General Physiology — MCQs

General Physiology Indian Medical PG Practice Questions and MCQs

Question 431: Increased BMR is associated with -

A. Increased body fat store
B. Increased glycolysis (Correct Answer)
C. Increased lipogenesis
D. Increased gluconeogenesis

Explanation: ***Increased glycolysis*** - An increased **basal metabolic rate (BMR)** signifies higher energy expenditure at rest, which reflects increased cellular metabolic activity and ATP consumption. - Among the given options, **increased glycolysis** is most consistent with increased BMR, as glycolysis is the primary pathway for ATP generation from glucose, and cells with higher metabolic rates require increased energy production. - Conditions that increase BMR (such as hyperthyroidism, fever, and increased muscle mass) are typically accompanied by **increased glycolytic activity** to meet higher energy demands. *Incorrect: Increased body fat store* - **Increased body fat** is generally associated with a *lower* BMR per unit of body weight, as adipose tissue is metabolically less active than lean tissue (especially muscle). - Higher body fat percentage reflects **energy storage**, not increased energy expenditure, and does not contribute to elevated BMR. *Incorrect: Increased lipogenesis* - **Lipogenesis** (synthesis of fatty acids and triglycerides) is an anabolic process that occurs during states of **energy surplus** for fat storage. - This process represents energy **storage** rather than energy **expenditure**, and is inversely related to BMR - it increases when energy intake exceeds expenditure. *Incorrect: Increased gluconeogenesis* - **Gluconeogenesis** (synthesis of glucose from non-carbohydrate sources) is primarily active during **fasting, starvation, or prolonged exercise** when glucose availability is low. - While gluconeogenesis is energy-consuming, it is characteristic of catabolic states with low energy availability, not the increased metabolic activity associated with elevated BMR. - In conditions that increase BMR (like hyperthyroidism), glucose is typically utilized via glycolysis rather than synthesized via gluconeogenesis.

Question 432: Sweat glands of palm can be differentiated from others by the following:

A. Secretion stimulated by emotional stimuli (Correct Answer)
B. High chloride content
C. Chemical mediators control the secretion.
D. Controlled by sympathetic adrenergic fibers

Explanation: ***Secretion stimulated by emotional stimuli*** - Sweat glands in the palms (and soles) are primarily regulated by the **sympathetic nervous system** and are uniquely responsive to **emotional or psychological stress**, leading to emotional sweating. - This response is mediated via **cholinergic postganglionic sympathetic fibers**, despite being part of the sympathetic system. *High chloride content* - While sweat does contain chloride, the overall **concentration of electrolytes** like sodium and chloride can vary, and a specifically "high" chloride content is not a unique distinguishing feature of palm sweat compared to other eccrine sweat. - **Cystic Fibrosis** is characterized by abnormally high sweat chloride due to a defect in the CFTR channel, but this represents a pathological condition, not a normal physiological differentiator of palm sweat. *Chemical mediators control the secretion.* - All sweat gland secretion, including that of the palms, is controlled by **neurotransmitters (chemical mediators)**, primarily acetylcholine acting on muscarinic receptors (M3) on eccrine sweat glands. This is not a differentiating factor. - The specific mediator (acetylcholine) is common to eccrine glands throughout the body and does not distinguish palm sweat. *Controlled by sympathetic adrenergic fibers* - Most eccrine sweat glands are innervated by **sympathetic cholinergic fibers** (they release acetylcholine), not adrenergic fibers (which release norepinephrine). - While sympathetic, their neurotransmitter **acetylcholine** is the primary mediator for thermoregulatory sweating, which also applies to palm sweat glands in their response to emotional stimuli.

Question 433: Energy expenditure in the resting state mainly depends on which of the following parameters?

A. Exercise
B. Lean body mass (Correct Answer)
C. Resting heart rate
D. Adipose tissue

Explanation: ***Lean body mass*** - **Lean body mass** (muscle, organs, bone) is metabolically active and requires significant energy, making it a primary determinant of Basal Metabolic Rate (BMR) or **resting energy expenditure**. - Tissues like **muscle** have a higher metabolic rate even at rest compared to adipose tissue. *Exercise* - **Exercise** accounts for the most variable component of daily energy expenditure, but it does not determine the energy expenditure in the **resting state**. - While physical activity consumes significant energy, that is separate from the baseline energy required to sustain life at rest. *Resting heart rate* - **Resting heart rate** is an indicator of cardiovascular fitness and sympathetic nervous system activity, but it is not a direct measure or primary determinant of total resting energy expenditure. - While a higher heart rate often correlates with a slightly elevated metabolic rate, the **amount of metabolically active tissue** is a more fundamental driver. *Adipose tissue* - **Adipose tissue** (fat) is metabolically less active than lean body mass, contributing minimally to resting energy expenditure compared to muscle or organ mass. - Although it does have some metabolic activity, its contribution is minor relative to the **energy demands of essential organs and muscle tissue**.

Question 434: In human physiology, the amount of heat required to convert water to vapor during processes like sweating and respiratory humidification is referred to as

A. Latent Heat of condensation
B. Latent Heat of vaporization (Correct Answer)
C. Latent Heat of sublimation
D. Latent Heat of fusion

Explanation: ***Latent Heat of vaporization*** - This term specifically refers to the **amount of heat energy absorbed** by a substance during a phase change from a **liquid to a gas** at a constant temperature. - In physiological processes like **sweating**, the absorption of this heat from the body's surface causes a **cooling effect** as the sweat evaporates. *Latent Heat of condensation* - This is the **heat released** when a substance changes from a **gas to a liquid**, which is the opposite of the process described in the question. - It describes the energy released when water vapor condenses, not the energy absorbed for vaporization. *Latent Heat of sublimation* - This term refers to the **heat required to change a substance directly from a solid to a gas** without passing through a liquid phase. - This process is not directly applicable to the conversion of liquid water to vapor in human physiology. *Latent heat of fusion* - This is the **heat absorbed** when a substance changes from a **solid to a liquid** (melting) at a constant temperature. - It is relevant to processes like ice melting but not to the liquid-to-gas conversion of water in the body.

Question 435: Two identical twins will not have same:

A. DNA
B. Iris color
C. Blood group
D. Fingerprints (Correct Answer)

Explanation: ***Fingerprints*** - **Fingerprints** are unique to each individual, even identical twins, because their formation is influenced by prenatal environmental factors such as **blood flow**, **amniotic fluid pressure**, and **baby's position in the womb**. - These environmental factors affect the development of **dermal ridges** during weeks 6-13 of gestation, leading to distinct patterns. *DNA* - **Identical twins** originate from a single fertilized egg that splits, meaning they share virtually **100% of their DNA**. - While minor epigenetic differences can occur, their core genetic code is the same. *Iris color* - **Iris color** is primarily determined by **genetics**, and since identical twins share the same genetic makeup, they typically have the same (or very similar) **eye color**. - Differences in iris patterns might exist, but the overall color is genetically programmed. *Blood group* - **Blood group** is an inherited trait determined by specific **antigens on red blood cells**, which are encoded by genes. - As identical twins share the same genetic information, they will have the **same blood type**.

Question 436: Protein metabolism after trauma is characterized by the following except:

A. Increased liver gluconeogenesis
B. Increased urinary nitrogen loss
C. Hepatic synthesis of acute phase reactants
D. Inhibition of skeletal muscle breakdown by interleukin 1 and tumour necrosis factor (Correct Answer)

Explanation: ***Inhibition of skeletal muscle breakdown by interleukin 1 and tumour necrosis factor*** - After trauma, **interleukin 1 (IL-1)** and **tumor necrosis factor (TNF)** actually **promote** skeletal muscle breakdown (catabolism) to provide amino acids for gluconeogenesis and acute phase protein synthesis. - This statement is incorrect because these cytokines are **pro-catabolic**, not inhibitory, in their effect on muscle protein. *Increased liver gluconeogenesis* - Trauma leads to a significant increase in **liver gluconeogenesis**, primarily to maintain glucose supply for **immune cells** and wound healing, which rely heavily on glucose. - This process utilizes amino acids obtained from muscle breakdown as substrates. *Increased urinary nitrogen loss* - The breakdown of muscle protein releases amino acids, which are then deaminated. The nitrogen waste product, **urea**, is excreted in the urine, leading to **increased urinary nitrogen loss**. - This is a direct consequence of the catabolic state. *Hepatic synthesis of acute phase reactants* - The liver increases the synthesis of **acute phase reactants** (e.g., C-reactive protein, fibrinogen, haptoglobin) in response to inflammatory cytokines like IL-1, **IL-6**, and TNF. - These proteins play a crucial role in the inflammatory response and tissue repair.

Question 437: Feed forward mechanism is seen in:

A. Salivation on smelling food (Correct Answer)
B. Increase in heart rate on standing up
C. Feeling thirsty while walking in hot temperature
D. Shivering on exposure to cold temperature

Explanation: ***Salivation on smelling food*** - This is a classic example of a **feedforward mechanism** because the body anticipates a future event (eating) based on a sensory cue (smelling food) and initiates a preparatory physiological response (salivation). - The response occurs *before* the actual need for digestion arises, demonstrating proactive regulation. - Part of the **cephalic phase of digestion** mediated by parasympathetic nervous system activation. *Increase in heart rate on standing up* - This is an example of a **feedback mechanism** mediated by baroreceptors and the autonomic nervous system. - When standing, blood pools in lower extremities causing a transient drop in blood pressure, which is detected by baroreceptors. - The body responds by increasing heart rate and peripheral resistance to maintain adequate blood pressure - a reactive response to detected change. *Feeling thirsty while walking in hot temperature* - Thirst in response to hot temperatures is typically a **feedback mechanism** where the body detects increased dehydration (e.g., via osmoreceptors) and signals the need for fluid intake. - It is a reaction to an existing physiological imbalance rather than an anticipation of future needs. *Shivering on exposure to cold temperature* - Shivering is a **feedback mechanism** where the body responds to a drop in core body temperature by generating heat to restore thermal homeostasis. - The body reacts to the cold stimulus *after* the temperature change has occurred, rather than anticipating it.

Question 438: Achondroplasia shows which type of inheritance?

A. X-linked dominant (XLD)
B. Autosomal recessive inheritance
C. Autosomal dominant inheritance (Correct Answer)
D. X-linked recessive (XLR)

Explanation: ***Autosomal dominant inheritance*** - Achondroplasia is caused by a **mutation in the FGFR3 gene**, which is located on an **autosomal chromosome** (chromosome 4). - The disease manifests with only **one copy of the mutated gene**, hence it follows an autosomal dominant pattern. *X-linked dominant (XLD)* - X-linked dominant disorders are caused by mutations on the **X chromosome** and typically affect females more severely or frequently than males. - Achondroplasia does not show sex-linked inheritance patterns, as its causative gene is on an autosome. *Autosomal recessive inheritance* - Autosomal recessive disorders require **two copies of the mutated gene** (one from each parent) for the disease to manifest. - Achondroplasia can occur with only one copy of the mutated gene, distinguishing it from recessive inheritance. *X-linked recessive (XLR)* - X-linked recessive disorders primarily affect **males** and are carried by females, who are usually asymptomatic carriers. - The inheritance pattern of achondroplasia is independent of sex, ruling out X-linked recessive inheritance.

Question 439: During starvation, what is the typical duration of the initial hunger pangs?

A. 12 - 24 hours
B. 24 - 36 hours
C. 36 - 48 hours
D. 6 - 12 hours (Correct Answer)

Explanation: ***6 - 12 hours*** - The sensation of initial hunger pangs typically begins within **6 to 12 hours** after the last meal, as the body starts to deplete readily available glucose. - This period marks the transition from using **exogenous glucose** to drawing on stored glycogen. *12 - 24 hours* - By this phase, the body is primarily utilizing **glycogen stores** in the liver and muscles. - While hunger may still be present, the initial sharp pangs often subside as the body adapts to using alternative energy sources. *24 - 36 hours* - Within this timeframe, **glycogen stores are largely depleted**, and the body begins to rely more heavily on **gluconeogenesis** from amino acids and catabolism of fat for energy. - Acute hunger pangs are usually less prominent as the metabolism shifts. *36 - 48 hours* - At this point, the body has fully transitioned into a state of **ketosis**, using fatty acids and **ketone bodies** as primary fuel. - Hunger sensations are often significantly reduced or even absent due to the **anorexigenic effect of ketone bodies** on the brain.

Question 440: What is the average survival time of a person without food and water under normal conditions?

A. 10 to 12 days
B. 3 to 5 days (Correct Answer)
C. 1 to 3 days
D. 5 to 10 days

Explanation: ***3 to 5 days*** - When deprived of **both food and water**, the human body can typically survive for **3 to 5 days** under normal conditions. - **Water is the critical limiting factor** - while the body can tolerate food deprivation for weeks, lack of water becomes life-threatening within days. - Water is essential for cellular metabolism, temperature regulation, waste elimination, and cardiovascular function. *1 to 3 days* - This represents the **absolute minimum survival time** without water, particularly under harsh environmental conditions (heat, physical exertion, humidity). - However, under normal/average conditions, most individuals can survive slightly longer than this range. *10 to 12 days* - This duration is **not possible** without water, even with optimal conditions. - This timeframe is more consistent with survival **without food but WITH water**, which can extend to 3-4 weeks or more. *5 to 10 days* - While exceptional cases might approach 5-7 days without water in cool, resting conditions with low metabolic demands, **10 days is physiologically implausible**. - Severe dehydration typically causes death by day 5-7 maximum, with most succumbing earlier.

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