INI-CET 2025 Practice Questions

Q: Tight junctions are primarily located at which part of the cell?

Apical. ***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].

Q: IGF-1 and IGF-2 are structurally most similar to which of the following molecules?

Insulin. ***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.

Q: 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)?

RFLP. ***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.

Q: In a normal awake person at rest with eyes closed, EEG waves that are reduced on opening the eyes:

Alpha waves. ### **Explanation** The correct answer is **Alpha waves**. #### **1. Why Alpha Waves are Correct** * **Alpha waves (8–13 Hz)** are the characteristic rhythm of a **relaxed, awake adult** with **eyes closed**. They are most prominent in the **parieto-occipital** regions. * The phenomenon described in the question is known as **Alpha Block** or **Desynchronization**. When the person opens their eyes or engages in focused mental activity (like solving a math problem), the synchronized alpha rhythm is replaced by fast, irregular, low-voltage activity. This happens because visual input "breaks" the synchronized firing of cortical neurons. #### **2. Why Other Options are Incorrect** * **Beta waves (13–30 Hz):** These are seen during **active thinking**, alertness, or tension. Opening the eyes usually *increases* beta activity rather than reducing it. * **Theta waves (4–7 Hz):** These are normal in **children** or during **Stage N1 sleep** in adults. In an awake adult, they may indicate emotional stress or certain brain disorders. * **Delta waves (<4 Hz):** These are the slowest waves with the highest amplitude. They are characteristic of **deep sleep (Stage N3)** or infancy. Their presence in an awake adult signifies serious organic brain disease. #### **3. High-Yield Clinical Pearls for INI-CET** * **Mnemonic for EEG Frequencies:** **D**on't **T**ouch **A**ll **B**uttons (**D**elta < **T**heta 2 microvolts is recorded.

Q: Which of the following are features of Bezold Jarisch reflex? 1. Bradycardia 2. Hypertension 3. Coronary vasodilation 4. Tachycardia

1,3. ### **Explanation: Bezold-Jarisch Reflex (BJR)** The **Bezold-Jarisch Reflex** is a cardio-inhibitory reflex originating from sensory receptors (chemoreceptors and mechanoreceptors) located in the **ventricular walls**, particularly the inferoposterior wall of the left ventricle. #### **Mechanism & Correct Features** When these receptors are stimulated by chemical substances (e.g., alkaloids, serotonin, contrast media) or mechanical triggers (e.g., severe hypovolemia, myocardial ischemia), signals are sent via **unmyelinated C-fibers** (vagal afferents) to the medulla. This results in: 1. **Bradycardia (Feature 1):** Increased parasympathetic (vagal) tone slows the heart rate. 2. **Hypotension:** Widespread peripheral vasodilation occurs due to decreased sympathetic outflow. 3. **Coronary Vasodilation (Feature 3):** A protective mechanism to improve myocardial perfusion during stress. #### **Why Other Options are Incorrect** * **Hypertension (Feature 2):** Incorrect. The reflex causes a profound **drop in blood pressure** (hypotension), not an increase. * **Tachycardia (Feature 4):** Incorrect. The reflex is characterized by **bradycardia**. It is often considered a "paradoxical" reflex because, in states of low blood volume, the body usually responds with tachycardia (Baroreceptor reflex); however, the BJR overrides this, causing the heart to slow down. --- ### **High-Yield Clinical Pearls for INI-CET** * **The Triad:** The classic BJR triad is **Apnea, Bradycardia, and Hypotension**. * **Clinical Trigger:** It is frequently seen during **Inferior Wall Myocardial Infarction (IWMI)** because the receptors are concentrated in the inferior wall of the LV. * **Anesthesia Link:** It is a common cause of sudden bradycardia and hypotension during **Spinal Anesthesia**, especially if the patient is dehydrated. * **Chemical Stimulants:** Veratridine, nicotine, and capsaicin are known to trigger this reflex experimentally.

Question 1

Tight junctions are primarily located at which part of the cell?

Accepted Answer

Apical

Answer

Apicolateral

Answer

Basolateral

Answer

Basal

Question 2

IGF-1 and IGF-2 are structurally most similar to which of the following molecules?

Accepted Answer

Insulin

Answer

Preproinsulin

Answer

Proinsulin

Answer

C-peptide

Question 3

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)?

Accepted Answer

RFLP

Answer

Pyrosequencing

Answer

Mutation analysis

Answer

RAPD

Question 4

Which of the following is not a mechanism of action of ADH?

Accepted Answer

Increases absorption of urea in descending limb of loop of Henle

Answer

Increases absorption of NaCl in thin ascending limb

Answer

Increases water permeability in collecting ducts

Answer

Increases absorption of urea in medullary collecting duct

Question 5

Patient presents to OPD with fever. Which area is most likely involved?

Accepted Answer

Pre-optic nucleus

Answer

Periventricular hypothalamus

Answer

Dorsomedial hypothalamus

Answer

Insular cortex

Question 6

Which of the following is an example of feed forward mechanism?

Accepted Answer

Temperature regulation

Answer

Vasoconstriction in response to cooling

Answer

Increase in cardiac output in response to anemia

Answer

HR increases from supine to standing

Question 7

In a normal awake person at rest with eyes closed, EEG waves that are reduced on opening the eyes:

Accepted Answer

Alpha waves

Answer

Theta waves

Answer

Beta waves

Answer

Delta waves

Question 8

Which of the following are features of Bezold Jarisch reflex?
1. Bradycardia
2. Hypertension
3. Coronary vasodilation
4. Tachycardia

Accepted Answer

1,3

Answer

1,2,3

Answer

1,3,4

Answer

All of the above

Question 9

Surface tension of the fluid lining the alveoli increases during:

Accepted Answer

Expiration

Answer

Inspiration

Answer

Standing

Answer

Supine

Question 10

Which of the following is seen in high altitude?

Accepted Answer

Respiratory alkalosis

Answer

Respiratory acidosis

Answer

Metabolic acidosis

Answer

Metabolic alkalosis

INI-CET 2025

Anatomy

Biochemistry

Microbiology

Physiology