FMGE 2025 - Physiology PYQs Practice Questions

Q: Which segment of the nephron has the lowest osmolality under the influence of antidiuretic hormone (ADH)?

Early distal tubule. ***Early distal tubule*** - This segment is known as the **cortical diluting segment** because it actively reabsorbs solutes (Na+ and Cl-) via the **Na+-Cl- cotransporter** while being impermeable to water. - This mandatory solute removal ensures the tubular fluid is maximally diluted (hypoosmolar, often around 100 mOsm/L), a process that is independent of **ADH** levels. *Descending limb of the loop of Henle* - This segment is highly permeable to **water** but largely impermeable to solutes, causing water to flow out into the surrounding hypertonic medulla. - Consequently, the osmolality of the tubular fluid **increases** significantly as it moves down toward the loop hairpin turn, making it highly concentrated, not dilute. *Collecting duct* - The influence of **ADH** is to insert **aquaporin 2** channels into the apical membrane, making this segment highly permeable to water. - This allows massive water reabsorption out of the tubule, concentrating the urine and leading to a **high osmolality** within the tubule lumen, especially near the end. *Late distal tubule* - While the fluid here is dilute, some water reabsorption is possible in the presence of **ADH** due to ADH-sensitive aquaporins, similar to the collecting duct. - This water movement slightly increases the osmolality compared to the maximally dilute fluid produced earlier in the **early distal tubule**. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following is the afferent limb of the corneal reflex?

Trigeminal nerve. ***Trigeminal nerve***- The **Trigeminal nerve (CN V)**, specifically its **ophthalmic division (V1)**, detects the tactile sensation on the cornea, making it the sensory input (afferent limb) of the reflex arc.- Sensory impulses travel through the nasociliary nerve (a branch of V1) to the **principal sensory nucleus of CN V** in the pons.*Optic nerve*- The **Optic nerve (CN II)** is crucial for the sense of **vision** and serves as the afferent limb for the **pupillary light reflex**.- It transmits light stimuli, whereas the corneal reflex is triggered by **tactile stimuli** (touch or pain).*Facial nerve*- The **Facial nerve (CN VII)** serves as the **efferent (motor) limb** of the reflex, responsible for causing the blink via innervation of the **orbicularis oculi** muscle.- It carries the motor command *away* from the nucleus to the muscle, contrasting with the afferent nerve which carries sensation *to* the nucleus.*Trochlear nerve*- The **Trochlear nerve (CN IV)** is a motor nerve responsible for innervating the **superior oblique muscle**, which controls eye movement (depression and intorsion).- It has no role in the sensation of the cornea or the motor response (blinking) that characterizes the corneal reflex. [Practice more Physiology PYQs on OnCourse]

Q: Which of the following changes occurs during muscle contraction while exercising, as shown in the image?

I length decrease. ***I length decrease*** - The **I band** is the region of the sarcomere containing only **thin filaments (actin)**. During contraction, these thin filaments slide over the thick filaments, causing the I band to shorten. - The shortening of the I band, along with the H zone, results in the **Z lines** moving closer together, which constitutes the shortening of the entire **sarcomere**. *M length increase* - The **M line** is a protein structure in the center of the H zone that anchors the **thick filaments (myosin)**. It is a line, not a band, and its own length does not change. - The region surrounding the M line, the **H zone**, actually *decreases* in width during contraction, it does not increase. *A length decrease* - The **A band** represents the entire length of the **thick myosin filaments**. The length of these filaments does not change during the sliding filament process of muscle contraction. - Because the thick filaments do not shorten, the length of the **A band remains constant** during both muscle contraction and relaxation. *M length increase and I decrease* - This option is partially correct, as the **I band** does decrease in length during contraction. - However, it is incorrect because the **M line** does not increase in length; it remains constant. The overall statement is therefore false. [Practice more Physiology PYQs on OnCourse]

Q: During spermatogenesis, which of the following hormones inhibits Follicle-Stimulating Hormone (FSH) secretion?

Inhibin. ***Inhibin*** - **Inhibin** is produced by **Sertoli cells** in the seminiferous tubules, acting as a crucial regulator of spermatogenesis. - It specifically targets the anterior pituitary gland to implement a **negative feedback loop**, reducing the secretion of **FSH** (Follicle-Stimulating Hormone) when sperm production levels are adequate. *Testosterone* - **Testosterone** is the primary androgen required for the maintenance and stimulation of spermatogenesis within the seminiferous tubules. - High systemic levels of testosterone primarily inhibit the secretion of **GnRH** (from the hypothalamus) and **LH** (from the pituitary), rather than specifically inhibiting FSH production. *Luteinizing Hormone (LH)* - **LH** acts on the **Leydig cells** in the testes, stimulating them to produce testosterone. - It does not directly inhibit FSH; rather, it is part of the **Hypothalamic-Pituitary-Gonadal (HPG) axis** regulation system. *Estrogen* - While small amounts of **estrogen** are produced in males (via aromatization of testosterone), it does not play a primary role in the negative feedback inhibition of FSH during spermatogenesis. - In males, **inhibin** is the specific hormone that directly targets FSH secretion from the anterior pituitary. [Practice more Physiology PYQs on OnCourse]

Q: Dehydration is more severe in infants compared to adults. What is the PRIMARY reason for this increased susceptibility?

Total body water in infants is more than in adults. ***Total body water in infants is more than in adults*** - Newborn infants have a significantly higher percentage of **Total Body Water (TBW)**, approximately **75-80%** of their body weight, compared to adults (~60%). - This large volume of water, combined with their greater **surface area-to-volume ratio** and higher **metabolic rate**, necessitates rapid fluid turnover, dramatically increasing their risk of severe dehydration. - This is the **primary physiological reason** why infants are more vulnerable to dehydration compared to adults. *Intracellular fluid (ICF) is more than extracellular fluid (ECF)* - This fluid distribution pattern is characteristic of **adults and older children**, not infants. - In young infants, the **ECF** compartment is actually greater than or nearly equal to the **ICF** compartment. - This represents the adult fluid distribution pattern, not the infant pattern. *Extracellular fluid (ECF) is more than intracellular fluid (ICF)* - While this statement is **anatomically true** for newborns (who have a disproportionately large ECF volume), it does not explain the **primary mechanism** of increased dehydration risk. - The ECF:ICF ratio changes with age, but the overall higher **total body water percentage** is the fundamental reason for severe dehydration susceptibility. - This is a characteristic of infant fluid distribution but not the main answer to why dehydration is more severe. *Extracellular fluid equals intracellular fluid* - In normal physiological states, the volume of the **ECF** compartment rarely equals the volume of the **ICF** compartment at any age. - In infants, ECF typically exceeds ICF; in adults, ICF exceeds ECF. - This statement is not accurate for either infants or adults. [Practice more Physiology PYQs on OnCourse]

Question 1

Which segment of the nephron has the lowest osmolality under the influence of antidiuretic hormone (ADH)?

Accepted Answer

Early distal tubule

Answer

Descending limb of the loop of Henle

Answer

Collecting duct

Answer

Late distal tubule

Question 2

Which of the following is the afferent limb of the corneal reflex?

Accepted Answer

Trigeminal nerve

Answer

Facial nerve

Answer

Trochlear nerve

Answer

Optic nerve

Question 3

Which of the following changes occurs during muscle contraction while exercising, as shown in the image?

Accepted Answer

I length decrease

Answer

M length increase

Answer

M length increase and I decrease

Answer

A length decrease

Question 4

During spermatogenesis, which of the following hormones inhibits Follicle-Stimulating Hormone (FSH) secretion?

Accepted Answer

Inhibin

Answer

Luteinizing Hormone (LH)

Answer

Testosterone

Answer

Estrogen

Question 5

Dehydration is more severe in infants compared to adults. What is the PRIMARY reason for this increased susceptibility?

Accepted Answer

Total body water in infants is more than in adults

Answer

Intracellular fluid (ICF) is more than extracellular fluid (ECF)

Answer

Extracellular fluid (ECF) is more than intracellular fluid (ICF)

Answer

Extracellular fluid equals intracellular fluid

Question 6

Scientists administered norepinephrine to guinea pigs, resulting in an increase in systolic and diastolic blood pressure and a decrease in heart rate. What mechanism explains this response?

Accepted Answer

Baroreceptor stimulation

Answer

Alpha-1 receptor blockade

Answer

Beta-1 receptor blockade

Answer

Baroreceptor inhibition

Question 7

A patient presents with high blood pressure accompanied by a decrease in heart rate. What is the most likely physiological mechanism responsible for this response?

Accepted Answer

Stimulation of baroreceptors

Answer

Inhibition of baroreceptors

Answer

Stimulation of chemoreceptors

Answer

Bezold-Jarisch reflex (J reflex)

Question 8

Which of the following describes the chloride ion exchange in red blood cells, where bicarbonate ions are exchanged for chloride ions to maintain electrical neutrality?

Accepted Answer

Chloride shift

Answer

Root effect

Answer

Bohr effect

Answer

Haldane effect

Question 9

Which of the following factors causes a rightward shift in the oxygen-hemoglobin dissociation curve?

Accepted Answer

Increase in CO₂

Answer

Increase in O₂

Answer

Decrease in CO₂

Answer

Decrease in temperature

Question 10

In the jugular venous pressure (JVP) waveform, the "a" wave corresponds to:

Accepted Answer

Right Atrial contraction

Answer

Tricuspid valve bulging into Right atria

Answer

Right Atrial relaxation

Answer

Right atrial filling

FMGE 2025 — Physiology