JNTU B.Pharmacy I PATHOPHYSIOLOGY Previous Question Paper (November/December-2020 - R17)

Cells adapt to physiological and pathological stressors by altering their size, number, or phenotype to maintain homeostasis. The primary adaptive responses include:

• Atrophy: A decrease in cell size and organ function due to reduced metabolic activity, often caused by disuse, loss of innervation, or inadequate nutrition.
• Hypertrophy: An increase in cell size resulting in increased organ size, typically occurring in non-dividing cells like cardiac muscle in response to increased workload.
• Hyperplasia: An increase in the number of cells in an organ or tissue, which can be physiological (hormonal or compensatory) or pathological (excessive hormonal stimulation).
• Metaplasia: A reversible change where one adult cell type is replaced by another better suited to withstand an adverse environment, such as squamous metaplasia in the respiratory tract of smokers.

Metabolic acidosis is a clinical disturbance characterized by a primary decrease in plasma bicarbonate (HCO3-) concentration, leading to a drop in blood pH below 7.35. It results from either increased acid production, loss of bicarbonate, or decreased renal acid excretion.

The underlying mechanisms include:

• Increased Anion Gap Acidosis: Caused by the accumulation of organic acids, such as ketoacids in diabetic ketoacidosis, lactic acid in tissue hypoxia, or toxins like methanol and salicylates.
• Normal Anion Gap (Hyperchloremic) Acidosis: Occurs due to the loss of bicarbonate from the gastrointestinal tract (e.g., severe diarrhea) or renal tubular acidosis where the kidneys fail to reabsorb bicarbonate or excrete hydrogen ions.

The body attempts to compensate for this state through respiratory mechanisms, primarily by increasing the rate and depth of breathing (Kussmaul respiration) to lower the partial pressure of carbon dioxide (pCO2), thereby shifting the equilibrium to raise the pH. Clinical manifestations include fatigue, confusion, tachypnea, and cardiac arrhythmias. Diagnosis is confirmed through arterial blood gas analysis showing low pH, low HCO3-, and low pCO2.