___ to the digestive system. ??? ??? ??? absorption The primary function of the small intestine is ____________. ??? ??? ??? speeds up A stimulant is a drug that __________ the activities of the nervous system. ??? ??? ??? urinary bladder The organ which stores urine before being expelled form the body is the _______________. ??? ??? ??? nephron The filtering unit of the kidney... ??? ??? ??? neur