Sensory Systems Practice Questions

Q: Sour taste is mediated by which of the following receptors?

OTOP1. ***OTOP1*** - The **OTOP1** receptor, an **otopetrin protein**, is responsible for detecting the **sour taste** sensation by mediating proton influx. - It functions as a **proton channel**, allowing hydrogen ions (H+) from acidic substances to enter taste receptor cells. *T1R1* - **T1R1** is a component of the **umami (savory) taste receptor**, forming a heterodimer with T1R3 to detect glutamate. - It does not directly detect sourness but is involved in the perception of amino acids. *T1R2* - **T1R2** is a component of the **sweet taste receptor**, forming a heterodimer with T1R3 to detect sugars. - This receptor is not involved in the transduction of sour taste. *T1R3* - **T1R3** is a common subunit that combines with **T1R1** for umami taste and with **T1R2** for sweet taste. - While essential for sweet and umami, it does not directly mediate the perception of sourness.

Q: Match the following receptors with their correct functions: Receptors: 1. Ruffini corpuscle 2. Merkel cells 3. Pacinian corpuscle 4. Meissner's corpuscle Functions: A. Vibration B. Sustained pressure C. Stretching D. Fine touch Select the option that correctly matches each receptor (1-4) with its function (A-D).

1C 2B 3A 4D. ***1C 2B 3A 4D*** - **Ruffini corpuscles** (1) detect **stretching** (C) of the skin. They are **slow-adapting Type II mechanoreceptors** located deep in the dermis, responding to sustained skin stretch and contributing to proprioception. - **Merkel cells** (2) detect **sustained pressure** (B) and fine texture discrimination. They are **slow-adapting Type I mechanoreceptors** with the highest spatial resolution, providing detailed information about touch. - **Pacinian corpuscles** (3) detect **vibration** (A), particularly high-frequency vibrations (200-300 Hz). They are **rapidly adapting receptors** with an onion-like lamellated structure located deep in the dermis and subcutaneous tissue. - **Meissner's corpuscles** (4) detect **fine touch** (D) and light pressure. They are **rapidly adapting receptors** located in dermal papillae of glabrous (hairless) skin, particularly abundant in fingertips and lips. *1C 2D 3B 4A* - Incorrectly assigns Merkel cells to fine touch (should be sustained pressure) and Pacinian corpuscles to sustained pressure (should be vibration). - Meissner's corpuscles are mismatched with vibration instead of fine touch. *1D 2C 3B 4A* - Incorrectly assigns Ruffini corpuscles to fine touch (should be stretching) and Merkel cells to stretching (should be sustained pressure). - Pacinian corpuscles are mismatched with sustained pressure (should be vibration). - Meissner's corpuscles are mismatched with vibration (should be fine touch). *1B 2A 3D 4C* - Completely incorrect matching: Ruffini to sustained pressure, Merkel to vibration, Pacinian to fine touch, and Meissner's to stretching. - Demonstrates fundamental misunderstanding of mechanoreceptor functions.

Q: The bitter taste of toxic substances prevents us from their consumption, which of the following elicits the bitterness?

Alkaloids. ***Alkaloids*** - **Alkaloids** are a large group of naturally occurring chemical compounds that are mostly produced by plants, often having marked physiological actions on humans and other animals. - Many alkaloids, such as **quinine** and **strychnine**, have a characteristic **bitter taste**, which serves as a natural defense mechanism for plants against herbivores. *Aldehyde* - **Aldehydes** are organic compounds characterized by a carbonyl group to which a hydrogen atom and an R-group are attached. - While some aldehydes may have strong or pungent odors, they do not typically elicit a **bitter taste** in the same way alkaloids do; some might be sweet or fruity. *Hydrogen ions* - **Hydrogen ions (H+)** are responsible for **acidity** and are detected as a **sour taste**. - The sensation of sourness is directly related to the concentration of hydrogen ions in a substance, not bitterness. *Amino acids* - **Amino acids** are the building blocks of proteins and can elicit various tastes depending on their specific structure. - Some amino acids are **sweet** (e.g., alanine, glycine), some are **umami** (e.g., glutamate), and some are **bitter** only in certain contexts or at high concentrations, but they are not the primary group defining a broad bitter taste like alkaloids.

Q: Pacinian corpuscle is stimulated by which of the following?

Pressure. ***Pressure*** - **Pacinian corpuscles** are rapidly adapting mechanoreceptors that detect **deep pressure** and **vibrations**. - Their layered, onion-like structure allows them to be very sensitive to rapid changes in pressure. *Pain* - **Pain** is primarily detected by **nociceptors**, which are free nerve endings, not Pacinian corpuscles. - Nociceptors respond to various noxious stimuli, including mechanical, thermal, and chemical. *Temperature* - **Temperature** changes are detected by **thermoreceptors**, such as Krause end bulbs for cold and Ruffini endings for warmth, not Pacinian corpuscles. - These receptors have specific temperature ranges over which they are active. *Touch* - **Touch** sensation is broadly detected by several mechanoreceptors, including **Meissner's corpuscles** (light touch), **Merkel discs** (sustained touch), and hair follicle receptors. - While Pacinian corpuscles contribute to sensing touch through deep pressure, they are not the primary receptors for general light or sustained touch.

Q: An exaggerated pain response to a normally painful stimulus is called:

Hyperalgesia. ***Hyperalgesia*** - This term describes an **increased sensitivity to pain** where a stimulus that is normally painful is perceived as even more painful than usual. - It often results from **damage to nociceptive afferent pathways** or central sensitization. *Causalgia* - This is an older term now largely replaced by complex regional pain syndrome type II (**CRPS II**), characterized by severe, burning pain following a **nerve injury**. - Unlike hyperalgesia, it specifically refers to a **syndrome of severe pain** after nerve trauma, not just an increased response to noxious stimuli. *Allodynia* - This refers to pain caused by a stimulus that **does not normally provoke pain**, such as light touch or brushing of the skin. - It differs from hyperalgesia, which is an exaggerated response to a **normally painful stimulus**. *Hypersensitivity* - This is a **general term** meaning an increased physical or allergic sensitivity to a substance or condition. - It is a **broader concept** and not as specific to pain perception as hyperalgesia or allodynia.

Q: The mechanoreceptors in joints and ligaments are:

Slow adapting. ***Slow adapting*** - **Mechanoreceptors** in joints and ligaments, such as **Ruffini endings** and **Golgi-type endings**, are primarily **slowly adapting**. - This characteristic allows them to provide continuous information about **joint position** and **pressure** over extended periods. *Adapt differentially for different stresses* - While different mechanoreceptors respond to different types of stimuli (e.g., pressure, stretch), this option describes varying responses rather than the fundamental **adaptation rate**. - The primary characteristic being asked for is how their firing rate changes over time in response to a constant stimulus. *Fast adapting* - **Fast-adapting mechanoreceptors**, like **Pacinian corpuscles** and **Meissner's corpuscles**, respond strongly at the onset and offset of a stimulus. - They are more involved in sensing **vibration** and **changes in pressure** rather than sustained joint position. *Non adapting* - All biological sensory receptors exhibit some degree of **adaptation** to a constant stimulus, meaning their firing rate changes over time. - A truly **non-adapting** receptor would fire at a constant rate indefinitely for a given stimulus, which is not characteristic of mechanoreceptors.

Q: A 10-year-old boy cuts his finger with a pocketknife and immediately applies pressure to the damaged area with his other hand to partially alleviate the pain. Inhibition of pain signals by tactile stimulation of the skin is mediated by which type of afferent neurons from mechanoreceptors?

Aβ. ***Aβ*** - **Aβ (A-beta) fibers** are large, myelinated afferent neurons that transmit discriminative touch and proprioception. - According to the **gate control theory of pain**, activation of these Aβ fibers by tactile stimulation can inhibit the transmission of pain signals (carried by Aδ and C fibers) in the spinal cord, explaining why rubbing an injured area can reduce pain. *Aδ* - **Aδ (A-delta) fibers** are thinly myelinated afferent neurons that transmit sharp, localized, and fast pain, as well as cold and touch. - While they are involved in pain transmission, they do not primarily mediate the inhibition of pain signals through tactile stimulation, but rather the initial painful sensation. *Type C* - **Type C fibers** are unmyelinated afferent neurons that transmit slow, dull, aching, and burning pain, as well as warmth and some touch. - These fibers are primarily responsible for the prolonged, chronic pain sensation and are inhibited by Aβ fiber activity, not the mediators of the pain inhibition themselves. *Aα* - **Aα (A-alpha) fibers** are the largest and fastest myelinated afferent neurons, primarily responsible for proprioception from muscle spindles (sensory information about muscle length and stretch), and motor innervation to extrafusal muscle fibers. - They are not directly involved in the tactile inhibition of pain signals.

Q: The vestibulocochlear nerve (VIII cranial nerve) carries afferent information for:

All of the options. ***All of the options*** - The **vestibulocochlear nerve (cranial nerve VIII)** is responsible for transmitting both **auditory (hearing)** and **vestibular (balance and spatial orientation)** information from the inner ear to the brain. - Its two main branches are the **cochlear nerve**, serving hearing, and the **vestibular nerve**, serving equilibrium and spatial orientation. *Equilibrium* - The vestibular component of the **VIII nerve** specifically relays sensory information concerning **head position and movement**, crucial for maintaining **equilibrium** and balance. - This input comes from the **semicircular canals** and **otolith organs (utricle and saccule)** in the inner ear. *Spatial orientation* - **Spatial orientation** refers to the body's awareness of its position and movement in space, a function directly supported by the **vestibular system** and transmitted via the **vestibular nerve** branch of cranial nerve VIII. - It involves processing cues about **linear and angular acceleration** from the inner ear. *Hearing* - The cochlear component of the **VIII nerve** transmits **auditory information** from the **cochlea** to the brain, enabling the perception of sound. - This involves converting **sound vibrations** into electrical signals.

Q: Which one of the following is not true about rods?

Useful for the color vision. ***Useful for the color vision*** - **Rods** are primarily responsible for **scotopic (low-light) vision** and **achromatic (black and white) vision**. - They lack the ability to differentiate between different wavelengths of light, thus contributing minimally to **color perception**. *Pigment is rhodopsin* - **Rhodopsin** is indeed the primary **photopigment** found in rod cells. - This pigment is highly sensitive to light, allowing rods to detect light even in **dim conditions**. *More sensitive to light than cones* - **Rods** are significantly more sensitive to light than cones, enabling vision in **low-light environments**. - This high sensitivity is due to their large number and the presence of **rhodopsin**, which is readily bleached by small amounts of light. *Least number is present in fovea centralis* - The **fovea centralis**, responsible for sharp central and color vision, is almost entirely composed of **cones**. - **Rods** are virtually absent in the fovea, increasing in density towards the periphery of the retina.

Question 1

Sour taste is mediated by which of the following receptors?

Accepted Answer

OTOP1

Answer

T1R1

Answer

T1R2

Answer

T1R3

Question 2

Match the following receptors with their correct functions:

Receptors:
1. Ruffini corpuscle
2. Merkel cells
3. Pacinian corpuscle
4. Meissner's corpuscle

Functions:
A. Vibration
B. Sustained pressure
C. Stretching
D. Fine touch

Select the option that correctly matches each receptor (1-4) with its function (A-D).

Accepted Answer

1C 2B 3A 4D

Answer

1C 2D 3B 4A

Answer

1D 2C 3B 4A

Answer

1B 2A 3D 4C

Question 3

Find the correct Auditory pathway sequence.

Accepted Answer

Eight nerve → cochlear nuclei → superior olivary nucleus → lateral lemniscus → inferior colliculus → medial geniculate body → auditory cortex

Answer

Superior olivary nucleus → lateral lemniscus → inferior colliculus → medial geniculate body → auditory cortex → Eight nerve → Cochlear nuclei

Answer

Cochlear nuclei → superior olivary nucleus → lateral lemniscus → inferior colliculus → medial geniculate body → auditory cortex → Eight nerve

Answer

Superior olivary nucleus → inferior colliculus → medial geniculate body → auditory cortex → Eight nerve → Cochlear nuclei → lateral lemniscus

Question 4

The bitter taste of toxic substances prevents us from their consumption, which of the following elicits the bitterness?

Accepted Answer

Alkaloids

Answer

Aldehyde

Answer

Hydrogen ions

Answer

Amino acids

Question 5

Pacinian corpuscle is stimulated by which of the following?

Accepted Answer

Pressure

Answer

Pain

Answer

Temperature

Answer

Touch

Question 6

An exaggerated pain response to a normally painful stimulus is called:

Accepted Answer

Hyperalgesia

Answer

Causalgia

Answer

Allodynia

Answer

Hypersensitivity

Question 7

The mechanoreceptors in joints and ligaments are:

Accepted Answer

Slow adapting

Answer

Adapt differentially for different stresses

Answer

Fast adapting

Answer

Non adapting

Question 8

A 10-year-old boy cuts his finger with a pocketknife and immediately applies pressure to the damaged area with his other hand to partially alleviate the pain. Inhibition of pain signals by tactile stimulation of the skin is mediated by which type of afferent neurons from mechanoreceptors?

Accepted Answer

Aβ

Answer

Aδ

Answer

Type C

Answer

Aα

Question 9

The vestibulocochlear nerve (VIII cranial nerve) carries afferent information for:

Accepted Answer

All of the options

Answer

Equilibrium

Answer

Spatial orientation

Answer

Hearing

Question 10

Which one of the following is not true about rods?

Accepted Answer

Useful for the color vision

Answer

Pigment is rhodopsin

Answer

More sensitive to light than cones

Answer

Least number is present in fovea centralis

Sensory Systems — MCQs

Sensory Systems — MCQs

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