Physiological changes in extreme environment: Hot, Cold, Hypobaric and Hyperbaric conditions.
- In hypobaric conditions (high altitude), what is the primary trigger for increased ventilation?
(a) Hypocapnia
(b) Hyperoxia
(c) Hypoxia
(d) Alkalosis
Answer: (c)
Explanation: Hypoxia (low oxygen) at high altitude stimulates peripheral chemoreceptors, increasing ventilation (hyperventilation). - Which physiological adaptation is CRITICAL for cold acclimatization?
(a) Reduced basal metabolic rate
(b) Non-shivering thermogenesis
(c) Peripheral vasodilation
(d) Decreased subcutaneous fat
Answer: (b)
Explanation: Non-shivering thermogenesis via brown adipose tissue generates heat without muscle contraction, crucial for cold adaptation. - Hyperbaric oxygen therapy is contraindicated in which condition?
(a) Decompression sickness
(b) Untreated pneumothorax
(c) Carbon monoxide poisoning
(d) Gas gangrene
Answer: (b)
Explanation: Increased pressure in hyperbaric chambers can expand trapped air, risking tension pneumothorax. - At high altitudes, polycythemia occurs due to:
(a) Increased erythropoietin secretion
(b) Splenic contraction
(c) Hemoconcentration
(d) Reduced plasma volume
Answer: (a)
Explanation: Hypoxia triggers renal EPO release, stimulating RBC production to enhance oxygen-carrying capacity. - Which response is IMMEDIATE during heat stress?
(a) Sweating
(b) Vasodilation
(c) Reduced cardiac output
(d) Piloerection
Answer: (b)
Explanation: Peripheral vasodilation increases blood flow to skin for radiative/convective heat loss within minutes of heat exposure. - Nitrogen narcosis in hyperbaric conditions resembles:
(a) Alcohol intoxication
(b) Hypoglycemia
(c) Hypothyroidism
(d) Ketoacidosis
Answer: (a)
Explanation: Elevated partial pressure of nitrogen disrupts neuronal membranes, causing euphoria and impaired judgment similar to alcohol. - Frostbite primarily results from:
(a) Direct cellular ice-crystal damage
(b) Vasoconstriction-induced ischemia
(c) Inflammatory cytokine release
(d) All of the above
Answer: (d)
Explanation: Cold causes vasoconstriction (reducing blood flow), ice formation in tissues, and later inflammation during rewarming. - Acute Mountain Sickness (AMS) is caused by:
(a) Cerebral edema
(b) Pulmonary hypertension
(c) Respiratory alkalosis
(d) All of the above
Answer: (d)
Explanation: Hypoxia at altitude triggers hyperventilation (causing alkalosis), pulmonary vasoconstriction (leading to HAPE), and cerebral edema. - Oxygen toxicity in hyperbaric conditions primarily affects:
(a) Liver
(b) Lungs
(c) Kidneys
(d) Spleen
Answer: (b)
Explanation: High PO₂ generates reactive oxygen species, damaging alveolar membranes and causing tracheobronchitis. - The “diving reflex” includes all EXCEPT:
(a) Bradycardia
(b) Peripheral vasoconstriction
(c) Splenic contraction
(d) Tachycardia
Answer: (d)
Explanation: Diving reflex conserves oxygen via bradycardia, vasoconstriction, and splenic RBC release. Tachycardia is absent. - Heat acclimatization REDUCES:
(a) Sweat sodium concentration
(b) Core temperature
(c) Plasma volume
(d) Heart rate
Answer: (a)
Explanation: Aldosterone-mediated sodium reabsorption in sweat glands reduces sweat [Na⁺], preventing electrolyte loss. - Decompression sickness occurs due to:
(a) Nitrogen bubble formation
(b) Oxygen free radicals
(c) CO₂ accumulation
(d) Lactic acidosis
Answer: (a)
Explanation: Rapid ascent reduces pressure, causing dissolved nitrogen to form bubbles in tissues/blood vessels. - Which hormone dominates cold stress response?
(a) Cortisol
(b) Thyroxine
(c) Insulin
(d) Estrogen
Answer: (b)
Explanation: Thyroxine increases metabolic rate and thermogenesis during prolonged cold exposure. - High-altitude pulmonary edema (HAPE) involves:
(a) Left ventricular failure
(b) Hypoxic vasoconstriction
(c) Reduced capillary permeability
(d) Hypervolemia
Answer: (b)
Explanation: Alveolar hypoxia triggers pulmonary vasoconstriction, increasing pressure and causing fluid leakage into lungs. - In heat exhaustion, the PRIMARY deficit is:
(a) Hyperglycemia
(b) Hypovolemia
(c) Hypocapnia
(d) Hypernatremia
Answer: (b)
Explanation: Sweat-induced water/salt loss reduces blood volume, causing dizziness, weakness, and tachycardia. - Chronic cold adaptation includes:
(a) Increased shivering
(b) Enhanced vasodilation
(c) Higher insulation (fat deposition)
(d) Reduced metabolic rate
Answer: (c)
Explanation: Subcutaneous fat increases insulation, while non-shivering thermogenesis replaces shivering over time. - Hyperventilation at high altitude causes:
(a) Respiratory acidosis
(b) Metabolic alkalosis
(c) Respiratory alkalosis
(d) Metabolic acidosis
Answer: (c)
Explanation: Blowing off CO₂ raises blood pH, leading to alkalosis. Renal compensation (bicarbonate excretion) follows later. - The MOST effective heat loss mechanism in dry heat is:
(a) Conduction
(b) Radiation
(c) Evaporation
(d) Convection
Answer: (b)
Explanation: Radiation accounts for ~60% of heat loss in thermoneutral conditions. Evaporation dominates in humid heat. - Oxygen-hemoglobin dissociation curve shifts RIGHT in hypoxia due to:
(a) Decreased 2,3-DPG
(b) Increased pH
(c) Hypothermia
(d) Elevated 2,3-DPG
Answer: (d)
Explanation: Hypoxia increases erythrocyte 2,3-DPG, reducing Hb-O₂ affinity and enhancing oxygen unloading in tissues. - “Chilblains” in cold exposure result from:
(a) Freezing of tissues
(b) Intermittent vasoconstriction/vasodilation
(c) Autonomic neuropathy
(d) Inadequate shivering
Answer: (b)
Explanation: Repeated cold-induced vasoconstriction followed by reactive hyperemia damages capillaries, causing inflammation. - A diver at 30m depth (4 ATM pressure) breathes air. What is PO₂ in alveoli?
(a) 160 mmHg
(b) 320 mmHg
(c) 640 mmHg
(d) 1280 mmHg
Answer: (c)
Explanation: At 4 ATM, total pressure ~3040 mmHg. Alveolar PO₂ = (760 × 4 × 0.21) – 40 ≈ 640 mmHg (since O₂ is 21% of air). - Heat stroke is characterized by:
(a) Hypotension and bradycardia
(b) Hyperpyrexia and anhidrosis
(c) Shivering and pallor
(d) Polyuria and polydipsia
Answer: (b)
Explanation: Core temperature >40°C with CNS dysfunction (e.g., confusion) and cessation of sweating (anhidrosis) define heat stroke. - Acclimatization to heat does NOT include:
(a) Earlier sweating onset
(b) Increased plasma volume
(c) Reduced cardiac output
(d) Lowered skin temperature
Answer: (c)
Explanation: Heat acclimatization INCREASES cardiac output to support skin blood flow. Sweating starts earlier, plasma volume expands, and skin cooling improves. - The Haldane effect describes:
(a) CO₂ binding to hemoglobin
(b) Enhanced O₂ loading due to CO₂ release
(c) Reduced CO₂ carrying capacity in oxygenated blood
(d) Bohr effect reversal
Answer: (c)
Explanation: Haldane effect: Deoxygenated Hb carries more CO₂. Oxygenation reduces Hb’s affinity for CO₂, promoting its release in lungs. - In hypothermia, the “afterdrop” phenomenon refers to:
(a) Continued core cooling after rescue
(b) Rebound hyperthermia
(c) Delayed shivering onset
(d) Post-rewarming tachycardia
Answer: (a)
Explanation: Cold peripheral blood returning to core during rewarming causes further temperature drop, risking cardiac arrhythmias.
Heat stress.
- What is the PRIMARY physiological response to acute heat stress?
(a) Shivering thermogenesis
(b) Cutaneous vasoconstriction
(c) Sweating and vasodilation
(d) Piloerection
Answer: (c)
Explanation: Immediate heat dissipation occurs via sweating (evaporative cooling) and cutaneous vasodilation (increased blood flow to skin). Shivering and piloerection are cold responses. - Heat acclimatization reduces sodium loss in sweat by increasing:
(a) Aldosterone secretion
(b) ADH production
(c) Cortisol release
(d) Thyroxine synthesis
Answer: (a)
Explanation: Aldosterone enhances sodium reabsorption in sweat glands, reducing electrolyte loss during prolonged heat exposure. - Heat exhaustion is primarily characterized by:
(a) Core temperature >40°C with CNS dysfunction
(b) Hypotension and syncope
(c) Hot, dry skin and coma
(d) Severe muscle cramps
Answer: (b)
Explanation: Heat exhaustion involves hypovolemia from fluid loss, causing hypotension, dizziness, and syncope. Core temperature is moderately elevated (<40°C). - Which factor MOST impairs evaporative cooling?
(a) Low wind speed
(b) High humidity
(c) Solar radiation
(d) Dry air
Answer: (b)
Explanation: High humidity reduces the vapor pressure gradient, limiting sweat evaporation. Dry air enhances evaporation. - During heat stress, blood flow is redirected AWAY from:
(a) Skin
(b) Splanchnic organs
(c) Skeletal muscles
(d) Heart
Answer: (b)
Explanation: Sympathetic activation reduces blood flow to gut/kidneys (splanchnic circulation) to prioritize skin and muscle perfusion. - The “Heat Index” combines temperature and:
(a) Wind speed
(b) Solar radiation
(c) Relative humidity
(d) Barometric pressure
Answer: (c)
Explanation: Heat Index quantifies perceived temperature by integrating air temperature and relative humidity, reflecting evaporative efficiency. - Which adaptation occurs after 7–10 days of heat exposure?
(a) Increased plasma volume
(b) Reduced sweat rate
(c) Delayed sweating onset
(d) Decreased cardiac output
Answer: (a)
Explanation: Plasma volume expands by 10–25% during acclimatization to improve stroke volume and thermoregulation. - Malignant hyperthermia is triggered by:
(a) Bacterial endotoxins
(b) Anesthetic gases
(c) Heavy metal poisoning
(d) Extreme dehydration
Answer: (b)
Explanation: Volatile anesthetics (e.g., halothane) induce uncontrolled skeletal muscle Ca²⁺ release, causing hypermetabolism and hyperthermia. - Heat stroke causes cellular damage primarily via:
(a) Hypoglycemia
(b) Protein denaturation
(c) Free radical production
(d) Mitochondrial uncoupling
Answer: (c)
Explanation: Hyperthermia generates reactive oxygen species (ROS), damaging lipids, proteins, and DNA, leading to multi-organ failure. - Which intervention is CRITICAL for heat stroke management?
(a) Oral rehydration with electrolytes
(b) Rapid whole-body cooling
(c) Intravenous corticosteroids
(d) Warming blankets
Answer: (b)
Explanation: Core temperature must be reduced to <39°C within 30 minutes using ice-water immersion or evaporative cooling to prevent mortality.
Acclimatization in high altitude, hot and cold environment Cardiovascular
- Chronic high-altitude acclimatization causes right ventricular hypertrophy due to:
(a) Systemic hypertension
(b) Pulmonary vasoconstriction
(c) Increased cardiac output
(d) Polycythemia
Answer: (b)
Explanation: Hypoxic pulmonary vasoconstriction increases pulmonary artery pressure, leading to right ventricular hypertrophy over time. - The INITIAL cardiovascular response to high altitude is:
(a) Bradycardia
(b) Increased stroke volume
(c) Tachycardia
(d) Systemic vasodilation
Answer: (c)
Explanation: Acute hypoxia triggers tachycardia to maintain oxygen delivery via increased cardiac output. - Polycythemia at high altitude increases blood viscosity, potentially causing:
(a) Reduced heart rate
(b) Decreased pulmonary resistance
(c) Increased risk of thrombosis
(d) Improved capillary perfusion
Answer: (c)
Explanation: Elevated hematocrit (>55%) raises viscosity, impairing blood flow and increasing thrombosis risk. - Which change improves oxygen delivery during high-altitude acclimatization?
(a) Ventricular atrophy
(b) Increased 2,3-DPG
(c) Reduced capillary density
(d) Left ventricular dilation
Answer: (b)
Explanation: 2,3-DPG shifts the oxygen dissociation curve rightward, enhancing O₂ unloading in tissues. - Heat acclimatization reduces heart rate during exercise by:
(a) Increasing plasma volume
(b) Decreasing stroke volume
(c) Promoting vasoconstriction
(d) Reducing sweat rate
Answer: (a)
Explanation: Plasma volume expansion (10–25%) improves stroke volume, allowing lower heart rate for same cardiac output. - During heat stress, cardiac output increases primarily to:
(a) Support renal filtration
(b) Fuel shivering thermogenesis
(c) Perfuse cutaneous vessels
(d) Enhance hepatic metabolism
Answer: (c)
Explanation: Up to 60% of cardiac output diverts to skin vasculature for radiative/convective cooling. - Heat syncope (fainting) results from:
(a) Cerebral hyperthermia
(b) Cutaneous vasoconstriction
(c) Orthostatic hypotension
(d) Hyperventilation
Answer: (c)
Explanation: Pooling of blood in dilated skin vessels reduces venous return, causing postural hypotension and fainting. - The “diving reflex” in cold water involves:
(a) Tachycardia and peripheral vasodilation
(b) Bradycardia and peripheral vasoconstriction
(c) Increased cardiac output
(d) Pulmonary vasodilation
Answer: (b)
Explanation: Cold water immersion triggers vagal-mediated bradycardia and intense vasoconstriction to conserve O₂ for vital organs. - Cold diuresis causes cardiovascular strain by:
(a) Expanding plasma volume
(b) Inducing hypovolemia
(c) Increasing blood viscosity
(d) Promoting hypertension
Answer: (b)
Explanation: Cold-induced diuresis reduces plasma volume, increasing hematocrit and impairing cardiac efficiency. - Chronic cold acclimatization may lead to:
(a) Reduced basal metabolic rate
(b) Decreased mean arterial pressure
(c) Elevated resting cardiac output
(d) Attenuated vasoconstriction
Answer: (c)
Explanation: Increased metabolic demands in cold-adapted individuals elevate resting cardiac output by 20–30%. - Which adaptation is UNIQUE to heat (not cold/altitude)?
(a) Plasma volume expansion
(b) Peripheral vasoconstriction
(c) Polycythemia
(d) Pulmonary hypertension
Answer: (a)
Explanation: Plasma expansion occurs only in heat acclimatization; cold/altitude cause hemoconcentration. - Cardiac workload increases in ALL environments due to:
(a) Chronic tachycardia
(b) Elevated stroke volume
(c) Increased blood viscosity
(d) Sympathetic activation
Answer: (d)
Explanation: Sympathetic nervous system activation (stress response) raises heart rate and contractility in all extreme environments. - High-altitude pulmonary edema (HAPE) worsens due to:
(a) Left ventricular failure
(b) Hypoxic pulmonary vasoconstriction
(c) Reduced capillary permeability
(d) Systemic hypotension
Answer: (b)
Explanation: Uneven pulmonary vasoconstriction increases pressure in non-constricted vessels, forcing fluid into alveoli. - Acclimatized high-altitude natives show:
(a) Lower hemoglobin than newcomers
(b) Suppressed hypoxic ventilatory response
(c) Reduced pulmonary artery pressure
(d) Higher resting cardiac output
Answer: (b)
Explanation: Genetic adaptations (e.g., in Tibetans) blunt hypoxic ventilatory drive to conserve energy. - Heat-acclimatized individuals maintain lower core temperatures by:
(a) Delayed sweating onset
(b) Enhanced cutaneous blood flow
(c) Reduced cardiac output
(d) Increased body fat
Answer: (b)
Explanation: Improved skin vasodilation and earlier sweat onset optimize radiative/evaporative cooling. - Cardiovascular drift during prolonged heat exposure refers to:
(a) Rising stroke volume
(b) Progressive tachycardia
(c) Systolic hypertension
(d) Ventricular hypertrophy
Answer: (b)
Explanation: Heart rate gradually increases while stroke volume decreases due to fluid loss and rising skin blood flow. - “Afterdrop” in hypothermia involves:
(a) Rewarming-induced hypertension
(b) Core cooling during peripheral reperfusion
(c) Cold-induced diuresis
(d) Shivering thermogenesis
Answer: (b)
Explanation: Cold blood from extremities returning to core during rewarming further lowers core temperature. - Non-shivering thermogenesis increases cardiac workload by:
(a) Activating β-adrenergic receptors
(b) Suppressing thyroid function
(c) Promoting vasodilation
(d) Reducing metabolic rate
Answer: (a)
Explanation: Norepinephrine release activates β3-receptors in brown fat, increasing metabolic rate and cardiac demand. - Which factor increases myocardial oxygen demand in ALL extreme environments?
(a) Hypocapnia
(b) Elevated heart rate
(c) Alkalosis
(d) Reduced blood viscosity
Answer: (b)
Explanation: Tachycardia (common to heat, cold, and altitude) raises cardiac oxygen consumption, risking ischemia. - Maladaptive cardiovascular response in chronic cold exposure:
(a) Decreased hematocrit
(b) Reduced systemic vascular resistance
(c) Elevated blood pressure
(d) Increased plasma volume
Answer: (c)
Explanation: Persistent vasoconstriction and cold diuresis-induced renin release cause chronic hypertension.
respiratory effects of positive and negative G-Forces,
- During +Gz acceleration (head-to-foot), pilots experience “blackout” due to:
(a) Cerebral hyperoxia
(b) Retinal ischemia
(c) Pulmonary hemorrhage
(d) Tracheal compression
Answer: (b)
Explanation: +Gz forces drain blood away from the brain and eyes, causing retinal hypoxia (“blackout”) before cerebral hypoxia (“G-LOC”). - The MOST effective maneuver against +Gz-induced loss of consciousness is:
(a) Valsalva maneuver
(b) Anti-G straining maneuver (AGSM)
(c) Hyperventilation
(d) Breath-holding
Answer: (b)
Explanation: AGSM combines skeletal muscle contraction and forced breathing to increase intrathoracic pressure and maintain cerebral blood flow. - +Gz forces reduce lung compliance primarily by:
(a) Compressing alveoli
(b) Depressing the diaphragm
(c) Shifting blood to lung bases
(d) Collapsing bronchi
Answer: (c)
Explanation: Blood pools in dependent (basal) lung regions, increasing congestion and reducing compliance. - At +5Gz, a pilot’s arterial oxygen saturation decreases due to:
(a) Hypoventilation
(b) Ventilation-perfusion mismatch
(c) Reduced hemoglobin affinity
(d) Diffusion impairment
Answer: (b)
Explanation: Overperfusion of lung bases and underperfusion of apices lead to V/Q mismatch. - “G-LOC” (G-force induced Loss Of Consciousness) typically occurs at:
(a) +3Gz sustained for 5 sec
(b) +5Gz sustained for 3 sec
(c) +7Gz sustained for 5 sec
(d) +9Gz sustained for 10 sec
Answer: (c)
Explanation: At +7Gz, unprotected individuals may lose consciousness in 3–5 seconds due to cerebral hypoperfusion. - During -Gz (foot-to-head) acceleration, redout occurs due to:
(a) Retinal venous congestion
(b) Cerebral edema
(c) Subconjunctival hemorrhage
(d) Carotid sinus reflex
Answer: (a)
Explanation: -Gz forces increase cranial venous pressure, causing retinal blood vessel engorgement (“redout”). - -Gz forces cause breathing difficulty primarily by:
(a) Depressing the diaphragm
(b) Elevating the diaphragm
(c) Tracheal stenosis
(d) Bronchospasm
Answer: (b)
Explanation: Abdominal contents push the diaphragm upward, restricting lung expansion and making inspiration difficult. - The greatest risk during sustained -Gz is:
(a) Pneumothorax
(b) Pulmonary edema
(c) Hemoptysis
(d) Tracheal rupture
Answer: (b)
Explanation: Increased pulmonary capillary pressure can lead to fluid leakage and pulmonary edema. - Compared to +Gz, -Gz causes GREATER:
(a) Cerebral ischemia
(b) Tolerance duration
(c) Thoracic pain
(d) Cardiac output reduction
Answer: (c)
Explanation: Thoracic and pleural stretching during -Gz acceleration causes discomfort and chest pain even at low G. - Which G-force direction REDUCES functional residual capacity (FRC) the most?
(a) +Gz
(b) -Gz
(c) +Gx (chest-to-back)
(d) -Gx (back-to-chest)
Answer: (b)
Explanation: -Gz pushes the diaphragm upward, reducing lung volumes including FRC by 30–40%. - Anti-G suits protect against +Gz by:
(a) Increasing intrathoracic pressure
(b) Compressing leg veins
(c) Stimulating carotid baroreceptors
(d) Elevating cerebral perfusion pressure
Answer: (b)
Explanation: The suit compresses the lower body, limiting venous pooling and helping maintain venous return. - During high +Gz, expiration becomes difficult due to:
(a) Air trapping in alveoli
(b) Increased airway resistance
(c) Flattening of the diaphragm
(d) Reduced elastic recoil
Answer: (c)
Explanation: The diaphragm flattens and the chest wall elongates, requiring more effort for expiration. - “Acceleration atelectasis” in fighter pilots is caused by:
(a) +Gz-induced alveolar collapse
(b) -Gz-induced pneumothorax
(c) Rapid pressure changes
(d) Breathing 100% oxygen
Answer: (d)
Explanation: 100% O₂ displaces nitrogen in alveoli, and without enough nitrogen to keep alveoli open, they collapse under high G. - Chronic +Gz exposure may lead to:
(a) Emphysema
(b) Pulmonary hypertension
(c) Tracheomalacia
(d) Pleural fibrosis
Answer: (b)
Explanation: Repetitive +Gz exposure can remodel pulmonary vessels, resulting in chronic pulmonary hypertension. - The G-force most likely to cause hemoptysis is:
(a) +2Gz
(b) -3Gz
(c) +5Gx
(d) -1Gz
Answer: (b)
Explanation: -Gz increases capillary pressure in lungs, possibly rupturing them and leading to hemoptysis. - During rapid transition from +Gz to -Gz, pilots risk:
(a) Pneumomediastinum
(b) Tension pneumothorax
(c) Barotrauma
(d) Valsalva sinus tear
Answer: (a)
Explanation: Sudden shifts can rupture alveoli, allowing air to escape into mediastinum (pneumomediastinum). - Centrifuge training improves G-tolerance by enhancing:
(a) Myocardial contractility
(b) Baroreflex sensitivity
(c) Hypoxic ventilatory response
(d) Cerebral autoregulation
Answer: (b)
Explanation: Repeated exposure improves baroreflex function, maintaining blood pressure during G-force changes. - The optimal posture to tolerate high +Gz is:
(a) Upright (90°)
(b) Supine (0°)
(c) Semi-reclined (45°)
(d) Prone (180°)
Answer: (c)
Explanation: A semi-reclined position minimizes the vertical distance between heart and brain, improving perfusion. - Astronauts returning to Earth experience “orthostatic intolerance” due to:
(a) Hypovolemia
(b) Carotid sinus hypersensitivity
(c) Impaired vestibulo-sympathetic reflex
(d) All of the above
Answer: (d)
Explanation: Microgravity leads to fluid loss, baroreceptor dysfunction, and impaired autonomic control, causing intolerance. - In hypergravity (+Gz), FEV₁/FVC ratio typically:
(a) Increases
(b) Decreases
(c) Remains unchanged
(d) Fluctuates
Answer: (a)
Explanation: Gravity assists in forceful expiration, increasing FEV₁ and raising the FEV₁/FVC ratio.
Noise pollution and its impact on human life,
- The unit used to measure noise pollution is:
(a) Hertz
(b) Decibel (dB)
(c) Pascal
(d) Lux
Answer: (b)
Explanation: Decibel (dB) quantifies sound intensity. A-weighted dB (dBA) is used for environmental noise as it aligns with human hearing sensitivity. - According to WHO, the safe daytime noise level for residential areas is:
(a) ≤45 dB
(b) ≤55 dB
(c) ≤65 dB
(d) ≤75 dB
Answer: (b)
Explanation: WHO recommends ≤55 dB during the day and ≤45 dB at night for residential zones to avoid health impacts. - Chronic noise exposure causes permanent hearing loss by damaging:
(a) Tympanic membrane
(b) Ossicles
(c) Hair cells in the cochlea
(d) Auditory nerve
Answer: (c)
Explanation: Loud noise damages the stereocilia of cochlear hair cells, reducing sound signal transduction and leading to sensorineural hearing loss. - “Temporary Threshold Shift” (TTS) refers to:
(a) Permanent hearing damage
(b) Short-term reduction in hearing sensitivity
(c) Complete deafness
(d) Tinnitus
Answer: (b)
Explanation: TTS is a reversible reduction in hearing sensitivity caused by brief exposure to loud sound. - Noise-induced cardiovascular problems are primarily mediated by:
(a) Increased insulin secretion
(b) Sympathetic nervous system activation
(c) Parasympathetic dominance
(d) Thyroid dysfunction
Answer: (b)
Explanation: Chronic noise activates stress pathways, increasing catecholamines and cortisol, which raise blood pressure and cardiovascular risk. - Chronic noise exposure is strongly linked to:
(a) Improved concentration
(b) Reduced stress hormones
(c) Elevated anxiety and depression
(d) Enhanced memory recall
Answer: (c)
Explanation: Noise affects the limbic system and hypothalamic-pituitary-adrenal axis, increasing psychological stress and risk of anxiety disorders. - Aircraft noise near schools is associated with:
(a) Improved reading comprehension
(b) Delayed cognitive development in children
(c) Higher IQ scores
(d) Better attention span
Answer: (b)
Explanation: Aircraft noise impairs reading, memory, and attention in children, affecting academic performance. - Nighttime noise above 45 dB primarily affects:
(a) REM sleep duration
(b) Sleep latency
(c) Sleep fragmentation
(d) Deep sleep (N3 stage)
Answer: (c)
Explanation: Sounds ≥45 dB cause micro-arousals and interruptions in sleep architecture, even without full awakening. - The “Lombard effect” refers to:
(a) Hearing loss in industrial workers
(b) Involuntary voice amplification in noisy environments
(c) Noise-induced tinnitus
(d) Vibration sensitivity
Answer: (b)
Explanation: Speakers unconsciously raise their voice volume in noisy environments to improve intelligibility. - Occupational noise exposure limits in India (Factories Act) are:
(a) 75 dB for 8 hours
(b) 90 dB for 8 hours
(c) 100 dB for 8 hours
(d) 115 dB for 8 hours
Answer: (b)
Explanation: The permissible limit for occupational noise is 90 dB for 8 hours; exposure beyond 85 dB requires protective measures. - Which population is MOST vulnerable to noise-induced hearing loss?
(a) Office workers
(b) Construction workers
(c) Librarians
(d) Software engineers
Answer: (b)
Explanation: Construction workers often face sound levels above 110 dB, exceeding safe thresholds even for short durations. - Tinnitus resulting from noise exposure is characterized by:
(a) Permanent hearing gain
(b) Phantom ringing/buzzing in ears
(c) Vertigo
(d) Aural discharge
Answer: (b)
Explanation: Tinnitus is a phantom perception of sound due to cochlear or neural damage, often triggered by loud noise exposure. - Noise pollution contributes to hypertension by:
(a) Suppressing renin production
(b) Decreasing vascular resistance
(c) Activating the RAAS system
(d) Lowering heart rate variability
Answer: (c)
Explanation: Chronic noise exposure activates the Renin-Angiotensin-Aldosterone System, raising blood volume and arterial pressure. - Low-frequency noise (e.g., wind turbines) causes:
(a) Vibroacoustic disease
(b) Improved sleep quality
(c) Reduced cortisol
(d) Enhanced mood
Answer: (a)
Explanation: Low-frequency infrasound has been associated with chest vibration, cardiac issues, and cognitive deficits in long-term exposure. - In neonates, NICU noise above 50 dB can disrupt:
(a) Weight gain
(b) Respiratory patterns
(c) Sleep-wake cycles
(d) All of the above
Answer: (d)
Explanation: Excessive NICU noise stresses neonates, disrupting physiological regulation, growth, and neural development. - The “Noise Pollution (Regulation & Control) Rules” in India were established under:
(a) Environment Protection Act, 1986
(b) Factories Act, 1948
(c) Air Act, 1981
(d) Water Act, 1974
Answer: (a)
Explanation: These rules, framed in 2000 under EPA-1986, provide decibel limits for various zones and mandate silence areas near hospitals/schools. - Green Muffler Scheme involves:
(a) Noise barriers along highways
(b) Tree plantations to absorb sound
(c) Industrial silencers
(d) Earplug distribution
Answer: (b)
Explanation: Rows of dense trees (green belts) are planted along roads to absorb and deflect sound waves, reducing noise pollution. - Recent studies link chronic traffic noise to increased risk of:
(a) Type 1 diabetes
(b) Alzheimer’s disease
(c) Osteoporosis
(d) Cataracts
Answer: (b)
Explanation: Prolonged noise exposure increases oxidative stress and amyloid accumulation, contributing to neurodegeneration. - Which frequency range is MOST harmful to humans?
(a) 20–150 Hz
(b) 2,000–5,000 Hz
(c) 10,000–20,000 Hz
(d) >20,000 Hz
Answer: (b)
Explanation: Human cochlea is most sensitive to 3–6 kHz, making this range particularly damaging to hair cells. - Active Noise Cancellation (ANC) technology works by:
(a) Absorbing sound waves
(b) Generating destructive interference
(c) Blocking ear canals
(d) Reflecting high frequencies
Answer: (b)
Explanation: ANC creates anti-phase waves to incoming sound, canceling them out through destructive interference.
lonizing radiation hazards,
- Which radiation has the HIGHEST linear energy transfer (LET)?
(a) Gamma rays
(b) X-rays
(c) Alpha particles
(d) Beta particles
Answer: (c)
Explanation: Alpha particles (helium nuclei) have high mass and charge, causing dense ionization with maximal LET (80–100 keV/μm). - The SI unit for measuring radiation absorption in biological tissue is:
(a) Becquerel
(b) Sievert
(c) Gray
(d) Curie
Answer: (c)
Explanation: Gray (Gy) measures absorbed radiation dose (1 Gy = 1 J/kg). Sievert (Sv) adjusts for biological impact. - Ionizing radiation causes DNA damage primarily through:
(a) Direct ionization of DNA molecules
(b) Thermal denaturation
(c) Free radical formation
(d) Enzyme-mediated cleavage
Answer: (c)
Explanation: Around 80% of DNA damage is indirect—radiation splits water into •OH radicals, which attack DNA. - The MOST radiosensitive phase of the cell cycle is:
(a) G0
(b) S
(c) G2
(d) M
Answer: (d)
Explanation: Cells in M phase are most sensitive because DNA is highly condensed and repair mechanisms are minimal. - Acute radiation syndrome (ARS) manifests as hematopoietic failure at doses:
(a) 0.1–1 Gy
(b) 1–6 Gy
(c) 6–10 Gy
(d) >10 Gy
Answer: (b)
Explanation: Doses of 1–6 Gy damage bone marrow, leading to decreased WBCs and platelets within weeks. - Which organ is LEAST susceptible to radiation damage?
(a) Bone marrow
(b) Thyroid
(c) Muscle
(d) Small intestine
Answer: (c)
Explanation: Muscle cells are non-dividing (post-mitotic), making them less vulnerable than proliferative tissues like marrow or gut lining. - Radiation-induced cataracts result from damage to:
(a) Retinal rods
(b) Lens epithelial cells
(c) Corneal endothelium
(d) Optic nerve
Answer: (b)
Explanation: Radiation disrupts lens epithelial cell proliferation, leading to opacity; cataract threshold: 2 Gy (acute), 8 Gy (chronic). - Long-term radiation exposure increases cancer risk MOST significantly in:
(a) Lung
(b) Thyroid
(c) Skin
(d) Breast
Answer: (b)
Explanation: The thyroid, especially in children, absorbs radioactive iodine, doubling cancer risk per Gy. - The “bystander effect” in radiobiology refers to:
(a) Damage in unirradiated cells near irradiated ones
(b) Radiation shielding by neighboring cells
(c) Enhanced DNA repair in targeted cells
(d) Apoptosis resistance
Answer: (a)
Explanation: Bystander cells show genomic damage due to signals like cytokines or gap junction communication from irradiated neighbors. - ALARA principle in radiation safety stands for:
(a) As Low As Reasonably Achievable
(b) Absolute Lowest Acute Radiation Allowance
(c) Average Lifetime Accumulated Radiation Assessment
(d) Accredited Limits for Annual Radiation Absorption
Answer: (a)
Explanation: ALARA promotes minimizing exposure using shielding, limiting time, and maximizing distance from the source. - For radiation workers, the annual effective dose limit is:
(a) 1 mSv
(b) 20 mSv
(c) 100 mSv
(d) 500 mSv
Answer: (b)
Explanation: ICRP recommends a dose limit of 20 mSv/year averaged over 5 years (not exceeding 50 mSv in any one year). - Radiation fibrosis in lungs typically occurs __ post-exposure:
(a) Immediately
(b) 1–6 months
(c) 6–24 months
(d) 5–10 years
Answer: (c)
Explanation: Fibrosis develops due to chronic inflammation and collagen buildup, peaking within 1–2 years of exposure. - Amifostine is used as a radioprotector because it:
(a) Scavenges free radicals
(b) Enhances DNA repair
(c) Blocks radioiodine uptake
(d) Induces hypoxia
Answer: (a)
Explanation: Amifostine is a thiol compound that neutralizes harmful hydroxyl radicals generated by radiation. - The LARGEST natural source of ionizing radiation exposure to humans is:
(a) Cosmic rays
(b) Terrestrial radon-222
(c) Potassium-40 in food
(d) Medical imaging
Answer: (b)
Explanation: Radon gas from soil and rock contributes the largest portion of natural background radiation (≈42%). - Chernobyl disaster released radioisotopes primarily affecting:
(a) Thyroid (I-131)
(b) Bones (Sr-90)
(c) Liver (Pu-239)
(d) Kidneys (U-238)
Answer: (a)
Explanation: Iodine-131 contaminated milk and was absorbed by the thyroid, causing thousands of thyroid cancer cases in exposed children.
Toxicology of industrial wastes-diseases due to excess accumulation of Pb, Hg and Cd in body. Addiction to tobacco, alcohol and narcoties,
- Chronic exposure to lead (Pb) primarily affects which system?
(a) Cardiovascular
(b) Nervous
(c) Digestive
(d) Endocrine
Answer: (b)
Explanation: Lead causes neurotoxicity, leading to encephalopathy, cognitive deficits, and peripheral neuropathy. - Minamata disease, caused by mercury poisoning, is characterized by:
(a) Itai-itai symptoms
(b) Blue line on gums
(c) Sensory disturbances and ataxia
(d) Osteomalacia
Answer: (c)
Explanation: Minamata disease (Hg toxicity) involves CNS damage, causing paresthesia, ataxia, and visual/hearing loss. - Accumulation of cadmium (Cd) in the body causes:
(a) Blackfoot disease
(b) Itai-itai disease
(c) Keshan disease
(d) Pneumoconiosis
Answer: (b)
Explanation: Itai-itai (“ouch-ouch”) results from Cd exposure via contaminated water, leading to severe bone pain and fractures. - Which heavy metal binds to hemoglobin, causing anemia?
(a) Mercury
(b) Cadmium
(c) Lead
(d) Arsenic
Answer: (c)
Explanation: Lead inhibits δ-aminolevulinic acid dehydratase (ALAD), disrupting heme synthesis and causing microcytic anemia. - The primary source of cadmium exposure in humans is:
(a) Dental amalgams
(b) Tobacco smoke
(c) Lead-based paints
(d) Batteries
Answer: (b)
Explanation: Tobacco plants bioaccumulate Cd; smoking releases Cd particles that deposit in lungs and kidneys. - Acrodynia (Pink Disease) is associated with toxicity of:
(a) Lead
(b) Mercury
(c) Cadmium
(d) Chromium
Answer: (b)
Explanation: Acrodynia involves painful pink discoloration of extremities due to Hg exposure (e.g., teething powders). - Which enzyme is inhibited by lead, disrupting heme synthesis?
(a) Catalase
(b) Cytochrome oxidase
(c) δ-aminolevulinic acid dehydratase (ALAD)
(d) Acetylcholinesterase
Answer: (c)
Explanation: ALAD inhibition by Pb causes accumulation of δ-ALA, contributing to anemia and neurotoxicity. - Chronic alcoholism causes Wernicke-Korsakoff syndrome due to deficiency of:
(a) Vitamin B₁ (Thiamine)
(b) Vitamin B₁₂
(c) Vitamin C
(d) Vitamin D
Answer: (a)
Explanation: Alcohol impairs thiamine absorption; deficiency damages thalamus/hypothalamus, causing confusion and ataxia. - “Emphysema” is a tobacco-related disease affecting the:
(a) Liver
(b) Lungs
(c) Kidneys
(d) Heart
Answer: (b)
Explanation: Tobacco smoke destroys alveolar walls, reducing gas exchange and causing emphysema (COPD). - The carcinogen in tobacco smoke responsible for lung cancer is:
(a) Nicotine
(b) Benzopyrene
(c) Carbon monoxide
(d) Formaldehyde
Answer: (b)
Explanation: Benzopyrene (a PAH) in tobacco is metabolized to epoxides that mutate DNA, causing cancer. - Blue line on gums (Burton’s line) is diagnostic of poisoning by:
(a) Mercury
(b) Cadmium
(c) Lead
(d) Arsenic
Answer: (c)
Explanation: Lead sulfide deposits form a blue-black line at the gingival margin in chronic Pb poisoning. - “Fetal Alcohol Syndrome” (FAS) is characterized by:
(a) Craniofacial deformities
(b) Osteoporosis
(c) Renal failure
(d) Cardiomegaly
Answer: (a)
Explanation: FAS causes microcephaly, smooth philtrum, and thin vermilion due to maternal alcohol consumption. - Which organ is the primary target for cadmium accumulation?
(a) Brain
(b) Kidneys
(c) Heart
(d) Pancreas
Answer: (b)
Explanation: Cd binds to metallothionein in proximal tubules, causing Fanconi syndrome and renal failure. - Methaemoglobinemia caused by nitrates in tobacco primarily affects:
(a) Oxygen transport
(b) Protein synthesis
(c) Fat metabolism
(d) Nerve conduction
Answer: (a)
Explanation: Nitrates oxidize Fe²⁺ in hemoglobin to Fe³⁺, reducing O₂-carrying capacity and causing cyanosis. - Narcotic addiction causes respiratory depression by acting on:
(a) Medulla oblongata
(b) Cerebellum
(c) Hypothalamus
(d) Frontal cortex
Answer: (a)
Explanation: Opioids suppress the respiratory center in the medulla, leading to hypoxia and death. - “Mad Hatter Syndrome” results from occupational exposure to:
(a) Lead
(b) Mercury
(c) Cadmium
(d) Asbestos
Answer: (b)
Explanation: Hat-makers used Hg(NO₃)₂ for felting; chronic inhalation caused erethism (tremors, irritability). - Chronic cadmium exposure may lead to:
(a) Hypertension
(b) Hyperthyroidism
(c) Hypocalcemia
(d) Hypoglycemia
Answer: (c)
Explanation: Cd damages renal tubules, impairing vitamin D activation and calcium reabsorption, causing hypocalcemia. - Nicotine addiction involves the release of:
(a) GABA
(b) Dopamine
(c) Serotonin
(d) Glutamate
Answer: (b)
Explanation: Nicotine binds to nicotinic receptors in the ventral tegmental area, increasing dopamine in the nucleus accumbens. - Which heavy metal causes “Itai-itai” disease?
(a) Lead
(b) Mercury
(c) Cadmium
(d) Chromium
Answer: (c)
Explanation: Cd-contaminated water in Japan caused Itai-itai, with severe osteoporosis and renal dysfunction. - Alcohol detoxification primarily occurs in the:
(a) Stomach
(b) Liver
(c) Kidneys
(d) Lungs
Answer: (b)
Explanation: Alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase (ALDH) in hepatocytes metabolize ethanol. - The “withdrawal syndrome” in heroin addiction includes:
(a) Euphoria
(b) Constipation
(c) Lacrimation and muscle cramps
(d) Hypertension
Answer: (c)
Explanation: Opioid withdrawal causes autonomic hyperactivity: tearing, sweating, cramps, and diarrhea. - “Blackfoot disease” is associated with chronic poisoning by:
(a) Lead
(b) Mercury
(c) Arsenic
(d) Cadmium
Answer: (c)
Explanation: Arsenic-contaminated water causes peripheral vascular disease (gangrene of feet), endemic in Taiwan. - Tobacco chewing is a major risk factor for cancer of the:
(a) Liver
(b) Oral cavity
(c) Stomach
(d) Bladder
Answer: (b)
Explanation: Smokeless tobacco contains nitrosamines causing leukoplakia and squamous cell carcinoma. - The antidote for severe lead poisoning is:
(a) BAL (Dimercaprol)
(b) Ethanol
(c) Atropine
(d) EDTA
Answer: (d)
Explanation: EDTA chelates Pb²⁺ ions, forming excretable complexes (used with BAL for encephalopathy). - Cirrhosis of the liver in alcoholism is due to:
(a) Fat accumulation and fibrosis
(b) Viral infection
(c) Autoimmunity
(d) Copper deposition
Answer: (a)
Explanation: Ethanol metabolism generates acetaldehyde and ROS, triggering hepatic stellate cell activation and cirrhosis.
Over population – its causes and effects.
- Which factor is NOT a primary cause of overpopulation?
(a) Decline in death rate
(b) Increased birth rate
(c) Sustainable resource management
(d) Lack of family planning education
Answer: (c)
Explanation: Sustainable resource management mitigates overpopulation effects but does not cause it. Overpopulation stems from birth/death rate imbalances and social factors. - The “Demographic Transition Model” stage characterized by high birth rates and declining death rates leads to:
(a) Population stability
(b) Population explosion
(c) Population decline
(d) Zero population growth
Answer: (b)
Explanation: Stage 2 of the model features rapid population growth due to falling mortality (medicine/sanitation) while birth rates remain high. - Overpopulation directly exacerbates which environmental issue?
(a) Ozone layer recovery
(b) Desertification
(c) Glacial advancement
(d) Reduced carbon footprint
Answer: (b)
Explanation: Overpopulation drives overgrazing, deforestation, and unsustainable agriculture, accelerating soil degradation and desertification. - Which country implemented the “One-Child Policy” to control population growth?
(a) India
(b) Brazil
(c) China
(d) Nigeria
Answer: (c)
Explanation: China enforced this policy (1979–2015) to curb rapid growth, reducing births by ~400 million but causing gender imbalance. - The “IPAT equation” (Impact = Population × Affluence × Technology) describes:
(a) Genetic drift
(b) Environmental impact
(c) Demographic transition
(d) Ecological succession
Answer: (b)
Explanation: IPAT quantifies human environmental impact, where overpopulation (P) multiplies resource consumption and technological damage. - Which effect is linked to overpopulation in urban areas?
(a) Increased green cover
(b) Housing surplus
(c) Slum expansion
(d) Reduced air pollution
Answer: (c)
Explanation: Rapid urbanization due to population pressure causes unplanned settlements, overcrowding, and slum proliferation. - High fertility rates in developing countries are primarily driven by:
(a) Universal higher education
(b) Women’s workforce participation
(c) Lack of contraceptive access
(d) State-sponsored family planning
Answer: (c)
Explanation: Limited reproductive health services and cultural barriers contribute to high birth rates in regions like Sub-Saharan Africa. - The “carrying capacity” of an ecosystem refers to:
(a) Maximum biodiversity it can support
(b) Peak resource extraction rate
(c) Maximum population size it can sustain
(d) Rate of invasive species colonization
Answer: (c)
Explanation: Carrying capacity is the maximum population an environment can support indefinitely without degradation. - Which disease spread is facilitated by overpopulation?
(a) Scurvy
(b) Hypertension
(c) Tuberculosis
(d) Alzheimer’s
Answer: (c)
Explanation: Overcrowding in settlements promotes airborne transmission of TB (caused by Mycobacterium tuberculosis). - Thomas Malthus’ theory predicts that population growth:
(a) Increases geometrically while food supply grows arithmetically
(b) Will stabilize with technological advancement
(c) Is unaffected by famine/disease
(d) Promotes equitable resource distribution
Answer: (a)
Explanation: Malthusian theory warns of population outstripping resources, leading to “positive checks” like famine/pandemic. - Overpopulation-induced eutrophication results from excess:
(a) Heavy metals
(b) Nitrogen/phosphorus
(c) Radioactive waste
(d) Greenhouse gases
Answer: (b)
Explanation: Agricultural runoff from population-driven farming introduces N/P into water bodies, causing algal blooms and hypoxia. - Which strategy effectively reduces birth rates?
(a) Subsidizing fossil fuels
(b) Expanding juvenile industries
(c) Women’s education empowerment
(d) Deforestation for agriculture
Answer: (c)
Explanation: Educated women delay marriage, use contraception, and have fewer children (e.g., Kerala’s literacy-driven fertility decline). - The “population pyramid” of a rapidly growing country typically shows:
(a) Narrow base and broad top
(b) Uniform width across ages
(c) Broad base tapering upward
(d) Inverted triangle shape
Answer: (c)
Explanation: A broad base (high youth percentage) indicates high birth rates and future growth potential. - Overpopulation contributes to climate change primarily through increased:
(a) Geothermal energy use
(b) Photosynthetic activity
(c) Fossil fuel consumption
(d) Oceanic carbon sequestration
Answer: (c)
Explanation: Larger populations increase energy/transport demands, elevating CO₂ emissions from coal/oil/gas. - Which term describes leaving one’s country due to overpopulation pressures?
(a) Immigration
(b) Forced migration
(c) Urbanization
(d) Ecotourism
Answer: (b)
Explanation: Resource scarcity and unemployment from overpopulation drive displacement (e.g., Sahel region migrations). - India’s “National Population Policy 2000” aims to achieve replacement-level fertility by:
(a) 1980
(b) 2005
(c) 2010
(d) 2025
Answer: (c)
Explanation: The policy targeted TFR 2.1 by 2010; India achieved it in 2021 (NFHS-5 data). - Biological control of overpopulation in species is observed in nature via:
(a) Keystone predators
(b) Symbiotic mutualism
(c) Genetic drift
(d) Endemism
Answer: (a)
Explanation: Predators regulate prey populations (e.g., wolves controlling deer overpopulation in ecosystems). - The “Green Revolution” contributed to overpopulation by:
(a) Reducing agricultural yields
(b) Increasing food security
(c) Promoting urbanization
(d) Encouraging birth control
Answer: (b)
Explanation: Enhanced crop yields reduced famine deaths, lowering mortality rates and accelerating growth in Asia/Latin America. - Which index measures a country’s resource consumption impact?
(a) Gross Domestic Product (GDP)
(b) Human Development Index (HDI)
(c) Ecological Footprint
(d) Gini Coefficient
Answer: (c)
Explanation: Ecological Footprint quantifies resource demand per capita; overpopulated regions often exceed biocapacity. - Paul Ehrlich’s “The Population Bomb” (1968) warned about:
(a) Antibiotic resistance
(b) Mass starvation from overpopulation
(c) Solar radiation decline
(d) Genetic engineering risks
Answer: (b)
Explanation: Ehrlich predicted catastrophic famines by the 1970s–1980s due to unchecked population growth.
