Complex sentence: However, when prazosin is initially started, heart rate and contractility go up in order to maintain the pre-treatment blood pressures because the body has reached homeostasis at its abnormally high blood pressure.
Split into simpler sentences: However, when prazosin is initially started, heart rate and contractility go up in order to maintain the pre-treatment blood pressures. This is because the body has reached homeostasis at this abnormally high blood pressure.