Practice all 33 Physiology MCQs from previous BCS Preliminary exams.
Primary blood buffer system is-
The carbonic acid-bicarbonate buffer system (H₂CO₃/HCO₃⁻) is the primary and most important extracellular buffer system in whole blood.
Plasma albumin helps in-
Albumin accounts for approximately 75-80% of plasma oncotic (colloidal osmotic) pressure, preventing fluid leakage into interstitial spaces.
First step in blood coagulation is-
Primary hemostasis starts with platelet adhesion, activation, and platelet aggregation forming the temporary platelet plug.
Bone metabolism is the primary concern of
Parathyroid hormone (PTH) directly regulates serum calcium homeostasis through bone resorption and renal reabsorption.
Protein is digested by
Trypsin is a pancreatic endopeptidase that hydrolyzes peptide bonds in proteins.
Excess CO₂ retention in blood leads to
Hypercapnia (retention of PaCO₂ > 45 mmHg) generates carbonic acid, lowering blood pH and causing Respiratory Acidosis.
Majority of body fluid remains in
Intracellular fluid (ICF) constitutes approximately two-thirds (~67%) of total body water.
Fibrinolysis is done by
Fibrinolysis is mediated by the conversion of inactive plasminogen to active plasmin, which breaks down the fibrin meshwork.
In normal pregnancy
Pregnancy induces a hypercoagulable state characterized by increases in clotting factors I (fibrinogen), VII, VIII, IX, X, and XII.
Fever is mediated by-
Interleukin-1 (IL-1), along with TNF-alpha and IL-6, functions as an endogenous pyrogen that stimulates PGE₂ synthesis in the anterior hypothalamus.
Respiratory Center is Located in-
The primary rhythmic respiratory center (dorsal and ventral respiratory groups) is located in the medulla oblongata.
Programmed cell death is regulated by-
The intrinsic pathway of apoptosis (programmed cell death) is regulated by mitochondrial outer membrane permeabilization and cytochrome c release.
Which of the following factor causes collapse of the lung?
Loss of negative intrapleural pressure (entry of atmospheric air resulting in pneumothorax) causes immediate elastic recoil collapse of the lung.
Facilitated diffusion-
Facilitated diffusion is passive carrier-mediated transport down an electrochemical/concentration gradient ('downhill') without ATP expenditure.
In metabolic acidosis-
In metabolic acidosis, peripheral and central chemoreceptors trigger hyperventilation (Kussmaul breathing) to blow off CO₂ and compensate pH.
Body water is regulated by-
Antidiuretic Hormone (ADH / Vasopressin) regulates renal free-water reabsorption via aquaporin-2 channels in the medullary collecting ducts.
Baroreceptor feedback mechanism decreases blood pressure by-
Increased arterial pressure stimulates carotid/aortic baroreceptors, increasing vagal (parasympathetic) efferent outflow to reduce heart rate and cardiac output.
Lack of insulin is characterized by-
Severe insulin deficiency leads to extracellular hyperglycemia, hyperosmolality, osmotic fluid shifting from cells, and cellular dehydration.
In secondary hypothyroidism
Secondary (central/pituitary) hypothyroidism is characterized by deficient anterior pituitary TSH secretion, resulting in both low free T4 and low (or inappropriately normal) TSH.
Which of the following hormones exhibits a diurnal rhythm in its secretion
Adrenocorticotropic hormone (ACTH) and cortisol exhibit classic circadian (diurnal) periodicity, peaking early in the morning (~6–8 AM) and nadiring around midnight.
In an immune mediated response, which of the following leukocytes becomes an activated macrophage.
Circulating blood monocytes extravasate into tissue spaces and differentiate into tissue-resident and activated inflammatory macrophages.
Which of the following does not have a membrane
Ribosomes and centrioles are non-membrane-bound ribonucleoprotein complexes, whereas nuclei, mitochondria, and lysosomes are enclosed by phospholipid bilayers.
Excitatory cells of nervous system includes
Anterior horn alpha motor neurons generate excitatory action potentials releasing acetylcholine at neuromuscular junctions, while Purkinje cells of the cerebellum are GABAergic inhibitory neurons.
Continuous capillaries gaseous exchange occurs in
Pulmonary alveolar capillaries are continuous capillaries with intact basement membranes optimized for alveolar-capillary gas exchange.
Normal saline is
Normal saline (0.9% NaCl) contains 9 g of NaCl per liter and has an osmolarity of approximately 308 mOsm/L, making it isotonic with human plasma.
Pancreatitis causes elevation of plasma
Serum lipase (and amylase) elevated at least 3-fold above the upper limit of normal confirms the laboratory diagnosis of acute pancreatitis.
Substance that can easily diffuse through lipid bilayer is
Small, non-polar, lipid-soluble molecules like Oxygen (O₂) and Carbon Dioxide (CO₂) diffuse rapidly and freely through the cell membrane phospholipid bilayer.
Major antibody content of the serum is
On serum protein electrophoresis, immunoglobulins (antibodies) migrate predominantly in the gamma-globulin (γ) fraction.
Following menopause there is increased secretion of
Ovarian follicular exhaustion after menopause eliminates negative feedback of estrogen and inhibin, leading to marked compensatory hypersecretion of Follicle-Stimulating Hormone (FSH).
Ionising radiation-following is true
Ionizing radiation can induce direct DNA double-strand breaks, radiation necrosis, microvascular endothelial injury, and secondary neoplasms in brain tissue.
Local blood vessels are dilated due to increased concentration of
Local accumulation of interstitial potassium ions (K⁺), lactate, adenosine, and H⁺ ions during active metabolic hyperemia causes vascular smooth muscle hyperpolarization and vasodilation.
Hemorrhagic lesions may occur in
Vitamin C (ascorbic acid) deficiency impairs collagen prolyl/lysyl hydroxylation, weakening capillary walls and producing perifollicular hemorrhages, purpura, and bleeding gums (scurvy).
Major source of progesterone in early 8 weeks of pregnancy is
During the first 7–8 weeks of gestation, the corpus luteum of pregnancy (maintained by hCG) is the primary source of progesterone until the luteal-placental shift is complete by week 10.
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