Acid-Base Balance, Renal Hormones and Micturition Reflex MCQs

Explanation: Erythropoietin (EPO) is a glycoprotein hormone that regulates red blood cell (RBC) production. Approximately 90% of erythropoietin is synthesized in the kidneys , while the remaining 10% is produced in the liver . In the kidneys, fibroblast-like interstitial cells in the cortex and outer medulla are the main sites of production, responding to tissue hypoxia. The liver contributes mainly during the fetal stage , serving as the predominant site of erythropoietin synthesis before birth. When hypoxia occurs, the hypoxia-inducible factor-1 (HIF-1) activates the erythropoietin gene , increasing hormone synthesis to stimulate erythropoiesis in the bone marrow. Key Takeaways: Kidney → 90% of erythropoietin production Liver → 10%, predominant in fetal life Stimulus: Tissue hypoxia via HIF-1 pathway Function: Stimulates proerythroblast formation and maturation in bone marrow

Large doses of estrogen inhibit the production of erythropoietin induced by hypoxia Reference: Ganong, 25th edition page no.706

Most powerful stimulus for aldosterone secretion is Hyperkalemia Reference: Ganong, 25th edition/page no.369

H + K + exchanger is present in nephrons. So usually H + ions and K + ions gets exchanged To conserve potassium in hypokalemia, acid secretion increases All acidotic conditions increase renal acid secretion Aldosterone increases acid secretion in kidney Reference: Ganong, 25th edition page no.715

Ammonia buffer system is the most important buffer system of kidney Reference: Ganong, 25th edition page no.711

Explanation: Thiamine (Vitamin B1) is an essential cofactor for several enzymes involved in carbohydrate metabolism, including pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, and transketolase . Thiamine deficiency leads to impaired conversion of pyruvate to acetyl-CoA. As a result, pyruvate accumulates and is diverted towards lactate production , leading to lactic acidosis . This explains the elevated lactate levels seen in thiamine deficiency, particularly in alcoholics. Explanation of other options: Niacin (Option A): Deficiency causes pellagra (dermatitis, diarrhoea, dementia), but not lactic acidosis. Riboflavin (Option B): Deficiency leads to cheilitis, glossitis, and angular stomatitis , but does not cause lactic acidosis. Pantothenic acid (Option C): Component of Coenzyme A ; its deficiency is rare and does not cause lactic acidosis.

Substances that are filtered and secreted by kidney are Potassium ions, creatinine and uric acid Reference: Ganong, 25th edition page no.679

In Diabetic Ketoacidosis there is an Increased Production of Acetoacetic acid and beta hydroxy Butyric Acid which leads to an increase in plasma concentration of Hydrogen ions leading to Metabolic Acidosis. This is compensated by hyperventilation i.e kussmall's breathing