Gas Exchange and Respiratory Control

Question 1

What 3 cell types make up alveoli?

Answer 1

• Type 1 pneumocytes (majority)
• Type 2 pneumocytes (septal cells)
• Alveolar macrophages (dust cells)

Question 2

what is the purpose of type 1 and type 2 pneumocytes?

Answer 2

type 1 - thin so gas exchange occurs through them
Type 2 (septal) - secrete pulmonary surfactant to line the alveoli preventing lungs from collapsing and alveoli sticking together

Question 3

What is the job of dust cells?

Answer 3

To remove any dust particles, and to clean the lungs

Question 4

List a few important properties of an alveolus:

Answer 4

• surrounded by elastic fibres to recoil
• have continuous blood supply via extensive capillary network
• thin walls made of type 1 pneumocytes
• large surface area
• surfactant

Question 5

what category of cells are type 1 pneumocytes?

Answer 5

• simple squamos

Question 6

What is Henry’s law?

Answer 6

As pressure increases by a constant, the solubility of the gas also increases by the same constant so linear

Question 7

What 5 factors cause efficient gas exchange?

Answer 7

1 - Large difference in partial pressures  across membrane
2 - short distance for gas exchange
3 - Large surface area
4 - O2 and CO2 are lipid soluble
5 - Coordinated blood flow and air flow

Question 8

What is the difference between external and internal respiration?

Answer 8

• External is everything where air is in contact with the external environment and the pulmonary circuit
• Internal is the systemic circuit and when O2 is taken up by body cells

Question 9

How does the majority of our O2 get transported?

Answer 9

• In RBC’s bound to haemoglobin

- a little is just diffused into blood plasma

Question 10

What factors affect the binding of O2 to Haemoglobin?

Answer 10

• Temperature
• blood PH
• Pp O2
• Other metabolic activities

Question 11

RBCs generate ATP by glycolysis and what 2 other biproducts?

Answer 11

• Lactic Acid

- BPG (2,3 Bisphosphoglycerate)

Question 12

What does BPG do?

Answer 12

• BPG lowers haemoglobins affinity for O2 causing it to release it

Question 13

What causes a rise in BPG levels?

Answer 13

• when blood pH increase

- when stimulated by hormones

Question 14

How does temperature affect haemoglobins affinity for O2? and why?

Answer 14

• a higher temp lowers haemoglobins affinity for O2
• so when blood reaches tissues generating lots of heat, and demand more O2, the higher temp causes O2 to unload from the haemoglobin
• Curve shifts right

Question 15

How does pH affect haemoglobins affinity for O2? and what is this called?

Answer 15

• Bohr affect
• As blood becomes more acidic (pH lowers), the curve shifts right
• More acidic blood has a lower affinity for oxygen

Question 16

what is the catalyst and the product of CO2 dissolving in the blood?

Answer 16

• CO2 dissolves into the water of the blood
• forming Carbonic acid
• catalysed by carbonic anhydrase

Question 17

What are the 3 methods of CO2 transport on the blood?

Answer 17

• Dissolve in plasma
• Bind to haemoglobin
• Convert to carbonic acid

Question 18

what are the 2 respiratory centres of the brain?

Answer 18

• The Pontine Respiratory centre

- The Medullary respiratory centres

Question 19

what is the job of the pontine respiratory centre?

Answer 19

• interacts with the medulla to smooth out respiration

Question 20

What makes up the Medullary respiratory centres?

Answer 20

• Ventral and dorsal group

Question 21

what is the job of the pontine respiratory centre?

Answer 21

to interact with the medulla to smooth out respiration

Question 22

what makes up the brainstem?

Answer 22

• the pontine respiratory centre

- the medullary respiratory centre (dorsal and ventral)

Question 23

what are peripheral chemo receptors and where are they found?

Answer 23

• found in the carotid and aortic bodies of the heart

- detect chemical changes in the blood

Question 24

describe the chain of events that take place when the aortic body detects a change in blood pH

Answer 24

• peripheral chemoreceptors are stimulated
• which stimulates or suppresses the pontine respiratory centre
• this goes on to stimulate the dorsal then ventral group of the medullary respiratory centre

Question 25

where else can we find chemoreceptors?

Answer 25

the medulla

muscles and joints

Question 26

what are the 2 centres in the pons>

Answer 26

• the apneustic centre

- the pneumatoxic centre

Question 27

what is the purpose of the apneustic and pneumatoxic centres of the Pons?

Answer 27

• peripheral chemoreceptors relay information to them
• pneumatoxic centre inhibits deep inspiration
• apneustic centre triggers deep inspiration
  they both respond from rhythmicity centres regulating breathing rate, rhythm and depth of inspiration

Question 28

describe the effect that the pneumatoxic centre has on the apneustic centre

Answer 28

• the pneumatoxic centre releases pneumatoxic output which inhibits the apneustic centre
• the pneumatoxic centre promotes passive exhalation (short and fast)
• the apneustic centre promotes deep and slower inhalation

Question 29

describe the relationship between the apneustic centre and the dorsal respiratory group

Answer 29

• the apneustic centre stimulates the dorsal respiratory group which stimulates forced inhalation

Question 30

what are the roles of the respiratory centres of the Medulla Oblongata?

Answer 30

• to establish pace and depth of respiration

Question 31

function of the dorsal respiratory group

Answer 31

• this is an inspiratory centre

- functions in quiet forced breathing

Question 32

function of the ventral respiratory group

Answer 32

• this is a inspiratory and expiratory centre

- functions in only forced breathing

Question 33

• What is active during passive breathing?

Answer 33

• the dorsal respiratory group but only during inspiration, during exhalation it is inhibited

Question 34

• what is active during forced breathing

Answer 34

• during inhalation, DRG and inspiratory centre of VRG are active
• during exhalation, VRG expiratory centre is active

Question 35

what are baroreceptors and where can they be found?

Answer 35

• stimulated by blood pressure

- in aortic and carotid sinuses or bodies

Question 36

What are stretch receptors?

Answer 36

receptors in walls of lungs that respond to a change in lung volume

Question 37

name the 2 types of mechanoreceptors

Answer 37

• baroreceptors

- stretch receptors

Question 38

What is the inflation reflex?

Answer 38

• as the lung volume increases the DRG (inspiratory centre) is inhibited
• and the VRG (expiratory centre) is stimulated
• preventing over expansion of the lungs

Question 39

what is the deflation reflex?

Answer 39

• as lung volume decreases the inspiratory centres are stimulated
• and the expiratory centre of the VRG is inhibited

Question 40

what 2 cranial nerves carry information from chemoreceptors

Answer 40

• CN 9 (glossopharyngeal) and CN 10 (Vagus)

Question 41

what things are chemoreceptors sensitive to?

Answer 41

• PpO2, PpCO2, pH, CSF

Question 42

summary of things that affect respiration

Answer 42

• pace is established by respiratory centres in the pons and medulla
• pace is modified in response to input from chemo, baro and stretch receptors
• respiratory activity can be interrupted by protective reflexes and voluntary control

Question 43

what changes in respiration occur at birth

Answer 43

• pulmonary vessels are collapsed, lungs contain no air

- after birth the surface tension in lungs is overcome so inflates

Question 44

what changes in respiration occur due to old age

Answer 44

• elastic tissue deteriorates
• arthritic changes and less flexibility
• emphysema from smoking