NEET-PG 2015 - Physiology Practice Questions

Q: Regarding Caisson's disease which statement among the following is CORRECT?

Pain in the joints is due to nitrogen bubbles. ***Pain in the joints is due to nitrogen bubbles*** - Caisson's disease, or **decompression sickness**, is characterized by the formation of nitrogen gas bubbles in tissues and blood due to rapid depressurization. - These gas bubbles can accumulate in joints, causing **severe pain** often referred to as "the bends." *Lung damage is caused by air embolism* - While air embolism can occur due to **pulmonary barotrauma** during ascent (rapid depressurization), the primary lung damage associated with decompression sickness is not typically directly caused by an air embolism reaching the lungs from within the body. - Air embolism from pulmonary barotrauma is a distinct complication, where air from ruptured alveoli enters the arterial circulation, potentially leading to cerebral or cardiac ischemia. *Tremors are seen due to nitrogen narcosis* - **Nitrogen narcosis** is a condition that occurs at high ambient pressures when breathing compressed air, causing a reversible alteration in consciousness similar to alcohol intoxication, but it does not primarily cause tremors. - Tremors are more characteristic of other neurological conditions or high-pressure nervous syndrome, not nitrogen narcosis itself. *High pressure Nervous syndrome can be prevented by using mixtures of Oxygen & Helium* - **High-pressure nervous syndrome (HPNS)** is indeed associated with deep dives using helium-oxygen mixtures. Its symptoms include tremors. - HPNS is actually **prevented or mitigated** by adding small amounts of narcotic gases like nitrogen to the helium-oxygen mixture (e.g., trimix) to counteract the excitatory effects of helium, rather than solely using oxygen and helium.

Q: What is the partial pressure for oxygen in the inspired air?

158 mm Hg. ***158 mm Hg*** - The partial pressure of oxygen in inspired air (PIO2) is calculated by multiplying the **fraction of inspired oxygen (FiO2)** by the total atmospheric pressure. - At sea level, atmospheric pressure is approximately **760 mm Hg** and FiO2 is 21% (0.21), so 0.21 × 760 mm Hg = **159.6 mm Hg**, which rounds to 158 mm Hg. - This represents **dry atmospheric air** before it enters the respiratory tract. *116 mm Hg* - This value does not correspond to a standard physiological measurement in respiratory physiology. - It is lower than inspired air PO2 but higher than alveolar PO2, making it an intermediate value used as a distractor. - **Humidified tracheal air** has PO2 of approximately 150 mm Hg: (760-47) × 0.21 = 149.7 mm Hg, where 47 mm Hg is water vapor pressure. *0.3 mm Hg* - This value is extremely low and represents the approximate **partial pressure of oxygen in mixed venous blood**, not inspired air. - Such a low value in inspired air would indicate **severe hypoxia** incompatible with life. - This is used as an unrealistic distractor. *100 mm Hg* - This value represents the approximate **partial pressure of oxygen in alveolar air (PAO2) and arterial blood (PaO2)**. - It is lower than inspired air due to humidification, mixing with residual air, and continuous oxygen uptake by blood. - It does not represent the partial pressure of oxygen in the inspired atmospheric air.

Q: Which transport process is mediated by carriers and occurs against the concentration gradient?

Active transport. ***Active transport*** - **Active transport** systems use carrier proteins to move molecules across a membrane **against their concentration gradient**, requiring **metabolic energy** (e.g., from ATP hydrolysis). - This process is crucial for maintaining cellular homeostasis, accumulating specific substances, and establishing ion gradients. *Facilitated diffusion* - **Facilitated diffusion** also uses **carrier proteins**, but it moves substances **down their concentration gradient**, thus **not requiring metabolic energy**. - It increases the rate of diffusion for molecules that cannot easily cross the lipid bilayer, like glucose. *Osmosis* - **Osmosis** is the movement of **water molecules** across a selectively permeable membrane **down their water potential gradient**, driven by solute concentration differences, and does **not involve carrier proteins**. - This process equalizes solute concentrations on both sides of the membrane. *Endocytosis* - **Endocytosis** is a bulk transport mechanism where cells **engulf substances** from outside by forming vesicles from the plasma membrane; it's a form of active transport but **does not typically involve specific carrier proteins** embedded in the membrane for individual molecules. - This process is used for taking in larger molecules, particles, or even other cells.

Q: Secretion of bile out of hepatocytes occurs via?

Active transport. ***Active transport*** - Bile secretion by hepatocytes is an **energy-dependent process** against concentration gradients, requiring specific transporter proteins. - This active mechanism ensures efficient bile flow and prevents reflux, crucial for processes like **fat digestion and absorption**. *Passive diffusion* - **Passive diffusion** involves substances moving down their concentration gradient without energy expenditure. - Bile components, like bile salts, are highly concentrated within hepatocytes and need to be moved against this gradient. *Facilitated diffusion* - This type of diffusion utilizes **transmembrane proteins** to move substances down their concentration gradient, but still does not directly consume ATP. - Bile components are often transported against their concentration gradient, which is not facilitated diffusion. *Osmosis* - **Osmosis** specifically refers to the movement of water across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration. - While water is a component of bile, the primary mechanism of moving bile solutes out of the hepatocyte is not osmosis.

Q: In the relaxation pressure curve, at zero relaxation pressure in chronic smokers:

Lung volume remains elevated. ***Lung volume remains elevated*** - In chronic smokers, conditions like **emphysema** lead to loss of elastic recoil and **air trapping**. - At zero relaxation pressure (the point where the respiratory system is at its resting equilibrium), the **functional residual capacity (FRC)** is higher due to less elastic recoil, which maintains the lungs at a more inflated state. - The balance between inward lung recoil and outward chest wall recoil shifts, resulting in a new equilibrium at a higher lung volume. *Lung volume decreases significantly* - This would imply increased elastic recoil or significant **airway obstruction** preventing air from entering, which is contrary to the typical pathophysiological changes in chronic smokers (e.g., emphysema). - In emphysema, the **loss of elastic recoil** actually prevents the lungs from deflating efficiently, leading to increased rather than decreased lung volume at rest. *No significant change in lung volume* - Chronic smoking often results in **structural changes** to the lungs, particularly **emphysema**, which significantly alters lung mechanics. - These changes directly impact the **resting lung volume (FRC)** as the balance between elastic recoil and chest wall compliance is disturbed, leading to a noticeable increase. *Lung compliance decreases* - This is incorrect; in emphysema, lung **compliance actually increases** due to destruction of alveolar walls and loss of elastic tissue. - Increased compliance means the lungs are more easily distensible but have reduced elastic recoil, contributing to air trapping and elevated FRC.

Q: Somatomedin-C deficiency causes?

Growth retardation. ***Growth retardation*** - **Somatomedin-C** (also known as **Insulin-like Growth Factor 1 or IGF-1**) is a crucial mediator of **growth hormone's** effects on growth. - A deficiency in Somatomedin-C, therefore, directly leads to **impaired growth** and **stature**, manifesting as **growth retardation**. *Genetic dwarfism* - This term generally refers to dwarfism caused by various **genetic conditions** (e.g., achondroplasia), which may or may not involve the **growth hormone/IGF-1 axis**. - While Somatomedin-C deficiency can be genetic, "genetic dwarfism" is a broader term and not the most precise answer for the direct consequence. *Congenital hypothyroidism* - This condition results from **deficient thyroid hormone production** from birth. - It leads to neurological impairment and **growth failure**, but it is due to **thyroid hormone deficiency**, not Somatomedin-C deficiency. *Type 1 diabetes mellitus* - This is an **autoimmune disease** characterized by the **destruction of pancreatic beta cells**, leading to **insulin deficiency**. - It is entirely unrelated to **Somatomedin-C** or the growth hormone axis.

Q: Which of the following statements is true about coronary circulation?

Major flow during diastole. ***Major flow during diastole*** - The **coronary arteries** are compressed during **systole** by the contracting myocardium, significantly reducing blood flow to the heart muscle. - During **diastole**, the myocardium relaxes, allowing the coronary arteries to open fully and deliver the majority (70-80%) of oxygenated blood to the heart. - This is the most distinctive feature of coronary circulation. *Flow rate is approximately 500 ml/min* - The typical **coronary blood flow** at rest is approximately **225-250 ml/min** (about 5% of cardiac output at rest). - 500 ml/min is significantly higher than normal resting coronary flow and would represent a pathological or high-demand state. *Uniform flow during full cardiac cycle* - **Coronary blood flow** is highly variable (phasic) throughout the cardiac cycle, being significantly higher during **diastole** and much lower during **systole**. - This non-uniform flow is a unique characteristic of coronary circulation due to mechanical compression from myocardial contraction. *All of the above* - Not all statements are correct, as the flow rate value is incorrect and flow is non-uniform throughout the cardiac cycle. - The **major flow during diastole** is the most accurate and physiologically important statement regarding coronary circulation.

Q: Where are the stretch receptors located in the left atrium?

Entrance of the pulmonary veins. ***Entrance of the pulmonary veins*** - **Stretch receptors** are mechanoreceptors that detect changes in pressure and volume. In the left atrium, they are primarily located at the **junction of the pulmonary veins and the left atrium** [1]. - These receptors play a crucial role in the **Bainbridge reflex** and the release of **atrial natriuretic peptide (ANP)** in response to increased blood volume [1]. *Atrioventricular septum* - The **atrioventricular septum** separates the atria from the ventricles and primarily contains components of the **cardiac conduction system**, such as the AV node and bundle of His [2]. - While it has specialized tissues, it is not the primary location for **stretch receptors** involved in volume sensing. *Septum between the atria* - The **interatrial septum** primarily separates the right and left atria. - Although it contains some myocardial cells, it is not the main site for **stretch receptors** responsible for monitoring left atrial volume. *None of the options* - This option is incorrect because the **entrance of the pulmonary veins** is indeed the primary location for stretch receptors in the left atrium [1].

Q: Which of the following conditions can lead to a decrease in afterload?

Severe anemia. ***Severe anemia*** - In **severe anemia**, the **blood viscosity** is reduced, and the body compensates by decreasing systemic vascular resistance to maintain tissue perfusion, thereby lowering **afterload**. - The reduced **oxygen-carrying capacity** triggers vasodilation to maximize blood flow to tissues, contributing to decreased afterload. - This represents a **chronic compensatory mechanism** that results in sustained reduction of afterload. *Hypothyroidism* - **Hypothyroidism** typically leads to an **increase in systemic vascular resistance** and thus can increase afterload. - It often results in **bradycardia** and reduced cardiac output, which can further elevate afterload to maintain pressure. *Increased physical activity* - During **physical activity**, there is **vasodilation in exercising muscles**, which acutely decreases systemic vascular resistance. - However, this is accompanied by **increased cardiac output** and **elevated blood pressure** due to sympathetic stimulation, and the afterload reduction is **transient** rather than sustained. - In the context of this question asking about conditions that lead to decreased afterload, **severe anemia** is the better answer as it represents a chronic pathological state with sustained afterload reduction, whereas exercise represents a temporary physiological response. *None of the options* - This option is incorrect because **severe anemia** is a recognized cause of decreased afterload.

Question 1

Regarding Caisson's disease which statement among the following is CORRECT?

Accepted Answer

Pain in the joints is due to nitrogen bubbles

Answer

Lung damage is caused by air embolism

Answer

Tremors are seen due to nitrogen narcosis

Answer

High pressure Nervous syndrome can be prevented by using mixtures of Oxygen & Helium

Question 2

What is the partial pressure for oxygen in the inspired air?

Accepted Answer

158 mm Hg

Answer

116 mm Hg

Answer

0.3 mm Hg

Answer

100 mm Hg

Question 3

Which transport process is mediated by carriers and occurs against the concentration gradient?

Accepted Answer

Active transport

Answer

Facilitated diffusion

Answer

Osmosis

Answer

Endocytosis

Question 4

Secretion of bile out of hepatocytes occurs via?

Accepted Answer

Active transport

Answer

Passive diffusion

Answer

Facilitated diffusion

Answer

Osmosis

Question 5

In the relaxation pressure curve, at zero relaxation pressure in chronic smokers:

Accepted Answer

Lung volume remains elevated

Answer

Lung volume decreases significantly

Answer

No significant change in lung volume

Answer

Lung compliance decreases

Question 6

Somatomedin-C deficiency causes?

Accepted Answer

Growth retardation

Answer

Genetic dwarfism

Answer

Congenital hypothyroidism

Answer

Type 1 diabetes mellitus

Question 7

Which of the following statements is TRUE regarding the Bohr effect?

Accepted Answer

Decreased affinity of Hb to O2 is associated with decreased pH & increased CO2

Answer

Decreased affinity of Hb to O2 is associated with increased pH & decreased CO2

Answer

Decreased affinity of Hb to O2 is associated with increased pH & CO2

Answer

Decreased affinity of Hb to O2 is associated with decreased pH & decreased CO2

Question 8

Which of the following statements is true about coronary circulation?

Accepted Answer

Major flow during diastole

Answer

Uniform flow during full cardiac cycle

Answer

Flow rate is approximately 500 ml/min

Answer

All of the above

Question 9

Where are the stretch receptors located in the left atrium?

Accepted Answer

Entrance of the pulmonary veins

Answer

None of the options

Answer

Atrioventricular septum

Answer

Septum between the atria

Question 10

Which of the following conditions can lead to a decrease in afterload?

Accepted Answer

Severe anemia

Answer

Hypothyroidism

Answer

Increased physical activity

Answer

None of the options

NEET-PG 2015 — Physiology