Sensory Systems Practice Questions

Q: Vibrations are felt by?

Pacinian corpuscle. ***Pacinian corpuscle*** - **Pacinian corpuscles** are rapidly adapting mechanoreceptors located deep in the dermis and subcutaneous tissue. - They are highly sensitive to **vibrations** and deep pressure, detecting rapid changes in mechanical stimuli. *Merkel's disc* - **Merkel's discs** are slowly adapting mechanoreceptors found in the basal epidermis. - They are primarily responsible for sensing **light touch**, pressure, and texture discrimination, not vibrations. *Ruffini's end organ* - **Ruffini's end organs** (or corpuscles) are slowly adapting mechanoreceptors located in the dermis and subcutaneous tissue. - They detect **skin stretch**, sustained pressure, and proprioception, contributing to the sense of position and continuous touch. *Meissner's corpuscle* - **Meissner's corpuscles** are rapidly adapting mechanoreceptors located in the dermal papillae, close to the skin surface. - They are responsible for sensing **light touch** and low-frequency vibrations (flutter), but the Pacinian corpuscles are more specialized for higher-frequency vibrations.

Q: The parvocellular pathway from lateral geniculate nucleus to visual cortex is most sensitive for the stimulus of

Fine spatial detail. ***Fine spatial detail*** - The **parvocellular pathway** is specialized for processing **high-acuity vision**, including color and fine spatial resolution. - Its neurons have **small receptive fields** and respond best to detailed patterns and stationary objects. *Saccadic eye movements* - **Saccadic eye movements** are rapid eye movements controlled by various brain regions, but their generation and control are not directly the primary function of the parvocellular pathway. - These movements are involved in scanning the visual field to bring objects of interest onto the fovea, which is then analyzed by the parvocellular pathway. *Luminance contrast* - While the parvocellular pathway does respond to contrast, the **magnocellular pathway** is more specialized for detecting rapid changes in **luminance contrast** and motion. - The magnocellular pathway has larger receptive fields and processes information about movement and depth. *Temporal frequency* - **Temporal frequency**, or the rate of flicker or motion, is primarily processed by the **magnocellular pathway**. - This pathway is optimized for detecting movement and rapid changes in the visual scene, rather than fine spatial details.

Q: Most recently identified taste sensation is?

Umami. ***Umami*** - **Umami** is the most recently identified **fifth basic taste**, often described as a savory or meaty taste. - Its discovery and recognition as a distinct taste sensation occurred in the **early 20th century** by Kikunae Ikeda, who isolated glutamate from kombu. *Sour* - The sensation of **sourness** is one of the traditionally recognized basic tastes, identified much earlier than umami. - It is typically associated with **acids**, such as those found in lemons or vinegar. *Bitter* - **Bitterness** is another long-standing basic taste that serves an important protective function, often signaling potential toxins. - It is one of the earliest tastes understood and recognized, with receptors for a wide range of bitter compounds. *Sweet* - **Sweetness** is a fundamental and ancient taste, universally recognized as pleasurable and indicating energy-rich foods. - The perception of sweet taste, primarily from sugars, has been understood for centuries.

Q: Which cells in the retina primarily depolarize in response to light stimulation?

Bipolar cells. ***Bipolar cells*** - **Bipolar cells** receive input from photoreceptors and are the first cells in the retinal pathway to depolarize in response to light stimulation. - Specifically, **ON-center bipolar cells** depolarize when light falls on the center of their receptive field, while OFF-center bipolar cells hyperpolarize. - The question refers to the **ON-center bipolar cells**, which show the characteristic depolarization response to light, transmitting excitatory signals to ganglion cells. *Amacrine cells* - **Amacrine cells** are interneurons that modulate signals between bipolar cells and ganglion cells. - They primarily process **temporal** and **spatial** aspects of visual information and provide lateral inhibition. - They do not primarily depolarize as a direct response to light stimulation. *Horizontal cells* - **Horizontal cells** provide **lateral inhibition** at the photoreceptor-bipolar cell synapse, enhancing contrast and spatial resolution. - They generally **hyperpolarize** in response to light and modulate photoreceptor output. - They do not serve as primary depolarizing cells in the light response pathway. *Rods and cones* - **Rods and cones** are photoreceptor cells that **hyperpolarize** (not depolarize) in response to light. - In darkness, they are depolarized and continuously release glutamate; light causes closure of cGMP-gated channels, leading to hyperpolarization. - This hyperpolarization is the initial transduction event that subsequently modulates bipolar cell activity.

Q: Sound intensity of whispering is:

30 dB. ***30 dB*** - The **sound intensity** of whispering is approximately **30 decibels (dB)**, which is a quiet but clearly audible sound level. - This level is often used as a reference point for very low-level ambient noise. - Whispering typically ranges from **20-30 dB**, making 30 dB the upper end of the normal whispering range. *90 dB* - **90 dB** represents a significantly louder sound, comparable to that of a **lawnmower** or **jackhammer** from a distance, and is much louder than a whisper. - Prolonged exposure to sound levels at or above **85 dB** can cause hearing damage. *120 dB* - **120 dB** is an extremely loud and potentially damaging sound level, similar to a **rock concert** or **jet engine at takeoff**. - Exposure to such high intensity can cause immediate pain and permanent hearing loss. *2 dB* - **2 dB** is an extraordinarily low sound intensity, barely audible, and would be perceived as almost **complete silence**. - This level is significantly quieter than a whisper and would typically be below the threshold of normal hearing in most environments.

Q: Which substance enhances the sensitivity of pain receptors but does not directly excite them?

Prostaglandins. ***Prostaglandins*** - **Prostaglandins** are lipid compounds that do not directly activate pain receptors, but they enhance the sensitivity of nociceptors to other painful stimuli. - They are released during **inflammation** and contribute to the sensation of pain by lowering the threshold for neuronal activation. *Potassium ions* - **Potassium ions** directly depolarize nociceptors, thereby **exciting them** and causing pain. - Tissue damage and cell lysis release intracellular potassium, leading to direct pain perception. *Bradykinin* - **Bradykinin** directly excites pain receptors via its specific receptors (B1 and B2 receptors), leading to rapid depolarization and pain signals. - It also contributes to inflammation and vasodilation. *Serotonin* - **Serotonin** (5-HT) can directly activate certain types of nociceptors (e.g., 5-HT3 receptors), thereby **directly exciting them**. - It is released by platelets at injury sites and contributes to both pain and inflammation.

Q: The rod receptor potential differs from other sensory receptors in that it shows

Hyperpolarization. ***Hyperpolarization*** - Rod photoreceptors are **unique among sensory receptors** because they **hyperpolarize** (rather than depolarize) in response to their adequate stimulus (light). - Light causes closure of **cGMP-gated sodium channels**, reducing sodium influx and causing membrane hyperpolarization. - This hyperpolarization **decreases** neurotransmitter (glutamate) release from the rod cell. - This is the **opposite** of most sensory receptors, which depolarize when stimulated. *Increased conductance of sodium* - In **darkness** (not light), rod cells maintain a high sodium conductance through open cGMP-gated channels, producing the "dark current." - **Light exposure decreases** (not increases) sodium conductance by causing channel closure. - This option represents what happens in the unstimulated (dark) state, not the light response. *Increased conductance of calcium* - Similar to sodium, **calcium ions** also flow through cGMP-gated channels that are open in darkness. - Light causes these channels to **close**, resulting in **decreased** calcium conductance. - This option incorrectly suggests an increase when the actual response is a decrease. *Depolarization* - **Most sensory receptors** (mechanoreceptors, chemoreceptors, thermoreceptors) respond to stimuli by **depolarizing**, which increases neurotransmitter release. - Rod photoreceptors are **depolarized in darkness** and **hyperpolarize when stimulated by light**. - This makes hyperpolarization the distinguishing feature of rod receptor potentials.

Q: A 60-year-old man presents to his primary care physician complaining that he often feels as if the room is spinning when he gets up from a recumbent position or turns his head. He has not lost consciousness and has had no chest pain. He has no cardiac history, and a recent treadmill test showed no abnormalities. On examination, the sensation can be produced by rapidly turning the head. It can be reproduced many times, but it eventually ceases. Nystagmus is elicited. Hearing is normal. Which of the following is the MOST likely mechanism for this patient's symptoms?

Aberrant stimulation of hair cells. ***Aberrant stimulation of hair cells*** - The symptoms of **positional vertigo** (room spinning with head movements) and fatigable nystagmus without hearing loss are characteristic of **benign paroxysmal positional vertigo (BPPV)**. - BPPV is caused by dislodged **otoconia** (calcium carbonate crystals) from the utricle that enter the semicircular canals, leading to inappropriate stimulation of the **hair cells** during head movements. *Insufficient cerebral perfusion* - While inadequate cerebral perfusion can cause dizziness or lightheadedness, it typically presents as **presyncope** or orthostatic hypotension, not the rotatory sensation of vertigo. - The patient's symptoms are specifically triggered by head movements and are not associated with changes in body position leading to systemic hypotension. *Insufficient cardiac output* - Insufficient cardiac output can lead to generalized weakness, lightheadedness, or syncope, but it rarely causes the specific sensation of **spinning vertigo** or movement-induced **nystagmus**. - The patient's recent **normal treadmill test** and lack of cardiac history make primary cardiac issues an unlikely cause for these specific symptoms. *Hair cell death in the semicircular canals* - **Hair cell death** would typically result in a permanent or persistent deficit, not a transient, positional vertigo that can be reproduced but eventually ceases (fatigues). - Conditions involving hair cell damage, such as **Meniere's disease** or **labyrinthitis**, often present with additional symptoms like hearing loss or tinnitus, which are absent in this patient.

Q: The parvocellular pathway, from the lateral geniculate nucleus to the visual cortex, carries signals for the detection of

Color vision, shape and fine details. ***Color vision, shape and fine details*** - The **parvocellular pathway** is specialized for processing **detailed visual information**, including **color vision**, **fine spatial resolution** for shape perception, and identifying small details. - This pathway has excellent spatial resolution but poor temporal resolution. *Luminance contrast* - While the parvocellular pathway contributes somewhat to luminance processing, the **magnocellular pathway** is primarily responsible for detecting **large-scale luminance differences** and contrasts. - Luminance contrast is a more general visual feature processed across multiple pathways, but not the primary specialization of the parvocellular pathway. *Temporal frequency* - **Temporal frequency** refers to how quickly an image changes over time, and its detection is chiefly handled by the **magnocellular pathway**, which is specialized for rapid changes and motion. - The parvocellular pathway has a relatively poor temporal resolution and is not optimized for detecting high temporal frequencies or rapid flicker. *Movement, depth and flicker* - The detection of **movement**, **depth**, and **flicker** (high temporal frequency changes) are primarily functions of the **magnocellular pathway**. - The parvocellular pathway's strength lies in static, detailed features rather than dynamic ones.

Q: Direction of sound is differentiated by

Superior olivary complex. ***Superior olivary complex*** - The **superior olivary complex** is crucial for **sound localization**, processing **interaural time differences (ITDs)** and **interaural level differences (ILDs)** to determine the direction of a sound source. - It receives **bilateral input from both cochlear nuclei**, allowing for the comparison of auditory signals from each ear, which is essential for directional hearing. - This is the **first level in the auditory pathway** where binaural processing occurs, making it the primary structure for sound direction differentiation. *Medial geniculate body* - The **medial geniculate body (MGB)** is the **thalamic relay station** for auditory information, projecting to the auditory cortex. - While it processes auditory information, its primary role is not in the initial differentiation of sound direction but rather in sensory relay and integration. *Auditory cortex* - The **auditory cortex** in the temporal lobe is responsible for the **conscious perception and interpretation of sound**, including identifying complex sounds and their meaning. - It receives processed information from the MGB but is not involved in the initial neural computations for sound localization. *Inferior colliculus* - The **inferior colliculus** is an important midbrain structure in the auditory pathway that integrates various auditory inputs and contributes to sound localization reflexes. - While it receives input from the superior olivary complex and contributes to sound localization, the **superior olivary complex is the primary site** for the initial processing of directional cues using binaural comparison.

Question 1

Vibrations are felt by?

Accepted Answer

Pacinian corpuscle

Answer

Merkel's disc

Answer

Ruffini's end organ

Answer

Meissner's corpuscle

Question 2

The parvocellular pathway from lateral geniculate nucleus to visual cortex is most sensitive for the stimulus of

Accepted Answer

Fine spatial detail

Answer

Saccadic eye movements

Answer

Luminance contrast

Answer

Temporal frequency

Question 3

Most recently identified taste sensation is?

Accepted Answer

Umami

Answer

Sour

Answer

Bitter

Answer

Sweet

Question 4

Which cells in the retina primarily depolarize in response to light stimulation?

Accepted Answer

Bipolar cells

Answer

Amacrine cells

Answer

Horizontal cells

Answer

Rods and cones

Question 5

Sound intensity of whispering is:

Accepted Answer

30 dB

Answer

90 dB

Answer

120 dB

Answer

2 dB

Question 6

Which substance enhances the sensitivity of pain receptors but does not directly excite them?

Accepted Answer

Prostaglandins

Answer

Potassium ions

Answer

Bradykinin

Answer

Serotonin

Question 7

The rod receptor potential differs from other sensory receptors in that it shows

Accepted Answer

Hyperpolarization

Answer

Increased conductance of sodium

Answer

Increased conductance of calcium

Answer

Depolarization

Question 8

A 60-year-old man presents to his primary care physician complaining that he often feels as if the room is spinning when he gets up from a recumbent position or turns his head. He has not lost consciousness and has had no chest pain. He has no cardiac history, and a recent treadmill test showed no abnormalities. On examination, the sensation can be produced by rapidly turning the head. It can be reproduced many times, but it eventually ceases. Nystagmus is elicited. Hearing is normal. Which of the following is the MOST likely mechanism for this patient's symptoms?

Accepted Answer

Aberrant stimulation of hair cells

Answer

Insufficient cerebral perfusion

Answer

Insufficient cardiac output

Answer

Hair cell death in the semicircular canals

Question 9

The parvocellular pathway, from the lateral geniculate nucleus to the visual cortex, carries signals for the detection of

Accepted Answer

Color vision, shape and fine details

Answer

Luminance contrast

Answer

Temporal frequency

Answer

Movement, depth and flicker

Question 10

Direction of sound is differentiated by

Accepted Answer

Superior olivary complex

Answer

Medial geniculate body

Answer

Auditory cortex

Answer

Inferior colliculus

Sensory Systems — MCQs

Sensory Systems — MCQs

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