FMGE 2023 — Physiology
11 Previous Year Questions with Answers & Explanations
The first heart sound coincides with which cardiac cycle phase?
Which among the following is true regarding creatinine clearance?
Which of the following statements is true about GFR? GFR-Glomerular filtration rate RPF-Renal Plasma Flow
A new resident to a high-altitude area develops hypoxia. What is the causative factor?
Which of the following is an orexigenic hormone?
Which of the following clotting factor participates in the extrinsic pathway of coagulation?
Which of the following is the principal constituent of serum osmolality?
What is the function of utricle and saccule?
What is the cause of LH (Luteinizing Hormone) surge?
Which of the following cells is responsible for destroying bacterial foreign bodies in liver sinusoids?
FMGE 2023 - Physiology FMGE Practice Questions and MCQs
Question 1: The first heart sound coincides with which cardiac cycle phase?
- A. Rapid atrial filling
- B. Aortic ejection
- C. Isovolumetric contraction (Correct Answer)
- D. Isovolumetric relaxation
Explanation: ***Isovolumetric contraction*** - The **first heart sound (S1)** is produced by the simultaneous closure of the **mitral** and **tricuspid** (atrioventricular) valves. - This closure occurs the moment ventricular pressure exceeds atrial pressure, marking the beginning of **ventricular systole** and the phase of isovolumetric contraction. *Rapid atrial filling* - Rapid atrial filling (or **rapid ventricular filling**) occurs during **early diastole** when the mitral and tricuspid valves open. - This phase is associated with the potential generation of a **third heart sound (S3)**, not S1. *Aortic ejection* - Aortic ejection occurs *after* S1, commencing when the **aortic valve** opens because left ventricular pressure exceeds aortic pressure. - This phase ends with the closure of the semilunar valves, which produces the second heart sound (**S2**). *Isovolumetric relaxation* - Isovolumetric relaxation begins immediately after the **second heart sound (S2)**, which is caused by the closure of the aortic and pulmonic valves. - This phase is fully contained within **early diastole**, preceding ventricular filling.
Question 2: Which among the following is true regarding creatinine clearance?
- A. Equal to inulin clearance
- B. It is less than inulin clearance
- C. It is more than inulin clearance (Correct Answer)
- D. Equal to renal plasma flow
Explanation: ***It is more than inulin clearance*** - Creatinine clearance **overestimates GFR** by approximately 10-20% compared to inulin clearance - This is because creatinine undergoes both **glomerular filtration AND tubular secretion** - The additional secretion increases the amount of creatinine excreted, making the calculated clearance higher - **Inulin clearance** remains the gold standard as inulin is only filtered (not secreted or reabsorbed) *Equal to inulin clearance* - Incorrect: Creatinine undergoes tubular secretion in addition to filtration, so clearances are not equal *It is less than inulin clearance* - Incorrect: This would only be true if creatinine were reabsorbed, but it is actually secreted, making its clearance higher *Equal to renal plasma flow* - Incorrect: Renal plasma flow is measured by PAH (para-aminohippuric acid) clearance (~650 mL/min), which is much higher than creatinine clearance (~120-130 mL/min) or GFR (~120 mL/min)
Question 3: Which of the following statements is true about GFR? GFR-Glomerular filtration rate RPF-Renal Plasma Flow
- A. An increase in sympathetic function increases GFR
- B. Afferent arteriolar constriction increases GFR
- C. An increase in RPF increases GFR (Correct Answer)
- D. A decrease in RPF increases GFR
Explanation: ***An increase in RPF increases GFR***- **GFR** is directly proportional to the amount of **plasma delivered** to the glomerular capillaries for filtration, meaning higher **Renal Plasma Flow (RPF)** generally increases GFR.- Increased RPF contributes to a higher **glomerular hydrostatic pressure** and delivers more solute/fluid load to the capillary surface area for filtration.*An increase in sympathetic function increases GFR*- Strong sympathetic activation causes generalized **vasoconstriction** of the renal blood vessels (via alpha-1 receptors), significantly reducing **RPF** and thus GFR.- This response is critical during conditions like hemorrhage or shock to conserve fluid volume by prioritizing systemic circulation over **renal filtration**.*Afferent arteriolar constriction increases GFR*- Constriction of the **afferent arteriole** restricts blood flow into the glomerulus, immediately dropping the **glomerular capillary hydrostatic pressure (PGC)**.- Since PGC is the chief driving force for filtration, afferent constriction invariably leads to a *decrease* in GFR; this mechanism is essential for **GFR autoregulation**.*A decrease in RPF increases GFR*- A decrease in **Renal Plasma Flow (RPF)** means less plasma is physically available to be filtered across the glomerular membrane per unit time.- A primary reduction in RPF, assuming stable filtration dynamics, generally results in a proportional *decrease* in the absolute **GFR**.
Question 4: A new resident to a high-altitude area develops hypoxia. What is the causative factor?
- A. Low hemoglobin levels
- B. Low partial pressure of O2 (Correct Answer)
- C. Low blood lactate levels
- D. High partial pressure of CO2
Explanation: ***Low partial pressure of O2***- At high altitudes, the **barometric pressure** is significantly lower, and while the fraction of oxygen remains 21%, the resulting **partial pressure of inspired O2 (PiO2)** is reduced.- This reduction in PiO2 lowers the **alveolar PO2**, thereby decreasing the driving pressure for oxygen diffusion into the blood and causing **hypoxic hypoxia**.*Low hemoglobin levels*- The immediate cause of high-altitude illness is **hypoxic hypoxia**, where the problem is low inspired oxygen, not an issue with the carrying capacity of the blood.- Over time, the body adapts by increasing red blood cell mass and thus **hemoglobin levels** (polycythemia).*Low blood lactate levels*- Hypoxia often triggers **anaerobic metabolism**, especially under exertion, leading to an *increase* in blood lactate (lactic acidosis), not a decrease.- Lactate levels are a metabolic consequence of tissue hypoxia, not the primary cause of developing low oxygen levels at altitude.*High partial pressure of CO2*- The hypoxia stimulates peripheral chemoreceptors, leading to an **increase in ventilation** (hyperventilation).- Hyperventilation causes the body to "blow off" CO2, resulting in **decreased arterial PCO2 (hypocapnia)** and respiratory alkalosis, not high PCO2.
Question 5: Which of the following is an orexigenic hormone?
- A. Melanocyte-stimulating hormone
- B. Cholecystokinin
- C. Ghrelin (Correct Answer)
- D. Leptin
Explanation: ***Ghrelin (Correct Answer)*** - Ghrelin is often termed the "hunger hormone" as it acts primarily as a powerful **orexigenic signal**, stimulating appetite and food intake. - It is primarily produced by specialized cells in the **stomach**, and its levels typically rise before meals. *Melanocyte-stimulating hormone (Incorrect)* - MSH, specifically **alpha-MSH**, is released from **proopiomelanocortin (POMC) neurons** in the hypothalamus. - It acts to suppress appetite and is classified as an **anorexigenic hormone**. *Cholecystokinin (Incorrect)* - CCK is a **satiety hormone** released in response to fat and protein entering the duodenum and jejunum. - It acts on the brainstem and peripheral nerves to inhibit gastric emptying and induce short-term feelings of **satiety** (anorexigenic effect). *Leptin (Incorrect)* - Leptin is produced mainly by **adipocytes (fat cells)** and signals the brain about long-term energy stores. - High circulating levels of leptin act on the hypothalamus to **inhibit appetite** and increase energy expenditure, making it an **anorexigenic hormone (satiety signal)**.
Question 6: Which of the following clotting factor participates in the extrinsic pathway of coagulation?
- A. Factor VIII
- B. Factor VII (Correct Answer)
- C. Factor XI
- D. Factor IX
Explanation: ***Factor VII***- This factor is the key component initiating the **extrinsic pathway** when complexed with **Tissue Factor (TF)**.- The TF-Factor VIIa complex activates Factor X, linking the extrinsic pathway to the **common pathway**.*Factor VIII*- Factor VIII is a crucial component of the **intrinsic pathway**, where it acts as a cofactor for Factor IXa to activate Factor X.- Deficiency of Factor VIII causes **Hemophilia A**, a common inherited bleeding disorder.*Factor XI*- Factor XI is involved in the initial steps of the **intrinsic pathway**, typically activated by Factor XIIa.- Its main function is to activate Factor IX, continuing the cascade in the intrinsic pathway.*Factor IX*- Factor IX is part of the **intrinsic pathway**; when activated (IXa), it forms the tenase complex with Factor VIIIa to activate Factor X.- Deficiency of Factor IX leads to **Hemophilia B** (Christmas disease).
Question 7: Which of the following is the principal constituent of serum osmolality?
- A. Potassium
- B. Sodium (Correct Answer)
- C. Bicarbonate
- D. Hydrogen ions
Explanation: ***Sodium*** - **Sodium** is the most abundant cation in the extracellular fluid (ECF) and serum, typically present at concentrations of 135-145 mEq/L. - It is the primary determinant of **serum osmolality**, accounting for approximately 90% of the total measured osmoles, along with its accompanying anions. *Potassium* - **Potassium** is the major intracellular cation; its concentration in the serum (ECF) is very low (3.5–5.0 mEq/L). - Due to its low serum concentration, it contributes minimally and is not considered a significant factor in determining overall **serum osmolality**. *Bicarbonate* - Bicarbonate is an anion that contributes to the charge balance, but its plasma concentration (around 22–26 mEq/L) is substantially lower than that of **sodium**. - While included in the calculation of total solutes, it is not the **principal constituent** determining osmolality. *Hydrogen ions* - The concentration of **hydrogen ions** is extremely low (measured in nanomoles per liter, reflecting the pH). - Although crucial for **acid-base homeostasis**, their negligible concentration precludes any meaningful contribution to total **serum osmolality**.
Question 8: What is the function of utricle and saccule?
- A. Hearing high-frequency sounds
- B. Linear acceleration (Correct Answer)
- C. Hearing low-frequency sounds
- D. Angular acceleration
Explanation: ***Linear acceleration***- The **utricle** and **saccule** are the two **otolithic organs** of the inner ear responsible for detecting mechanical forces related to **linear motion** (acceleration, deceleration) and the pull of gravity.- The **utricle** senses horizontal linear acceleration (e.g., walking), while the **saccule** senses vertical linear acceleration (e.g., riding an elevator).*Hearing high-frequency sounds*- Sound detection (hearing) is carried out by the **cochlea** and its associated structures, primarily the hair cells in the **Organ of Corti**.- High frequencies stimulate hair cells located near the **base** of the **basilar membrane** but this is unrelated to the vestibular functions of the utricle and saccule.*Angular acceleration*- Rotational movements of the head, or **angular acceleration**, are detected solely by the three **semicircular canals**.- The canals use the movement of endolymph to displace the **cupula** within the **ampullae**, stimulating the enclosed hair cells.*Hearing low-frequency sounds*- The **cochlea** is the auditory apparatus; the utricle and saccule are part of the **vestibular system** responsible for balance and spatial orientation.- Low frequencies primarily stimulate hair cells located near the **apex** of the **basilar membrane** (apex is furthest from the oval window).
Question 9: What is the cause of LH (Luteinizing Hormone) surge?
- A. LH
- B. Progesterone
- C. FSH
- D. Estradiol (Correct Answer)
Explanation: ***Estradiol*** - The cause of LH surge- During the late follicular phase, the dominant follicle secretes increasingly high levels of **Estradiol** (a potent estrogen). When these levels remain high for a prolonged period (typically 48–50 hours) above a critical threshold, it switches from exerting negative feedback to **positive feedback** on the hypothalamus and anterior pituitary. - This positive feedback stimulates a massive release of **GnRH** and, subsequently, a sudden, sharp, increase in **LH** secretion, known as the LH surge, which prepares the dominant follicle for ovulation. *FSH* - FSH is essential for initiating the **follicular development** (growth and maturation of ovarian follicles) preceding the surge, but it is not the direct trigger for the LH surge. - Although FSH levels also rise slightly during the surge (known as the **FSH surge**), this rise is secondary to the primary positive feedback mechanism driven by Estradiol. *Progesterone* - Progesterone levels are typically low during the late follicular phase when the LH surge occurs; its primary rise happens **after ovulation** during the luteal phase. - While Progesterone contributes to the total feedback loop around the surge, it cannot initiate the surge itself, and its main role is preparing the **endometrium** and supporting a potential pregnancy. *LH* - LH (*Luteinizing hormone*) is the hormone whose concentration surges; it is the **effect** of the positive feedback loop, not the underlying cause. - The rise in LH concentration is a direct response of the **anterior pituitary** to the high levels of Estradiol acting upon it.
Question 10: Which of the following cells is responsible for destroying bacterial foreign bodies in liver sinusoids?
- A. Hepatocytes
- B. Sinusoidal endothelial cells
- C. Kupffer cells (Correct Answer)
- D. Ito cells
Explanation: ***Kupffer cells***- These are resident **macrophages** specifically located within the **liver sinusoids**.- Their primary role is **phagocytosis**, enabling them to clear the blood of **bacteria**, old red blood cells, and other foreign particulate matter entering the liver via the portal vein.*Hepatocytes*- These are the main parenchymal cells of the liver, primarily responsible for metabolic functions such as **bile production**, **protein synthesis**, and **detoxification**.- They lack the specialized migratory and high-volume **phagocytic capacity** needed to clear circulating bacteria.*Ito cells*- Also known as **hepatic stellate cells**, they reside in the **Space of Dissé** and are specialized for storing **Vitamin A**.- Upon activation (e.g., due to injury), they differentiate into myofibroblasts and are central to **liver fibrosis**.*Sinusoidal endothelial cells*- These cells line the vascular space of the sinusoid and are characterized by numerous **fenestrations** (pores) that allow fluid exchange with the Space of Dissé.- Although they form the barrier, they are generally less active in high-capacity microbial clearance compared to the dedicated **Kupffer cell macrophages**.