NEET-PG 2012 Practice Questions

Q: Progressive distal-to-proximal motor recovery following nerve regeneration is most characteristic of which type of nerve injury?

Axonotmesis. ***Axonotmesis*** - Involves damage to the **axon** and myelin sheath, while the surrounding **epineurium** remains intact. - This preservation of the connective tissue allows for guided **regeneration** of axons from distal to proximal, leading to a good prognosis for recovery [1]. *Neurotmesis* - Refers to the **complete transection** of the nerve, including the axon, myelin, and all connective tissue sheaths. - Recovery is often **incomplete** or requires surgical repair, as significant misdirection of regenerating axons is common. *Neuropraxia* - Characterized by a **temporary block** in nerve conduction, typically due to **demyelination**, with the axon remaining intact. - Recovery is usually **rapid** and complete, occurring within days to weeks, as no axonal regeneration is needed. *Nerve injury* - This is a **general term** that encompasses all types of nerve damage, from mild to severe. - It does not specify a particular mechanism or pattern of recovery, making it less precise than the more specific classifications.

Q: PNH patients have deficient surface proteins that normally protect red blood cells from activated complements. Which two surface proteins are deficient in these patients?

CD 45 and CD 55. ***CD 55 and CD 59*** - **CD 55 (decay accelerating factor)** and **CD 59 (protectin)** are crucial for inhibiting the complement system, protecting red blood cells from lysis in PNH. - Deficiencies in these proteins lead to increased **susceptibility** of red cells to **complement-mediated hemolysis**. *CD58 and CD 59* - **CD 58** is involved in T-cell interaction but does not solely protect red cells from complement. - While **CD 59** is a correct answer, the absence of **CD 55** makes this option incorrect for PNH. *CD 45 and CD 59* - **CD 45** is primarily a **leukocyte common antigen**, not involved in protecting red cells from complement activation. - This orrectly mentions **CD 59**, but lacks **CD 55**, making it unsuitable as an answer. *CD 51 and CD 59* - **CD 51** is associated with integrin functions and does not play a role in protecting red blood cells from complements. - Although **CD 59** is relevant, the deficiency in **CD 55** highlights the incompleteness of this option.

Q: What is the difference between the amount of Oxygen consumed and Carbon Dioxide produced per minute at rest?

50 ml/min. ***50 ml/min*** - The body typically consumes about **250 ml/min of oxygen** at rest and produces approximately **200 ml/min of carbon dioxide**. - The difference between oxygen consumed and carbon dioxide produced is therefore **50 ml/min** (250 - 200 = 50). - This difference exists because the **respiratory quotient (RQ)** is approximately **0.8** (200/250), meaning less CO2 is produced than O2 consumed on a molar basis. *20 ml/min* - This value is **too low** and underestimates the physiological difference between oxygen consumption and carbon dioxide production. - With typical O2 consumption of 250 ml/min and RQ of 0.8, the difference cannot be this small. *75 ml/min* - This value represents an **overestimation** of the difference between oxygen consumption and carbon dioxide production under normal resting conditions. - This would imply an RQ of approximately 0.7, which is lower than the typical mixed diet RQ of 0.8. *100 ml/min* - This value is a significant **overestimation** of the physiological difference. - This would suggest an RQ of 0.6, which is not physiologically normal for resting conditions on a mixed diet.

Q: What is the average daily volume of pancreatic secretion in humans?

1.5 L. ***1.5 L*** - The **pancreas** produces approximately **1.5 liters (1200-1500 mL) of pancreatic juice** daily in humans. - This secretion is rich in **digestive enzymes** (amylase, lipase, proteases) and **bicarbonate** for neutralization of gastric acid in the duodenum. - This is the standard value cited in **major physiology textbooks** (Ganong, Guyton & Hall). *2.5 L* - **2.5 liters** overestimates the typical daily pancreatic secretion volume. - This value may represent **combined secretions** from multiple sources or confuse pancreatic output with total upper GI secretions. - Normal pancreatic secretion ranges from **1-2 liters**, making 2.5 L above the physiological range. *5.0 L* - **5.0 liters** represents an abnormally high volume for daily pancreatic secretion alone. - This volume is closer to the **total daily secretions** from stomach, pancreas, and bile combined. - Not consistent with **normal pancreatic physiology**. *10 L* - **10 liters** is grossly excessive for pancreatic secretion and represents approximately the **total volume of all gastrointestinal secretions** (saliva, gastric, pancreatic, bile, intestinal) combined daily. - This is **not physiologically realistic** for pancreatic output alone.

Q: What is the duration of the second heart sound (S2)?

0.08 sec. ***0.08 sec*** - The second heart sound (S2) is composed of two components: A2 (aortic valve closure) and P2 (pulmonic valve closure). The normal duration of S2, encompassing both components, is approximately **0.08 seconds**. - This short duration reflects the rapid closure of the aortic and pulmonic valves at the beginning of **diastole**. *0.15sec* - A duration of **0.15 seconds** for S2 is significantly longer than normal, which could indicate abnormal valve function or conditions causing delayed valve closure. - Such prolonged duration might be observed in conditions like **severe pulmonic stenosis** or **pulmonic hypertension**, which are not the typical duration of a healthy S2. *0.12 sec* - A duration of **0.12 seconds** is also longer than the typical normal range for S2. - While still shorter than 0.15 seconds, it could suggest subtle delays in valve closure or splitting that exceeds the usual physiological splitting. *0.1 sec* - A duration of **0.1 seconds** is slightly prolonged but generally falls within a range that might be considered borderline or indicative of minimal physiological variations. - However, in typical healthy individuals, the S2 duration is closer to 0.08 seconds, making 0.1 seconds less precise for the most common duration.

Q: Which tract is responsible for the loss of proprioception and fine touch?

Dorsal column. ***Dorsal column*** - The **dorsal column-medial lemniscus pathway** is responsible for transmitting **fine touch**, **vibration**, and **proprioception** from the body to the cerebral cortex. - Damage to this tract (e.g., in **tabes dorsalis** or **vitamin B12 deficiency**) leads to a loss of these sensations. *Anterior spinothalamic tract* - This tract primarily conveys crude touch and pressure sensations. - While it carries tactile information, it does not transmit the fine discriminative touch or proprioception associated with the dorsal columns. *Lateral spinothalamic tract* - This pathway is responsible for transmitting **pain** and **temperature** sensations. - It does not play a role in proprioception or fine touch. *Corticospinal tract* - The **corticospinal tract** is a **motor pathway** responsible for voluntary movement. - It has no role in transmitting sensory information such as proprioception or fine touch.

Q: Which of the following statements is true regarding the function of the spinocerebellar tract?

Smoothens and coordinates movements. ***Smoothens and coordinates movements*** - The spinocerebellar tract provides the cerebellum with **unconscious proprioceptive information** from muscle spindles and Golgi tendon organs. - This information allows the cerebellum to compare intended movements with actual movements, thereby **smoothing and coordinating voluntary motor activity**. *Involved in planning and programming motor activities* - This function is primarily attributed to the **cerebral cortex** (e.g., premotor and supplementary motor areas) and the **basal ganglia**. - While the cerebellum is involved in motor learning and fine-tuning, the initial **planning and programming** of complex movements are cortical functions. *Involved in maintaining equilibrium* - Maintaining equilibrium and balance is primarily a function of the **vestibulocerebellum** (flocculonodular lobe), which receives input from the vestibular system. - While the spinocerebellum indirectly influences balance by coordinating limb movements, its direct role is less pronounced than that of the vestibulocerebellum. *Facilitates learning through vestibulo-ocular reflex changes* - This function is specific to the **vestibulocerebellum** and is crucial for adapting the vestibulo-ocular reflex (VOR) to maintain visual stability during head movements. - The spinocerebellar tract's primary role is proprioception for limb coordination, not VOR adaptation.

Q: What happens to the concentration of inulin as fluid passes through the Proximal Convoluted Tubule (PCT)?

Concentration of inulin increases. ***Concentration of inulin increases*** - Inulin is **freely filtered** at the glomerulus and is neither reabsorbed nor secreted along the renal tubule, making it an excellent marker for **glomerular filtration rate (GFR)**. - As water is reabsorbed from the PCT, the volume of tubular fluid decreases, causing the concentration of **unreabsorbed solutes**, like inulin, to increase. *Concentration of urea remains constant* - Urea is **reabsorbed** along the tubule, though passively; its concentration typically **increases** initially in the PCT due to water reabsorption, but then decreases as some is reabsorbed. - The statement is incorrect because urea concentration changes significantly throughout the nephron, particularly increasing as water is reabsorbed and then decreasing with some reabsorption. *Concentration of HCO3- increases* - The majority (approximately 80-90%) of **bicarbonate (HCO3-)** is reabsorbed in the PCT, primarily through its conversion to CO2 within the tubular lumen and then back to HCO3- intracellularly. - Therefore, the concentration of HCO3- in the tubular fluid actually **decreases** significantly as fluid passes through the PCT. *Concentration of Na+ decreases* - **Sodium (Na+)** is actively reabsorbed along the entire nephron, with about 65-70% reabsorbed in the PCT. - While Na+ is reabsorbed, water follows passively, so its concentration in the tubular fluid remains relatively **iso-osmotic** with plasma, meaning its concentration does not significantly decrease as fluid passes through the PCT, remaining fairly constant.

Q: Gastric secretions are essential for absorption of -

Cobalamin. ***Cobalamin*** - **Intrinsic factor**, secreted by gastric parietal cells, is crucial for the absorption of **vitamin B12 (cobalamin)** in the terminal ileum [1]. - Without sufficient intrinsic factor, **pernicious anemia** can develop due to impaired B12 absorption [2]. *Fat* - Fat digestion primarily occurs in the **small intestine** with the help of **bile salts** and **pancreatic lipases**. - While gastric lipase begins some fat digestion, it's not essential for overall fat absorption. *Thiamine* - **Thiamine (vitamin B1)** is absorbed in the jejunum and ileum, primarily via **active transport** and passive diffusion. - Gastric secretions do not play a direct, essential role in its absorption. *Folic acid* - **Folic acid** is absorbed in the **duodenum and jejunum** as monoglutamates after being deconjugated from polyglutamate forms. - This process is not directly dependent on gastric secretions [2].

Q: Which of the following hormones does not mediate its action through cAMP?

Estrogen. ***Estrogen*** - **Estrogen** is a **steroid hormone** that mediates its action by binding to intracellular receptors, forming a complex that directly influences gene transcription. - Steroid hormones, due to their **lipophilicity**, can cross the cell membrane and do not typically rely on cell surface receptors or second messengers like cAMP. *Glucagon* - **Glucagon** acts on a **G protein-coupled receptor (GPCR)**, specifically a Gs-coupled receptor, leading to the activation of adenylyl cyclase. - This activation increases the intracellular concentration of **cAMP**, which then activates protein kinase A to mediate its effects, primarily on glucose metabolism. *Follicle stimulating hormone* - **FSH** binds to a **GPCR** on target cells, activating the Gs protein pathway. - This activation stimulates **adenylyl cyclase** and increases intracellular **cAMP** levels, which are critical for its role in gamete development. *Luteinizing hormone* - **LH**, like FSH, binds to a cell surface **GPCR** that activates the Gs protein. - This leads to the stimulation of **adenylyl cyclase** and an increase in **cAMP**, mediating its effects on steroidogenesis and ovulation.

Question 1

Progressive distal-to-proximal motor recovery following nerve regeneration is most characteristic of which type of nerve injury?

Accepted Answer

Axonotmesis

Answer

Neurotmesis

Answer

Neuropraxia

Answer

Nerve injury

Question 2

PNH patients have deficient surface proteins that normally protect red blood cells from activated complements. Which two surface proteins are deficient in these patients?

Accepted Answer

CD 45 and CD 55

Answer

CD 55 and CD 58

Answer

CD 55 and CD 59

Answer

CD 51 and CD 55

Question 3

What is the difference between the amount of Oxygen consumed and Carbon Dioxide produced per minute at rest?

Accepted Answer

50 ml/min

Answer

20 ml/min

Answer

75 ml/min

Answer

100 ml/min

Question 4

What is the average daily volume of pancreatic secretion in humans?

Accepted Answer

1.5 L

Answer

5.0 L

Answer

10 L

Answer

2.5 L

Question 5

What is the duration of the second heart sound (S2)?

Accepted Answer

0.08 sec

Answer

0.15 sec

Answer

0.1 sec

Answer

0.12 sec

Question 6

Which tract is responsible for the loss of proprioception and fine touch?

Accepted Answer

Dorsal column

Answer

Anterior spinothalamic tract

Answer

Lateral spinothalamic tract

Answer

Corticospinal tract

Question 7

Which of the following statements is true regarding the function of the spinocerebellar tract?

Accepted Answer

Smoothens and coordinates movements

Answer

Involved in planning and programming motor activities

Answer

Involved in maintaining equilibrium

Answer

Facilitates learning through vestibulo-ocular reflex changes

Question 8

What happens to the concentration of inulin as fluid passes through the Proximal Convoluted Tubule (PCT)?

Accepted Answer

Concentration of inulin increases

Answer

Concentration of urea remains constant

Answer

Concentration of HCO3- increases

Answer

Concentration of Na+ decreases

Question 9

Gastric secretions are essential for absorption of -

Accepted Answer

Cobalamin

Answer

Fat

Answer

Thiamine

Answer

Folic acid

Question 10

Which of the following hormones does not mediate its action through cAMP?

Accepted Answer

Estrogen

Answer

Glucagon

Answer

Follicle stimulating hormone

Answer

Luteinizing hormone

NEET-PG 2012

Internal Medicine

Pathology

Physiology