Homeostatic Integration Across Systems - Anatomy and Physiology

1. Which hormone links low arterial oxygen at high altitude to increased red blood cell production, and which organ secretes it?

   Erythropoietin (EPO), secreted by the kidneys, which stimulates red bone marrow.

2. A person with diabetes takes too much insulin and develops sweating, tremor, and a rapid heart rate. What causes these signs?

   Sympathetic activation and epinephrine release, part of the body's counterregulatory response to low blood glucose.

3. Advanced liver disease lowers plasma albumin. Why does generalized edema develop?

   Less albumin lowers plasma oncotic pressure, so more fluid filters out of capillaries into the interstitium than returns.

4. How do neural, hormonal, and renal compensations compare in speed?

   Neural reflexes act within seconds, hormonal responses over minutes to hours, and renal adjustments of fluid volume over hours to days.

5. Why does prolonged severe hypoglycemia cause confusion and loss of consciousness?

   The brain depends almost entirely on blood glucose for energy and stores very little, so neurons fail when glucose falls.

6. In heart failure, cardiac output falls and the kidneys retain Na+ and water. Why does this response worsen edema?

   The kidneys sense low perfusion as low volume and activate the RAAS; added volume raises capillary hydrostatic pressure, pushing fluid into tissues.

7. Which brain region integrates signals to control thirst, ADH release, body temperature, and hunger?

   The hypothalamus, which links the nervous and endocrine systems.

8. A patient with hypothyroidism has a slow heart rate, cold intolerance, and weight gain. What single change explains these findings across systems?

   A reduced metabolic rate. Thyroid hormone normally raises metabolism, heat production, and heart rate in most tissues.

9. Which three organs act in sequence to produce active vitamin D (calcitriol)?

   Skin (UV light forms cholecalciferol), liver (first hydroxylation), and kidney (second hydroxylation to calcitriol).

10. Why does chronically elevated cortisol increase the risk of infection?

    Cortisol suppresses inflammation and lymphocyte activity, weakening immune defenses.

11. Which organ produces urea, and which organ excretes it?

    The liver produces urea from ammonia, and the kidneys excrete it in urine.

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