Arterial Blood Pressure & Its Control

• Arterioles are small diameter blood vessels in the microcirculation that extend and branch out from the artery, leading to the capillary system. These provide most of the peripheral resistance.
• Capillaries are the smallest blood vessels, that make up the microcirculation. Their endothelial linings are only one cell layer thick to enable gaseous exchange between blood and tissues.
• Venules are arterioles but for the veinous system.
• The pulmonary and umbilical veins carry oxygenated blood to the heart.
• Venous pressure is lower than arterial pressure. The pressure at distal regions is lower. Systolic pressure in red, diastolic pressure in blue

  
• The baroreflex is a negative feedback loop

  
• The control system is located within the medulla: baroreceptors project to nucleus tractus solitarus (NTS), which then sends excitatory projections to the caudal ventrolateral medulla (CVLM) and nucleus ambiguous (NA) and the dorsal motor nucleus of the vagus (DMX); CVLM sends inhibitory projections to the rostral ventrolateral medulla (RVLM). From the carotids the pathway is the glossopharyngeal nerve, from the aortic is the vagus nerve. Green is parasympathetic. Red is sympathetic.