In the human body, baroreceptors (pressure sensory bodies, also called pressoreceptors ) register the pressure of the flowing arterial blood on the vessel walls. As mechanoreceptors , they are activated by stretching the vessel wall. The degree of their activity - i.e. the frequency of the signals sent - depends on the degree of vascular wall expansion.
Your impulses reach the medulla oblongata , a partial structure of the central nervous system (CNS). There they cause an inhibition of neurons , the task of which is to increase the heart rate (the number of heartbeats per minute). Active baroreceptors therefore prevent the heart rate from increasing.
Baroreceptors are mainly located in the vessel walls ( adventitia and media ) of the aorta , but also in most of the other arteries . Their task is to keep the arterial blood pressure at a constant level and thus to guarantee the blood supply to the individual organs as required. For example, if the blood pressure falls (e.g. in hypovolemic shock ), the stretching of the aortic wall decreases and the activity of the baroreceptors decreases. As a result, the frequency of its signals to the medulla oblongata also decreases. After the baroreceptor-mediated inhibition has ceased, the neurons of the medulla oblongata now send signals to the heart muscle , to the pacemaker and to various veins and arteries in the body. Baroreceptors are constantly active: Even with constant pressures in the physiological range, impulses are constantly supplied to neurons that regulate circulation.
In response to these signals, the heart rate accelerates. This increases the amount of blood discharged from the heart . The running time of the baroreceptors is around one second, so that the next cardiac interval can be shortened in the event of a spontaneous pressure drop. The arterioles and veins contract, less blood flows to non-vital organs. These two reactions cause the blood pressure in the arteries to quickly return to normal. The redistribution of the blood takes place via the release of adrenaline and is mainly mediated via beta-adrenoceptors . But other catecholamines such as noradrenaline are released when blood pressure is low and have a vasoconstricting effect.
Baroreceptors not only register a change in pressure, but also "how fast" it occurs, i.e. the rate of change.
Baroreceptors are also said to cause the controversial phenomenon of weather sensitivity.
- Klaus Golenhofen: basic physiology textbook . 4th edition. Urban & Fischer, S. 241 .