Sensory Systems Practice Questions

Q: What is the SI unit of luminous intensity?

Candela. ***Candela*** - The **candela (cd)** is the **SI base unit** used to measure **luminous intensity**. - **Luminous intensity** quantifies the power emitted by a light source in a particular direction per unit solid angle. *Lumen* - The **lumen (lm)** is the **SI derived unit** for **luminous flux**, which measures the total perceived power of light. - It describes the total amount of visible light emitted by a source in all directions, not its intensity in a specific direction. *Lux* - The **lux (lx)** is the **SI derived unit** for **illuminance**, which measures how much luminous flux is spread over a given area. - It indicates the perceived brightness of a surface, rather than the intensity of the light source itself. *Coulomb* - The **coulomb (C)** is the **SI derived unit** for **electric charge**. - It is completely unrelated to light or luminous intensity.

Q: Miracle fruit is used to change the taste from?

Sour to Sweet. ***Sour to Sweet*** - The **miracle fruit** (Synsepalum dulcificum) contains a glycoprotein called **miraculin**. - Miraculin binds to taste receptors on the tongue and modifies their perception, making **sour foods taste sweet**. *Sour to Bitter* - The primary effect of miracle fruit is to convert **sour tastes into sweet tastes**, not bitter ones. - No known natural compound consistently changes sour perception to bitter. *Bitter to Sweet* - While miraculin makes sour foods sweet, it does not typically convert **bitter tastes into sweet sensations**. - Bitter taste perception involves different receptor pathways that are not significantly altered by miraculin. *Salty to Sweet* - Miracle fruit primarily targets **sour taste receptors**. - It does not have a significant effect on altering the perception of **salty tastes to sweet**.

Q: Which of the following receptors is stimulated by sustained pressure?

Ruffini's end organ. ***Ruffini's end organ*** - These are **slowly adapting mechanoreceptors** located deep in the dermis and subcutaneous tissue. - They are responsible for detecting **sustained pressure**, stretch, and position sense. *Merkel's disc* - These are **slowly adapting mechanoreceptors** found in the basal epidermis. - They are crucial for sensing **light touch** and **two-point discrimination**. *Hair cells* - These are **mechanoreceptors** primarily found in the inner ear, responsible for hearing and balance. - They are not involved in the perception of somatosensory stimuli like pressure on the skin. *Meissner Corpuscles* - These are **rapidly adapting mechanoreceptors** located in the dermal papillae, close to the skin surface. - They are primarily involved in detecting **light touch** and **discriminative touch**, especially changes in texture.

Q: Vibrations are detected by which types of receptors?

Rapidly adapting. ***Rapidly adapting*** - **Rapidly adapting mechanoreceptors**, such as **Pacinian corpuscles** and **Meissner's corpuscles**, are highly sensitive to changes in pressure and movement. - They fire at the **onset and offset of a stimulus**, making them ideal for detecting vibrations, which are rhythmic changes in pressure. *Slowly adapting* - **Slowly adapting mechanoreceptors**, such as **Merkel cells** and **Ruffini endings**, are responsible for sustained pressure and touch. - They continue to fire as long as the stimulus is present, making them less suited for detecting transient vibratory stimuli. *Non-adapting* - The human body does not typically have **truly non-adapting** sensory receptors; most receptors show some form of adaptation to continuous stimuli. - This term is not standard in the classification of mechanoreceptors based on their adaptation rates. *None of the above* - This option is incorrect because rapidly adapting receptors are indeed responsible for detecting vibrations.

Q: Stapedius pulls stapes in which direction?

Posterior. ***Posterior*** - The **stapedius muscle** attaches to the **posterior surface of the stapes neck**. - Contraction of the stapedius muscle pulls the stapes **posteriorly and laterally** (posterolaterally), tilting the footplate away from the oval window and reducing sound transmission. - This action dampens excessive vibrations and protects the inner ear from loud sounds as part of the **acoustic reflex**. *Anterior* - Pulling the stapes anteriorly would push the footplate further into the **oval window**, which would increase sound transmission rather than dampen it. - No muscle pulls the stapes anteriorly in the context of the **acoustic reflex**. *Superior* - The stapedius muscle's action is primarily along the **posterolateral axis**, not superiorly. - Pulling superiorly would not effectively dampen sound vibrations or protect the inner ear from acoustic trauma. *Inferior* - The anatomy and function of the stapedius muscle do not support an inferior pulling action. - The stapedius acts to stabilize and retract the stapes **posterolaterally**, not inferiorly.

Q: Which of the following stimuli is detected by the vestibular macula?

Linear acceleration. ***Linear acceleration*** - The **maculae** (in the utricle and saccule) are specifically designed to detect **linear acceleration**, including both dynamic movements (speeding up in a car, elevator motion) and the constant linear acceleration of **gravity**. - Hair cells in the maculae are displaced by movements of the **otolithic membrane** containing **otoconia** (calcium carbonate crystals) in response to linear acceleration forces. - The utricle primarily detects **horizontal linear acceleration**, while the saccule detects **vertical linear acceleration**. *Gravity* - While gravity is indeed detected by the maculae, gravity is actually a form of **constant linear acceleration** (9.8 m/s²). - The maculae use gravity to determine **static head position** and orientation, but this is a subset of their broader function of detecting linear acceleration. - "Linear acceleration" is the more comprehensive and physiologically accurate term. *Change in head position* - This term is too broad and encompasses both **linear** and **angular (rotational)** movements. - **Angular acceleration** (rotation) is detected by the **semicircular canals**, not the maculae. - The maculae specifically detect linear position changes relative to gravity, not rotational changes. *None of the options* - This is incorrect because the vestibular macula clearly detects linear acceleration as its primary function.

Q: Which of the following is responsible for localization of sound ?

Superior olivary nucleus. ***Superior olivary nucleus*** - The **superior olivary nucleus** is the first site in the auditory pathway where binaural (two-ear) input is integrated, which is crucial for **sound localization**. - It processes **interaural time differences (ITDs)** and **interaural level differences (ILDs)** to determine the horizontal position of a sound source. *Cochlear nerve* - The **cochlear nerve** transmits auditory information from the cochlea to the brainstem but does not perform the initial processing for sound localization. - It carries impulses for both ears independently, which are then integrated at higher centers. *Cochlea* - The **cochlea** is responsible for converting sound vibrations into electrical signals (transduction), encoding properties like pitch and loudness, but not directly for sound localization. - It acts as a mechanical analyzer, separating sound into its frequency components. *Cochlear nuclei* - The **cochlear nuclei** receive input solely from the ipsilateral cochlear nerve and primarily process monaural (one-ear) auditory information. - While they are a crucial relay in the auditory pathway, they do not integrate binaural cues for sound localization.

Q: Ossicles of middle ear are responsible for which of the following ?

Reduction of impedance for sound transmission. ***Reduction of impedance for sound transmission*** - The ossicles (malleus, incus, and stapes) act as a **lever system** to match the impedance between the air-filled outer ear and the fluid-filled inner ear. - This impedance matching ensures that maximum sound energy is transferred to the cochlea, preventing significant **sound reflection**. *Amplification of sound intensity* - While the ossicles do slightly amplify the sound pressure, their primary role is not extensive amplification but rather **impedance matching**. - The amplification achieved is a byproduct of efficient energy transfer, rather than a direct goal of increasing sound intensity for its own sake. *Reduction of sound intensity* - This function is primarily attributed to the **acoustic reflex**, where the middle ear muscles contract to stiffen the ossicular chain in response to loud sounds. - The primary function of the ossicles themselves is to transmit sound efficiently, not to reduce intensity under normal conditions. *Protecting the inner ear* - While the **acoustic reflex** (involving middle ear muscles attached to the ossicles) offers some protection against very loud sounds by stiffening the ossicular chain, this is a separate, reflexive mechanism. - The intrinsic structure and primary mechanical function of the ossicles are centered on efficient sound transmission, not direct physical protection of the inner ear.

Q: Stimulation of horizontal semicircular canal causes nystagmus in which directions?

Horizontal. ***Horizontal*** - Stimulation of the **horizontal semicircular canal** primarily detects **angular acceleration** in the horizontal plane, causing compensatory eye movements. - This results in a **horizontal nystagmus**, where the slow phase of the eye movement is opposite to the direction of head rotation, and the fast phase is in the same direction. *Vertical nystagmus* - **Vertical nystagmus** is typically associated with stimulation of the **anterior** or **posterior semicircular canals**, which detect angular acceleration in the sagittal and coronal planes, respectively. - It can also indicate **central nervous system lesions**, particularly in the brainstem or cerebellum. *Rotary nystagmus* - **Rotary (torsional) nystagmus** is often associated with stimulation of the **posterior semicircular canal** or can be a sign of specific central vestibular disorders. - It involves eye movements that rotate around the visual axis. *Any of the three* - The type of nystagmus (horizontal, vertical, or rotary) is specific to the **semicircular canal** being stimulated and the plane of angular acceleration. - A single canal stimulation typically elicits a specific direction of eye movement, not a mixture of all types.

Q: Which of the following is classified as a pain receptor?

Free nerve endings. ***Free nerve endings*** - **Free nerve endings** are the most common type of sensory receptor in the skin and are responsible for detecting **pain**, temperature, and crude touch. - They lack specialized structures and are found throughout the epidermis and dermis. *Meissner's corpuscle* - **Meissner's corpuscles** are encapsulated nerve endings that detect **light touch** and **vibration**. - They are rapidly adapting and are abundant in sensitive, hairless skin areas like fingertips and lips. *Pacinian corpuscle* - **Pacinian corpuscles** are large, encapsulated receptors that detect **deep pressure** and **vibration**. - They are rapidly adapting and respond to high-frequency stimuli. *Merkel disc* - **Merkel discs** are specialized epithelial cells associated with nerve endings that detect **sustained pressure** and **texture**. - They are slowly adapting receptors crucial for tactile discrimination.

Question 1

What is the SI unit of luminous intensity?

Accepted Answer

Candela

Answer

Lumen

Answer

Lux

Answer

Coulomb

Question 2

Miracle fruit is used to change the taste from?

Accepted Answer

Sour to Sweet

Answer

Sour to Bitter

Answer

Bitter to Sweet

Answer

Salty to Sweet

Question 3

Which of the following receptors is stimulated by sustained pressure?

Accepted Answer

Ruffini's end organ

Answer

Merkel's disc

Answer

Hair cells

Answer

Meissner Corpuscles

Question 4

Vibrations are detected by which types of receptors?

Accepted Answer

Rapidly adapting

Answer

Slowly adapting

Answer

Non-adapting

Answer

None of the above

Question 5

Stapedius pulls stapes in which direction?

Accepted Answer

Posterior

Answer

Answer

Superior

Answer

Inferior

Question 6

Which of the following stimuli is detected by the vestibular macula?

Accepted Answer

Linear acceleration

Answer

Change in head position

Answer

None of the options

Answer

Gravity

Question 7

Which of the following is responsible for localization of sound ?

Accepted Answer

Superior olivary nucleus

Answer

Cochlear nerve

Answer

Cochlea

Answer

Cochlear nuclei

Question 8

Ossicles of middle ear are responsible for which of the following ?

Accepted Answer

Reduction of impedance for sound transmission

Answer

Amplification of sound intensity

Answer

Reduction of sound intensity

Answer

Protecting the inner ear

Question 9

Stimulation of horizontal semicircular canal causes nystagmus in which directions?

Accepted Answer

Horizontal

Answer

Any of the three

Answer

Vertical nystagmus

Answer

Rotary nystagmus

Question 10

Which of the following is classified as a pain receptor?

Accepted Answer

Free nerve endings

Answer

Meissner's corpuscle

Answer

Pacinian corpuscle

Answer

Merkel disc

Sensory Systems — MCQs

Sensory Systems — MCQs

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