Sensory Systems Practice Questions

Q: What is the most accepted theory for the conduction of pain?

Gate control theory. ***Gate control theory*** - The **gate control theory** of pain proposes that non-painful input closes the "gates" to painful input, which prevents pain sensation from traveling to the central nervous system. - It suggests that the spinal cord contains a neurological "gate" that either blocks pain signals or allows them to continue to the brain. *Specificity theory* - The **specificity theory** suggests the existence of a direct pathway from pain receptors to "pain centers" in the brain, implying that pain is simply a sensation like touch or temperature, which is too simplistic. - It does not account for the **psychological and cognitive modulation of pain**, nor the significant variability in pain perception among individuals. *Membrane stabilization theory* - The **membrane stabilization theory** is not a widely accepted theory for the conduction of pain. - This term is more commonly associated with the actions of certain drugs (e.g., local anesthetics, antiarrhythmics) that stabilize cell membranes to prevent nerve impulse transmission or abnormal cardiac rhythms, rather than a general theory of pain conduction. *None of the options* - This option is incorrect because the **gate control theory** is a well-established and accepted theory for explaining pain conduction and modulation.

Q: Initiation of visual impulse is associated with which of the following?

Photoisomerization of 11-cis-retinal. ***Photoisomerization of 11-cis-retinal*** - The initiation of a visual impulse begins with the **photoisomerization of 11-cis-retinal** to **all-trans-retinal** upon absorption of light by rhodopsin. - This is the **primary photochemical event** that triggers the entire phototransduction cascade. - The conformational change in retinal subsequently causes a conformational change in the associated **opsin protein**, activating the **rhodopsin molecule** (visual purple) and initiating signal transduction through the G-protein cascade. - This process is also known as **photoactivation** or the first step in **bleaching of rhodopsin**. *Condensation of opsin with vitamin A aldehyde* - **Condensation of opsin with 11-cis-retinal** (vitamin A aldehyde derivative) occurs in the **dark** to form rhodopsin (visual purple). - This process represents the **regeneration of the photopigment**, not the light-triggered initiation of the visual impulse. - This is the reverse process that restores rhodopsin after bleaching. *NADP* - **NADP (nicotinamide adenine dinucleotide phosphate)** is primarily involved in **anabolic reactions** and oxidative stress response, acting as a cofactor in various metabolic pathways. - It is **not directly involved in the phototransduction cascade** that initiates a visual impulse. *NAD* - **NAD (nicotinamide adenine dinucleotide)** is a coenzyme crucial for **catabolic reactions** and energy metabolism, particularly in glycolysis and the citric acid cycle. - Similar to NADP, it plays **no direct role in the primary photochemistry** or signal transduction mechanisms that initiate a visual impulse.

Q: Which site contains endolymph?

Scala media. ***Scala media*** - The **scala media** (also known as the cochlear duct) is the only cochlear compartment filled with **endolymph**. - **Endolymph** is a unique fluid with a high **potassium concentration** and a low sodium concentration, essential for the transduction of sound. *Scala vestibuli* - The **scala vestibuli** contains **perilymph**, which has a high sodium and low potassium concentration, similar to extracellular fluid. - It is separated from the scala media by Reissner's membrane. *Helicotrema* - The **helicotrema** is the apex of the cochlea where the scala vestibuli and scala tympani communicate, allowing the **perilymph** to flow between them. - It does not contain endolymph and is not a separate compartment for fluid storage. *Organ of Corti* - The **Organ of Corti** is the sensory organ of hearing, located within the **scala media** and bathed in endolymph. - While it is surrounded by endolymph, the Organ of Corti itself is a collection of cells and not a fluid-filled space.

Question 1

What is the most accepted theory for the conduction of pain?

Accepted Answer

Gate control theory

Answer

Membrane stabilization theory

Answer

Specificity theory

Answer

None of the options

Question 2

Initiation of visual impulse is associated with which of the following?

Accepted Answer

Photoisomerization of 11-cis-retinal

Answer

Condensation of opsin with vitamin A aldehyde

Answer

NADP

Answer

NAD

Question 3

Which of the following statements regarding the inheritance of red-green color blindness is most accurate?

Accepted Answer

Color blindness is primarily inherited in an X-linked recessive pattern.

Answer

Protanopia is the most common type of color blindness.

Answer

Individuals with trichromacy can perceive all colors.

Answer

Color blindness results from a defect in one or more of the primary colors.

Question 4

Which site contains endolymph?

Accepted Answer

Scala media

Answer

Scala vestibuli

Answer

Organ of Corti

Answer

Helicotrema

Sensory Systems — MCQs

Sensory Systems — MCQs

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