Gas Exchange And Control Of Breathing

Question 1

What is the atmospheric pressure at sea level?

Answer 1

760mmhg

Question 2

What is Dalton’s law of partial pressures?

Answer 2

In a mixture of gasses each gas will contribute to the total pressure in direct proportion to it’s percentage in the mixed gas

Question 3

What happens to CO2 as atmospheric air enters the alveoli?

Answer 3

PCO2 increases due to the mixing with CO2 from the blood

Question 4

What happens to the partial pressure of oxygen as air enters the alveoli?

Answer 4

PO2 decreases due to the increase of CO2 and water

Question 5

What happens to partial pressure of O2 when air leaves the alveoli?

Answer 5

PO2 increases due to mixing with dead space air

Question 6

What happens to the partial pressure of CO2 when air leaves the alveoli?

Answer 6

PCO2 decreases due to mixing with dead space air

Question 7

What happens in alveolar gas exchange?

Answer 7

As blood flows past alveoli pressures equiliberate

Question 8

What is the alveolar partial pressure of CO2?

Answer 8

40 mmHg

Question 9

What is the alveolar pressure of O2?

Answer 9

105 mmHg

Question 10

What is the effect of a diffusion barrier on gas exchange?

Answer 10

An increased diffusion barrier would slow the exchange of oxygen but not CO2 because CO2 is more soluble than oxygen

Question 11

Does ventilation differ throughout the lungs?

Answer 11

Yes, some areas get more oxygen than others

Question 12

What is ventilation perfusion mismatch?

Answer 12

Sometimes there are regions of the lung where there is an imbalance between how well its ventilated and how much blood flow it gets

Question 13

What is high ventilation/pefusion mismatch?

Answer 13

Not enough blood flow to a well ventilated area. Common cause is pulmonary embolism

Question 14

What is low ventilation/perfusion mismatch?

Answer 14

Not enough ventilation of an area of good blood flow

Question 15

How do you correct high ventilation/perfusion mismatch?

Answer 15

Arteriole relax to allow blood flow to the well ventilated areas

Question 16

How do you correct low ventilation/pefusion mismatch?

Answer 16

Arteriole constrict to divert blood elsewhere

Question 17

How is carbon dioxide carried in the blood?

Answer 17

2% dissolved, 70% as bicarbonate and 22% bound to hemoglobin

Question 18

What is carbonic anhydrase?

Answer 18

An enzyme that assists conversion of carbon dioxide and water into carbonic acid, protons and bicarbonate

Question 19

How is oxygen carried in the blood?

Answer 19

1.5% dissolved and 98% bound to hemoglobin

Question 20

What are the properties of hemoglobin?

Answer 20

• binds CO better than O2
• binds up to 4O2
• O2 binding leads to more O2 binding
• binding with O2 can be reversed
• binds O2 in relation to partial pressure

Question 21

What is cooperativity?

Answer 21

More oxygen binding leads to more oxygen binding

Question 22

What does the flat top of the hb dissociation curve mean?

Answer 22

Allows for lots of 02 pick up with respiratory failure

Question 23

What does the steep slope of the hb curve mean?

Answer 23

Allows tissue to pull off as much oxygen as needed

Question 24

How much O2 from Hb is released to tissues at rest?

Answer 24

25%

Question 25

How much O2 from Hb is released to tissues exercising?

Answer 25

65%

Question 26

What do tissues with a high metabolism do to the Hb-dissociation curve?

Answer 26

Shifts it to the right due to increase of carbon dioxide, decrease ph and increase temperature

Question 27

What is the purpose of breathing?

Answer 27

Maintain arterial blood gas levels

Question 28

What does the dorsal respiratory group do?

Answer 28

Sends bursts of neural activity to the muscles of inspiration during quiet breathing

Question 29

What does the ventral respiratory group do?

Answer 29

Sends outputs to accessory muscles during forced breathing

Question 30

Where are central chemoreceptors located?

Answer 30

Ventral surface of the medulla

Question 31

What do central chemoreceptors do?

Answer 31

Sense CSF H+ levels which are influenced by carbon dioxide. They provide input to respiratory centres to maintain carbon dioxide at 40 mmHg

Question 32

Where are peripheral chemoreceptors located?

Answer 32

Carotid bodies and aortic arch

Question 33

What do peripheral chemoreceptors do?

Answer 33

Ensures alveolar ventilation is at an appropriate level for the amount of tissue respiration occurring. They monitor PaCO2, PaI2 and arterial pH levels

Question 34

What are peripheral chemoreceptors stimulated by?

Answer 34

Increased PaCO2, decreased arterial pH and decreased PaO2

Question 35

What does the medulla control?

Answer 35

Muscles of breathing

Question 36

What does the pons control?

Answer 36

Smoothness, intensity and frequency via influence on dorsal and ventral respiratory groups

Question 37

What happens when barometric pressure increases?

Answer 37

Volume of gas contracts

Question 38

What happens when barometric pressure decreases?

Answer 38

The volume of gas expands

Question 39

Where in the body is oxygen content highest and lowest?

Answer 39

Highest in alveoli and lowest at the tissues where they're consuming it

Question 40

Why is a high v/q ratio at the apex of the lung?

Answer 40

When you breathe in most of the air goes to the apex first because it's closer to the primary bronchi

Question 41

Why is low v/q ratio at the base of the lungs?

Answer 41

Blood has an easier time getting to the base of the lung than air that has to go through all the bronchi

Question 42

What is carbamino hemoglobin?

Answer 42

Compound of carbon dioxide and hemoglobin, when it binds and is transported by hemoglobin

Question 43

What structure modifies breathing patterns?

Answer 43

The brainstem

Question 44

What is the pontine respiratory group?

Answer 44

Acts as an off switch controlling the point at which inspiration stops and therefore determining the depth and frequency of breathing

Question 45

What does the dorsal respiratory group do in inspiration?

Answer 45

Diaphragm and intercostal muscles contract leading to quiet inspiration

Question 46

What does the dorsal respiratory group do in expiration?

Answer 46

Diaphragm and external intercostal relax followed by elastic recoil of lungs which lead to normal quiet exhalation

Question 47

How does high blood pressure affect ventilation and gas exchange?

Answer 47

High bp can rupture the small vessels of the lungs resulting in an inadequate supply of oxygen and carbon dioxide (pulmonary hypertention)