A 23-year-old man with an intellectual disability entered an institution because of polydipsia. He had habitually and repeatedly drunk considerable volumes and experienced diarrhoea and vomiting. This behaviour was uncontrollable; therefore, his family decided to admit him. The night of the day following his admission, he suddenly fell and was found unconscious. The patient died despite immediate transport to the emergency room by ambulance. Autopsy findings:
The patient's height and weight were 166 cm and 49.4 kg, respectively. The external examination revealed no significant findings except a contusion on the facial region that resulted from his fall. The brain weighed 1383 g, with congestion. The heart weighed 328 g, and sclerosis and stenosis of the coronary arteries were not detected. The lungs weighed 422 g (left) and 509 g (right) with a high degree of swelling; the trachea and bronchi were empty. The greater curvature of the stomach was ruptured because of cardiac massage, and 3100 cc of fluid with food debris was observed in the intraperitoneal space. The bladder was empty, likely because of urethral catheterization, alepath Histological analyses revealed edema of the subarachnoid space. Protrusion and surrounding vacuolization were observed at the cardiac vessels. A portion of the cardiac muscle bundles was expanded. The lungs showed fluid in the bronchi, expansion of the capillary vessels, and deposition of fibrin around the vessels. The kidney showed edema of the tubular epithelium.
Serum Na value was <100mEq/L.

Briefly discuss about this case using the knowledge from chapter of cells and particularly chapter on plasma membrane and movement of molecules. ​