Physiology: respiratory control systems

Question 1

How long do RBCs spend in pulmonary capillaries (between pulmonary arteriole and venule?)
How long does it take for gas pressure to equilbriate?

Answer 1

0.75 seconds, 0.5 seconds

Question 2

Describe the partial pressures of oxygen and carbon dioxide in the
- Air
- Alveoli
- Artery
- Vein
- Tissues

Answer 2

Question 3

Break down the alveolar gas equation

Answer 3

First part: amount of oxygen entering alveoli, considering the humidification of water
Second part: how much oxygen exits the alveoli
First part - second part = total amount of oxygen reaching alveolar sacs

Question 4

Is oxygen poorly soluble in blood?
In 1L of blood with 100mmHg O2 (200mL O2):
__mL of O2 is dissolved in blood (__%)
__mL of O2 is bound to haemoglobin (__%)

Answer 4

3mL - 1.5%
197mL - 98.5%

Question 5

What protein makes up RBCs?
How many subunits does hemoglobin have?
Describe binding of O2 to heme group

Answer 5

Hemoglobin
4
Each subunit has its own heme group - which one O2 molecule binds to.

Question 6

The O2 hemoglobin dissocation curve:
Why is it sigmoidal?
What is the advantage of having a sigmoidal shape, in terms of offloading/onloading of O2?

Answer 6

Because of cooperative binding - the binding of one O2 encourages the binding of another, and vice versa for release
Means in high O2, it can onload oxygen; in low O2, can offload

Question 7

The Bohr effect: tissues
- What happens metabolically in tissues?
- What does this do to the saturation curve?

Answer 7

Tissues are metabolically active - increased Co2, increased H+/decreased pH, increased BPG, increased temperature.
Curve shifts to the right, favouring O2 unloading from Hb to tissues

Question 8

The Bohr effect: alveoli
- What happens metabolically in alveoli?
- What does this do to the saturation curve?

Answer 8

There is decreased CO2, hence decreased H+ and increased pH, decreased temperature.
Curve shifts to the left - favouring O2 loading

Question 9

Carbon monoxide poisoning:
- Describe its affinity for O2 binding sites of hemoglobin, compared to O2 itself
- 2 effects of CO on oxygen binding to hemoglobin?

Answer 9

Much higher - 200x
Binds in place of oxygen; causes oxygen to bind irreversibly

Question 10

Describe the 3 main ways CO2 is transported in blood, from least to most common.

Answer 10

Dissolved in plasma (5-10%)
Chemically bound to hemoglobin (20-30%)
As bicarbonate ions in plasma (60-70%)

Question 11

Describe the Haldane effect

Answer 11

inding of O2 to hemoglobin in the alveoli reduces the affinity of hemoglobin for CO2 –> unloading of CO2 in alveoli

Question 12

Central pattern generator (creates breathing rhythm)
- Label the parts

Answer 12

Question 13

What are the 2 main motor pathways?

Answer 13

Phrenic nerve to diaphragm
Spinal nerves to intercostal muscles

Question 14

Central chemoreceptors
- Where are they found?
- What do they respond to and how?

Answer 14

Medulla (medullary chemosensitive area)
They measure CO2 via H+
- The central chemoreceptors are sensitive to H+.
- However H+ doesn’t pass easily into the BBB, while CO2 does.
- When CO2 passes the BBB, it releases H+ close to chemoreceptors - which the chemoreceptors detect
Signals to the dorsal respiratory group - initiate inspiration

Question 15

Peripheral chemoreceptors
- Where are they found?
- What do they respond to?
- Where do they project to?

Answer 15

Carotid and aortic bodies
Changes in O2, CO2, H+ (all 3 as not separated by BBB)
Carotid body –> glossopharyngeal nerve –> dorsal respiratory group
Aortic body –> vagus nerve –> dorsal respiratory group

Question 16

What is the most efficient parameter for the respiratory system to monitor and control?

Answer 16

CO2