NEET-PG 2012 Practice Questions

Q: From which ribs does the spleen extend?

9th to 11th rib. ***9th to 11th rib*** - The **spleen** is located in the **left upper quadrant** of the abdomen, deep to the 9th, 10th, and 11th ribs. - Its protected position beneath these ribs makes it vulnerable to injury from trauma to the left lower chest or upper abdomen. *5th to 9th rib* - This range primarily covers the location of the **heart** and the upper part of the **lungs**. - While the spleen is superior to other abdominal organs, it does not extend as high as the 5th rib. *2nd to 5th rib* - This region is mainly associated with the **upper lobes of the lungs** and the **superior mediastinum**. - The spleen is an abdominal organ and is situated much lower in the thoracic cavity. *11th to 12th rib* - This range is too low and posterior for the typical position of the spleen, especially for its superior border. - The 12th rib primarily overlies the **kidneys** and the more inferior aspects of the diaphragm.

Q: Which of the following is not a branch of the inferior mesenteric artery?

Middle rectal. ***Middle rectal artery*** - The **middle rectal artery** [2] is typically a branch of the **internal iliac artery** [2], supplying the middle part of the rectum. - It is not a direct branch of the inferior mesenteric artery. *Left colic artery* - The left colic artery is a direct branch of the **inferior mesenteric artery** [1], supplying the distal transverse colon and descending colon. - It forms an important anastomosis with the middle colic artery [1]. *Superior rectal artery* - The **superior rectal artery** is the terminal branch of the **inferior mesenteric artery**, supplying the upper rectum. - This artery provides the primary arterial supply to the proximal large intestine structures. *Sigmoidal artery* - The **sigmoidal arteries** are typically 2-4 branches arising from the **inferior mesenteric artery**, supplying the sigmoid colon. - These arteries anastomose with branches of the superior rectal and left colic arteries.

Q: Why is oxidized LDL considered more atherogenic?

Is taken up by scavenger receptors. ***Is taken up by scavenger receptors*** - **Oxidized LDL (oxLDL)** is taken up by **scavenger receptors (CD36, SR-A)** on macrophages, which have **no feedback regulation**. - Unlike native LDL receptors that downregulate when cells have sufficient cholesterol, **scavenger receptors continue unlimited uptake**, leading to foam cell formation. - This **unregulated uptake mechanism** is the key reason why oxLDL is **more atherogenic** than native LDL. - The result is lipid-laden macrophages forming **fatty streaks**, the initial lesions of **atherosclerosis**. *Is not recognized by LDL receptors* - While true that oxLDL has **reduced affinity** for native LDL receptors due to oxidative modification, this alone doesn't explain increased atherogenicity. - The critical factor is what happens instead—its uptake via an **alternative, unregulated pathway**. *Accumulates in macrophages* - This is a **consequence** of scavenger receptor uptake, not the primary mechanism. - Foam cell formation occurs **because** of unregulated scavenger receptor uptake, making this a downstream effect. *Promotes inflammation in arterial walls* - OxLDL does promote inflammation through multiple mechanisms (cytokine release, endothelial dysfunction). - However, this is a **secondary effect** that occurs after uptake and accumulation—not the primary reason for atherogenicity.

Q: Which vitamin is considered the most potent antioxidant?

Vit E. ***Vit E*** - **Vitamin E** is a **lipid-soluble antioxidant** that primarily protects cell membranes from **oxidative damage** by scavenging free radicals. - Its ability to interrupt **lipid peroxidation** makes it highly effective in protecting tissues rich in polyunsaturated fatty acids, such as cell membranes. *Vit A* - **Vitamin A**, particularly in its carotenoid forms like **beta-carotene**, is an antioxidant, but its primary role is in **vision** and **immune function**. - While it can quench **singlet oxygen** and trap free radicals, it is generally considered less potent than vitamin E in protecting against lipid peroxidation. *Vit K* - **Vitamin K** is crucial for **blood coagulation** and **bone metabolism**, but it does not have significant antioxidant properties. - Its primary biological functions are unrelated to scavenging **free radicals** or preventing oxidative stress. *Vit C* - **Vitamin C** is a potent **water-soluble antioxidant** that works in aqueous environments, such as the cytoplasm and extracellular fluid. - While it can neutralize **reactive oxygen species** and regenerate other antioxidants like vitamin E, its solubility limits its direct activity in protecting lipid membranes, making vitamin E more potent in that specific context.

Q: Glycogen synthase is activated by?

Insulin. **Insulin** - Insulin activates **glycogen synthase** through a signaling cascade that dephosphorylates the enzyme, shifting it to its active form (glycogen synthase a). - This activation promotes **glycogen synthesis** in the liver and muscles, lowering blood glucose levels. *Glucagon* - **Glucagon** primarily acts to increase blood glucose levels by activating **glycogen phosphorylase** and inhibiting glycogen synthase. - It promotes the breakdown of glycogen (glycogenolysis) rather than its synthesis. *Epinephrine* - **Epinephrine** (adrenaline) also promotes **glycogenolysis** (glycogen breakdown) by activating glycogen phosphorylase. - Its main role is to provide rapid energy during stress, not to store glucose as glycogen. *AMP* - **AMP** (adenosine monophosphate) is a key allosteric activator of **AMP-activated protein kinase (AMPK)**, which phosphorylates and inactivates glycogen synthase. - High AMP levels signal a low energy state, prompting ATP-generating pathways like glycogenolysis, not glycogen synthesis.

Q: Enzyme deficient in Type I Hyperlipidemia?

Lipoprotein lipase. ***Lipoprotein lipase*** - **Type I hyperlipidemia**, also known as **familial hyperchylomicronemia**, is characterized by a deficiency in **lipoprotein lipase (LPL)**. - LPL is crucial for hydrolyzing triglycerides in **chylomicrons** and **VLDLs** into fatty acids and glycerol, allowing their uptake by tissues. *HMG CoA reductase* - This enzyme is involved in the **rate-limiting step of cholesterol synthesis** in the liver. - While it plays a role in lipid metabolism, its deficiency is not characteristic of **Type I hyperlipidemia**. *Peroxidase* - **Peroxidase** is an enzyme involved in various oxidative reactions, including the breakdown of **hydrogen peroxide**. - It is not directly involved in the metabolism of **chylomicrons** or **triglycerides**, and its deficiency is unrelated to hyperlipidemia. *Cholesterol acyl transferase* - This enzyme, often referring to **lecithin-cholesterol acyltransferase (LCAT)** or **acyl-CoA:cholesterol acyltransferase (ACAT)**, is involved in **cholesterol esterification**. - While important for cholesterol transport and storage, its deficiency is not the primary cause of **Type I hyperlipidemia**, which is marked by severe **chylomicronemia**.

Q: Which acquired condition is most commonly associated with spherocytes?

Autoimmune hemolytic anemia (AIHA). ***Autoimmune haemolytic anemia*** - This condition is characterized by the **production of antibodies** against the patient's own red blood cells, leading to **destruction** and the formation of spherocytes [1]. - The presence of ***maximum spherocytes*** in blood smears is a hallmark of this disorder due to **extravascular hemolysis** [1]. *Aplastic anemia* - Aplastic anemia is mainly due to **failure of hematopoiesis**, resulting in pancytopenia rather than spherocyte formation. - It typically presents with **normocytic** or **macrocytic anemia**, not spherocytes, as the bone marrow is not producing enough red blood cells [2]. *Vit B12 deficiency* - Vit B12 deficiency usually causes **macrocytic anemia** characterized by **megaloblastic changes** in the bone marrow and peripheral blood, not the formation of spherocytes. - The primary indicators would be **hypersegmented neutrophils** and large, ovalocytes rather than spherocytes. *None* - This option incorrectly implies that no condition causes maximum spherocytes, while autoimmune hemolytic anemia is the known condition for this finding. - Spherocytes are a specific sign in hemolytic processes and are definitely seen in conditions like **autoimmune hemolytic anemia**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Blood And Bone Marrow Disease, pp. 602-603. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Red Blood Cell and Bleeding Disorders, pp. 662-663.

Q: What change is seen in the vessels during the initial stage of Raynaud's phenomenon?

No pathological changes (functional vasospasm only). ***No pathological changes (functional vasospasm only)*** - Raynaud's phenomenon, particularly **primary Raynaud's** (Raynaud's disease), is characterized by **functional vasospasm** of arterioles, especially in fingers and toes, in response to cold or stress [1]. - In its initial stages, there are no structural changes or pathological alterations within the vessel walls; the vasoconstriction is entirely **functional** [1]. *Thrombosis* - **Thrombosis** involves the formation of a blood clot within a vessel, obstructing blood flow. - While severe Raynaud's can, in rare cases, lead to digital ischemia and microthrombosis, it is **not the primary or initial change** seen in typical Raynaud's phenomenon. *Fibrinoid necrosis* - **Fibrinoid necrosis** is a type of vascular damage associated with severe autoimmune diseases or malignant hypertension, where fibrin and plasma proteins deposit in the vessel wall. - This is a **structural, irreversible change** and is not characteristic of the initial, functional vasospasm seen in Raynaud's phenomenon. *Hyaline sclerosis* - **Hyaline sclerosis** is a change in small arteries and arterioles, often seen in benign essential hypertension or as part of the aging process, where the vessel wall thickens and becomes hyaline (glassy) due to plasma protein leakage and fibrosis. - This represents a **chronic structural change** and is not the acute, intermittent, functional vasoconstriction defining the initial stage of Raynaud's. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of Infancy and Childhood, pp. 520-522.

Q: Which mechanism is primarily responsible for the transport of glucose in renal tubular cells?

Sodium-glucose cotransport. ***Sodium-glucose cotransport*** - Glucose reabsorption in the renal tubules, particularly in the **proximal tubule**, occurs primarily via **secondary active transport** involving **sodium-glucose cotransporters (SGLTs)**. - SGLT proteins use the **sodium concentration gradient** (maintained by the Na+/K+-ATPase on the basolateral membrane) to move glucose against its concentration gradient from the tubular lumen into the cell. *Glucose diffusion* - While passive diffusion may play a minor role, it is insufficient to reabsorb the large amounts of **filtered glucose** - Diffusion would lead to significant **glucose loss in urine**, even at normal blood glucose levels. *Sodium antiport* - Antiport systems move two different ions or molecules in **opposite directions** across a membrane. - While present in renal cells, sodium antiport mechanisms are not the primary means of **glucose reabsorption**; rather, glucose transport is mostly symport. *Facilitated diffusion* - Facilitated diffusion involves carrier proteins (like **GLUT transporters**) that move molecules down their **concentration gradient**. - While GLUT transporters are present on the **basolateral membrane** of tubular cells to move glucose into the interstitium, they are not the primary mechanism for glucose uptake from the tubular lumen, which occurs against a concentration gradient.

Q: Mechanism by which Ach decreases heart rate is by:

Delayed diastolic depolarization. ***Delayed diastolic depolarization*** - Acetylcholine (ACh) binding to muscarinic receptors on nodal cells increases **potassium permeability**, leading to a more negative maximal diastolic potential. - This slows the rate of **spontaneous depolarization** (pacemaker potential), thereby delaying the point at which the threshold for an action potential is reached and reducing heart rate. *Prolongation of action potential duration* - ACh typically **shortens** the action potential duration in atrial and nodal cells by increasing potassium efflux, which hyperpolarizes the cell and hastens repolarization. - A prolonged action potential duration would generally lead to a **slower heart rate** by increasing the refractory period, but this is achieved through different ionic mechanisms and is not the primary mechanism of ACh. *Reduction in calcium influx* - While ACh does reduce the inward **calcium current (ICa)** in nodal cells, contributing to a slower heart rate and weaker contractility, this effect primarily influences the upstroke and peak of the action potential. - The more **fundamentally important mechanism** for heart rate reduction is the impact on the pacemaker potential's slope, which is governed by altered ion conductances, predominantly potassium. *Inhibition of sympathetic activity* - ACh acts directly on **muscarinic receptors** on cardiac cells to decrease heart rate, which is a parasympathetic effect. - It does not directly inhibit sympathetic nerve activity but rather **counteracts sympathetic effects** by directly modulating cardiac cell physiology.

Question 1

From which ribs does the spleen extend?

Accepted Answer

9th to 11th rib

Answer

5th to 9th rib

Answer

2nd to 5th rib

Answer

11th to 12th rib

Question 2

Which of the following is not a branch of the inferior mesenteric artery?

Accepted Answer

Middle rectal

Answer

Left colic

Answer

Superior rectal

Answer

Sigmoidal artery

Question 3

Why is oxidized LDL considered more atherogenic?

Accepted Answer

Is taken up by scavenger receptors

Answer

Is not recognized by LDL receptors

Answer

Promotes inflammation in arterial walls

Answer

Accumulates in macrophages

Question 4

Which vitamin is considered the most potent antioxidant?

Accepted Answer

Vit E

Answer

Vit A

Answer

Vit K

Answer

Vit C

Question 5

Glycogen synthase is activated by?

Accepted Answer

Insulin

Answer

Glucagon

Answer

AMP

Answer

Epinephrine

Question 6

Enzyme deficient in Type I Hyperlipidemia?

Accepted Answer

Lipoprotein lipase

Answer

HMG CoA reductase

Answer

Peroxidase

Answer

Cholesterol acyl transferase

Question 7

Which acquired condition is most commonly associated with spherocytes?

Accepted Answer

Autoimmune hemolytic anemia (AIHA)

Answer

Vitamin B12 deficiency anemia

Answer

Aplastic anemia

Answer

None of the options

Question 8

What change is seen in the vessels during the initial stage of Raynaud's phenomenon?

Accepted Answer

No pathological changes (functional vasospasm only)

Answer

Thrombosis

Answer

Fibrinoid necrosis

Answer

Hyaline sclerosis

Question 9

Which mechanism is primarily responsible for the transport of glucose in renal tubular cells?

Accepted Answer

Sodium-glucose cotransport

Answer

Facilitated diffusion

Answer

Glucose diffusion

Answer

Sodium antiport

Question 10

Mechanism by which Ach decreases heart rate is by:

Accepted Answer

Delayed diastolic depolarization

Answer

Prolongation of action potential duration

Answer

Reduction in calcium influx

Answer

Inhibition of sympathetic activity

NEET-PG 2012

Anatomy

Biochemistry

Pathology

Physiology