NEET-PG 2013 - Physiology Practice Questions

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: 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: 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 markedly decreased in restrictive lung disease?

FVC. ***FVC*** - In **restrictive lung disease**, there is a reduction in lung volume due to various causes, leading to a markedly decreased **Forced Vital Capacity (FVC)**. - **FVC** directly measures the total amount of air a person can exhale after a maximal inhalation, which is inherently limited in restrictive conditions. - This is the **hallmark finding** in restrictive lung disease and the most clinically significant decrease. *FEV1* - While **FEV1** (Forced Expiratory Volume in 1 second) is also decreased in restrictive lung disease, its decrease is proportional to the FVC decrease. - A decrease in FEV1 alone is less specific, as it could also indicate obstructive lung disease. - The key is that both FEV1 and FVC decrease together, maintaining a normal or increased ratio. *FEV1/FVC* - The **FEV1/FVC ratio** is typically **normal or even increased** in restrictive lung disease, as both FEV1 and FVC decrease proportionally or FEV1 decreases slightly less. - A decreased FEV1/FVC ratio is characteristic of **obstructive lung disease**, not restrictive. *RV* - **Residual Volume (RV)** is also **decreased** in restrictive lung disease, along with all other lung volumes (TLC, VC, FRC). - However, RV is not measured by standard spirometry and requires body plethysmography or gas dilution techniques. - While RV does decrease, **FVC** is the more clinically significant and readily measurable parameter that is "markedly decreased" and defines restrictive disease on routine pulmonary function testing.

Q: Result of liquorice ingestion

Hypokalemic alkalosis. ***Hypokalemic alkalosis*** - **Licorice** contains **glycyrrhizic acid**, which inhibits **11β-hydroxysteroid dehydrogenase** in the kidneys, preventing the conversion of cortisol to inactive cortisone. - This leads to increased cortisol acting on **mineralocorticoid receptors**, mimicking **aldosterone excess**, resulting in **sodium reabsorption**, **potassium excretion** (hypokalemia), and **hydrogen ion excretion** (metabolic alkalosis). *Hyperkalemic alkalosis* - This option is incorrect because licorice ingestion leads to **hypokalemia** due to increased potassium excretion, not hyperkalemia. - While it does cause alkalosis, the associated potassium imbalance is the opposite of this choice. *Hypokalemic acidosis* - This option is incorrect because licorice ingestion causes a **metabolic alkalosis** due to increased hydrogen ion excretion, not acidosis. - Although it correctly identifies hypokalemia, the acid-base disturbance is wrong. *Hypernatremic acidosis* - This option is incorrect as licorice ingestion initially causes **sodium and water retention** (which can lead to hypernatremia in severe cases, but is not the primary driver of the acid-base), but primarily leads to **metabolic alkalosis**, not acidosis. - The combination of hypernatremia and acidosis is not characteristic of licorice toxicity.

Q: Metabolic change in severe vomiting is

Metabolic alkalosis due to loss of gastric acid. **Metabolic alkalosis due to loss of gastric acid** - Severe vomiting leads to the loss of **hydrochloric acid (HCl)** from the stomach, causing an increase in plasma bicarbonate and subsequently **metabolic alkalosis** [1], [3]. - This condition is often accompanied by **hypokalemia** due to renal compensation and increased aldosterone activity [1]. *Respiratory alkalosis due to hyperventilation* - **Hyperventilation** causes a decrease in arterial partial pressure of carbon dioxide (PaCO2), leading to **respiratory alkalosis** [2]. - While vomiting can sometimes cause mild hyperventilation due to discomfort, the primary metabolic derangement from severe vomiting is related to acid loss, not CO2 expulsion [4]. *Hyperkalemia due to renal dysfunction* - **Hyperkalemia** is an elevated potassium level, typically associated with **renal failure** or certain medications. - In severe vomiting, the loss of gastric fluid and subsequent fluid shifts tend to cause **hypokalemia** as the kidneys try to conserve hydrogen and excrete potassium [1]. *Metabolic acidosis due to renal failure* - **Metabolic acidosis** is characterized by a decrease in blood pH and bicarbonate, often caused by the accumulation of acids or loss of bicarbonate [3]. - **Renal failure** is a common cause of metabolic acidosis due to impaired acid excretion, which is not the primary issue in severe vomiting.

Q: Why do eyebrows not grow beyond a certain length?

Anagen phase. **Anagen phase** - The **anagen phase**, or growing phase, is significantly shorter for eyebrow hairs (typically 30-45 days) compared to scalp hair (2-7 years), which limits their maximum length. - The duration of this active growth phase **determines the ultimate length** hair can reach before it transitions to resting and shedding. *Telogen phase* - The **telogen phase** is a **resting phase** where the hair follicle is completely inactive; it does not contribute to the hair's growth or final length. - During this phase, the old hair is shed to make way for new hair growth, but it is not the phase that dictates the maximum length. *Catagen phase* - The **catagen phase** is a **transitional phase** lasting about 2-3 weeks, during which hair growth stops and the hair follicle shrinks. - This phase prepares the hair for resting and shedding but does not directly limit how long the hair grows. *Exogen phase* - The **exogen phase** is when a hair is **shed from the follicle**, often aided by activities like washing or brushing. - This phase is responsible for hair shedding, not for limiting the maximum length hair can attain.

Q: Haarscheiben Cells in epidermis are responsible for

Touch. ***Touch*** - **Haarscheiben cells**, also known as **Merkel cells**, are specialized epidermal cells associated with nerve endings. - They are primarily responsible for sensing **light touch** and **discriminative touch**, playing a crucial role in tactile sensation. *Pressure* - While Merkel cells contribute to touch sensation, the primary receptors for **deep pressure** and vibration are **Pacinian corpuscles**, located deeper in the dermis and hypodermis. - Light pressure can be detected by other mechanoreceptors such as **Meissner's corpuscles**. *Proprioception* - **Proprioception** refers to the sense of body position and movement. - Receptors for proprioception are mainly located in **muscles, tendons, and joints** (e.g., muscle spindles, Golgi tendon organs), not primarily in the epidermis. *Temperature* - **Temperature sensation** is mediated by **thermoreceptors**, which are free nerve endings in the skin. - These receptors (e.g., Krause end bulbs for cold, Ruffini endings for warmth) are distinct from Haarscheiben/Merkel cells.

Q: Hormone primarily responsible for blood pressure regulation following acute blood loss is:

ADH. ***ADH*** - **Antidiuretic hormone (ADH)**, also known as **vasopressin**, is released in response to decreased blood volume and pressure detected by **baroreceptors**. - Its primary role is to increase water reabsorption in the **renal collecting ducts** and cause **vasoconstriction**, both of which help restore blood volume and pressure. - This makes ADH the key **hormonal mechanism** for BP regulation following acute blood loss. *Aldosterone* - **Aldosterone** is crucial for long-term **blood pressure regulation** by increasing sodium and water reabsorption in the kidneys. - While important for volume restoration, its effects are **slower** (hours) and more focused on electrolyte balance rather than immediate BP stabilization after acute blood loss. *ANP* - **Atrial natriuretic peptide (ANP)** is released in response to **atrial stretch** due to increased blood volume and acts to lower blood pressure. - It promotes **vasodilation** and **sodium/water excretion**, counteracting the body's efforts to raise blood pressure after blood loss. - ANP levels are **suppressed** during hypovolemia. *Epinephrine* - **Epinephrine** increases heart rate and cardiac contractility, and causes vasoconstriction, providing an immediate increase in blood pressure. - However, it's primarily a **catecholamine** (not a classic hormone) part of the **sympathetic nervous system** response, and while it acts immediately, ADH provides the sustained hormonal BP regulation.

Question 1

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 2

Which of the following is responsible for localization of sound ?

Accepted Answer

Superior olivary nucleus

Answer

Cochlear nerve

Answer

Cochlea

Answer

Cochlear nuclei

Question 3

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 4

Which of the following is markedly decreased in restrictive lung disease?

Accepted Answer

FVC

Answer

RV

Answer

FEV1/FVC

Answer

FEV1

Question 5

Coronary steal phenomenon caused due to

Accepted Answer

Preferential vasodilation of normal coronary vessels over stenotic vessels

Answer

Dilation of large coronary arteries

Answer

Dilation of epicardial coronary vessels

Answer

Dilation of capacitance vessels

Question 6

Result of liquorice ingestion

Accepted Answer

Hypokalemic alkalosis

Answer

Hyperkalemic alkalosis

Answer

Hypokalemic acidosis

Answer

Hypernatremic acidosis

Question 7

Metabolic change in severe vomiting is

Accepted Answer

Metabolic alkalosis due to loss of gastric acid

Answer

Respiratory alkalosis due to hyperventilation

Answer

Hyperkalemia due to renal dysfunction

Answer

Metabolic acidosis due to renal failure

Question 8

Why do eyebrows not grow beyond a certain length?

Accepted Answer

Anagen phase

Answer

Telogen phase

Answer

Catagen phase

Answer

Exogen phase

Question 9

Haarscheiben Cells in epidermis are responsible for

Accepted Answer

Touch

Answer

Pressure

Answer

Proprioception

Answer

Temperature

Question 10

Hormone primarily responsible for blood pressure regulation following acute blood loss is:

Accepted Answer

ADH

Answer

Aldosterone

Answer

ANP

Answer

Epinephrine

NEET-PG 2013 — Physiology