1. State the importance of regulating the carbon dioxide content in blood.
Carbon dioxide will dissolve in water to become acid,
which lowers the pH of the blood,
as enzymes only function within a narrow range of pH,
the activities of enzymes will be lowered.
2. What does the human body control to regulate the gas content in blood?
(1) breathing
(2) heartbeat
3. Which part of which organ controls breathing?
Respiratory centre of the medulla oblongata
4. How is the regular breathing rhythm controlled? (Hint: first state the nervous control, then state the standard mechanism of breathing in, then state the nervous control again, then state the standard mechanism of breathing out in about 10 steps.)
1. The respiratory centre send nerve impulses to the intercoastal muscles and
diaphragm muscles,
2. intercoastal muscles and diaphragm muscles contract,
3. rib cage moves upwards and outwards and diaphragm becomes flattened,
4. lungs expand, pressure in the lungs decreases
5. when the pressure in the lungs decrease to smaller than the pressure of the
atmosphere
6. air enters the lungs (Note that point 1-6 is the mechanism of breathing in)
7. after that, the respiratory centre stop sending nerve impulses to the intercoastal muscles and diaphragm muscles,
8. intercoastal muscles and diaphragm muscles relax,
9. the rib cage moves downwards and inwards,
10. the lungs deflate due to elastic recoil which lead to exhalation.
5. What is the usual breathing rate (number of breath per minute) of the human body? What is the volume of each breath?
18 breaths per minute 500cm3
6. What is the meaning of breathing rate?
Number of breath per minute
7. What is the meaning of depth of breathing?
Volume of air that we breath in and out in each breath
8. What are the factors affecting the amount of oxygen diffusing into the blood?
rate of breathing and depth of breathing
9. In the control mechanism of breathing rate, which stimuli is the most important?
The carbon dioxide content in the blood
10. How is the rate and depth of breathing controlled?
(1) When the carbon dioxide concentration in the blood rises, more carbon
dioxide will dissolve in the water to produce acid, causing pH to decrease.
(2) The chemoreceptors in the aortic and carotid bodies detect the change in pH
and send nerve impulses to the respiratory centre in the medulla oblongata.
(3) There are also chemoreceptors in the respiratory centre to detect the change
in pH value in the spinal cord.
(4) After the respiratory centre processed these nerve impulses, it will send
nerve impulses to the intercostal muscles and diaphragm muscles
(5) to cause them to contract faster and more strongly,
(6) leading to the increase in rate and depth of breathing.
11. What is the difference of cardiac muscles from other skeletal muscles?
Cardiac muscles can contract by itself without nervous stimulation.
12. What is heart beat?
The beating of the heart
13. How is heart beat coordinated by the cardiac muscle cells?
(1) Heart beat begins at the SA node located on the wall of the right atrium, the
SA node can automatically generates electrical impulses.
(2) These electrical impulses first spread to the two atria and cause them to
contract at the same time.
(3) The electrical impulses then travel to the AV node (the cells
located between the right atrium and right ventricle.
(4) The AV node pass on the impulses to both ventricles and cause them to
contract together.
14. Why is the SA node called the pacemaker?
Because the SA node determines the heart beat rate.
15. What is the cardiac cycle?
It is the sequence of events that take place in one heart beat
16. How long is one cardiac cycle?
0.8 second
17. Which 3 stages can the cardiac cycle be separated into?
(1) Atrial systole (0.1 second)
- Only the atria contract
(2) Ventricular systole
- Only the ventricles contract
(3) diastole
- both the atria and ventricles relax
18. What are the changes in the heart during atrial systole?
(1) atria contracts, pressure in the atria increase
(2) blood will be pumped into the ventricles through the tricuspid and
bicuspid valves.
(3) the semilunar valves are closed.
19. What are the changes in the heart during ventricular systole?
(1) ventricles contract, pressure in the ventricle increase
(2) When the pressure inside the ventricles becomes higher than that of
the aorta and the pulmonary artery, the semilunar valve will open,
(3) blood is pumped into the pulmonary artery and the aorta.
(4) the higher pressure of the ventricles also cause the bicuspid valves and
The tricuspid valves to close, cause the first heart sound.
20. What are the changes in the heart during diastole?
(1) Both the atria and ventrocles relax, the blood pressure in the ventricles
decreases,
(2) because the blood pressure in the aorta and the pulmonary artery is
higher, therefore the blood backflow,
(3) The backflow of the blood causes to semilunar valve to close,
leading to the second heart sound.
21. What is the function of the tricuspid valve?
Prevent blood from flowing back from the right ventricle to the right atrium.
22. Whatis the function of the bicuspid valve?
Prevent blood from flowing back from the left ventricle to the left atrium.
23. What is the function of the semilunar valves?
Prevent blood from flowing back to the ventricles
24. What is the function of the valves?
Prevent the backflow of blood
25. What is the most critical factor that cause blood to flowing from one place
to another?
Blood pressure!!!
26. How can cardiac output be calculated?
Cardiac output (mL/min) = stroke volume(mL/beat) x heart rate(beats/min)
27. What are the systems involved in regulating the cardiac output?
(1) nervous system
(2) endocrine system
28. How can the nervous system control the cardiac output?
(1) The cardiovascular centre inside the medulla oblongata controls the
cardiac output.
(2) It generates nerve impulses and send them to the SA node through the
sympathetic nerve and the parasympathetic nerve
(3) which then affect the cardiac output.
29. How is the cardiac output coordinated by the nervous system when the body is at rest?
(1) mainly by the parasympathetic nerve which send nerve impulses to the
SA node.
(2) more acetylcholine is released
(3) to inhibit the activity of the SA node and the cardiac muscle,
(4) this causes the heart rate and the stroke volume to decrease, which
reduce the cardiac output.
30. How is the cardiac output coordinated by the nervous system when the body is carrying out exercises?
(1) mainly by the sympathetic nerve which send nerve impulses to the
SA node.
(2) more noradrenaline is released
(3) to stimulates the activity of the SA node and the cardiac muscle,
(4) this causes the heart rate and the stroke volume to increase, which
increase the cardiac output.
31. How is the cardiac output controlled by hormones?
(1) When a person is feeling stressed or excited, the sympathetic nerve
will stimulate the adrenal glands located on top of the kidneys
(2) to release more adrenaline.
(3) The adrenaline will enter the blood and stimulate the SA node and
cardiac muscles when it reaches the heart,
(4) causing heart rate and stroke volume to increase, increasing the
cardiac output.
(note: the adrenaline has other functions)
32. What are the effect of exercise on the breathing and heart beat?
(1) cause the rate and depth of breathing to increase
(2) cause the cardiac output to increase
33. What is ventilation rate?
Ventilation rate = depth of breathing x rate of breathing
34. What is the advantages of regular exercise?
(1) strengthen the intercostal muscles and diaphragm muscles, increasing
the vital capacity
(2) increase the thickness of the cardiac muscle wall, causing the heart to
be stronger and contract more powerfully.