NEET-PG 2013 - Physiology PYQs Practice Questions

Q: Conversion of chondrocytes into osteogenic cells is caused by

IGF-1. ***IGF-1*** - **Insulin-like Growth Factor 1 (IGF-1)** is the primary direct mediator in endochondral ossification, stimulating chondrocyte proliferation, differentiation, and hypertrophy in the growth plate. - IGF-1 acts directly on chondrocytes to promote their maturation and the subsequent invasion of osteoprogenitor cells that form bone. - It plays a crucial role in longitudinal bone growth by regulating various cellular processes in the growth plate and promoting the replacement of cartilage with bone tissue. *Insulin* - While insulin has anabolic effects on bone and can interact with IGF-1 receptors due to structural similarity, its primary role is in **glucose metabolism** rather than direct regulation of chondrocyte activity in endochondral ossification. - Insulin may have supportive effects on bone formation but is not the primary hormone driving growth plate chondrocyte function. *Growth hormone* - **Growth hormone (GH)** stimulates the production of IGF-1 both systemically (from the liver) and locally (from chondrocytes and other skeletal tissues). - GH acts upstream by increasing IGF-1 levels, which then directly mediates the effects on chondrocytes. - While GH is essential for normal bone growth, IGF-1 is considered the direct effector molecule on chondrocytes. *Thyroxine* - **Thyroxine (T4)** is essential for normal skeletal development and bone maturation, particularly in regulating the timing of growth plate fusion and overall metabolic support for bone growth. - However, it does not directly regulate chondrocyte proliferation and differentiation in the growth plate during endochondral ossification. - Thyroid hormone deficiency causes growth retardation, but thyroxine is not the primary hormonal driver of chondrocyte activity. [Practice more Physiology PYQs on OnCourse]

Q: The temperature centre is?

Preoptic nucleus of hypothalamus. **Preoptic nucleus of hypothalamus** - The **preoptic nucleus** within the **hypothalamus** serves as the primary **thermoregulatory center** in the brain. - It contains both **heat-sensitive** and **cold-sensitive neurons** that monitor core body temperature and initiate appropriate responses to maintain homeostasis. *Supraoptic nucleus of hypothalamus* - The **supraoptic nucleus** is primarily involved in the production of **antidiuretic hormone (ADH)**, which regulates water balance. - It plays a crucial role in **fluid and electrolyte balance**, not temperature regulation. *Paraventricular nucleus of hypothalamus* - The **paraventricular nucleus** is multifunctional, producing **oxytocin** and **vasopressin** (ADH), and is involved in stress response and feeding. - While it has broad regulatory roles, it is not the primary center for **temperature control**. *Suprachiasmatic nucleus of hypothalamus* - The **suprachiasmatic nucleus (SCN)** is the body's main **circadian clock**, regulating daily rhythms like the sleep-wake cycle. - Its primary function is to synchronize biological activities with the **24-hour light-dark cycle**, not directly control body temperature. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following best describes hypoxic pulmonary vasoconstriction?

Reversible pulmonary vasoconstriction due to hypoxia. ***Reversible pulmonary vasoconstriction due to hypoxia*** - Hypoxic pulmonary vasoconstriction (HPV) is a physiological response in which **pulmonary arterioles constrict** in areas of the lung with low oxygen levels. - This mechanism is **reversible**, meaning that when oxygen levels improve, the constricted vessels will dilate again. - The underlying mechanism involves hypoxia-induced inhibition of voltage-gated K⁺ channels in pulmonary arterial smooth muscle, leading to membrane depolarization, Ca²⁺ influx, and smooth muscle contraction. *Irreversible pulmonary vasoconstriction due to hypoxia* - This statement is incorrect because HPV is fundamentally a **reversible process**, designed to adapt to transient changes in alveolar oxygen. - Irreversible vasoconstriction typically occurs in chronic hypoxia, leading to **pulmonary hypertension** and structural remodeling (vascular remodeling with medial hypertrophy), which is a pathological state rather than the acute physiological response of HPV. *Redirects blood to well-ventilated areas* - While this is the **physiological purpose** and overall effect of hypoxic pulmonary vasoconstriction, it describes the functional outcome rather than what HPV fundamentally is. - The redirection of blood flow is the **consequence** of vasoconstriction in hypoxic areas, which optimizes ventilation-perfusion matching. *Occurs immediately in response to hypoxia* - While HPV does begin rapidly in response to hypoxia (within seconds to minutes), this describes the **timing characteristic** rather than what HPV is. - This statement is also somewhat imprecise, as the response involves intracellular signaling pathways that take time to manifest fully, though the onset is relatively quick compared to other vascular responses. [Practice more Physiology PYQs on OnCourse]

Q: Which equation is used to calculate physiological dead space?

Bohr equation. ***Bohr equation*** - The Bohr equation is used to calculate **physiological dead space**, which is the sum of anatomical dead space and alveolar dead space. - It relates the partial pressure of carbon dioxide in arterial blood to the partial pressure of carbon dioxide in expired air, along with **tidal volume** and expired volume. *Dalton's law* - Dalton's law states that the **total pressure** exerted by a mixture of non-reactive gases is equal to the **sum of the partial pressures** of individual gases. - It is used to calculate partial pressures of gases in a mixture, not dead space. *Charles's law* - Charles's law describes the relationship between the **volume and temperature** of a gas at constant pressure. - It states that the volume of a given mass of gas is directly proportional to its absolute temperature. *Boyle's law* - Boyle's law describes the inverse relationship between the **pressure and volume** of a gas at constant temperature. - It is fundamental to understanding mechanics of breathing, but not dead space calculation. [Practice more Physiology PYQs on OnCourse]

Q: What does Boyle's Law state?

PV = constant. ***PV = constant*** - **Boyle's Law** states that at constant temperature, the pressure and volume of a gas are inversely proportional. - Mathematically expressed as **PV = constant** or **P₁V₁ = P₂V₂** - This means that if the volume of a gas decreases, its pressure increases proportionally, and vice versa. - **Clinically relevant** in understanding lung mechanics during respiration - as thoracic volume increases during inspiration, intrapulmonary pressure decreases, allowing air to flow in. *Pressure divided by temperature is constant.* - This describes **Gay-Lussac's Law** (P/T = constant), which relates pressure and temperature at constant volume. - Shows the direct relationship between pressure and temperature. *Volume divided by temperature is constant.* - This statement describes **Charles's Law** (V/T = constant), which relates the volume and temperature of a gas at constant pressure. - Indicates a direct relationship between volume and temperature. *Pressure multiplied by volume equals the number of moles times the gas constant times temperature.* - This represents the **Ideal Gas Law**: PV = nRT - Combines Boyle's, Charles's, and Avogadro's laws to relate pressure, volume, temperature, and the number of moles of a gas. [Practice more Physiology PYQs on OnCourse]

Question 1

Conversion of chondrocytes into osteogenic cells is caused by

Accepted Answer

IGF-1

Answer

Insulin

Answer

Thyroxine

Answer

Growth hormone

Question 2

The temperature centre is?

Accepted Answer

Preoptic nucleus of hypothalamus

Answer

Supraoptic nucleus of hypothalamus

Answer

Paraventricular nucleus of hypothalamus

Answer

Suprachiasmatic nucleus of hypothalamus

Question 3

Which of the following best describes hypoxic pulmonary vasoconstriction?

Accepted Answer

Reversible pulmonary vasoconstriction due to hypoxia

Answer

Irreversible pulmonary vasoconstriction due to hypoxia

Answer

Redirects blood to well-ventilated areas

Answer

Occurs immediately in response to hypoxia

Question 4

Which equation is used to calculate physiological dead space?

Accepted Answer

Bohr equation

Answer

Dalton's law

Answer

Charles's law

Answer

Boyle's law

Question 5

What does Boyle's Law state?

Accepted Answer

PV = constant

Answer

Pressure divided by temperature is constant.

Answer

Volume divided by temperature is constant.

Answer

Pressure multiplied by volume equals the number of moles times the gas constant times temperature.

Question 6

What is the air remaining in the lung after normal expiration?

Accepted Answer

Functional Residual Capacity (FRC)

Answer

Tidal Volume (TV)

Answer

Residual Volume (RV)

Answer

Vital Capacity (VC)

Question 7

Which of the following statements about breathing is incorrect?

Accepted Answer

Normal breathing occurs when transpulmonary pressure is 5-8 cm H2O

Answer

Inspiration is an active process

Answer

Expiration during quiet breathing is passive

Answer

Compliance is influenced by multiple factors including surfactant.

Question 8

What is the minimum fluid urine output for neutral solute balance?

Accepted Answer

400 ml

Answer

300 ml

Answer

750 ml

Answer

500 ml

Question 9

Fever increases water loss by how much for each degree Celsius increase in body temperature?

Accepted Answer

200 ml/day

Answer

100 ml/day

Answer

400 ml/day

Answer

800 ml/day

Question 10

Maximum voluntary ventilation is:

Accepted Answer

150 L/min

Answer

25 L/min

Answer

50 L/min

Answer

100 L/min

NEET-PG 2013 — Physiology