Final answer:
The chemical released to cause vasoconstriction during the vascular spasm phase of hemostasis is serotonin. This occurs as the first step in the complex process of hemostasis to reduce blood flow following an injury.
Step-by-step explanation:
The chemical that is released to bring about vasoconstriction during the vascular spasm phase of hemostasis is serotonin. The vascular spasm is the first step in hemostasis, where blood vessels constrict to reduce blood flow following an injury. Serotonin is one of the vasoconstrictors that is released from the platelets when they become activated and is responsible for the narrowing of the blood vessels to decrease blood loss temporarily.
Hemostasis involves three general steps:
- Vascular spasm
- Platelet plug formation
- Coagulation
Throughout this process, various chemicals are released to control vasoconstriction and vasodilation. For example, during the resolution phase, where the clot needs to be degraded (fibrinolysis), bradykinin, a vasodilator, is released to reverse the effects of vasoconstrictors like serotonin, helping to restore normal blood circulation.