This medical pathophysiology diagram illustrates the conceptual link between Major Depressive Disorder (MDD) and the development of autoimmune or immune-mediated processes. On the left, an icon of a person with highlighted brain pathology represents MDD. Nine converging pathways are identified as central mediators: Tryptophan-Melatonin pathway dysregulation; Inflammation (involving IDO and Kynurenine); Gut dysbiosis; increased Gut permeability; decreased Serotonin levels; Circadian dysregulation; Oxidative and Nitrosative Stress (O&NS); Mitochondrial dysfunction; and Cytolytic cell alterations. These factors are depicted as contributing to a central red arrow pointing toward the right-side focal point: 'Autoimmunity.' The autoimmunity component is visually represented by a yellow glowing sphere containing three cells surrounded by Y-shaped antibody icons, accompanied by a green upward arrow indicating increased activity. This diagram serves as an educational summary of how neuro-progressive psychiatric conditions and systemic immune dysfunction share overlapping biological underpinnings, particularly emphasizing mitochondrial and metabolic dysregulation.

This medical pathophysiology diagram illustrates the mechanisms of mast cell mediator release and the specific inflammatory pathways of Platelet-Activating Factor (PAF). Section A outlines a three-stage mast cell activation sequence: 1) First mediators (pre-formed in granules) including histamine and tryptase; 2) Second mediators (newly synthesized from phospholipids within minutes) including arachidonic acid derivatives like prostaglandins and leukotrienes, and PAF; and 3) Third mediators (newly transcribed and translated) consisting of cytokines and chemokines. Section B details the downstream effects of PAF on target cells via G-protein-coupled receptors. It depicts two primary pathways: one involving eosinophils, neutrophils, and monocytes leading to cell activation, migration, and prolonged inflammation; the other involving endothelial cells resulting in vascular extension and increased translucency. These effects culminate in local allergic inflammation (urticaria, allergic rhinitis) or systemic allergic inflammation (anaphylaxis). The diagram serves as an educational tool for understanding the temporal and biological progression of type I hypersensitivity reactions.

This pathophysiology diagram illustrates the signaling pathway by which SARS-CoV-2 infection triggers inflammation via transient receptor potential vanilloid (TRPV) channels. At the top of the image, SARS-CoV-2 virions are shown interacting with immune cells (represented as green circles). Red arrows indicate that these immune cells release 'Inflammatory mediators' (red dots) into the extracellular space. Embedded within the phospholipid bilayer of the 'Cellular membrane' is a blue-colored 'TRPV channel,' depicted as a multi-pass transmembrane protein. An arrow shows that the activation of this channel by inflammatory mediators leads to the influx of calcium ions (Ca2+) into the intracellular space. This rise in intracellular calcium subsequently triggers an 'Inflammatory response,' shown as an orange starburst at the bottom right. The diagram provides a molecular model for how COVID-19-induced activation of sensory neurons or supporting cells contributes to pathogenesis, such as anosmia (olfactory dysfunction), through neurogenic inflammation and cytokine release.

This pathophysiology diagram illustrates the immune response and signaling pathways involved in Inflammatory Bowel Disease (IBD). At the top, a row of intestinal epithelial cells shows 'Epithelial barrier damage,' allowing blue rectangular pathogens to penetrate into the lamina propria. The diagram depicts the 'Weakening intestinal barrier' as a consequence of inflammatory feedback. Key cellular components include monocytes and macrophages, which, upon stimulation by pathogens, secrete pro-inflammatory cytokines such as IL-1 (including IL-1α and IL-1β), IL-6, TNF-α, and IL-18. These mediators trigger several downstream effects: the infiltration of multi-lobed neutrophils into the inflammatory site, the activation of the NF-κB signal transduction pathway, and the secretion of TGF-β, which is shown inhibiting the proliferation of blue T cells and purple B cells. The illustration serves as a pedagogical tool for understanding how macrophage-driven cytokine release perpetuates epithelial injury and chronic inflammation in gastrointestinal pathology.