Respiratory Physiology

Question 1

what is internal respiration

Answer 1

intracellular mechanisms which consume O2 and produce CO2

Question 2

what is external respiration

Answer 2

sequence of events that lead to the exchange of O2 and CO2 between external environment and cells of the body

Question 3

four steps of external respiration

Answer 3

1. ventilation between atmosphere and alveoli
2. O2 and CO2 exchange between alveoli and blood
3. transport of O2 and CO2 between lungs and tissues
4. exchange of O2 and CO2 between blood and tissues

Question 4

what is ventilation?

Answer 4

mechanical process of moving air between atmosphere and alveoli

Question 5

pressure change for ventilation to occur? (boyle’s law)

Answer 5

intra alveolar pressure must be less than atmospheric pressure

Question 6

2 forces that hold thoracic wall and lungs close

Answer 6

1. intrapleural fluid cohesiveness

2. negative intrapleural pressure (lungs force out, chest forced in)

Question 7

muscles of inspiration and function

Answer 7

• external intercostal muscles, elevates ribs and sternum

- diaphragm, lowers to increase size of thoracic cavity

Question 8

expiration - passive of active?

Answer 8

passive

Question 9

what abolishes the transmural pressure gradient?

Answer 9

pneumothorax

Question 10

what causes lungs to recoil?

Answer 10

1. elastic connective tissue

2. alveolar surface tension

Question 11

what is alveolar surface tension?

Answer 11

water and air molecules are attracted in the alveoli, which produces a force that resists stretching

Question 12

what is surfactant and what does it do?

Answer 12

• it is secreted by type II alveoli

- it lowers alveolar surface tension, as it mixes with water molecules lining the alveoli

Question 13

What does LaPlace’s law state?

Answer 13

smaller alveoli have a higher tendency to collapse

Question 14

what is alveolar interdependence?

Answer 14

if an alveolus begins to collapse, surrounding stretch to pull the collapsing one open

Question 15

what does parasympathetic stimulation do to the airways?

Answer 15

causes bronchoconstriction

Question 16

what does sympathetic stimulation do to the airways?

Answer 16

causes bronchodilatation

Question 17

what is pulmonary compliance?

Answer 17

this is a measure of how much effort goes into stretching or distending the lungs

Question 18

what is alveolar ventilation?

Answer 18

the volume of air exchanged between the atmosphere and alveoli per minute

Question 19

what is pulmonary ventilation?

Answer 19

the volume of air breathed in and out per minute

Question 20

what is alveolar dead space?

Answer 20

this is ventilated alveoli which are not adequately perfused with blood

Question 21

effect on systemic arterioles in decrease/increase of O2?

Answer 21

vasodilation/vasoconstriction

Question 22

effect on pulmonary arterioles in decrease/increase of O2?

Answer 22

vasoconstriction/vasodilation

Question 23

four factors influencing rate of gas exchange across alveolar membranes?

Answer 23

1. partial pressure gradient for O2 and CO2
2. diffusion coefficient for O2 and CO2
3. surface area of alveolar membrane
4. thickness of alveolar membranes

Question 24

how is oxygen present in the blood?

Answer 24

• bound to Hb

- physically dissolved

Question 25

what is the Bohr Effect?

Answer 25

• shift of the sigmoid Hb saturation curve to the right

- occurs in active tissues, where increased release of O2 is needed

Question 26

what four factors increase the release of O2 at tissues?

Answer 26

• increased PCO2
• increased H+ conc
• increased temp
• increased 2,3 BDP

Question 27

what does foetal haemoglobin do to the Hb curve?

Answer 27

shifts to the left (higher affinity for O2)

Question 28

how is CO2 transported in the blood?

Answer 28

• in solution (10%)
• as bicarbonate (60%)
• as carbamino acid (30%)

Question 29

what is the haldane effect?

Answer 29

removing O2 from Hb increases the ability of Hb to pick up CO2 and H+

Question 30

where is rhythm generated in the brain?

Answer 30

Pre-Botzinger complex in the medulla (causes inspiration), by stimulating dorsal

Question 31

where is active expiration generated in the brain?

Answer 31

ventral neurones, which are stimulated by increased firing from dorsal

Question 32

what, when stimulated, terminates inspiration?

Answer 32

pneumotaxic centre (in the pons)

Question 33

what, when stimulated, prolongs inspiration?

Answer 33

apneustic centre

Question 34

where are peripheral chemoreceptors?

Answer 34

carotid and aortic bodies

Question 35

what do peripheral chemoreceptors do?

Answer 35

sense tension of O2, CO2 and H+ in the blood

Question 36

where are central chemoreceptors?

Answer 36

situated near the surface of the medulla in the brainstem

Question 37

what do central chemoreceptors do?

Answer 37

they respond to H+ of the cerebrospinal fluid

- only CO2 diffuses across the blood/brain barrier

Question 38

what effector causes the hypoxic drive of respiration?

Answer 38

peripheral chemoreceptors, when PO2 falls below 8.0kPa

Question 39

what effector causes the H+ drive of respiration?

Answer 39

peripheral chemoreceptors (cause hyperventilation, as there will be increased CO2)