Anatomy
1 questionsTight junctions are primarily located at which part of the cell?
INI-CET 2025 - Anatomy INI-CET Practice Questions and MCQs
Question 181: Tight junctions are primarily located at which part of the cell?
- A. Apicolateral
- B. Basolateral
- C. Apical (Correct Answer)
- D. Basal
Explanation: ***Apical*** - Tight junctions, also known as **zonula occludens**, are located at the **apical region** of polarized epithelial cells [1]. - They form the most **apical component** of the junctional complex, positioned at the apical-most part of the lateral cell membrane, just below the free apical surface [1]. - They are crucial for forming a **permeability barrier** that controls paracellular transport and maintains cell polarity by separating apical from basolateral membrane domains [2]. *Incorrect Apicolateral* - While tight junctions are technically at the interface between apical and lateral domains, "apicolateral" is **not standard anatomical terminology** used in medical textbooks. - The standard anatomical description places tight junctions at the **apical region** of epithelial cells. *Incorrect Basolateral* - The **basolateral domain** encompasses the lateral cell membrane (where adhesion junctions like desmosomes and communication junctions like gap junctions are located) and the basal membrane. - Tight junctions are positioned **above** these other junctional complexes, at the apical-most position [1]. *Incorrect Basal* - The basal surface rests on the **basement membrane**. - The characteristic junction here is the **hemidesmosome**, which anchors the cell to the underlying extracellular matrix, not to seal adjacent cells [1].
Biochemistry
1 questionsIGF-1 and IGF-2 are structurally most similar to which of the following molecules?
INI-CET 2025 - Biochemistry INI-CET Practice Questions and MCQs
Question 181: IGF-1 and IGF-2 are structurally most similar to which of the following molecules?
- A. Preproinsulin
- B. Insulin (Correct Answer)
- C. Proinsulin
- D. C-peptide
Explanation: ***Insulin*** - **Insulin-like growth factors (IGFs)**, including IGF-1 and IGF-2, belong to the same peptide growth factor superfamily as insulin, sharing notable **sequence homology** (~50% amino acid similarity) and a similar three-dimensional structure. - Both IGFs and insulin are small peptides stabilized by **disulfide bonds** forming A and B domains, and act via similar receptor tyrosine kinases (the insulin receptor and IGF-1 receptor can cross-react). - Mature insulin represents the **structurally closest molecule** to the secreted, functional IGFs. *Preproinsulin* - **Preproinsulin** is the earliest precursor and includes an N-terminal **signal peptide** (the 'pre' sequence) which is cleaved off upon entry into the endoplasmic reticulum. - Since IGFs mature into secreted proteins without this transient signal sequence in their final structure, preproinsulin is structurally less similar than mature insulin. *Proinsulin* - **Proinsulin** consists of the A chain and B chain linked by the connecting **C-peptide** domain. - Although IGFs are derived from a single precursor chain like proinsulin, **mature insulin** (two chains, A and B) is structurally closer to the secreted IGFs than proinsulin (which has three domains: A, B, and C). *C-peptide* - The **C-peptide** is the connecting segment linking the A and B chains of proinsulin, which is cleaved and removed before insulin becomes mature. - It is a short, linear peptide with little structural resemblance to the complex, disulfide-bonded domains of functional IGFs or insulin.
Microbiology
1 questionsTwo different specimens from two patients are received. Which of the following techniques can confirm they are from different individuals (in the context of Mycobacterium tuberculosis)?
INI-CET 2025 - Microbiology INI-CET Practice Questions and MCQs
Question 181: Two different specimens from two patients are received. Which of the following techniques can confirm they are from different individuals (in the context of Mycobacterium tuberculosis)?
- A. RFLP (Correct Answer)
- B. Pyrosequencing
- C. Mutation analysis
- D. RAPD
Explanation: ***Correct: RFLP*** - **RFLP** (Restriction Fragment Length Polymorphism), particularly using the **IS6110 insertion sequence**, is the traditional gold standard tool for **epidemiological strain typing** of *M. tuberculosis*. - Confirmation that two specimens are from different individuals relies on visualizing two distinct banding patterns, indicating different arrangements of the **IS6110** elements in their respective genomes. - RFLP has **high discriminatory power** for differentiating between strains and establishing epidemiological links. *Incorrect: Mutation analysis* - This technique primarily focuses on detecting **point mutations** in specific genes (e.g., *rpoB*, *katG*) to determine drug susceptibility or resistance patterns. - While differences in resistance profiles suggest different strains, it lacks the **high discriminatory power** of RFLP or VNTR for broad epidemiological linkage assessment. *Incorrect: Pyrosequencing* - Pyrosequencing is a rapid method of DNA sequencing often used to detect **single nucleotide polymorphisms (SNPs)** or specific mutations, such as those related to drug resistance. - It is utilized for sequencing short regions and is not the primary technique for comparing the **large-scale genomic structures** necessary for definitive strain fingerprinting. *Incorrect: RAPD* - **RAPD** (Random Amplification of Polymorphic DNA) is an older PCR-based method that uses arbitrary primers to generate a pattern of amplified DNA fragments. - While used for strain comparison in some bacteria, RAPD is generally considered **less reproducible** and has **lower discriminatory power** than RFLP or VNTR for *M. tuberculosis* typing.
Physiology
7 questionsWhich of the following is not a mechanism of action of ADH?
Patient presents to OPD with fever. Which area is most likely involved?
Which of the following is an example of feed forward mechanism?
In a normal awake person at rest with eyes closed, EEG waves that are reduced on opening the eyes:
Which of the following are features of Bezold Jarisch reflex? 1. Bradycardia 2. Hypertension 3. Coronary vasodilation 4. Tachycardia
Surface tension of the fluid lining the alveoli increases during:
Which of the following is seen in high altitude?
INI-CET 2025 - Physiology INI-CET Practice Questions and MCQs
Question 181: Which of the following is not a mechanism of action of ADH?
- A. Increases absorption of NaCl in thin ascending limb
- B. Increases water permeability in collecting ducts
- C. Increases absorption of urea in medullary collecting duct
- D. Increases absorption of urea in descending limb of loop of Henle (Correct Answer)
Explanation: ***Increases absorption of urea in descending limb of loop of Henle*** - The mechanism of action of **Antidiuretic Hormone (ADH)** does not involve increasing urea absorption in the **descending limb** of the loop of Henle. - The descending limb is primarily permeable to **water only** and lacks ADH-responsive urea transporters. - This is **NOT** a mechanism of ADH action, making this the correct answer. *Increases water permeability in collecting ducts* - ADH binds to **V2 receptors** in the principal cells of the collecting ducts, triggering the insertion of **aquaporin-2 (AQP2)** channels into the luminal membrane. - This is the **primary mechanism** of ADH, allowing water reabsorption and urine concentration. *Increases absorption of urea in medullary collecting duct* - ADH stimulates the insertion of **urea transporters (UT-A1 and UT-A3)** in the inner medullary collecting duct (IMCD). - This passive diffusion of urea into the medullary interstitium helps maintain the high osmolarity required for maximal water reabsorption. - This is an established **direct mechanism** of ADH. *Increases absorption of NaCl in thin ascending limb* - While the thin ascending limb has passive NaCl permeability, ADH's effects on salt handling are primarily mediated through the **thick ascending limb (TAL)** where it enhances Na-K-2Cl cotransporter activity. - ADH contributes to medullary hypertonicity, which indirectly affects the concentration gradient for passive NaCl movement in the thin ascending limb. - This represents an **indirect effect** rather than a primary mechanism, but is still considered an ADH action in generating concentrated urine.
Question 182: Patient presents to OPD with fever. Which area is most likely involved?
- A. Periventricular hypothalamus
- B. Pre-optic nucleus (Correct Answer)
- C. Dorsomedial hypothalamus
- D. Insular cortex
Explanation: ***Pre-optic nucleus*** - The **pre-optic nucleus** in the anterior hypothalamus contains heat-sensitive and cold-sensitive neurons and functions as the body's primary **thermoregulatory center** or **thermostat**. - Fever results when **pyrogens** (like **IL-1, IL-6**, and **TNF-α**) raise the set-point of this nucleus, leading to heat production and conservation. *Insular cortex* - The insular cortex is involved in processing emotions, interoception (awareness of the body's internal state), and pain, not primarily in regulating core body temperature. - It has a role in complex functions like taste, visceral sensation, and autonomic control but is not the central area for initiating fever. *Periventricular hypothalamus* - The periventricular zone of the hypothalamus is involved in various neuroendocrine functions, including releasing hormones like **somatostatin** and **vasopressin**. - It is not the principal area responsible for setting the body's core temperature or initiating the febrile response. *Dorsomedial hypothalamus* - The **dorsomedial nucleus** of the hypothalamus mainly regulates gastrointestinal activity and some affective behaviors, like fear and aggression. - While the hypothalamus is a thermal regulation hub, this specific nucleus is not the primary target for pyrogens causing fever.
Question 183: Which of the following is an example of feed forward mechanism?
- A. Temperature regulation (Correct Answer)
- B. Vasoconstriction in response to cooling
- C. Increase in cardiac output in response to anemia
- D. HR increases from supine to standing
Explanation: ***Temperature regulation*** - Temperature regulation is the correct answer because it demonstrates **feed-forward control** through **anticipatory mechanisms** that act *before* core body temperature changes. - Classic feed-forward example: When **skin thermoreceptors** detect intense sunlight or environmental heat, the body initiates protective responses (behavioral changes like seeking shade, peripheral vasodilation, sweating) *before* core temperature rises. - This anticipatory control contrasts with feedback mechanisms that respond *after* detecting changes in the regulated variable. - The feed-forward component uses **peripheral sensors** and central command signals to proactively maintain **homeostasis**, preventing disturbances rather than correcting them. *Incorrect: HR increases from supine to standing* - This is a classic **negative feedback loop** controlled by the **baroreflex**. - Sequence: Standing → blood pools → BP drops → baroreceptors detect change → HR increases to restore BP. - The response occurs *after* detecting the disturbance (reactive, not anticipatory). *Incorrect: Vasoconstriction in response to cooling* - This is **negative feedback** to maintain core body temperature. - **Peripheral thermoreceptors** detect temperature drop → hypothalamus responds → **vasoconstriction** via **sympathetic stimulation** minimizes heat loss. - The response follows detection of cooling (reactive mechanism). *Incorrect: Increase in cardiac output in response to anemia* - This is homeostatic **negative feedback** compensating for reduced **oxygen delivery**. - Tissue hypoxia from anemia → increased **sympathetic drive** → elevated **Cardiac Output (CO)** to maximize oxygen transport. - The compensation occurs *after* oxygen delivery becomes inadequate.
Question 184: In a normal awake person at rest with eyes closed, EEG waves that are reduced on opening the eyes:
- A. Theta waves
- B. Beta waves
- C. Alpha waves (Correct Answer)
- D. Delta waves
Explanation: ***Alpha waves*** - These waves (8-13 Hz) are characteristic of the **relaxed wakefulness** state, present chiefly over the occipital areas when the eyes are closed (the **Berger rhythm**). - When the eyes are opened or the person concentrates, the alpha waves are immediately abolished and replaced by fast, low-voltage **Beta waves**, a phenomenon known as **alpha block** or desynchronization. *Beta waves* - These waves (>13 Hz) are associated with **active concentration**, mental alertness, or the act of opening the eyes. - The opening of the eyes causes the brain activity to shift *towards* the Beta rhythm, thus they are increased, not reduced, in this scenario. *Theta waves* - Theta waves (4-7 Hz) are typically observed during **NREM sleep stages 1 and 2** (light sleep) and are usually infrequent in the normal awake, resting adult. - Their presence or absence is not primarily governed by the action of opening or closing the eyes in an awake individual; they reflect stages of sleep or deep emotional arousal. *Delta waves* - Delta waves (<4 Hz) are the slowest waves, typically dominating the EEG during **deep slow-wave sleep (N3)** or indicative of serious brain pathology when seen in an awake adult. - They are absent in the normal awake, resting state, so the act of opening the eyes does not lead to their reduction.
Question 185: Which of the following are features of Bezold Jarisch reflex? 1. Bradycardia 2. Hypertension 3. Coronary vasodilation 4. Tachycardia
- A. 1,2,3
- B. 1,3,4
- C. All of the above
- D. 1,3 (Correct Answer)
Explanation: ***1, 3 (Correct Answer)*** - The **Bezold-Jarisch reflex (BJR)** is a cardio-inhibitory reflex initiated by stimulating cardiac sensory receptors (C-fibers, particularly in the inferoposterior wall of left ventricle). - The efferent limb is mediated by the **vagus nerve**, resulting in the classic triad: **bradycardia**, **hypotension**, and **coronary vasodilation**. - **Bradycardia (1)** occurs due to parasympathetic (vagal) stimulation of the SA node. - **Coronary vasodilation (3)** is a direct effect that helps reduce myocardial oxygen demand. - This reflex is protective, reducing cardiac workload during ischemic conditions. *1, 2, 3 (Incorrect)* - **Hypertension (2)** does not occur in BJR; instead, the reflex causes **hypotension** due to peripheral vasodilation and reduced cardiac output. - The BJR is fundamentally a depressor reflex, not a pressor reflex. *1, 3, 4 (Incorrect)* - **Tachycardia (4)** is the opposite of what occurs in BJR. - The reflex is mediated by parasympathetic activation, which decreases heart rate, not increases it. - Tachycardia would be a sympathetic response, contradicting the BJR mechanism. *All of the above (Incorrect)* - Since options 2 and 4 represent physiological responses opposite to BJR (hypertension and tachycardia), this cannot be correct. - The BJR produces bradycardia, hypotension, and coronary vasodilation only.
Question 186: Surface tension of the fluid lining the alveoli increases during:
- A. Inspiration
- B. Standing
- C. Expiration (Correct Answer)
- D. Supine
Explanation: ***Expiration*** - During expiration, the alveoli **decrease in size** and the alveolar radius becomes smaller. - As the surface area contracts, surfactant molecules become **compressed** and less effective at reducing surface tension. - According to the **Law of Laplace** (P = 2T/r), with a smaller radius and increased surface tension, alveoli would tend to collapse—surfactant normally prevents this, but surface tension is **highest at end-expiration**. - This physiological increase in surface tension during expiration is why **surfactant is critical** to prevent alveolar collapse, especially in premature infants with respiratory distress syndrome. *Incorrect: Inspiration* - During inspiration, alveoli **expand** and increase in radius. - Surfactant's unique property is that it **lowers surface tension more effectively** when spread over a larger surface area. - This dynamic behavior of surfactant ensures that surface tension actually **decreases during inspiration**, facilitating alveolar expansion and reducing the work of breathing. *Incorrect: Standing* - Standing affects the **distribution of ventilation and perfusion** (V/Q ratio) due to gravitational effects on blood flow and lung mechanics. - It does **not directly alter** the surface tension of the alveolar fluid lining on a molecular level. - Regional differences may occur, but there is no consistent, predictable increase in overall surface tension with standing. *Incorrect: Supine* - The supine position redistributes lung volumes and may cause some **airway closure** in dependent regions. - While functional residual capacity (FRC) may decrease slightly, this does **not cause a specific increase** in alveolar surface tension. - Effects on surface tension are indirect and not the primary physiological change with postural alterations.
Question 187: Which of the following is seen in high altitude?
- A. Respiratory alkalosis (Correct Answer)
- B. Respiratory acidosis
- C. Metabolic acidosis
- D. Metabolic alkalosis
Explanation: ***Respiratory alkalosis*** - High altitude exposure leads to **hypoxia** (low inspired oxygen), which stimulates peripheral chemoreceptors. - This stimulation increases the **respiratory rate and depth** (hyperventilation), resulting in excessive blowing off of **carbon dioxide (CO₂)**, which causes a decrease in arterial pCO₂ and elevates the blood pH (alkalosis). *Metabolic acidosis* - This is a condition where the blood pH is low due to a low bicarbonate (HCO₃⁻) concentration, which is not the primary immediate response to high altitude. - However, in a later stage, the kidneys attempt to compensate for respiratory alkalosis by **excreting bicarbonate**, leading to a compensatory metabolic acidosis. *Metabolic alkalosis* - This condition involves a high blood pH due to an excess of bicarbonate, which is typically seen in conditions like severe vomiting or use of diuretics, not acute high altitude exposure. - It is the opposite of the renal compensation mechanism seen in response to high altitude. *Respiratory acidosis* - Characterized by reduced ventilation (hypoventilation) leading to **retention of CO₂** (increased pCO₂), resulting in a lowered blood pH. - High altitude causes hyperventilation, not hypoventilation, and therefore results in respiratory *alkalosis*.