After the vessel injury, thrombocytes adhere to the damaged vessel wall. This is most likely a specific reaction between collagen and thrombocytes. Small amount of ATP from the damaged tissues is activated. The reaction is pretty fast and reversible, occurring without the presence of calcium ions. Along with this significant ion sequences there is secretion of active substances ( serotonin, adrenaline, noradrenaline, histamine, ATP, ADP, etc.) into the nearby plasma. This reaction, called the “release reaction”, most likely develops in two stages. The first stage of the process is active.