Pathogen Invasion Triggers Pyrogenic Cytokine Release
Placeholder: immune cells detect pathogens and release fever-inducing cytokines.
- IL-1, IL-6: Key cytokines (Placeholder short caption)
- Macrophages: Source cells (Placeholder short caption)
- PAMPs: Trigger (Placeholder short caption)
- 0–2 h: Onset window (Placeholder short caption)
Innate immune activation
Placeholder: pathogen recognition activates cytokine-releasing immune cells.
Cytokines Reach the Hypothalamic Thermoregulatory Center
Placeholder: IL-1 and IL-6 signal the brain via the OVLT circumventricular organ.
- OVLT: Entry route (Placeholder short caption)
- Blood-brain: Barrier crossed (Placeholder short caption)
- IL-1R, gp130: Receptor (Placeholder short caption)
- ~2–4 h: Delay (Placeholder short caption)
Circumventricular signaling
Placeholder: cytokines act near leaky capillaries bypassing the blood-brain barrier.
Prostaglandin E2 Raises the Hypothalamic Set-Point
Placeholder: PGE2 synthesis shifts the thermoregulatory set-point upward.
- PGE2: Mediator (Placeholder short caption)
- COX-2: Enzyme (Placeholder short caption)
- EP3 receptor: Target (Placeholder short caption)
- 1–3°C: Typical shift (Placeholder short caption)
Prostaglandin pathway
Placeholder: COX-2 converts arachidonic acid to PGE2 in the preoptic area.
Shivering and Vasoconstriction Drive Heat Production
Placeholder: the body shivers and constricts vessels to reach the new set-point.
- Shivering: Muscle response (Placeholder short caption)
- Vasoconstriction: Skin response (Placeholder short caption)
- Chills, cover-seeking: Behavior (Placeholder short caption)
- Up to 5x: Heat gain (Placeholder short caption)
Effector mechanisms
Placeholder: hypothalamus drives shivering thermogenesis and skin vasoconstriction.
Body Temperature Stabilizes at the Elevated Set-Point
Placeholder: temperature plateaus once it matches the new set-point.
- Fastigium: Phase (Placeholder short caption)
- 38–40°C: Plateau temp (Placeholder short caption)
- Defervescence: Resolution (Placeholder short caption)
- Set-point falls: Sweating onset (Placeholder short caption)
Equilibrium and resolution
Placeholder: temperature holds steady until cytokine signaling declines.
Defervescence
Placeholder: falling set-point triggers sweating and vasodilation to cool down.
Placeholder highlight: children can spike fevers rapidly but usually resolve quickly.