The respiratory system pt.2

Question 1

How does the RCC receive information?

Answer 1

1. Chemical control:
   - Chemoreceptors, located in the aorta and carotid arteries, detect changes in blood acidity when CO2 increases and O2 decreases.
2. Neural control:
   - Thermoreceptors, inform increases in blood temp
   - Proprioceptors, inform of motor activity in muscles and joints
   - Baroreceptors, located in the lung tissue and bronchioles, inform of the state of lung inflation.

Question 2

What is gaseous exchange?

Answer 2

Gaseous exchange is the exchange of O2 with CO2 by the process of diffusion.

Question 3

What is diffusion?

Answer 3

1. Diffusion is the movement of gas from an area of high pressure to an area of low pressure
2. The difference between high and low pressure is called the diffusion gradient
3. The larger the gradient, the larger the diffusion/gaseous exchange that takes place.

Question 4

What is partial pressure (pp)?

Answer 4

1. Partial pressure is the pressure a gas exerts within a mixture of gases
2. Gas always moves from areas of high partial pressure to areas of low partial pressure.

Question 5

What is gaseous exchange at rest?

Answer 5

1. External respiration, the exchange of gases at the lungs between the deoxygenated blood that arrives in capillaries and the oxygen-rich air in alveoli:

• Oxygen moves from high pp in alveoli to low pp in capillary blood down the diffusion gradient
• Carbon dioxide moves from high pp in the capillary blood to low pp in the alveoli down the diffusion gradient

2. Internal respiration, the exchange of gases at muscle cells between the oxygenated blood that arrives in the capillaries and the carbon dioxide-producing muscle cells. Haemoglobin molecules release the oxygen as they pass the muscle cells:

• Oxygen moves from high pp in capillary blood to low pp of the muscle cell down the diffusion gradient
• Carbon dioxide moves from high pp in the muscle cell to low pp in capillary blood down the diffusion gradient.

Question 6

What is gaseous exchange during exercise?

Answer 6

1. External respiration, during exercise muscle tissues use a greater volume of O2 and produce a greater volume of CO2. This means deoxygenated blood that returns to the lungs has a lower p02 and higher pCO2 than at rest:

• The O2 diffusion gradient steepens and O2 diffuses from high pO2 in the alveoli to lower pO2 in the blood
• The CO2 diffusion gradient steepens and CO2 diffuses from high pCO2 in capillary blood to lower pCO2 in the alveoli.

2. Internal respiration, more intense the exercise, the more the muscle tissue’s demand for oxygen will increase. Therefore, the more intense the exercise, the lower the pO2 and the higher the pCO2 in the muscle tissue:

• O2 diffusion gradient steepens and O2 diffuses from high pO2 in capillary blood to lower pO2 in the muscle cell
• CO2 diffusion gradient steepens and the CO2 diffuses from high pCO2 in the muscle cell to lower pCO2 in the capillary blood.

Question 7

What is haemoglobin dissociation of oxygen?

Answer 7

1. Haemoglobin dissociation of oxygen is the unloading of oxygen from haemoglobin
2. Haemoglobin fully loaded with oxygen is referred to as being saturated
3. The oxyhaemoglobin dissociation curve informs us of the amount of haemoglobin saturated with oxygen.

Question 8

What is the Bohr shift?

Answer 8

1. In addition to the pO2 lowering, there are 3 other effects of exercise which increase the dissociation of O2 from haemoglobin:
   - Increase in blood and muscle temperature
   - Increase in pp of CO2
   - Increase in production of lactic acid and carbonic acid
2. These effects move the oxyhaemoglobin dissociation curve to the right
3. This is known as the Bohr shift.

Question 9

What is the impact of the Bohr shift?

Answer 9

1. At any given pO2 for exercising muscle tissue, the percentage saturation of oxyhaemoglobin is far lower and therefore dissociation of O2 to respiring tissues is greater
2. This enhances the volume of O2 available for diffusion and therefore aerobic energy production for exercise.

Question 10

What are the mechanics inspiration at exercise, effect?

Answer 10

Inspiration:

1. In addition to the external intercostal muscles and diaphragm:
   - The sternocleidomastoid lifts the sternum
   - The scalene and pectoralis minor contract to lift the ribs more

Effect:
2. The volume of the thoracic cavity increases, creating a larger concentration gradient between inside the lungs and outside the body, therefore more air enters the lungs quicker

Question 11

What are the mechanics expiration at exercise, effect?

Answer 11

Expiration:

1. In addition to the external intercostal muscles and the diaphragm:
   - Internal intercostal muscles contract and pull the ribs down and in
   - Rectus abdominus contracts and pushes the diaphragm up

Effect:
2. a decrease in volume of the thoracic cavity increases pressure in the lungs, therefore air is forced out quickly because of the larger concentration gradient