Category: Biology Second Paper Lecture Sheet

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.

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.

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

The pressure exerted by the blood as it flows through the blood vessels is called blood pressure. A sphygmomanometer is a device for measuring blood pressure. It is of two types.
1. Hypertension: Systolic pressure is the maximum pressure exerted by the flowing blood on the walls of the arteries when the ventricles of the heart are contracted. It is equal to 120 mm Hg pressure.
2. Hypotension: Diastolic pressure is the pressure exerted by the flowing blood on the walls of the arteries when the ventricles of the heart are dilated. It is equal to 80 mm Hg pressure.

Blood flow through the heart is controlled by the ventricles. The capillaries open only to the forward flow of blood. Never open to backflow of blood. If the blood pressure in the atrium is high and the blood pressure in the ventricle is low, the bicuspid and tricuspid valves open. As a result, blood enters the ventricles from the atrium. When the ventricles contract with blood, the semilunar valves open and the bicuspid and tricuspid valves close. As a result blood enters the pulmonary artery and aorta. But cannot return to the atrium. Then, when the ventricular pressure decreases, the blood wants to flow back into the ventricle, but because the semilunar valve is closed, backflow does not occur. Blood flow is unidirectional as all capillaries are always open in one direction.

The heart is made up of cardiac muscle. Cardiac muscle has the longest resting period. It never ceases. Normally, when metabolic waste (lactic acid) accumulates in a cell, it is depleted. But because the cardiac muscle has a long resting period, metabolic wastes are released more easily. In addition, the heart muscle directly uses lactic acid as a nutrient. Therefore, waste cannot accumulate in the heart muscle. So the heart is sometimes exhausted.

The circulation in which the blood passes through the heart twice to circulate once throughout the body is called double circuit circulation. Bi-circular circulation occurs in the human heart. Two-circuit circulation consists of pulmonary circulation and systemic circulation.
1. Pulmonary Circulation: In pulmonary circulation, blood containing CO2 from the right ventricle of the heart enters the pulmonary artery through the semilunar ventricles. Blood comes to the lungs from the pulmonary artery. Blood is purified in the lungs. The O2-rich blood from the lungs then enters the left atrium through the pulmonary veins.
2. Systemic Circulation: In systemic circulation, O2 enriched blood enters the aorta or aorta from the left ventricle of the heart. From the aorta, blood flows through arteries and capillaries to various organs, tissues and cells. O2, nutrients, hormones etc reach the cells through blood.

Capillaries arise from some organs. Capillary networks join together to form veins. Blood travels from one organ to another through veins. In vertebrates there are two types of portal circulation namely hepatic and renal.

Coronary arteries arise from the roots of systemic arteries. O2-rich blood passes through the coronary arteries to the heart wall. The CO2-rich blood then returns to the heart through the coronary veins from the heart wall.

In pulmonary circulation, blood containing CO2 from the right ventricle of the heart enters the pulmonary artery through the semilunar ventricles. Blood comes to the lungs from the pulmonary artery. Blood is purified in the lungs. The O2-rich blood from the lungs then enters the left atrium through the pulmonary veins.