Complement proteins and antibodies coat a microorganism and provide binding sites, enabling macrophages and neutrophils to phagocytize the organism. This phenomenon is termed

A. Swelling:Swelling, or edema, is a classic cardinal sign of inflammation. It occurs due to increased vascular permeability, which allows fluid, proteins, and immune cells to accumulate in the affected tissue, contributing to the inflammatory response.

B. All are signs of inflammation:All the listed options-swelling, heat, pain, and redness-are classic cardinal signs of inflammation. Therefore, it is not correct to say that any one of them is absent; collectively, they define the inflammatory process.

C. Heat:Heat at the site of inflammation results from increased blood flow (hyperemia) due to vasodilation. It is one of the four primary cardinal signs and reflects the body’s attempt to deliver immune cells and proteins to the affected area.

D. Pain:Pain arises from the release of chemical mediators like prostaglandins and bradykinin that stimulate nerve endings. It signals tissue injury and serves as an alert to prevent further damage.

E. Redness:Redness, or erythema, is caused by increased blood flow to the affected area as part of the vasodilation response. It is a hallmark feature of inflammation and helps identify the affected site visually.

A. Angiotensin II:Angiotensin II is commonly released during prolonged exercise because dehydration and sweating reduce plasma volume, activating the renin–angiotensin system. Its release helps constrict blood vessels and maintain blood pressure despite fluid losses. This hormone therefore supports circulatory stability during long-duration exertion such as a marathon.

B. Atrial natriuretic peptide (ANP):ANP is least likely to be released because it is normally secreted when the atria are stretched by increased blood volume. During a marathon, plasma volume typically decreases due to sweating and fluid shifts, reducing atrial stretch. With lower circulating volume, ANP secretion falls rather than rises, making it the least expected hormone in this scenario.

C. Epinephrine:Epinephrine release increases significantly during endurance events due to activation of the sympathetic nervous system. It supports cardiac output, mobilizes glucose and fatty acids, and maintains perfusion to active muscles. Elevated epinephrine is therefore a natural and necessary response to prolonged physical stress.

D. Antidiuretic hormone (ADH):ADH secretion rises during prolonged exercise because reduced blood volume and increased plasma osmolality stimulate its release. This hormone promotes water reabsorption in the kidneys, helping conserve fluid and maintain blood pressure. Its release is essential to counteract dehydration during a marathon.

E. Aldosterone:Aldosterone release increases as part of the renin–angiotensin–aldosterone system during extended physical activity. It enhances sodium and water reabsorption, supporting blood pressure and fluid balance as the runner loses electrolytes through sweat. This hormone plays a key role in maintaining volume homeostasis during endurance exercise.