Anatomy
1 questionsIn the context of blood pressure regulation, where are baroreceptors primarily located?
NEET-PG 2015 - Anatomy NEET-PG Practice Questions and MCQs
Question 351: In the context of blood pressure regulation, where are baroreceptors primarily located?
- A. Tunica intima
- B. None of the options
- C. Tunica media
- D. Tunica adventitia (Correct Answer)
Explanation: ***Tunica adventitia*** - **Baroreceptors** are specialized mechanoreceptive nerve endings that detect changes in blood pressure by sensing arterial wall stretch. - These sensory nerve endings are primarily located in the **tunica adventitia** (outermost layer) of the **carotid sinus** and **aortic arch** [1]. - The adventitia contains the **nerve fibers and endings** (including baroreceptors), as well as the vasa vasorum and connective tissue supporting the vessel wall [1]. - The nerve terminals extend from the adventitia toward the adventitial-medial border where they sense wall tension changes. *Tunica media* - The **tunica media** is the middle layer composed of **smooth muscle cells** and elastic fibers. - While this layer responds to stretch and changes thickness with blood pressure variations, it does **not contain nerve endings or baroreceptors** [1]. - The media is responsible for vasoconstriction and vasodilation but lacks the sensory innervation needed for baroreception. *Tunica intima* - The **tunica intima** is the innermost layer lined by **endothelial cells**. - Its primary functions include providing a smooth surface for blood flow and regulating vascular permeability. - This layer does not house baroreceptors or other mechanoreceptive nerve endings. *None of the options* - This option is incorrect because **tunica adventitia** is indeed the correct location of baroreceptors. - The adventitia contains the neural elements necessary for blood pressure sensing in these specialized arterial regions [1].
Biochemistry
2 questionsWhich of the following is the most reactive free radical?
Unfolded protein metabolism is associated with
NEET-PG 2015 - Biochemistry NEET-PG Practice Questions and MCQs
Question 351: Which of the following is the most reactive free radical?
- A. Alkyl radical
- B. Superoxide radical
- C. Peroxide radical
- D. Hydroxyl radical (Correct Answer)
Explanation: ***Hydroxyl radical*** - The **hydroxyl radical (•OH)** is the most reactive free radical in biological systems due to its extremely high oxidation potential and short half-life. - It readily reacts with virtually all cellular macromolecules, including **DNA, proteins, and lipids**, causing widespread damage. *Peroxide radical* - The **peroxide radical (ROO•)**, or more specifically the peroxyl radical, is less reactive than the hydroxyl radical, but still significant in lipid peroxidation. - It plays a role in propagating chain reactions of **lipid damage** in cell membranes. *Alkyl radical* - **Alkyl radicals (R•)** are generally formed as intermediates during the abstraction of hydrogen atoms from saturated compounds. - While reactive, they are typically less reactive and less frequently encountered in biological systems compared to oxygen-centered radicals like the hydroxyl radical. *Superoxide radical* - The **superoxide radical (O₂•−)** is a relatively less reactive free radical compared to the hydroxyl radical, but it is the precursor to many other reactive oxygen species (ROS). - It is primarily involved in **initiation of oxidative stress** and can lead to the formation of more damaging species through reactions like the Haber-Weiss reaction.
Question 352: Unfolded protein metabolism is associated with
- A. Endoplasmic reticulum (Correct Answer)
- B. Golgi apparatus
- C. Mitochondria
Explanation: ***Endoplasmic reticulum*** - The **endoplasmic reticulum (ER)** is the primary site for protein folding, modification, and assembly, especially for secreted and transmembrane proteins. - When misfolded proteins accumulate, the ER triggers the **unfolded protein response (UPR)** to restore homeostasis or induce apoptosis. *Golgi apparatus* - The Golgi apparatus is primarily involved in **further processing**, sorting, and packaging of proteins and lipids synthesized in the ER. - It does not directly manage the initial folding of proteins or the response to widespread protein misfolding. *Mitochondria* - **Mitochondria** are known for their role in **energy production** (ATP synthesis) through cellular respiration. - While they possess their own protein synthesis machinery for some essential mitochondrial proteins, they are not involved in the overall cellular management of unfolded protein metabolism from the ER.
Internal Medicine
1 questionsDiabetic foot is associated with following type of gangrene -
NEET-PG 2015 - Internal Medicine NEET-PG Practice Questions and MCQs
Question 351: Diabetic foot is associated with following type of gangrene -
- A. Dry gangrene
- B. Wet gangrene (Correct Answer)
- C. Gas gangrene
- D. Fournier's gangrene
Explanation: ***Wet gangrene*** - Diabetic foot commonly leads to **ischemia** and **infection** [1], resulting in wet gangrene characterized by moist, necrotic tissue. - This type of gangrene is associated with **rapid progression** and can result in systemic toxicity, making prompt treatment essential. *Fournier's gangrene* - This type of gangrene specifically affects the **perineal** region and is not directly associated with diabetic foot. - It usually arises from infections related to **perineal trauma** or surgical procedures. *Gas gangrene* - Caused by **Clostridium** species and typically follows a traumatic injury or surgical procedure, not specifically related to diabetes. - Presents with **crepitus** and rapid systemic symptoms, different from the chronic nature of diabetic ulcers. *Dry gangrene* - Associated with **chronic ischemia** and necrosis, it occurs in conditions like peripheral arterial disease, not primarily with infections seen in diabetic foot [1]. - It usually develops gradually without the sudden onset of symptoms characteristic of wet gangrene.
Pathology
4 questionsWhich of the following is not considered an example of excess tissue growth?
Rolling of leucocytes on endothelial cells is mediated by which of the following?
Which substance plays a significant role in the tumor metastasis cascade?
Which of the following is derived from fibroblast cells?
NEET-PG 2015 - Pathology NEET-PG Practice Questions and MCQs
Question 351: Which of the following is not considered an example of excess tissue growth?
- A. Granulation tissue (Correct Answer)
- B. Neoplasia
- C. Hyperplasia
- D. Fibrosis
Explanation: ***Granulation tissue*** - Granulation tissue is a normal part of the healing process and does not represent an **excessive growth** of tissue [3]. - It consists mainly of **new connective tissue** and blood vessels formed during healing, rather than a pathological proliferation [3]. *Hyperplasia* - Hyperplasia is characterized by an **increase in the number** of cells in a tissue, leading to tissue enlargement [1][2]. - This process is often a response to a stimulus, such as hormonal changes or injury, indicating **excess tissue growth** [2]. *Neoplasia* - Neoplasia refers to the **abnormal proliferation** of cells, forming a neoplasm or tumor, which can be benign or malignant. - This is a clear example of **excess tissue growth**, as it involves uncontrolled cell division. *Fibrosis* - Fibrosis implies the formation of excess **fibrous connective tissue**, leading to a stiff or thickened tissue, signifying abnormal tissue growth [4]. - It often results from chronic inflammation or injury, again reflecting **excessive tissue** formation [4]. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 87-88. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 85-87. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 105-106. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 111-112.
Question 352: Rolling of leucocytes on endothelial cells is mediated by which of the following?
- A. ICAM-1
- B. Integrin
- C. IL-8
- D. P-selectin (Correct Answer)
Explanation: ***P- selectin*** - P-selectin is a **cell adhesion molecule** crucial for the **rolling** of leukocytes on endothelial cells during the inflammatory response [1]. - It is expressed on activated endothelial cells and binds to **sialylated carbohydrates** on leukocytes, facilitating their transient adhesion [1]. *IL-8* - IL-8 is a **chemokine** that primarily acts as a chemotactic factor for neutrophils rather than mediating rolling on endothelium. - While it attracts leukocytes to sites of inflammation, it does not play a role in the initial contact or rolling process. *ICAM-1* - ICAM-1 is an **intercellular adhesion molecule** that facilitates **firm adhesion** rather than rolling of leukocytes. - It primarily interacts with **integrins** on leukocytes to stabilize their adhesion after rolling has occurred. *(3, integrin* - Integrins play a significant role in **firm adhesion** and not the rolling phase, interacting with receptors like ICAM-1. - The binding of integrins to their ligands occurs after leukocytes have initially rolled on the endothelium. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, p. 87.
Question 353: Which substance plays a significant role in the tumor metastasis cascade?
- A. TNF-alpha
- B. CD99
- C. NM23
- D. MMP-2 (Matrix Metalloproteinase-2) (Correct Answer)
Explanation: ***Collagenase IV*** - Collagenase IV is involved in the **degradation of extracellular matrix**, facilitating tumor invasion and metastasis [1,2]. - It plays a crucial role in breaking down **type IV collagen**, a major component of the **basement membrane**, allowing cancer cells to migrate [2]. *TNF-alpha* - While TNF-alpha is a cytokine that can promote **tumor growth**, it is not directly involved in the **metastatic cascade** like collagenase IV [3,4]. - It primarily functions in **inflammation** and immune response, affecting tumor microenvironment rather than directly facilitating invasion. *NM23* - NM23 is noted for its potential role as a **tumor suppressor**, and lower levels are associated with metastasis. - However, it does not play a direct role in the *metastatic cascade* itself [3,4], as it primarily influences **tumor progression** rather than matrix degradation. *CD99* - CD99 is a cell adhesion molecule implicated in **cell migration**, but it is not a significant factor in the **enzymatic breakdown** of tissue during metastasis [1,2]. - Its expression has more to do with **cell adhesion characteristics**, rather than directly promoting invasive capabilities. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 315-316. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 232-233. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 314-315. [4] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 233-234.
Question 354: Which of the following is derived from fibroblast cells?
- A. MMP2
- B. Collagen (Correct Answer)
- C. Angiopoietin
- D. TGF-β
Explanation: ***Collagen*** - Collagen is a structural protein that is predominantly produced by **fibroblast cells** in the extracellular matrix [1][2]. - It provides tensile strength and structural support to various tissues, playing a crucial role in wound healing and tissue repair [2]. *TGF-13* - Transforming Growth Factor-beta 1 (TGF-β1) is primarily produced by **immune cells** and is involved in cell growth and differentiation, not primarily by fibroblasts. - It plays a role in **fibrosis** and inflammation, but is not directly synthesized by fibroblast cells themselves. *MMP2* - Matrix Metalloproteinase-2 (MMP-2) is produced by various cell types, including **endothelial and epithelial cells**, but not predominantly by fibroblasts. - It is involved in the degradation of **extracellular matrix** components rather than being a product of fibroblast synthesis. *Angiopoietin* - Angiopoietin is primarily secreted by **endothelial cells** and plays a significant role in blood vessel formation and maturation. - It is not derived from fibroblast cells and is unrelated to their primary function of producing the extracellular matrix. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 31-32. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. With Illustrations By, pp. 34-35.
Physiology
2 questionsWhich of the following conditions can lead to a decrease in afterload?
Which of the following structures contains baroreceptors that detect changes in blood pressure?
NEET-PG 2015 - Physiology NEET-PG Practice Questions and MCQs
Question 351: Which of the following conditions can lead to a decrease in afterload?
- A. Severe anemia (Correct Answer)
- B. Hypothyroidism
- C. Increased physical activity
- D. None of the options
Explanation: ***Severe anemia*** - In **severe anemia**, the **blood viscosity** is reduced, and the body compensates by decreasing systemic vascular resistance to maintain tissue perfusion, thereby lowering **afterload**. - The reduced **oxygen-carrying capacity** triggers vasodilation to maximize blood flow to tissues, contributing to decreased afterload. - This represents a **chronic compensatory mechanism** that results in sustained reduction of afterload. *Hypothyroidism* - **Hypothyroidism** typically leads to an **increase in systemic vascular resistance** and thus can increase afterload. - It often results in **bradycardia** and reduced cardiac output, which can further elevate afterload to maintain pressure. *Increased physical activity* - During **physical activity**, there is **vasodilation in exercising muscles**, which acutely decreases systemic vascular resistance. - However, this is accompanied by **increased cardiac output** and **elevated blood pressure** due to sympathetic stimulation, and the afterload reduction is **transient** rather than sustained. - In the context of this question asking about conditions that lead to decreased afterload, **severe anemia** is the better answer as it represents a chronic pathological state with sustained afterload reduction, whereas exercise represents a temporary physiological response. *None of the options* - This option is incorrect because **severe anemia** is a recognized cause of decreased afterload.
Question 352: Which of the following structures contains baroreceptors that detect changes in blood pressure?
- A. Carotid body
- B. Carotid sinus (Correct Answer)
- C. Aortic body
- D. None of the options
Explanation: ***Carotid sinus*** - The **carotid sinus** is a dilation at the bifurcation of the common carotid artery, containing **baroreceptors** sensitive to changes in blood pressure [1]. - These baroreceptors are **mechanoreceptors** that respond to the stretching of the vessel wall due to increased arterial pressure, sending signals to the brainstem to regulate blood pressure. *Carotid body* - The **carotid body** is a chemoreceptor that primarily detects changes in **blood oxygen, carbon dioxide, and pH** levels, not blood pressure [2]. - It plays a crucial role in regulating **respiration** in response to hypoxemia. *Aortic body* - The **aortic body** is a **chemoreceptor** located near the aortic arch that primarily monitors **blood oxygen, carbon dioxide, and pH levels**. - Note: While the aortic body itself is a chemoreceptor, the **aortic arch** (a different structure) does contain baroreceptors [1]. However, this option specifically refers to the aortic body, which is not a baroreceptor. - The aortic body contributes to the regulation of **respiration** in response to hypoxemia, not directly blood pressure. *None of the options* - This option is incorrect because the **carotid sinus** is a well-known site for baroreceptors involved in blood pressure regulation.