance* - **Ocular dominance columns** are organized bands of neurons in V1 that preferentially respond to input from either the left or the right eye. - While related to visual processing, ocular dominance is distinct from the function of the blobs. *Saccadic eye movements* - **Saccadic eye movements** are rapid, ballistic movements of the eyes that allow us to quickly shift our gaze from one point to another. - These movements are primarily controlled by brainstem and cortical areas separate from the blobs, such as the **frontal eye fields** and **superior colliculus**. *Orientation* - **Orientation columns** in V1 are groups of neurons that preferentially respond to visual stimuli with specific orientations (e.g., horizontal, vertical, diagonal). - This function is performed by neurons in the **interblob regions**, which are distinct from the blobs themselves.

Q: Action of ciliary muscle:

Change in shape of lens. ***Change in shape of lens*** - The ciliary muscle contracts or relaxes to alter the tension on the **suspensory ligaments**, which in turn changes the **curvature and thickness of the lens**. - This process, known as **accommodation**, allows the eye to focus on objects at various distances. *Constriction of pupil* - **Pupillary constriction** is primarily controlled by the **sphincter pupillae muscle**, which is innervated by the parasympathetic nervous system. - This action regulates the amount of light entering the eye, a function distinct from the ciliary muscle's role in focusing. *Dilatation of pupil* - **Pupillary dilatation** is mediated by the **dilator pupillae muscle**, which is innervated by the sympathetic nervous system. - Like pupillary constriction, this action controls light entry and is separate from the functions of the ciliary muscle. *Facilitates aqueous humor drainage* - **Aqueous humor drainage** primarily occurs through the **trabecular meshwork** and **Schlemm's canal**. - While the ciliary body produces aqueous humor, the ciliary muscle's direct action is not to facilitate its drainage, though its position can indirectly influence outflow pathways.

Q: Which among the following is determined by the higher auditory centre?

Sound localization. ***Sound localization*** - The **higher auditory centers**, particularly in the cerebral cortex (auditory association areas), integrate **binaural cues** (interaural time differences and interaural intensity differences) to determine the precise **spatial location of a sound source**. - This complex cortical processing of information from both ears allows for accurate three-dimensional sound localization. - This is the primary function specifically **determined by** higher auditory cortical centers through binaural integration. *Loudness* - **Loudness** is primarily determined by the **amplitude of sound waves** and is encoded at the **peripheral level** (cochlea) and lower brainstem levels as the firing rate of auditory nerve fibers and the number of activated neurons. - While perceived at the cortical level, its fundamental determination occurs at earlier stages in the auditory pathway. *Speech discrimination* - While speech discrimination does involve higher auditory cortex (Wernicke's area, superior temporal gyrus), it is considered a **specialized language function** rather than a basic auditory property. - It involves **complex linguistic processing** including phoneme recognition, semantic processing, and language comprehension that extends beyond fundamental auditory processing. - In the context of basic auditory physiology, speech discrimination is classified as a language cortical function rather than a primary auditory center function. *Sound frequency* - **Sound frequency** (pitch) is initially encoded at the **peripheral level** by the **basilar membrane's tonotopic organization** and the firing pattern of auditory nerve fibers (place theory and frequency theory). - This fundamental property is determined at the cochlear and lower brainstem levels, with higher centers perceiving the already-encoded pitch information.

Q: Which of the following phrases adequately describes Pacinian corpuscles?

Rapidly adapting touch receptors. ***Rapidly adapting touch receptors*** - **Pacinian corpuscles** are classic examples of **rapidly adapting (phasic)** mechanoreceptors, meaning they respond strongly to the onset and offset of a stimulus but quickly cease firing during sustained stimulation. - They are responsible for detecting **vibration** and deep pressure due to their concentric lamellar structure which filters out static pressure. *Slowly adapting touch receptors* - **Slowly adapting (tonic)** receptors, such as **Merkel cells** and **Ruffini endings**, continuously fire during sustained stimulation. - These receptors are involved in sensing **sustained pressure** and **texture**. *A type of pain receptors* - **Pain receptors** are known as **nociceptors**, which are free nerve endings that respond to noxious stimuli (e.g., thermal, mechanical, chemical). - Pacinian corpuscles specifically detect mechanical stimuli like **vibration** and pressure, not pain. *Located in the joints* - While present in the deep layers of the skin, such as the **hypodermis**, and in some organs like the pancreas and mesentery, their primary location for touch sensation is not specifically within the joints. - **Receptors in joints** are typically involved in proprioception and kinesthesia, detecting position and movement.

Question 1

Fine touch and rapidly adapting receptor is

Accepted Answer

Meissners corpuscle

Answer

Ruffini's nerve ending

Answer

Pacinian corpuscle

Answer

Merkel's disc

Question 2

Stapedial reflex is mediated by-

Accepted Answer

VII and VIII nerves

Answer

V and VIII nerves

Answer

V and VII nerves

Answer

VII and VI nerves

Question 3

Motor protein in organ of Corti -

Accepted Answer

Myosin

Answer

Kinesin

Answer

Albumin

Answer

Dynein

Question 4

A 50-year-old woman who is a known diabetic and hypertensive has developed vesicular eruption on the trunk in T6 dermatome. The dermatologist confirmed it as Herpes Zoster. She is complaining of severe pain and increased sensitivity to touch. Which of the following receptors sense sustained pressure?

Accepted Answer

Ruffini corpuscles

Answer

Pacinian corpuscle

Answer

Meissner's corpuscles

Answer

Merkel cells

Question 5

The only neurons in retina showing action potentials are

Accepted Answer

Ganglion cells

Answer

Bipolar cells

Answer

Amacrine cells

Answer

Rods and cones

Question 6

Function of Merkel's cells is:

Accepted Answer

Tactile sensation

Answer

Chemoreceptor

Answer

Proprioception

Answer

Temperature sensation

Question 7

The blobs of the visual cortex are associated with:

Accepted Answer

Color processing

Answer

Ocular dominance

Answer

Saccadic eye movements

Answer

Orientation

Question 8

Action of ciliary muscle:

Accepted Answer

Change in shape of lens

Answer

Constriction of pupil

Answer

Dilatation of pupil

Answer

Facilitates aqueous humor drainage

Question 9

Which among the following is determined by the higher auditory centre?

Accepted Answer

Sound localization

Answer

Loudness

Answer

Speech discrimination

Answer

Sound frequency

Question 10

Which of the following phrases adequately describes Pacinian corpuscles?

Accepted Answer

Rapidly adapting touch receptors

Answer

Slowly adapting touch receptors

Answer

A type of pain receptors

Answer

Located in the joints

Sensory Systems — MCQs

Sensory Systems — MCQs

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