Barrow means pressure or stretch so Barrow receptors are special nerve cells or receptors that sense blood pressure by the way that the walls of the blood vessels stretch that information is sent from the barrel receptors to the brain to help keep blood pressure balanced so Barrow receptors are actually groups of nerve endings found within the blood vessel walls and they can be classified into two types based on their location the arterial ones and the cardiopulmonary ones the arterial Barrel receptors can be found on the wall of the aortic Arch as well as on the wall of the kateed sinus which is basically a bulge of the internal kateed artery just above its split from the common kateed artery in the neck in the aortic Arch these nerve endings join up to form the vegus or 10th cranial nerve and in the kateed sinus they form the glossop Fingal or ninth cranial nerve both of these cranial nerves travel up towards the brain stem carrying information about the stretch they sense in the arteries these guys synapse at the nucleus tractus solitarius in the Medela oblongata of the brain stem which then relays the information to the cardiovascular centers the cardiovascular centers are areas in the lower one-third of the ponds in Medela oblongata of the brain stem and they're responsible for the autonomic or involuntary control of the cardiac and vascular function they do that by coordinating the sympathetic and parasympathetic branches of the autonomic nervous system there are two main cardiovascular centers the first is the vasom motor control center which controls the diameter of the blood vessels using the sympathetic nerve fibers to cause Vaso constriction the second is the cardiac control center which is further divided into the cardiac accelerator and the cardiac decelerator centers the cardiac accelerator Center speeds up the heart rate and increases cardiac contractility through the sympathetic outflow tract while the cardiac decelerator center slows down the heart rate through the parasympathetic outflow tract notice that both the sympathetic and parasympathetic systems affect the heart rate but only the sympathetic system has an effect on the diameter of the blood vessels as well as the contractility of the heart muscle this whole process is known as the barrel receptor reflex or Barrel reflex in short and takes place in seconds to minutes allowing us to w rapidly adjust our blood pressure all right so as blood pulses through the cored sinus in the aortic Arch the arterial walls get stretched out and in response the barrel receptors start firing more nerve impulses up to those cardiovascular centers the higher the pressure the higher the frequency of nerve impulses so let's say you're running to catch the bus and your blood pressure Rises the increased pressure stretches the walls of the aortic arch in the cored sinus and the barrel receptors start firing at an increased frequency the glossop Fingal and vagus nerve carry that increased signal to the cardiovascular centers of the brain stem to bring the pressure back down to normal these centers inhibit the sympathetic and stimulate the parasympathetic nervous systems specifically the vasom motor Center decreases the vasoconstrictive effect of the sympathetic nervous system in other words the arterials dilate decreasing total Peripheral arterial resistance and there's decreased constriction of veins which allows blood to pull in the periphery rather than returning to the heart decreased Venus return means that there's less preload or less diastolic filling of the heart and that also decreases cardiac output meanwhile remember that the cardiac accelerator Center is also inhibited reducing the sympathetic effect on the heart and letting the heart work slower and less forcefully in other words decreasing the heart rates and contractility while the cardiac decelerator center is activated boo boosting the parasympathetic effects on the heart which again slows down the heart rate combined these effects result in a decreased cardiac output since blood pressure roughly equals cardiac output times total peripheral resistance the decrease in cardiac output and the decreasing total peripheral resistance means that the blood pressure will decrease back down to normal as well hopefully by that point you've made the bus on the flip side let's say that you're in a terrible traumatic accident in start losing a lot of blood causing your blood pressure to fall the decreased pressure causes the walls of the aortic Arch and kateed sinus to become less stretched and the barrel receptors start firing less frequently the glossop ferial and vus nerve carry that decreased signal to the cardiovascular centers of the brain stem to bring the pressure back up to normal these centers stimulate the sympathetic and inhibit the parasympathetic nervous systems specifically the vasom motor Center increases the vasoconstrictive effect of the sympathetic nervous system in other words the arterials narrow increasing total Peripheral arterial resistance and there's increased constriction of veins which returns more blood to the heart rather than allowing it to pull in the periphery increased Venus return means that there's more preload and that also increases cardiac output meanwhile remember that the cardiac accelerator Center is also stimulated increasing the sympathetic effect on the heart and letting the heart work faster and more forcefully meaning that it increases the heart rate and contractility at the same time the cardiac decelerator center is deactivated which reduces the parasympathetic effect on the heart which again speeds up the heart rate combined these effects result in an increased cardiac output as well as an increase in total peripheral resistance which raises the blood pressure back to normal in this case these changes can save your life now the other type of barrel receptors are called cardiopulmonary Barrel receptors and they're embedded within the walls of the right atrium right ventricle and pulmonary artery and veins these are all relatively low press areas so the stretch of the walls mainly depends on the blood volume flowing through or the fullness of these vessels this is why these Barrow receptors are mainly responsible for the regulation of blood volume and are also known as low pressure or volume Barrow receptors if the blood volume increases the cardiopulmonary Barrel receptors start firing more frequently through the vagus nerve toward the cardiovascular centers of the brain stem these centers then send signals toward the heart increasing its rate and thus the cardiac output increased cardiac output means more blood reaches the kidneys so more water and sodium can get excreted in an attempt to lower blood volume this is called a bane Bridge reflex in addition when cardiopulmonary Barrel receptors sense high blood volume they also send their signal via the vagus nerve to the hypothalamus of the brain telling it to reduce the production of vasopressin or anti-diuretic hormone this results in decreased water reabsorption from the kidney letting more water get lost in the urine cardiopulmonary barel receptors also stimulate the secretion of atrial natriuretic peptide which comes from the atrial muscle cells a dnp causes renal arterials to dilate allowing them to receive and filter even more blood while also inhibiting water and sodium reabsorption on the other hand if the volume of blood decreases cardiopulmonary Barrel receptors get less stretched which reverses all of the effects the heart rate slows down more anti-diuretic hormone is made while less atrial natriuretic peptide is made all this results in less water and sodium excretion which helps restore blood vol volume all right as a quick recap arterial Barrow receptors are located in the aortic arch in kateed sinus and respond to blood pressure changes sending information through the glossop Fingal and vus nerves to the cardiovascular centers in the ponds in Medela these in turn through the autonomic nervous system modify total peripheral resistance in cardiac output cardiopulmonary Barrow receptors are found in the low press regions of the heart and the pulmonary vessel and regulate blood volume by influencing water excretion by the kidneys helping current and future clinicians Focus learn retain and Thrive learn more