Sensory Systems Practice Questions

Q: What is the characteristic of the second Purkinje image in relation to eye movement?

Erect and moves in same direction. ***Erect and moves in same direction*** - The second Purkinje image (P2) is formed by reflection from the **posterior surface of the cornea**. - This surface acts as a convex mirror, producing a **virtual, erect, and diminished image**. - The image moves in the **same direction** as the eye movement, characteristic of reflections from the first three Purkinje images (P1, P2, P3). - P2 is clinically used in keratometry and assessment of corneal curvature. *Erect and moves in opposite direction* - While the image orientation (erect) would apply to P2, the direction of movement is incorrect. - Only the **fourth Purkinje image (P4)**, formed by the **posterior lens surface**, moves in the opposite direction to eye movement. - P4 is the only inverted Purkinje image due to reflection from the concave posterior lens surface. *Inverted and moves in same direction* - The second Purkinje image is **erect, not inverted**. - All Purkinje images are erect except P4, which is inverted due to reflection from the concave posterior lens surface. - This combination (inverted + same direction) does not correspond to any Purkinje image. *Inverted and moves in opposite direction* - This describes the **fourth Purkinje image (P4)**, not the second. - P4 is formed by reflection from the **posterior surface of the lens** (concave surface), which produces an inverted image. - The second Purkinje image (P2) is always erect, being formed by the posterior corneal surface.

Q: A wave in ERG is due to activity of:

Rods and cones. ***Rods and cones*** - The **electroretinogram (ERG)** measures the electrical responses of various retinal cells to light stimuli. - The **a-wave** of the ERG primarily reflects the activity of the **photoreceptors (rods and cones)** as they hyperpolarize in response to light. *Pigmented epithelium* - The **retinal pigmented epithelium (RPE)** plays a crucial role in photoreceptor health and function but does not directly generate the primary electrical waves measured by the standard ERG. - Its dysfunction can lead to secondary changes in ERG, but its activity is not the direct source of the a-wave. *Ganglion cell* - **Ganglion cells** are the output neurons of the retina, transmitting visual information to the brain. - Their activity is generally not well-represented in the standard ERG, which primarily assays outer and middle retinal layers. *Bipolar cell* - **Bipolar cells** transmit signals from photoreceptors to ganglion cells and contribute to the **b-wave** component of the ERG. - The b-wave, not the a-wave, is largely generated by the depolarizing activity of bipolar cells and Müller cells.

Q: Transducin is a protein found in:

Retina. ***Retina*** - **Transducin** is a **G-protein** crucial for **phototransduction** in the retina. - It plays a key role in the cascade that converts light signals into electrical impulses within **rod** and **cone photoreceptor cells**. *Glomerulus* - The **glomerulus** is a capillary network in the **kidney** responsible for filtering blood. - Its primary proteins are involved in filtration barriers, such as **podocin** and **nephrin**, not transducin. *Skeletal muscle* - **Skeletal muscle** contains proteins like **actin**, **myosin**, and **troponins** for contraction. - Transducin is not involved in muscle contraction or skeletal muscle function. *Adrenal medulla* - The **adrenal medulla** produces **catecholamines** like epinephrine and norepinephrine. - Proteins in this gland are involved in hormone synthesis, storage, and release, not light perception.

Q: Salty taste is due to?

Sodium ion channels. ***Sodium ion channels*** - The sensation of **salty taste** is primarily mediated by the direct influx of **sodium ions (Na+)** into taste receptor cells. - This influx leads to **depolarization** of the cell membrane, triggering neurotransmitter release and signaling to the brain. *Calcium ion channels* - While calcium ions are crucial for various cellular processes, including **neurotransmitter release**, they are not the primary initiators of the salty taste transduction pathway. - Calcium channels are more directly involved in the sensation of **umami** and **sweet tastes**, often via G-protein coupled receptors. *G-protein coupled receptors* - **G-protein coupled receptors (GPCRs)** are responsible for the transduction of **sweet, bitter, and umami tastes**. - They are not involved in the direct detection of **saline compounds**, which operate through ion channels. *Proton channels* - **Proton channels (H+)** are primarily involved in the sensation of **sour taste**. - The influx of protons causes intracellular acidification, leading to cell depolarization.

Q: Following are the changes during accommodation, except:

Dilatation of pupil. ***Dilatation of pupil*** - During **accommodation**, the pupils constrict (miosis) to increase the **depth of field** and sharpen the image on the retina. - Dilatation of the pupil (mydriasis) would lead to a larger circle of confusion and a **blurred image** for near vision. *Constriction of pupil* - This is a normal part of the **accommodation reflex**, driven by **parasympathetic activation**, which helps to improve the focus of near objects. - Pupillary constriction **increases the depth of field**, reducing spherical aberration and improving image clarity. *Convergence of eye ball* - As part of the **near reflex triad**, both eyes turn inward (converge) to ensure that the image of the near object falls on the **fovea** of each eye. - This movement helps maintain **binocular single vision** and prevents double vision (diplopia). *Increase in the anterior curvature of lens* - The **ciliary muscles contract**, relaxing the zonular fibers, allowing the **elastic lens** to become more convex, specifically increasing its anterior curvature. - This increased convexity **enhances the refractive power** of the lens, bringing the focal point of near objects onto the retina.

Q: Meissner's corpuscles are for

Touch. ***Touch*** - **Meissner's corpuscles** are specialized mechanoreceptors located in the **dermal papillae** of glabrous (hairless) skin, particularly abundant in fingertips, palms, and soles. - They are responsible for sensing **light touch**, discrimination of textures, and low-frequency vibrations (flutter), playing a crucial role in tactile discrimination. - These are **rapidly adapting** receptors that respond to dynamic skin deformation. *Temperature* - **Thermoreceptors** are primarily **free nerve endings** with specific ion channels (TRPM8 for cold, TRPV1 for heat) that detect temperature changes, not Meissner's corpuscles. - These receptors detect thermal stimuli and are distinct from the mechanoreceptors involved in touch. *Pressure* - **Pacinian corpuscles** detect deep pressure and high-frequency vibrations, while **Merkel cells** sense sustained pressure and fine spatial details. - Meissner's corpuscles respond to light touch and dynamic changes in tactile stimuli, not deep or sustained pressure. *Proprioception* - **Proprioception** is the sense of the relative position of body parts and strength of effort used in movement, mediated by receptors found in muscles (**muscle spindles**), tendons (**Golgi tendon organs**), and joints. - Meissner's corpuscles are cutaneous receptors and do not contribute to proprioception.

Q: What is the primary function of the otolith organs?

Detecting the position of the head in space. ***Detecting the position of the head in space*** - The **otolith organs**, comprising the **utricle** and **saccule**, are responsible for detecting **linear acceleration** and **gravitational forces**. - This information allows the brain to perceive the **static head position** relative to gravity and linear movements. *Producing the vestibular-ocular reflex* - While the otolith organs contribute to overall vestibular function, the primary role in producing the **vestibular-ocular reflex (VOR)**, especially for rotational movements, is mainly attributed to the **semicircular canals**. - The VOR helps stabilize gaze during head movements, coordinating eye movements in the opposite direction of head motion. *Producing rotary nystagmus* - **Rotary nystagmus** is typically associated with stimulation of the **semicircular canals**, which detect angular acceleration. - The otolith organs detect linear acceleration and static head position, not rotational movements causing nystagmus. *Detecting angular acceleration* - The **semicircular canals** are specialized structures within the inner ear designed to detect **angular acceleration** (rotational movements of the head). - The otolith organs are sensitive to **linear acceleration** and the pull of gravity, not angular motion.

Q: Parvocellular pathway carries signals for the detection of

Color contrast. ***Color contrast*** - The **parvocellular pathway** is specialized for processing **fine spatial details** and **color information**. - It receives input primarily from **red and green cones**, contributing to the perception of hue and saturation. *Luminous contrast* - The detection of **luminosity** or **brightness contrast** is primarily mediated by the **magnocellular pathway**. - The magnocellular pathway is more sensitive to **changes in light intensity** and achromatic contrasts. *Temporal frequency* - **Temporal frequency** (motion detection and flicker) is predominantly handled by the **magnocellular pathway**. - This pathway has a faster response and is better suited for perceiving rapid changes in visual stimuli. *Saccadic eye movements* - While related to vision, **saccadic eye movements** are controlled by motor systems in the brainstem and frontal eye fields, not directly by the parvocellular pathway itself. - The parvocellular pathway processes **visual input** that informs these movements but does not generate them.

Q: Perception of ordinarily non-noxious stimuli as pain is better known as?

Allodynia (pain from non-painful stimuli). ***Allodynia (pain from non-painful stimuli)*** - This term precisely describes the phenomenon where a typically **non-painful stimulus**, such as light touch or brushing, is perceived as painful. - It results from **altered processing** of sensory information, often due to central or peripheral sensitization. *Hyperalgesia (increased pain response)* - This refers to an **exaggerated response** to a stimulus that is *normally painful*, meaning the pain is felt more intensely than expected. - Unlike allodynia, the stimulus itself is inherently noxious, but the patient's reaction is disproportionately severe. *Hyperesthesia (increased sensitivity to stimuli)* - This is a general term for **increased sensitivity** to *any* sensory stimulus, which could include touch, temperature, or sound. - It does not specifically denote pain from non-noxious stimuli, but rather an amplified perception of normal sensations. *Radiculopathy (nerve root compression)* - This is a neurological condition caused by the **compression or irritation of a nerve root**, typically in the spine. - While it can cause pain, numbness, or weakness in the distribution of the affected nerve, it is a diagnosis of the *cause* of symptoms, not a description of the *type* of pain perception itself like allodynia.

Q: What is the range of sonic frequencies that can be heard by humans?

20-20,000 Hz. **20-20,000 Hz** - This is the standard **audible frequency range** for human hearing, also known as the audible spectrum - Frequencies below 20 Hz are **infrasound** (inaudible to humans) - Frequencies above 20,000 Hz are **ultrasound** (inaudible to humans) - This range represents the full capacity of the human cochlea and auditory system *1500-6000 Hz* - This represents only the **speech frequency range**, critical for understanding human conversation - This is a narrow subset within the full audible spectrum - Excludes perception of both very low-pitched sounds (bass) and very high-pitched sounds (treble) *10,000-15,000 Hz* - This covers only a **small portion of high frequencies** within human hearing - Omits all low and mid-frequency sounds as well as the highest audible frequencies - Does not represent the complete audible range *20,000-25,000 Hz* - This range consists primarily of **ultrasound frequencies** above human hearing threshold - While some young individuals may detect sounds slightly above 20,000 Hz, this is exceptional and not the standard audible range - Most of this range is completely inaudible to humans

Question 1

What is the characteristic of the second Purkinje image in relation to eye movement?

Accepted Answer

Erect and moves in same direction

Answer

Inverted and moves in same direction

Answer

Inverted and moves in opposite direction

Answer

Erect and moves in opposite direction

Question 2

A wave in ERG is due to activity of:

Accepted Answer

Rods and cones

Answer

Pigmented epithelium

Answer

Ganglion cell

Answer

Bipolar cell

Question 3

Transducin is a protein found in:

Accepted Answer

Retina

Answer

Glomerulus

Answer

Skeletal muscle

Answer

Adrenal medulla

Question 4

Salty taste is due to?

Accepted Answer

Sodium ion channels

Answer

Calcium ion channels

Answer

G-protein coupled receptors

Answer

Proton channels

Question 5

Following are the changes during accommodation, except:

Accepted Answer

Dilatation of pupil

Answer

Constriction of pupil

Answer

Convergence of eyeball

Answer

Increase in the anterior curvature of lens

Question 6

Meissner's corpuscles are for

Accepted Answer

Touch

Answer

Temperature

Answer

Pressure

Answer

Proprioception

Question 7

What is the primary function of the otolith organs?

Accepted Answer

Detecting the position of the head in space

Answer

Producing the vestibular-ocular reflex

Answer

Producing rotary nystagmus

Answer

Detecting angular acceleration

Question 8

Parvocellular pathway carries signals for the detection of

Accepted Answer

Color contrast

Answer

Luminous contrast

Answer

Temporal frequency

Answer

Saccadic eye movements

Question 9

Perception of ordinarily non-noxious stimuli as pain is better known as?

Accepted Answer

Allodynia (pain from non-painful stimuli)

Answer

Hyperalgesia (increased pain response)

Answer

Hyperesthesia (increased sensitivity to stimuli)

Answer

Radiculopathy (nerve root compression)

Question 10

What is the range of sonic frequencies that can be heard by humans?

Accepted Answer

20-20,000 Hz

Answer

1500-6000 Hz

Answer

10,000-15,000 Hz

Answer

20,000-25,000 Hz

Sensory Systems — MCQs

Sensory Systems — MCQs

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