General Physiology Practice Questions

Q: Which of the following statements is true regarding Basal Metabolic Rate (BMR)?

BMR may decrease up to 50% during periods of starvation.. ### Explanation **1. Why the Correct Answer is Right:** Basal Metabolic Rate (BMR) represents the minimum energy expenditure required to maintain vital functions (heartbeat, respiration, kidney function) at rest. During periods of **starvation or chronic calorie restriction**, the body initiates an adaptive mechanism to conserve energy and ensure survival. This involves a reduction in sympathetic nervous system activity and a decrease in the peripheral conversion of T4 to the active T3 hormone. Consequently, the BMR can drop significantly—by as much as **50%**—to minimize the depletion of endogenous energy stores (glycogen, fat, and muscle protein). **2. Analysis of Incorrect Options:** * **Option A:** BMR is heavily influenced by energy intake. Overfeeding can slightly increase BMR (thermogenesis), while underfeeding significantly decreases it. * **Option B:** This is the opposite of physiological reality. BMR **decreases** during starvation to prevent rapid metabolic exhaustion. * **Option D:** BMR is highly sensitive to hormones. **Thyroid hormones (T3, T4)** are the primary regulators; hyperthyroidism increases BMR, while hypothyroidism decreases it. Epinephrine and cortisol also influence metabolic rates. **3. High-Yield Facts for NEET-PG:** * **Surface Area Rule:** BMR is directly proportional to the body surface area (Rubner’s Law). * **Gender & Age:** BMR is generally higher in males (due to higher muscle mass) and decreases with age (approx. 2% per decade after age 20). * **Specific Dynamic Action (SDA):** Also known as the Thermic Effect of Food; **Proteins** have the highest SDA (30%), followed by carbohydrates (5-6%) and fats (4%). * **Fever:** For every 1°C rise in body temperature, BMR increases by approximately **12-13%**.

Q: Bradykinin causes which of the following effects?

Stimulation of the visceral smooth muscle. **Explanation:** Bradykinin is a potent pharmacologically active nonapeptide belonging to the kinin system. Its physiological effects are mediated primarily through B1 and B2 receptors, and its action on smooth muscle is **tissue-specific**, which is a high-yield distinction for competitive exams. **1. Why Option A is Correct:** Bradykinin acts as a potent **stimulant of visceral (non-vascular) smooth muscle**. It causes contraction of the smooth muscles in the gastrointestinal tract, bronchioles, and uterus. This is why bradykinin is associated with bronchoconstriction in asthma and increased intestinal motility. **2. Why Other Options are Incorrect:** * **Options B & D:** While bradykinin "stimulates" the endothelial cells to release nitric oxide (NO) and prostacyclin ($PGI_2$), the net effect on the **vascular smooth muscle** itself is **relaxation (vasodilation)**. Therefore, it does not stimulate vascular smooth muscle (which would cause vasoconstriction); rather, it inhibits its tone indirectly. * **Option C:** As established, bradykinin is an excitatory mediator for visceral organs, not an inhibitor. **High-Yield Clinical Pearls for NEET-PG:** * **The "Triple Response":** Bradykinin causes vasodilation, increased capillary permeability (edema), and pain (by stimulating nociceptors). * **ACE Inhibitor Link:** Angiotensin-Converting Enzyme (ACE) is responsible for breaking down bradykinin. ACE inhibitors prevent this breakdown, leading to increased bradykinin levels, which results in the classic side effect of a **dry cough** (due to bronchial irritation) and, rarely, **angioedema**. * **Receptor Type:** Most of the acute inflammatory effects of bradykinin are mediated by the **B2 receptor**.

Q: Chromatolysis is seen in which cellular component?

Nissl substance. **Explanation:** **Chromatolysis** is a reactive change observed in the cell body (soma) of a neuron following axonal injury (axotomy). It is a hallmark of **retrograde degeneration**. 1. **Why Nissl Substance is Correct:** Nissl bodies are large granules composed of **Rough Endoplasmic Reticulum (RER)** and free ribosomes, responsible for protein synthesis. When an axon is injured, the neuron must shift its metabolic focus from neurotransmission to structural repair. During chromatolysis, the Nissl bodies undergo **dissolution and dispersal** throughout the cytoplasm, causing the cell body to appear pale and swollen under a microscope. This process is essential for increasing protein synthesis to regenerate the damaged axon. 2. **Why Other Options are Incorrect:** * **Mitochondria:** While mitochondria may increase in number or migrate during cell stress to provide ATP for repair, they do not undergo "chromatolysis," which specifically refers to the loss of staining in granular bodies. * **Microtubules:** These are structural components of the cytoskeleton involved in axonal transport. While they may reorganize, they are not the primary site of chromatolysis. * **Golgi Body:** The Golgi apparatus may shift to the periphery of the cell during injury, but the term chromatolysis is histologically defined by the disappearance of the basophilic Nissl substance. **High-Yield NEET-PG Pearls:** * **Histological features of Chromatolysis:** Swelling of the cell body, **peripheral displacement of the nucleus**, and disappearance of Nissl substance. * **Wallerian Degeneration:** Refers to the degeneration of the axon *distal* to the site of injury. * **Nissl Staining:** Nissl substance is basophilic and stains intensely with dyes like **Cresyl Violet** or Methylene Blue. * **Location:** Nissl bodies are found in the soma and dendrites but are notably **absent in the Axon Hillock** and the Axon.

Q: Which of the following is regulated by a negative feedback system in the body?

All the above. **Explanation:** In physiology, **negative feedback** is the primary mechanism for maintaining homeostasis. It works by detecting a deviation from a set point and initiating responses that negate or reverse the original stimulus. 1. **Thyroid Production:** This is a classic example of the **Hypothalamic-Pituitary-Thyroid (HPT) axis**. High levels of circulating Thyroxine (T4) and Triiodothyronine (T3) inhibit the release of TRH from the hypothalamus and TSH from the anterior pituitary, thereby decreasing further thyroid hormone production. 2. **Ovulation:** While the mid-cycle LH surge is a famous example of *positive* feedback, the overall regulation of the menstrual cycle is predominantly negative feedback. For most of the follicular and luteal phases, Estrogen and Progesterone inhibit FSH and LH to prevent overstimulation of the ovaries. 3. **Blood Pressure Regulation:** The **Baroreceptor Reflex** is a rapid negative feedback loop. An increase in blood pressure stretches baroreceptors in the carotid sinus and aortic arch, leading to increased parasympathetic and decreased sympathetic outflow, which lowers heart rate and causes vasodilation to bring BP back to normal. **Why "All the Above" is Correct:** While students often associate ovulation strictly with positive feedback, it is important to recognize that the body utilizes negative feedback loops in almost every physiological system to ensure stability. **High-Yield NEET-PG Pearls:** * **Positive Feedback Examples:** LH surge (ovulation), Oxytocin in parturition (Ferguson reflex), Blood clotting cascade, and Nerve action potential (Hodgkin cycle). * **Negative Feedback** is the most common regulatory mechanism in the body. * **Feed-forward Control:** Anticipatory regulation (e.g., cephalic phase of gastric secretion or increased heart rate before a race).

Q: All of the following are properties of synovial fluid except:

Normal WBC count in synovial fluid is 350–3500/mm³.. **Explanation:** The correct answer is **D** because the normal White Blood Cell (WBC) count in synovial fluid is significantly lower than the range provided. In a healthy joint, the WBC count is typically **less than 200 cells/mm³**, with polymorphonuclear (PMN) leukocytes making up less than 25%. A count of 350–3500/mm³ is characteristic of non-inflammatory or mildly inflammatory conditions (like osteoarthritis), but not a normal physiological state. **Analysis of other options:** * **Option A:** Synovial fluid is indeed pale yellow and clear. Its high viscosity is due to **Hyaluronic acid**. The "string sign" (forming a 3–5 cm string when dropped) is a classic test for normal viscosity. * **Option B:** It is a **Non-Newtonian fluid**. Its viscosity is not constant; it decreases as the shear rate increases (thixotropy). This allows the fluid to provide better lubrication during rapid joint movement. * **Option C:** Normal synovial fluid **does not clot** because it lacks fibrinogen and other clotting factors. If a sample clots, it indicates an underlying pathology (like inflammation or trauma) that has increased capillary permeability, allowing larger proteins to enter the joint. **NEET-PG High-Yield Pearls:** * **Mucin Clot Test:** Adding acetic acid to normal synovial fluid forms a tight, ropy clot (indicates good quality hyaluronic acid). * **Septic Arthritis:** WBC count is typically **>50,000/mm³** with >75% PMNs. * **Rice Bodies:** Small white free-floating bodies seen in synovial fluid, classic for Rheumatoid Arthritis or Tuberculosis. * **Color:** "Straw-colored" is normal; "Turbid/Purulent" suggests infection; "Bloody" suggests trauma, hemophilia, or PVNS.

Q: An index of the binding affinity of a hormone for its receptor can be obtained by examining which parameter?

The slope of a Scatchard plot. ### Explanation The binding affinity of a hormone for its receptor is a measure of how tightly the hormone binds to its receptor. In physiology and pharmacology, this is quantitatively analyzed using a **Scatchard Plot**. #### Why Option B is Correct The Scatchard plot graphs the ratio of **Bound/Free hormone (B/F)** on the Y-axis against the **Bound hormone (B)** on the X-axis. The relationship is expressed by the equation: **$B/F = (R_0 - B) / K_d$** Where $R_0$ is the total number of receptors and $K_d$ is the dissociation constant. * The **slope** of the resulting straight line is equal to **$-1/K_d$**. * Since affinity ($K_a$) is the reciprocal of the dissociation constant ($1/K_d$), the **slope directly represents the binding affinity**. A steeper negative slope indicates a higher affinity. #### Why Other Options are Incorrect * **Option A (Y-intercept):** The Y-intercept represents the ratio of Bound/Free hormone when the concentration of bound hormone is zero ($R_0/K_d$). It does not independently represent affinity. * **Option D (X-intercept):** The X-intercept represents the **$B_{max}$** (or $R_0$), which is the **total number of binding sites** (receptor capacity) available in the tissue. * **Option C (Dose-response curve):** The maximum point on a biological dose-response curve represents **Efficacy** ($V_{max}$), not affinity. Affinity is better reflected by the $EC_{50}$ (potency) on such a curve. #### High-Yield NEET-PG Pearls * **Scatchard Plot:** Used to distinguish between changes in receptor **number** (X-intercept) vs. receptor **affinity** (slope). * **Upregulation/Downregulation:** Primarily affects the **X-intercept** (number of receptors). * **Competitive Inhibition:** Changes the **slope** (decreases affinity) but not the X-intercept (number of receptors remains the same). * **Non-linear Scatchard Plot:** Suggests **cooperativity** in binding (e.g., heme-heme interaction in hemoglobin).

Q: The Donnan effect of ion movement across the capillary wall is due to which of the following?

Proteins. **Explanation:** The **Gibbs-Donnan Effect** describes the behavior of charged particles near a semi-permeable membrane when one of the ions is **non-diffusible**. In the context of the capillary wall, **plasma proteins** (primarily albumin) act as these non-diffusible anions because they are too large to pass through the capillary pores. 1. **Why Proteins are correct:** Plasma proteins carry a net negative charge. Because they cannot cross the capillary wall, they exert an electrostatic pull on diffusible cations (like $Na^+$) to maintain electroneutrality and repel diffusible anions (like $Cl^-$). This results in a higher concentration of cations and a higher osmotic pressure (oncotic pressure) inside the capillary compared to the interstitial fluid. 2. **Why other options are incorrect:** * **Cations (A) and Anions (C):** Most small ions like $Na^+$, $K^+$, and $Cl^-$ are freely diffusible across the capillary wall. The Donnan effect is not *caused* by them, but rather *affects* their distribution due to the presence of the non-diffusible proteins. * **Albumin (D):** While albumin is the most abundant plasma protein contributing to this effect, the term **"Proteins"** is the more comprehensive and standard physiological answer, as globulins and other plasma proteins also contribute to the total non-diffusible anionic charge. **High-Yield Clinical Pearls for NEET-PG:** * **Donnan Factor:** In plasma, the concentration of cations is about **5% higher** than in the interstitial fluid due to this effect. * **Osmotic Implications:** The Donnan effect increases the total osmotic pressure of plasma by approximately **6-7 mmHg** more than what would be exerted by proteins alone. * **Formula:** At equilibrium, the product of diffusible ions on one side equals the product on the other: $[Na^+]_{in} \times [Cl^-]_{in} = [Na^+]_{out} \times [Cl^-]_{out}$.

Q: On changing position from lying down to standing, there is a drop in blood pressure of 10 mm Hg. Immediately, the blood pressure recovers by 8 mm Hg, leaving behind a drop of 2 mm Hg. What is the gain for the baroreceptor system in the control of blood pressure?

4 mm Hg. ### Explanation The concept of **Feedback Gain** is a measure of the effectiveness of a control system (like the baroreceptor reflex) in maintaining homeostasis. It is calculated using the following formula: $$\text{Gain} = \frac{\text{Correction}}{\text{Residual Error}}$$ **1. Why Option B is Correct:** In this scenario: * **Initial Change (Disturbance):** 10 mm Hg (The drop that would occur without compensation). * **Correction:** 8 mm Hg (The amount the baroreceptor reflex successfully restored). * **Residual Error:** 2 mm Hg (The remaining deviation from the original baseline). Applying the formula: $$\text{Gain} = \frac{8\text{ mm Hg}}{2\text{ mm Hg}} = 4$$ Therefore, the gain of the baroreceptor system in this individual is **4**. **2. Why Other Options are Incorrect:** * **Option A (2 mm Hg):** This represents the **Residual Error**, not the gain. * **Option C (8 mm Hg):** This represents the **Correction** achieved by the system. * **Option D (10 mm Hg):** This is the total **Initial Disturbance** caused by the change in posture. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Definition of Gain:** A higher gain indicates a more efficient regulatory system. * **Negative Feedback:** Most physiological systems (e.g., BP control, body temperature, hormone regulation) operate via negative feedback. The gain for negative feedback systems is technically a negative value (e.g., -4), but in exams, the absolute value is typically used. * **Baroreceptor Reflex:** This is a **short-term** regulator of BP. It is most sensitive at pressures near the normal mean arterial pressure (approx. 95–100 mm Hg). * **Highest Gain System:** The **Renal-Body Fluid System** for long-term blood pressure control has an "infinite gain," meaning it can eventually return the pressure exactly to the starting point (zero residual error).

Question 1

Which of the following statements is true regarding Basal Metabolic Rate (BMR)?

Accepted Answer

BMR may decrease up to 50% during periods of starvation.

Answer

BMR is not influenced by energy intake.

Answer

BMR increases in response to starvation.

Answer

BMR is not responsive to changes in hormonal levels.

Question 2

Bradykinin causes which of the following effects?

Accepted Answer

Stimulation of the visceral smooth muscle

Answer

Stimulation of the vascular smooth muscle

Answer

Inhibition of the visceral smooth muscle

Answer

Inhibition of the vascular smooth muscle

Question 3

Chromatolysis is seen in which cellular component?

Accepted Answer

Nissl substance

Answer

Mitochondria

Answer

Microtubule

Answer

Golgi body

Question 4

Which of the following is regulated by a negative feedback system in the body?

Accepted Answer

All the above

Answer

Thyroid production

Answer

Ovulation

Answer

Blood pressure regulation

Question 5

All of the following are properties of synovial fluid except:

Accepted Answer

Normal WBC count in synovial fluid is 350–3500/mm³.

Answer

It is a pale yellow, clear, and sufficiently viscous fluid that droplets expelled from a needle tip fall in a long string.

Answer

It is a Non-Newtonian fluid.

Answer

It doesn't clot since it lacks fibrinogen.

Question 6

Which of the following transport processes does NOT follow saturation kinetics?

Accepted Answer

Simple diffusion

Answer

Facilitated diffusion

Answer

Na+ - Ca2+ exchanger

Answer

Na+ coupled active transport

Question 7

An index of the binding affinity of a hormone for its receptor can be obtained by examining which parameter?

Accepted Answer

The slope of a Scatchard plot

Answer

The Y-intercept of a Scatchard plot

Answer

The maximum point on a biological dose-response curve

Answer

The X-intercept of a Scatchard plot

Question 8

The Donnan effect of ion movement across the capillary wall is due to which of the following?

Accepted Answer

Proteins

Answer

Cations

Answer

Anions

Answer

Albumin

Question 9

Which statement is true about the lipid bilayer of a cell membrane?

Accepted Answer

It has an asymmetrical arrangement of membrane components.

Answer

It allows for the lateral diffusion of ions.

Answer

It has a symmetrical arrangement of membrane components.

Answer

It is not made up of amphipathic lipids.

Question 10

On changing position from lying down to standing, there is a drop in blood pressure of 10 mm Hg. Immediately, the blood pressure recovers by 8 mm Hg, leaving behind a drop of 2 mm Hg. What is the gain for the baroreceptor system in the control of blood pressure?

Accepted Answer

4 mm Hg

Answer

2 mm Hg

Answer

8 mm Hg

Answer

10 mm Hg

General Physiology — MCQs

General Physiology — MCQs

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