4 To prevent backflow of blood into the left ventricle.
Explanation:
(d) Valves of heart maintain unidirectional flow of blood (i.e from the atria to the ventricles and from the ventricles to the pulmonary artery or aorta) and opening and closing of valve depends upon the pressure on opposite sides. It prevents its regurgitation in the opposite direction. These valves act like one way doors and allows blood to flow either forward into the next chamber or out of the heart via one of two main blood vessels that carry blood away from the heart. The valves close to prevent the back flow. The heart has 4 valves: mitral valve and tricuspid valve (which control blood flow from the atria to the ventricles); and aortic valve and pulmonary valve (which control blood flow out of the ventricles).
NCERT Page-284 / N-199
Body fluids and circulation
278342
In which part of the heart SA node is present
1 sinus-venosus
2 interatrial septum
3 right atrium
4 atrioventricular septum
Explanation:
(c) $SA$ (sino - atrial) node is called the natural pacemaker of the heart. It controls the heart rate by generating electrical impulses and then sending them through the heart muscle, causing the heart to contract and pump blood throughout the body. It is made up of a group of cells (called myocytes) and positioned on the wall of the right atrium, at the centre of the heart and near the entrance of the superior vena cava. These cells contract at a rate of about 70-80 times per minute, which make up the natural heartbeat.
NCERT Page-284 / N-199
Body fluids and circulation
278343
Which of the following has the thickest walls?
1 Right ventricle
2 Right auricle
3 Left ventricle
4 Left auricle
Explanation:
(b) Ventricle is one of two large chambers in the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. Ventricles are far more thick walled than atria and left ventricle is at least three times thicker than the right one.
NCERT Page-284 / N-199
Body fluids and circulation
278344
Cardiac cycle in man takes about
1 1.0 second
2 0.5 seconds
3 1.2 seconds
4 0.8 seconds
Explanation:
(d) A cardiac cycle (atrial systole + ventricular systole + diastole) is completed in 0.8 seconds.
4 To prevent backflow of blood into the left ventricle.
Explanation:
(d) Valves of heart maintain unidirectional flow of blood (i.e from the atria to the ventricles and from the ventricles to the pulmonary artery or aorta) and opening and closing of valve depends upon the pressure on opposite sides. It prevents its regurgitation in the opposite direction. These valves act like one way doors and allows blood to flow either forward into the next chamber or out of the heart via one of two main blood vessels that carry blood away from the heart. The valves close to prevent the back flow. The heart has 4 valves: mitral valve and tricuspid valve (which control blood flow from the atria to the ventricles); and aortic valve and pulmonary valve (which control blood flow out of the ventricles).
NCERT Page-284 / N-199
Body fluids and circulation
278342
In which part of the heart SA node is present
1 sinus-venosus
2 interatrial septum
3 right atrium
4 atrioventricular septum
Explanation:
(c) $SA$ (sino - atrial) node is called the natural pacemaker of the heart. It controls the heart rate by generating electrical impulses and then sending them through the heart muscle, causing the heart to contract and pump blood throughout the body. It is made up of a group of cells (called myocytes) and positioned on the wall of the right atrium, at the centre of the heart and near the entrance of the superior vena cava. These cells contract at a rate of about 70-80 times per minute, which make up the natural heartbeat.
NCERT Page-284 / N-199
Body fluids and circulation
278343
Which of the following has the thickest walls?
1 Right ventricle
2 Right auricle
3 Left ventricle
4 Left auricle
Explanation:
(b) Ventricle is one of two large chambers in the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. Ventricles are far more thick walled than atria and left ventricle is at least three times thicker than the right one.
NCERT Page-284 / N-199
Body fluids and circulation
278344
Cardiac cycle in man takes about
1 1.0 second
2 0.5 seconds
3 1.2 seconds
4 0.8 seconds
Explanation:
(d) A cardiac cycle (atrial systole + ventricular systole + diastole) is completed in 0.8 seconds.
4 To prevent backflow of blood into the left ventricle.
Explanation:
(d) Valves of heart maintain unidirectional flow of blood (i.e from the atria to the ventricles and from the ventricles to the pulmonary artery or aorta) and opening and closing of valve depends upon the pressure on opposite sides. It prevents its regurgitation in the opposite direction. These valves act like one way doors and allows blood to flow either forward into the next chamber or out of the heart via one of two main blood vessels that carry blood away from the heart. The valves close to prevent the back flow. The heart has 4 valves: mitral valve and tricuspid valve (which control blood flow from the atria to the ventricles); and aortic valve and pulmonary valve (which control blood flow out of the ventricles).
NCERT Page-284 / N-199
Body fluids and circulation
278342
In which part of the heart SA node is present
1 sinus-venosus
2 interatrial septum
3 right atrium
4 atrioventricular septum
Explanation:
(c) $SA$ (sino - atrial) node is called the natural pacemaker of the heart. It controls the heart rate by generating electrical impulses and then sending them through the heart muscle, causing the heart to contract and pump blood throughout the body. It is made up of a group of cells (called myocytes) and positioned on the wall of the right atrium, at the centre of the heart and near the entrance of the superior vena cava. These cells contract at a rate of about 70-80 times per minute, which make up the natural heartbeat.
NCERT Page-284 / N-199
Body fluids and circulation
278343
Which of the following has the thickest walls?
1 Right ventricle
2 Right auricle
3 Left ventricle
4 Left auricle
Explanation:
(b) Ventricle is one of two large chambers in the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. Ventricles are far more thick walled than atria and left ventricle is at least three times thicker than the right one.
NCERT Page-284 / N-199
Body fluids and circulation
278344
Cardiac cycle in man takes about
1 1.0 second
2 0.5 seconds
3 1.2 seconds
4 0.8 seconds
Explanation:
(d) A cardiac cycle (atrial systole + ventricular systole + diastole) is completed in 0.8 seconds.
4 To prevent backflow of blood into the left ventricle.
Explanation:
(d) Valves of heart maintain unidirectional flow of blood (i.e from the atria to the ventricles and from the ventricles to the pulmonary artery or aorta) and opening and closing of valve depends upon the pressure on opposite sides. It prevents its regurgitation in the opposite direction. These valves act like one way doors and allows blood to flow either forward into the next chamber or out of the heart via one of two main blood vessels that carry blood away from the heart. The valves close to prevent the back flow. The heart has 4 valves: mitral valve and tricuspid valve (which control blood flow from the atria to the ventricles); and aortic valve and pulmonary valve (which control blood flow out of the ventricles).
NCERT Page-284 / N-199
Body fluids and circulation
278342
In which part of the heart SA node is present
1 sinus-venosus
2 interatrial septum
3 right atrium
4 atrioventricular septum
Explanation:
(c) $SA$ (sino - atrial) node is called the natural pacemaker of the heart. It controls the heart rate by generating electrical impulses and then sending them through the heart muscle, causing the heart to contract and pump blood throughout the body. It is made up of a group of cells (called myocytes) and positioned on the wall of the right atrium, at the centre of the heart and near the entrance of the superior vena cava. These cells contract at a rate of about 70-80 times per minute, which make up the natural heartbeat.
NCERT Page-284 / N-199
Body fluids and circulation
278343
Which of the following has the thickest walls?
1 Right ventricle
2 Right auricle
3 Left ventricle
4 Left auricle
Explanation:
(b) Ventricle is one of two large chambers in the heart that collect and expel blood received from an atrium towards the peripheral beds within the body and lungs. Ventricles are far more thick walled than atria and left ventricle is at least three times thicker than the right one.
NCERT Page-284 / N-199
Body fluids and circulation
278344
Cardiac cycle in man takes about
1 1.0 second
2 0.5 seconds
3 1.2 seconds
4 0.8 seconds
Explanation:
(d) A cardiac cycle (atrial systole + ventricular systole + diastole) is completed in 0.8 seconds.
