Sensory Systems Practice Questions

Q: Receptors that are stimulated by a change in the chemical composition of the environment are:

Chemoreceptors. ***Chemoreceptors*** - They are specifically designed to detect and respond to **chemical stimuli**, such as the concentration of various substances in the environment or bodily fluids. - Examples include receptors for taste, smell, blood pH, and oxygen levels. *Nociceptors* - These receptors are responsible for detecting and signaling **painful stimuli**, which can be thermal, mechanical, or chemical, but their primary function is pain detection, not chemical composition change itself. - They are activated by noxious stimuli that threaten tissue damage. *Mechanoreceptors* - These receptors respond to **mechanical forces** such as pressure, stretch, touch, and vibration. - Examples include Pacinian corpuscles, Meissner's corpuscles, and receptors in the skin and muscles responsible for touch and proprioception. *None of the options* - This option is incorrect because **chemoreceptors** accurately describe receptors stimulated by changes in chemical composition.

Q: Which of the following will occur in a girl who suddenly stops spinning after several seconds of spinning to the left?

Her eyes will move slowly to the right. ***Her eyes will move slowly to the right*** - After spinning to the left and suddenly stopping, **post-rotatory nystagmus** occurs due to continued endolymph movement. - The endolymph continues to move to the LEFT due to **inertia**, creating a sensation of rotating to the **RIGHT**. - This produces **nystagmus** with the **slow phase to the right** (direction of perceived rotation) and fast corrective phase to the left. - The **vestibulo-ocular reflex** generates this nystagmus as the brain interprets the continued endolymph movement as actual rotation. *The hair cells in the right semicircular canal will depolarize* - This is incorrect. Upon stopping a left spin, the endolymph continues moving LEFT due to inertia. - In the **right horizontal canal**, this creates **ampullary-petal flow** (toward the ampulla), which causes **hyperpolarization**, not depolarization. - During the actual left spin, it was the **left canal** that was depolarized (ampullary-fugal flow in horizontal canals causes excitation). *When asked to point to a target, the girl will point to the right of the target* - After stopping from spinning left, the sensation is of spinning to the RIGHT, causing a **past-pointing phenomenon**. - This perceived rightward rotation causes the person to point to the **LEFT** of the target, not the right. - The brain compensates for the perceived motion in the wrong direction. *The cupula in the right semicircular canal will move away from the utricle* - Upon stopping, the endolymph in the right canal continues moving to the LEFT (original spin direction) due to inertia. - This deflects the cupula **toward the utricle** (ampullary-petal), not away from it. - Ampullary-petal deflection in horizontal canals causes hyperpolarization of hair cells.

Q: Ruffini end organ is associated with sensation of?

Position sense. ***Position sense*** - **Ruffini end organs** are slow-adapting mechanoreceptors located in the **dermis** and subcutaneous tissue that are primarily specialized for detecting **skin stretch**. - They play a significant role in **proprioception** (position sense) by sensing static skin displacement and joint angles, particularly in the fingers and joints. - Modern physiology emphasizes their contribution to **position sense** and detection of sustained stretch rather than just pressure. *Pressure* - While Ruffini endings can detect sustained pressure, this is not their primary function. - **Merkel discs** are the main receptors for sustained pressure and fine touch discrimination. - **Pacinian corpuscles** detect deep pressure and vibration. *Vibration* - **Pacinian corpuscles** are rapidly adapting mechanoreceptors specialized for detecting **vibration** and deep pressure. - **Meissner's corpuscles** detect light touch and low-frequency vibration. *Cold* - The sensation of **cold** is detected by specialized **cold thermoreceptors** (free nerve endings). - **Krause end bulbs** (whose existence as distinct receptors is now debated) were historically associated with cold sensation.

Q: Two point discrimination test exhibits maximum sensitivity in -

Finger pads. ***Finger pads*** - The **finger pads** have a high density of **Meissner's corpuscles** and other sensory receptors, allowing for fine tactile discrimination. - This region is crucial for activities requiring high tactile sensitivity and dexterity, resulting in a very small **two-point discrimination threshold**. *Toes* - While toes have some tactile sensitivity, their receptor density is **significantly lower** than that found in the finger pads. - The primary function of toes involves balance and propulsion rather than fine tactile discrimination. *Shin* - The **shin** (anterior lower leg) has a relatively sparse distribution of tactile receptors compared to distal extremities. - This area is not designed for fine touch perception, resulting in a **large two-point discrimination threshold**. *Soles* - The **soles of the feet** are adapted for sensory input related to pressure, texture, and proprioception for balance and locomotion. - Although the soles have numerous receptors, they are generally less sensitive for **two-point discrimination** than the finger pads, reflecting a different functional specialization.

Q: Fine touch is detected by

Merkel's disc. ***Merkel's disc*** - **Merkel's discs** are specialized cells located in the **basal layer of the epidermis** that are responsible for detecting sustained pressure and light/fine touch. - They are **slowly adapting mechanoreceptors**, meaning they continue to fire as long as the stimulus is present, providing detailed information about touch. *Pacinian corpuscle* - **Pacinian corpuscles** are **rapidly adapting mechanoreceptors** located deeper in the dermis and subcutaneous tissue. - They are primarily involved in detecting **vibration** and **deep pressure**, not fine touch. *Ruffini's nerve ending* - **Ruffini's corpuscles** are **slowly adapting mechanoreceptors** found in the deep dermis, subcutaneous tissue, and joint capsules. - They respond to **stretch** and **sustained pressure**, contributing to our sense of joint position and skin stretch. *Krausse's bulb* - **Krause's end bulbs** (or Krause's corpuscles) are believed to be **thermoreceptors** that detect **cold sensation**. - They are found in mucous membranes (e.g., mouth, conjunctiva) and some skin areas, not primarily involved in fine touch.

Q: Stimulation by touching or pulling on which structure is least likely to cause a painful sensation?

The postcentral gyrus. ***The postcentral gyrus*** - The **brain parenchyma**, including the postcentral gyrus, **lacks pain receptors (nociceptors)**. Therefore, direct stimulation or manipulation of brain tissue itself does not elicit a sensation of pain. - Patients can be fully conscious during some brain surgeries without pain from the brain tissue being operated on, though they may experience other sensations or deficits depending on the stimulated area. *The dura overlying the postcentral gyrus* - The **dura mater** is highly innervated by **nociceptors**, particularly in certain areas like the anterior and middle cranial fossae. Traction or irritation of the dura can cause significant pain, often referred to specific head regions. - This pain is mediated by cranial nerves, such as the trigeminal and vagus nerves, and cervical spinal nerves. *Branches of the middle cerebral artery that supply the postcentral gyrus* - The **blood vessels** supplying the brain, including branches of the **middle cerebral artery**, are invested with **pain fibers**. - Stretching or irritation of these blood vessels, especially during procedures or in pathological conditions like **vasospasm**, can cause referred pain sensations. *Branches of the middle meningeal artery that lie between the skull and dura over the postcentral gyrus* - The **middle meningeal artery** and its branches run in the **epidural space** (between the skull and dura mater) and contribute to pain sensation in this region. - Like the dura itself, these vessels and their surrounding tissues contain **nociceptors**, and their manipulation or irritation can cause significant pain, often perceived as a headache.

Q: Cochlear microphonic potentials are primarily produced by

Produced by outer hair cells. ***Outer hair cells*** - **Cochlear microphonic potentials** are primarily generated by the activity of **outer hair cells** in response to sound stimulation. - These potentials represent the **AC receptor potential** of the hair cells, directly reflecting the mechanical vibrations of the basilar membrane. - Outer hair cells have electromotile properties and their depolarization/hyperpolarization generates the cochlear microphonic. *Inner hair cells primarily transmit auditory signals* - **Inner hair cells** are primarily responsible for transmitting **auditory signals** to the brain via the auditory nerve (95% of afferent nerve fibers). - While inner hair cells also generate receptor potentials, the predominant contribution to the **cochlear microphonic potential** is from the **outer hair cells**. - Inner hair cells function mainly in sensory transduction rather than amplification. *Electrodes near the round window provide stronger signals* - This is true for **measurement** of cochlear microphonics, but doesn't describe what produces them. - Round window placement offers stronger signals for recording cochlear potentials due to proximity to the source. *Surface electrodes can measure it with reduced sensitivity* - This describes a **measurement technique**, not the cellular source of production. - While detection is possible, the signal is heavily attenuated through temporal bone and tissues.

Q: At what decibel level does auditory fatigue occur?

90 dB. ***90 dB*** - Auditory fatigue, a temporary shift in hearing threshold, typically begins with prolonged exposure to sound levels around **90 dB**. - This level is considered the lower limit for continuous exposure that can lead to **temporary threshold shift (TTS)**, a precursor to permanent damage if exposure continues. *80 dB* - While prolonged exposure to 80 dB can be irritating or cause a sense of discomfort, it is generally considered the threshold for initiating noise-induced hearing damage over a very long period, rather than the immediate onset of **auditory fatigue**. - The risk of **auditory fatigue** and **temporary threshold shift** is significantly lower at 80 dB compared to 90 dB, especially for shorter exposures. *50 dB* - Sound levels at 50 dB are comparable to a quiet conversation or a refrigerator hum and are well below the threshold for experiencing **auditory fatigue** or hearing damage. - Exposure to 50 dB is generally considered safe and comfortable, with no significant impact on **auditory thresholds**. *60 dB* - 60 dB is a common sound level for normal conversation and is not associated with the onset of **auditory fatigue** or risk of hearing damage. - At this level, the **auditory system** is not under significant stress that would cause a temporary change in hearing acuity.

Q: What is the function of the tip of the hair cell in utricle?

Receptor membrane Depolarization. ***Receptor membrane Depolarization*** - The **utricle** is part of the vestibular system, containing hair cells with stereocilia that bend in response to head movements, specifically **horizontal linear acceleration** and **static head tilt**. - This bending creates tension in tip links, opening **potassium channels** at the hair cell tips, leading to an influx of K+ ions and subsequent **depolarization** of the receptor membrane. *Vision* - Vision is the sense of sight, which is the function of the **eyes** and the visual processing centers in the brain, not the inner ear structures like the utricle. - The **photoreceptor cells** (rods and cones) in the retina are responsible for transducing light into electrical signals. *Hearing* - Hearing is the function of the **cochlea**, another part of the inner ear, where sound vibrations are converted into electrical signals by hair cells. - The utricle is primarily involved in **balance and spatial orientation**, not auditory perception. *Formation of perilymph* - Perilymph is a fluid found in the **scala tympani** and **scala vestibuli** of the cochlea, important for the mechanics of hearing, but its formation is not directly a function of the hair cell tips. - Perilymph is similar in composition to cerebrospinal fluid and is secreted by cells within the bony labyrinth.

Question 1

Receptors that are stimulated by a change in the chemical composition of the environment are:

Accepted Answer

Chemoreceptors

Answer

Nociceptors

Answer

Mechanoreceptors

Answer

None of the options

Question 2

Which of the following will occur in a girl who suddenly stops spinning after several seconds of spinning to the left?

Accepted Answer

Her eyes will move slowly to the right

Answer

The hair cells in the right semicircular canal will depolarize

Answer

When asked to point to a target, the girl will point to the right of the target

Answer

The cupula in the right semicircular canal will move away from the utricle

Question 3

Ruffini end organ is associated with sensation of?

Accepted Answer

Position sense

Answer

Vibration

Answer

Cold

Answer

Pressure

Question 4

Two point discrimination test exhibits maximum sensitivity in -

Accepted Answer

Finger pads

Answer

Toes

Answer

Shin

Answer

Soles

Question 5

Fine touch is detected by

Accepted Answer

Merkel's disc

Answer

Pacinian corpuscle

Answer

Ruffini's nerve ending

Answer

Krause's end bulb

Question 6

Stimulation by touching or pulling on which structure is least likely to cause a painful sensation?

Accepted Answer

The postcentral gyrus

Answer

The dura overlying the postcentral gyrus

Answer

Branches of the middle cerebral artery that supply the postcentral gyrus

Answer

Branches of the middle meningeal artery that lie between the skull and dura over the postcentral gyrus

Question 7

Which statement concerning sensory neurons or their functional properties is true?

Accepted Answer

In spatial summation, increasing signal strength is transmitted by using progressively greater numbers of sensory fibers

Answer

Continuous subthreshold stimulation of a pool of sensory neurons results in disfacilitation of those neurons

Answer

Increased stimulus intensity is signaled by a progressive decrease in the receptor potential

Answer

All sensory fibers are unmyelinated

Question 8

Cochlear microphonic potentials are primarily produced by

Accepted Answer

Produced by outer hair cells

Answer

Inner hair cells

Answer

Supporting cells of the organ of Corti

Answer

Spiral ganglion neurons

Question 9

At what decibel level does auditory fatigue occur?

Accepted Answer

90 dB

Answer

80 dB

Answer

50 dB

Answer

60 dB

Question 10

What is the function of the tip of the hair cell in utricle?

Accepted Answer

Receptor membrane Depolarization

Answer

Vision

Answer

Hearing

Answer

Formation of perilymph

Sensory Systems — MCQs

Sensory Systems — MCQs

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