Answer:
homeostatic protection, mechanical protection, circulation
Step-by-step explanation:
Homeostatic protection: cerebrospinal fluid transports polypeptide hormones and its PH allows for cerebral blood flow as well as pulmonary ventilation
Mechanical protection: cerebrospinal fluid absorbs shock, so that energy from an impact does not directly first affect the spine
Circulation: helps allow for the exchange of nutrients between the blood and adjacent nervous tissue