All of the following increase venous return, except: Increasing flextion and extension of the knee joint
Increasing the myocardial contractility of the left ventricle
Increasing the pressure within thoracic cavity during inhalation
Increasing the pressure difference between venules and the right atrium

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.  

answer; an inhibitory postsynaptic potential;