Homeostasis

Homeostasis:= a set of fast, controlled, localised responses that prevent significant blood loss when there is a breach in the vessel wall3 stages - Vascular spasm                - Platelet plug formation                - CoagulationVascular spasm- VC of the blood vessels to minimise blood loss- 20-30mins- buys time for platelet plug formation- Triggered by: - damage to the vascular smooth muscle                           - chemicals released from the damaged endothelium                           - pain reflexesPlatelet plug formation- Platelets aggregate and attach to each other and the exposed collagen from the vessel wall- They become sticky, swollen and spikey.- They then release chemicals: SEROTONIN - enhances vascular spasm                                                       ADP - attracts platelets                                                       THROMBOXANE A2 - both- Platelets release these chemicals, attracting more platelets which release more chemicals - postive feedback cycle.Coagulation- Changing from a liquid state to a gel-like state

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