The sensory neurons in the blood vessels of vertebrates that regulate blood pressure are called baroreceptors. It regulates heart rate and energy and converts abnormal blood pressure to normal blood pressure. Hence this process is called Baroreflex. There are two types of baroreceptors. High pressure baroreceptor and low pressure baroreceptor
1. High pressure baroreceptors: The sensory nerve cells in the aortic arch and carotid sinus are called high pressure baroreceptors. They regulate systemic blood pressure and cerebral blood pressure.
(i) Control of low blood pressure: When the blood pressure in the heart and blood vessels decreases, the baroreceptor signal level decreases. This message travels to the medulla oblongata via the glossopharyngeal and vagus nerves. Signals from the medulla oblongata are sent to the heart muscle, pressor, and blood vessels. It increases heart rate and constricts blood vessels. As a result, the blood pressure becomes normal.
(ii) Regulation of high blood pressure: When the blood pressure in the heart and blood vessels increases, the baroreceptor signal increases. This message passes through the medulla oblongata. It shuts down the vasomotor center. As a result, blood flow through the heart and blood vessels decreases. As a result, the blood pressure becomes normal.
2. Low pressure or volume baroreceptors: Baroreceptors that regulate blood volume and control blood pressure are called low pressure or volume baroreceptors. A larger baroreceptor than this. They control the blood pressure of the systemic veins, pulmonary veins, right atrium and right ventricle. A decrease in blood volume or volume results in a decrease in blood pressure. This message reaches the hypothalamus. It then comes from the hypothalamus to the pituitary gland. Antidiuretic or vasopressin hormone is released from the pituitary gland. Antidiuretic hormone (ADH) increases renal water absorption. The kidneys reabsorb water from the urine and mix it with the blood. As a result, blood volume increases and blood pressure increases.
Vasopressin hormone directly causes vasoconstriction and increases blood pressure. The renin hormone is produced by the cells of the juxta-glomerulus. It increases blood volume and blood pressure.