gas exchange and transport

Question 1

what is total gas pressure

Answer 1

the sum of all partial pressures
Ptotal = P1 + P2 + P3 + … Pn

Question 2

what does partial pressure depend on

Answer 2

Fractional concentration of the gas
Total pressure of gas mixture

Question 3

what percentage of the air is nitrogen

Answer 3

79%

Question 4

what percentage of the air is oxygen

Answer 4

21%

Question 5

how do you calculate partial pressure

Answer 5

Pgas = % gas x Ptotal
e.g.
P air = 760 mm Hg = PN2 + PO2
– PN2 = 0.79 x 760 mm Hg = 600 mm Hg
– PO2 = 0.21 x 760 mm Hg = 160 mm Hg

Question 6

what does fick’s law calculate

Answer 6

rate of diffusion

Question 7

what do the letters stand for in fick’s law

Answer 7

A - surface area
T - thickness
AP - pressure difference
D - diffusion constant
S - gas solubility
MW - melecular weight

Question 8

at rest how long does blood spend in a capillary

Answer 8

0.75 secs

Question 9

what is pulmonary oedema

Answer 9

fluid accumulation in alveoli or interstitial space

Question 10

what are the effects of pulmonary oedema

Answer 10

impairs diffusion
increased work breathing
leakage in unprotected capillaries

Question 11

what are the causes of pulmonary oedema

Answer 11

Increased capillary pressure
– Via left heart failure
Reduced atmospheric pressure

Question 12

what is treatment for pulmoary oedema

Answer 12

Administering oxygen and diuretics

Question 13

how is oxygen transported

Answer 13

dissolved in plasma or bound to haemoglobin

Question 14

what is the function of haemoglobin

Answer 14

to provide greater oxygen carrying capacity

Question 15

how much oxygen does haemoglobin transport

Answer 15

98.5%

Question 16

what is the structure of haemoglobin

Answer 16

Tetrameric globular protein

Question 17

how much haemoglobin is in a person

Answer 17

150 g.litre-1 in men
* 130 g.litre-1 in women (13 g.dl-1

Question 18

how many haemoglobin groups are there

Answer 18

4 (each contain 1 Fe2+ ion)

Question 19

what is the Haemoglobin-Oxygen Dissociation Curve

Answer 19

describes how oxygen binds to hemoglobin in red blood cells and how easily it is released into tissues.

Question 20

what does the Haemoglobin-Oxygen Dissociation Curveshow

Answer 20

S shape shows that as one oxygen molecule binds, haemoglobin’s affinity for oxygen increases, making it easier for additional oxygen to bind.

Question 21

what does the x and y axis on the Haemoglobin-Oxygen Dissociation Curve represent

Answer 21

X-Axis (Pₒ₂ of blood, mm Hg): Represents the partial pressure of oxygen in the blood.

Y-Axis (% Hemoglobin Saturation): Indicates the percentage of hemoglobin molecules bound to oxygen.

Question 22

what is the average resting pressure of oxygen and saturation at Systemic Capillaries

Answer 22

40 mm Hg Pₒ₂, ~75% saturation

Oxygen is released into tissues during rest.

Question 23

what is the average resting pressure of oxygen and saturation at Pulmonary Capillaries

Answer 23

100 mm Hg Pₒ₂, ~97% saturation

Oxygen binds to hemoglobin in the lungs.

Question 24

what factors cause a right shift (Reduced O₂ Affinity) in the Haemoglobin-Oxygen Dissociation Curve

Answer 24

Increased CO₂ (Bohr effect)
Lower pH (more acidic)
Higher temperature

Question 25

what factors cause a left shift (Increased O₂ Affinity) in the Haemoglobin-Oxygen Dissociation Curve

Answer 25

Decreased CO₂ Higher pH (more alkaline) Lower temperature

Question 26

how is carbon dioxide transported

Answer 26

dissolved in plasma- 10% bound to haemoglobin - 30% As bicarbonate ions (in plasma) - 60%

Question 27

what is hypoxia

Answer 27

insufficient cellular O2

Question 28

name the types of hypoxia

Answer 28

Hypoxic Hypoxia (Low Oxygen in Blood) Anemic Hypoxia (Low Hemoglobin or Oxygen-Carrying Capacity) Histotoxic Hypoxia (Cells Can’t Use Oxygen) Circulatory hypoxia (low supply of oxygenated blood)

Question 29

what are Abnormal PaCO2 conditions

Answer 29

Hypercapnia * Excess PaCO2 Hypocapnia * Below normal PaCO2

Question 30

where are respiratory control centres

Answer 30

in brainstem

Question 31

what is in the pons respiratory centre

Answer 31

pneumotaxic center apneustic center

Question 32

what is in the medullary respiratory center

Answer 32

dorsal and ventral respiratory groups

Question 33

what respiratory control centers are in the brainstem

Answer 33

pons respiratory center medullary respiratory center pre-Botzinger complex

Question 34

what are the steps of Respiratory Control During Quiet Breathing

Answer 34

1. chemoreceptors, pons and cortex 2. central pattern generator (medulla) 3. inspiratory neurons in dorsal and ventral respiratory group 4. breathing rhythm

Question 35

what are Pulmonary stretch receptors (Hering-breuer reflex) responsible for

Answer 35

Inflation and deflation

Question 36

what are chemoreceptors responsible for

Answer 36

oxygen and carbon dioxide pressure changes

Question 37

where are peripheral chemoreceptors found

Answer 37

carotid bodies and aortic bodies

Question 38

what is the function of peripheral chemoreceptors

Answer 38

responds to low arterial oxygen pressure responds to high arterial carbon dioxide pressure aortic bodies respond ro low total arterial oxygen content

Question 39

where are central chemoreceptors

Answer 39

medulla

Question 40

what is the function of central chemoreceptors

Answer 40

provide 80% respiratory drive detect changes in CO₂ (carbon dioxide) and pH in cerebrospinal fluid (CSF

Question 41

when does arterial O2 effect ventilation

Answer 41

when PO2 < 60 mm Hg

Question 42

describe carbon transport in haemoglobin

Answer 42

CO₂ binds to the globin (protein) portion of hemoglobin (Hb) to form carbaminohemoglobin (HbCO₂). This binding is reversible, allowing CO₂ to be released in the lungs for exhalation

Question 43

how does the presence of oxygen effect carbon transport

Answer 43

When oxygen levels are high (like in the lungs), O₂ binds to hemoglobin, reducing hemoglobin’s affinity for CO₂. This promotes CO₂ release into the lungs, where it is exhaled.

Question 44

describe carbon transport through bicarbonate ions

Answer 44

Inside red blood cells (RBCs), CO₂ reacts with water (H₂O) under the action of the enzyme carbonic anhydrase, forming carbonic acid (H₂CO₃) Carbonic acid then dissociates into bicarbonate ions (HCO₃⁻) and hydrogen ions (H⁺) Bicarbonate ions leave RBCs and enter plasma in exchange for chloride ions (Cl⁻) to maintain electrical neutrality.

Question 45

describe carbon transport in plasma

Answer 45

CO₂ is directly dissolved in plasma due to its relatively high solubility in water compared to oxygen. This dissolved CO₂ is readily available for diffusion into the lungs for exhalation.