What happens to the orbit of earth when its velocity is halved?   a. the orbit of earth around the sun becomes smallerc. the earth escapes the sunb. the orbit of earth does not changed. the orbit becomes more elliptical 

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.