NEET-PG 2012 - Physiology Practice Questions

Q: A wave in ERG is due to activity of:

Rods and cones. ***Rods and cones*** - The **electroretinogram (ERG)** measures the electrical responses of various retinal cells to light stimuli. - The **a-wave** of the ERG primarily reflects the activity of the **photoreceptors (rods and cones)** as they hyperpolarize in response to light. *Pigmented epithelium* - The **retinal pigmented epithelium (RPE)** plays a crucial role in photoreceptor health and function but does not directly generate the primary electrical waves measured by the standard ERG. - Its dysfunction can lead to secondary changes in ERG, but its activity is not the direct source of the a-wave. *Ganglion cell* - **Ganglion cells** are the output neurons of the retina, transmitting visual information to the brain. - Their activity is generally not well-represented in the standard ERG, which primarily assays outer and middle retinal layers. *Bipolar cell* - **Bipolar cells** transmit signals from photoreceptors to ganglion cells and contribute to the **b-wave** component of the ERG. - The b-wave, not the a-wave, is largely generated by the depolarizing activity of bipolar cells and Müller cells.

Q: What is the characteristic of the second Purkinje image in relation to eye movement?

Erect and moves in same direction. ***Erect and moves in same direction*** - The second Purkinje image (P2) is formed by reflection from the **posterior surface of the cornea**. - This surface acts as a convex mirror, producing a **virtual, erect, and diminished image**. - The image moves in the **same direction** as the eye movement, characteristic of reflections from the first three Purkinje images (P1, P2, P3). - P2 is clinically used in keratometry and assessment of corneal curvature. *Erect and moves in opposite direction* - While the image orientation (erect) would apply to P2, the direction of movement is incorrect. - Only the **fourth Purkinje image (P4)**, formed by the **posterior lens surface**, moves in the opposite direction to eye movement. - P4 is the only inverted Purkinje image due to reflection from the concave posterior lens surface. *Inverted and moves in same direction* - The second Purkinje image is **erect, not inverted**. - All Purkinje images are erect except P4, which is inverted due to reflection from the concave posterior lens surface. - This combination (inverted + same direction) does not correspond to any Purkinje image. *Inverted and moves in opposite direction* - This describes the **fourth Purkinje image (P4)**, not the second. - P4 is formed by reflection from the **posterior surface of the lens** (concave surface), which produces an inverted image. - The second Purkinje image (P2) is always erect, being formed by the posterior corneal surface.

Q: What does colostrum have compared to normal milk?

Increased proteins. ***Increased proteins*** - **Colostrum** is rich in **immunoglobulins (antibodies)** like IgA, IgG, and IgM, which are proteins crucial for passive immunity in the newborn, making its protein content **2-3 times higher** than mature milk (approximately 2.3 g/100 mL vs 0.9 g/100 mL). - These high protein levels also include **lactoferrin** and **growth factors**, which support the development of the infant's gut and immune system. - This is the **most clinically significant** distinguishing feature of colostrum. *Decreased potassium* - **Potassium (K)** levels in colostrum are actually **similar to or slightly higher** than mature milk (approximately 74 mg/100 mL vs 51 mg/100 mL). - This option is incorrect as potassium is not decreased. *Decreased sodium* - **Sodium (Na)** levels are actually **significantly higher** in colostrum than in mature milk (approximately 48 mg/100 mL vs 15 mg/100 mL). - This elevated sodium gives colostrum a distinct salty taste, differentiating it from mature milk. - This option is incorrect as sodium is increased, not decreased. *Decreased calories* - While colostrum has a **lower fat content** than mature milk, leading to somewhat lower caloric density (54-58 kcal/100 mL vs 65-70 kcal/100 mL), this is not the primary distinguishing characteristic. - The most important feature of colostrum is its **high protein and immunoglobulin content** for immune protection, not its caloric value.

Q: What is the primary mechanism underlying hyperthermia?

Failure of thermoregulation. ***Failure of thermoregulation*** - **Hyperthermia** is fundamentally caused by the body's inability to dissipate heat effectively, leading to an uncontrolled rise in core body temperature. - This differentiates it from fever, where the **hypothalamic set point** is elevated, and the body actively tries to reach that higher temperature. *Temperature > 41.5°C* - While a temperature exceeding **41.5°C** is often seen in severe hyperthermia, it is a *consequence* of the failure of thermoregulation, not its primary cause. - This extreme temperature indicates a critical state, but the underlying problem is the body's inability to control internal heat. *Temperature > 40°C with autonomic dysfunction* - A temperature above **40°C** combined with **autonomic dysfunction** (e.g., altered mental status, seizures) describes a severe *manifestation* of hyperthermia, often seen in heat stroke. - This is a symptom complex resulting from, rather than the primary cause of, the body's thermoregulatory failure. *No change in hypothalamic set point* - This statement is a *characteristic* of hyperthermia, distinguishing it from fever, where the **hypothalamic set point** is elevated. - However, the *absence* of this change is not the primary cause; rather, the underlying issue is the body's inability to manage its heat load despite a normal set point.

Q: Tetany is seen in

Respiratory alkalosis. ***Respiratory alkalosis*** - **Respiratory alkalosis** is caused by **hyperventilation**, which leads to a decrease in arterial partial pressure of carbon dioxide (**PaCO2**). - This decrease in PaCO2 causes an increase in pH (alkalemia) and a shift in the albumin-bound calcium equilibrium, reducing the amount of **ionized calcium** in the blood, leading to symptoms of **hypocalcemia** such as tetany. *Respiratory acidosis* - **Respiratory acidosis** is characterized by an increase in PaCO2 and a decrease in pH due to inadequate ventilation, which would not typically cause tetany. - In fact, the acidosis would tend to increase **ionized calcium** levels, thereby counteracting any tendency towards symptoms of hypocalcemia. *Metabolic acidosis* - **Metabolic acidosis** involves a decrease in bicarbonate concentration and pH, often due to conditions like diabetic ketoacidosis or lactic acidosis. - Similar to respiratory acidosis, the acidic environment of **metabolic acidosis** tends to increase **ionized calcium** levels, making tetany unlikely. *Hyperkalemia* - **Hyperkalemia** refers to elevated potassium levels in the blood, which primarily affects cardiac and neuromuscular function. - While it can cause muscle weakness and cardiac arrhythmias, it does not directly lead to **tetany**, which is a sign of **hypocalcemia**.

Q: In pregnancy, plasma volume increase is maximum at what gestational age?

30 wks. ***30 wks*** - **Plasma volume** typically reaches its maximum expansion around **30-34 weeks of gestation**, increasing by approximately 40-50% compared to pre-pregnancy levels. - This increase is crucial for supporting the **fetoplacental unit**, enhancing nutrient delivery, and protecting against supine hypotension. *10 wks* - At **10 weeks**, the increase in plasma volume is still modest, with significant expansion primarily occurring in the **second trimester**. - Most of the rapid expansion begins after the **first trimester**, around the 12-week mark. *20 wks* - While plasma volume is significantly increasing by **20 weeks**, it has not yet reached its peak. - The continuous expansion continues through the **third trimester** before stabilizing. *25 wks* - At **25 weeks**, plasma volume is substantially elevated, but the maximum expansion is usually observed a few weeks later. - The peak is generally in the **early third trimester**, around 30-34 weeks.

Q: Narcolepsy is due to abnormality in ?

Hypothalamus. **Hypothalamus** - Narcolepsy is primarily caused by the loss of **orexin (hypocretin)** producing neurons in the **hypothalamus**, which are crucial for maintaining wakefulness. - This deficiency leads to dysregulation of **sleep-wake cycles**, causing excessive daytime sleepiness and other narcolepsy symptoms. *Neocortex* - The neocortex is involved in higher-level cognitive functions, sensory perception, and voluntary movement, but it is not the primary site of pathology in narcolepsy. - While sleep stages involve cortical activity, the core deficit in narcolepsy does not originate here. *Cerebellum* - The cerebellum is mainly responsible for motor control, coordination, and balance. - Its dysfunction is associated with ataxic gait and coordination problems, not the sleep disturbances characteristic of narcolepsy. *Medulla oblongata* - The medulla oblongata controls vital autonomic functions like breathing, heart rate, and blood pressure. - While involved in sleep regulation pathways, it is not the primary anatomical location affected in narcolepsy.

Q: Which of the following is used for the diagnosis of asthma?

FEV1. ***FEV1*** - **Forced expiratory volume in 1 second (FEV1)** is the gold standard spirometric parameter for asthma diagnosis - Key diagnostic criteria include: - Reduced **FEV1/FVC ratio** (<0.70 or <0.75-0.80 in adults) - **Bronchodilator reversibility**: ≥12% and ≥200 mL increase in FEV1 after inhaled short-acting β2-agonist - This reversibility distinguishes asthma from fixed obstructive diseases like COPD - Serial **peak expiratory flow (PEF)** monitoring can also demonstrate variability characteristic of asthma *Measurement of tidal volume* - **Tidal volume** measures the amount of air inhaled or exhaled during normal breathing (typically ~500 mL at rest) - Not a diagnostic parameter for asthma as it doesn't assess **airway obstruction** or **hyperresponsiveness** - May be reduced during acute exacerbations but lacks specificity for asthma diagnosis *End expiratory flow rate* - Not a standard diagnostic parameter for asthma - While **mid-expiratory flow rates** (FEF25-75%) and **peak expiratory flow (PEF)** are assessed, **FEV1** remains the primary diagnostic measure - FEV1 provides better reproducibility and standardization for diagnosis *Total lung capacity* - **Total lung capacity (TLC)** represents total lung volume after maximal inhalation - May be normal or increased in asthma due to **air trapping** and hyperinflation - Not used as a primary diagnostic criterion as asthma diagnosis focuses on demonstrating **reversible airflow limitation**, not lung volumes

Q: Which hormone surge indicates the fertile period in females?

LH. ***LH*** - The **luteinizing hormone (LH) surge** triggers **ovulation**, releasing a mature egg from the follicle. - This surge is a key indicator of the **fertile window** in a woman's menstrual cycle. *FSH* - **Follicle-stimulating hormone (FSH)** primarily stimulates the growth and development of **ovarian follicles** early in the menstrual cycle, prior to the fertile period. - While essential for follicle maturation, it does not directly signal the immediate fertile window or ovulation. *Estrogen* - **Estrogen levels peak** just before the LH surge, playing a role in triggering the surge itself through positive feedback. - However, estrogen itself does not directly indicate the onset of the fertile period; rather, the subsequent LH surge does. *Oxytocin* - **Oxytocin** is largely involved in processes like **uterine contractions during childbirth** and **milk ejection during lactation**. - It has no direct role in indicating a female's fertile period or timing of ovulation.

Q: In the context of blunt trauma affecting the entire body, what is the estimated daily nitrogen loss in grams due to protein metabolism?

Approximately 35 grams. ***Approximately 35 grams*** - In **severe trauma**, such as blunt trauma affecting the entire body, the body undergoes a significant stress response leading to marked **protein catabolism**. Approximately **35 grams of nitrogen** can be lost daily under such conditions. - This represents a highly catabolic state where muscle protein is broken down to provide amino acids for energy and synthesis of acute-phase proteins, impacting overall nitrogen balance. *Approximately 45 grams* - While severe trauma does lead to substantial nitrogen loss, **45 grams** would typically indicate an even more extreme or prolonged catabolic state, which is less common in the initial stages of post-trauma protein metabolism than 35 grams. - Such a high nitrogen loss might be seen in very extensive burns or sepsis, which are different clinical contexts. *Approximately 55 grams* - A daily nitrogen loss of **55 grams** is beyond what is commonly observed even in severe, whole-body blunt trauma. This level of catabolism would likely be unsustainable or indicative of a rare, super-catabolic condition. - This magnitude of protein breakdown would lead to rapid and severe muscle wasting and organ dysfunction if sustained. *Approximately 65 grams* - Losing **65 grams of nitrogen** per day is an exceptionally high rate of protein catabolism, rarely, if ever, observed in blunt trauma alone. - This level of protein breakdown would represent a profound and life-threatening metabolic derangement, far exceeding typical post-trauma responses.

Question 1

A wave in ERG is due to activity of:

Accepted Answer

Rods and cones

Answer

Pigmented epithelium

Answer

Ganglion cell

Answer

Bipolar cell

Question 2

What is the characteristic of the second Purkinje image in relation to eye movement?

Accepted Answer

Erect and moves in same direction

Answer

Inverted and moves in same direction

Answer

Inverted and moves in opposite direction

Answer

Erect and moves in opposite direction

Question 3

What does colostrum have compared to normal milk?

Accepted Answer

Increased proteins

Answer

Decreased potassium

Answer

Decreased sodium

Answer

Decreased calories

Question 4

What is the primary mechanism underlying hyperthermia?

Accepted Answer

Failure of thermoregulation

Answer

Temperature > 40°C with autonomic dysfunction

Answer

Temperature > 41.5°C

Answer

No change in hypothalamic set point

Question 5

Tetany is seen in

Accepted Answer

Respiratory alkalosis

Answer

Respiratory acidosis

Answer

Metabolic acidosis

Answer

Hyperkalemia

Question 6

In pregnancy, plasma volume increase is maximum at what gestational age?

Accepted Answer

30 wks

Answer

10 wks

Answer

20 wks

Answer

25 wks

Question 7

Narcolepsy is due to abnormality in ?

Accepted Answer

Hypothalamus

Answer

Neocortex

Answer

Cerebellum

Answer

Medulla oblongata

Question 8

Which of the following is used for the diagnosis of asthma?

Accepted Answer

FEV1

Answer

Measurement of tidal volume

Answer

End expiratory flow rate

Answer

Total lung capacity

Question 9

Which hormone surge indicates the fertile period in females?

Accepted Answer

LH

Answer

FSH

Answer

Estrogen

Answer

Oxytocin

Question 10

In the context of blunt trauma affecting the entire body, what is the estimated daily nitrogen loss in grams due to protein metabolism?

Accepted Answer

Approximately 35 grams

Answer

Approximately 45 grams

Answer

Approximately 55 grams

Answer

Approximately 65 grams

NEET-PG 2012 — Physiology