Askydiver prepares to jump out of a plane. explain how gravity and air resistance will affect the motion of the skydiver before and after he or she opens the parachute.

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.