Myogenic theory: resistance cells in arterioles are sensitive to pressure; can adjust resistance based on resistance changes. Metabolic theory: adjusts vascular resistance as well. Vasoconstrictors: epinephrine, norepinephrine, angiotensin ii see renal notes to review formation of aii, vasopressin (adh, has direct & indirect effects, high concentration in blood following hemorrhage. Vasodilators: bradykinin: formed from alpha-2 globulin in plasma, histamine: derived from eosinophils & mast cells, adenosine: product of atp metabolism, nitric oxide. Neural (mainly within the ans) mostly control of blood pressure; function is to maintain a normal arterial pressure. Mechanoreceptor (baroreceptor reflex pathway); respond to mechanical stretch; pathway conveys info to cv centres in brainstem, which then feeds into efferent pathway to effector organs (i. e. vascular muscle, heart, and sometimes glands) Sensors; can"t tell you absolute pressure detect deviations. Baroreceptors located in aorta and carotid artery. Vasomotor centre sympathetic output; solitary tract nucleus regulates this area.