Integrated Tissue Metabolism -LAQs and SAQs OmpathStudy

a. Xenobiotic A xenobiotic is any chemical substance that is foreign to a biological system, including drugs, pollutants, and food additives. b. Hyperplasia Hyperplasia is an increase in the number of cells in a tissue or organ, leading to its enlargement, often in response to a stimulus. c. Tetany Tetany is a condition characterized by involuntary muscle cramps or spasms, typically due to hypocalcemia (low blood calcium levels). d. Fast-twitch fibers Fast-twitch fibers are skeletal muscle fibers that contract quickly and powerfully but fatigue rapidly. They rely primarily on anaerobic metabolism. e. Caul A caul is a membrane, part of the amniotic sac, that may cover a newborn's head or face at birth. It is rare and usually harmless. Mononuclear agranulocytes are white blood cells with a single, non-lobed nucleus and no visible cytoplasmic granules. The two main types are: a. Lymphocytes Types : B cells, T cells, and Natural Killer (NK) cells. Roles : B cells produce antibodies for humoral immunity. T cells mediate cellular immunity (e.g., cytotoxic and helper functions). NK cells destroy virus-infected and tumor cells without prior sensitization. b. Monocytes Role :Circulate in the blood and migrate to tissues where they differentiate into macrophages or dendritic cells . Macrophages perform phagocytosis , antigen presentation, and cytokine secretion. Dendritic cells act as antigen-presenting cells to initiate immune responses. Together, mononuclear agranulocytes play crucial roles in adaptive and innate immunity, inflammation, and tissue repair. (2 marks each) Vascular Spasm Immediate vasoconstriction of injured blood vessels to reduce blood loss. Platelet Plug Formation Platelets adhere to exposed collagen, become activated, release chemical signals, and aggregate to form a temporary plug. Coagulation (Blood Clotting) A cascade of clotting factors activates the conversion of fibrinogen to fibrin, stabilizing the plug into a solid clot. (3 marks each) Neuro-glial metabolic coupling refers to the metabolic interaction between neurons and astrocytes , ensuring energy supply during neuronal activity. Glucose uptake : Astrocytes take up glucose from the blood. Lactate production : Astrocytes metabolize glucose to lactate via glycolysis. Lactate shuttle : Lactate is released and taken up by neurons as a preferred energy source during activation. Regulation : This supports neurotransmission and prevents excitotoxicity through neurotransmitter clearance (e.g., glutamate uptake by astrocytes). To convert lipophilic xenobiotics into hydrophilic forms for easier excretion. To detoxify potentially harmful substances. To sometimes activate prodrugs into their active pharmacological forms. --- Non-shivering Thermogenesis (8 Marks) Thermoreceptor Activation :Cold exposure triggers thermoreceptors in the skin, sending signals to the hypothalamus to initiate heat production. Sympathetic Nervous System Activation :The sympathetic nervous system (SNS) is activated and releases norepinephrine into brown adipose tissue (BAT) . Norepinephrine Effect : Norepinephrine binds to β3-adrenergic receptors on BAT cells, activating adenylate cyclase and increasing cAMP levels. Hormone-Sensitive Lipase Activation : cAMP activates protein kinase A (PKA) , which stimulates hormone-sensitive lipase , leading to lipolysis in BAT. Fatty Acid Release :Lipolysis breaks down triglycerides (TAGs) into free fatty acids (FFAs) and glycerol , which are released into the bloodstream. Fatty Acid Transport : FFAs are transported into the mitochondria of BAT for oxidation. Beta-Oxidation :In the mitochondria, FFAs undergo beta-oxidation , producing acetyl-CoA , which enters the citric acid cycle . Electron Transport Chain (ETC) :The citric acid cycle generates high-energy electrons, which fuel the electron transport chain (ET C) , creating a proton gradient across the inner mitochondrial membrane. Uncoupling by UCP1 : Uncoupling Protein 1 (UCP1) in BAT uncouples the proton gradient, allowing energy to be released as heat instead of ATP, a process known as non-shivering thermogenesis . --- Fuel Substrate Shifting : Low-intensity exercise : Muscles primarily use fatty acids as they are abundant and provide long-lasting energy. High-intensity exercise : The body switches to glycogen , which provides a faster ATP supply for rapid energy production. Oxygen Availability : Aerobic exercise : Sufficient oxygen allows muscles to use fatty acids and glucose for ATP production through oxidative phosphorylation. Anaerobic exercise : When oxygen is limited, muscles rely on glycogen which is converted into lactate through anaerobic glycolysis. Energy Efficiency : Fatty acids generate more ATP per molecule but are slower to metabolize, making them suitable for sustained, lower-intensity exercise. Glycogen , while limited in storage, provides a faster ATP supply, making it ideal for high-intensity, short-duration exercise. Hormonal Regulation : Insulin promotes lipog