This medical illustration presents a pathophysiology diagram of the central metabolism of ethanol superimposed on a lateral view of the human brain. The diagram outlines three primary oxidative pathways for the conversion of ethanol to acetaldehyde within the CNS: 1) the Catalase pathway, requiring H2O2 and NAD+ co-factors; 2) the CYP2E1 (Cytochrome P450 2E1) pathway, involving NADPH and oxygen; and 3) the Alcohol Dehydrogenase (ADH) pathway. Acetaldehyde is subsequently metabolized into acetate by the enzyme Aldehyde Dehydrogenase (ALDH), a reaction coupled with the conversion of NAD+ to NADH. The resulting acetate enters the Tricarboxylic Acid (TCA) cycle to generate energy (ATP, NADH, FADH2). Additionally, the diagram illustrates the clinical significance of brain-generated acetaldehyde, indicating its role in motivational properties, ethanol intake, and the formation of adducts. This educational resource is designed to explain the biochemical basis of alcohol addiction and neurotoxicity, highlighting the regional metabolic processes that occur within brain tissue.

This pathophysiology diagram illustrates the mechanisms leading to post-operative hypoglycemia following the resection of pheochromocytoma and paraganglioma (PPGL). The algorithm starts with the surgical removal of the PPGL tumor, resulting in a sudden drop in catecholamine secretion. This drop triggers two main pathways. First, pre-operative insulin resistance combined with the removal of catecholamine-induced inhibition leads to increased insulin secretion from pancreatic beta cells, causing hyperinsulinism. Second, pre-operative use of beta-blockers results in beta-2 receptor blockade. This blockade inhibits both beta cells and alpha cells; specifically, it decreases glucagon secretion from alpha cells. The reduction in glucagon leads to diminished hepatic gluconeogenesis and glycogenolysis. The convergence of hyperinsulinism and decreased glucose production by the liver results in the clinical outcome of post-operative hypoglycemia. The diagram utilizes icons for the adrenal gland, pancreas, and liver to represent the multi-organ involvement in glucose homeostasis alterations post-PPGL resection.

This pathophysiology diagram overlays the metabolic pathway of ethanol on a sagittal cross-section of a human brain. The illustration details the oxidative processes converting ethanol to acetaldehyde and subsequently to acetate. The primary pathway is facilitated by enzymes including Alcohol Dehydrogenase (ADH) and Catalase, represented by large yellow arrows, alongside the Cytochrome P450 2E1 (CYP2E1) system. Acetaldehyde is further processed by Aldehyde Dehydrogenase (ALDH) into acetate, which then enters the Tricarboxylic acid (TCA) cycle (Krebs cycle) to generate energy in the form of ATP, with associated cofactors NADH and FADH2. The diagram also highlights clinical associations with ethanol consumption in the brain, including 'Addiction,' 'Alcohol intake,' 'Alcohol effects,' and the formation of 'Adducts.' A supplementary table at the bottom summarizes the principal roles of the key metabolic enzymes: ADH (alcohol intake), Catalase (alcohol metabolism), CYP2E1 (alcohol metabolism and Reactive Oxygen Species/ROS generation), and ALDH (acetaldehyde metabolism). This educational resource illustrates the biochemical mechanisms of alcohol processing and neurobiological impact.