Respiratory System

Question 1

What are the 3 processes involved in exchange of air?

Answer 1

1. pulmonary ventilation - inspiration, and expiration (air exchange btwn the atmosphere and lungs) 2. external respiration (air exchange btwn the lungs and blood) 3. internal respiration. (air exchange btwn blood and ISF/cells).

Question 2

What is pulmonary ventilation the result of?

Answer 2

pressure gradients caused by changes in thoracic cavity volume.

Question 3

What is Boyle’s law?

Answer 3

volume and pressure are inversely proportional. so when volume increases pressure decreases and vice versa, provided the temp and number of gas mols stays constant.

Question 4

What are the pressures involved in pulmonary ventilation? (list)

Answer 4

1. atmospheric pressure (Patm) 2. intrapulmonary pressure (Ppul) 3. intrapleural pressure (Pip)

Question 5

What is Patm?

Answer 5

at sea lvl it’s 760mmHg.

Question 6

What is Ppul?

Answer 6

air pressure inside lungs. btwn breaths it is equal to Patm. during inspiration it decrease and during expiration it increases.

Question 7

What is Pip?

Answer 7

fluid pressure in the pleural cavity which is inbtwn the thoracic wall and lungs. always less than Ppul (has to keep suction) and usually less than Patm - around 4mmHg less = 756 mmHg. Pip usu lower than Patm bc the thoracic wall expands outward and the lungs recoil inward, but they’re held together by plural cavity (like a suction).

Question 8

What are the types of pulmonary ventilation? (List)

Answer 8

1. quiet inspiration 2. forced inspiration 3. quiet expiration 4. forced expiration.

Question 9

What is quiet inspiration?

Answer 9

active process where mms contract. at start Patm = Ppul (760mmHg) no air moves. then, diaphragm and ext intercostal mms contract which increases the vol of thoracic cavity. lungs resist expansion, causing Pip to decrease (bc vol increases since thoracic cavity expands but lungs dont) 756 –> 754. higher pressure difference btwn Ppul and Pip pushes lungs outward, they expand, and Ppul decreases 760 –> 758mmHg. air moves in down P grad until Ppul = Patm. Summary: mms contract –> thoracic cavity expands –> lungs resist –> Pip decreases –> higher P grad btwn Ppul and Pip causes lungs to expand –> ppul decreases to 758 –> change in pressure causes air to move into lungs down its P grad until Ppul and Patm are equal.

Question 10

What is forced inspiration?

Answer 10

diaphragm, ext intercostals, sternocleidomastoids, pectoralis minors, and scalenes contract (active). big increase in vol of thoracic cavity, therefore pressure gradient increases and more air moves into lungs. Summary: mms contract –> big increase in vol of thoracic cavity –> pressure gradient increases (Ppul decreases) –> more air moves into lungs down presure gradient.

Question 11

What is quiet expiration?

Answer 11

passive process. mms relax –> lungs go back to resting size, thoracic cavity volume decreases –> Pip increases 754 –> 756. Ppul increases 760 –> 762 –> air moves out down pressure gradient. Summary: mms relax –> thoracic cavity vol decreases so Pip increases –> lungs go back to resting size (vol decrease) so Ppul increases –> air moves out of lungs down pressure grad to atmosphere.

Question 12

What is forced expiration?

Answer 12

laboured or impeded breathing. relax diaphragm and ext intercostals but contract int intercostals and abdominals (active). Pip increases (thoracic cavity vol decreases). lung vol decreases so Ppul increases and air moves out. Summary: some mms relax other contract –> decrease in thoracic cavity vol and lung vol –> Pip increases and Ppul increases –> air moves out sown pressure grad.

Question 13

What is the stretch in the lungs determined by?

Answer 13

1. compliance - effort needed to stretch lungs. low compliance = much effort, high compliance = low effort. 2. recoil - ability to return to resting size after stretch. bc of elastic CT and surfactant.

Question 14

What is lung collapse prevented by?

Answer 14

1. Pip always below Ppul - pneumothorax. 2. presence of surfactant - lipoprotein/phospholipid mixture. in watery film coating alveoli, decreases surface tension. allows easier stretch of the lungs/ increased compliance. prevents alveolar collapse.

Question 15

What is pneumothorax?

Answer 15

when opening into pleural cavity causes air to move into it which increases Pip and stops suction that was holding lung out, therefore lung collapses while thoracic wall expands. Patm = Ppul = Pip.

Question 16

What is respiratory distress syndromE?

Answer 16

happens in newborns that have inadequate surfactant so alveoli collapse bc they have low compliance so theres high effort leading to exhaustion and death.

Question 17

What is the air flow and airway resistance formula and the variables?

Answer 17

F= ∆P/R. F= air flow ∆P= Patm-Ppul R= airway resistance.

Question 18

What is airway resistance determined by?

Answer 18

diameter of bronchi/bronchioles. asthma, bronchitis, emphysema increase airway resistance. expiration is more difficult than inspiration. bc inspiratory mechanics open airways and expiratory mechanics close airways. so with increase resistance to already constricted bronchioles, expiration is harder. SNS - dilates bronchiolar smooth mm (bronchodilation) PSNS - constricts bronchiolar smooth mm (bronchoconstriction).

Question 19

What are respiratory volumes in pulmonary ventilation and how are they measured?

Answer 19

1 respiration is 1 inspiration and 1 expiration. measured using spirometer.

Question 20

What are the respiratory volumes of pulmonary ventilation?

Answer 20

1. Tidal volume - normal breath. vol of air in quiet inspiration OR quiet expiration ˜500 mL. 2. inspiratory reserve volume - excess air inspired on top of TV in a max/deepest breath (so max inspiration) ˜3000mL. 3. expiratory reserve volume - excess air expired on top of TV in max expiration ˜1200 mL (so max expiration). 4. residual volume - vol of air in lungs left over after ERV/max expiration ˜1200 mL. 5. Minute respiratory volume - TV x RR; 55mL x 12 breaths/min = 6L/min on avg. 6. forced expiratory volume in 1 second - volume expired in 1 sec, with max effort after max inhalation.

Question 21

What are respiratory capacities?

Answer 21

comparing 2 or more respiratory volumes.

Question 22

What are the respiratory capacities?

Answer 22

1. Inspiratory capacity - TV + IRV. 2. vital capacity - largest vol in and out of lungs. TV + IRV + ERV. 3. total lung capacity - either TV + IRV + ERV +RV OR VC + RV.

Question 23

How do you measure %VC?

Answer 23

measure FEV1 while measuring vital capacity and get %VC. always correction for body size. usu FEV1 = ˜80% VC

Question 24

What does measuring %VC allow diagnoses of?

Answer 24

1. obstructive disorders - asthma, ephysema, cystic fibrosis. hard to expire bc obstruct air mvmt in bronchioles, so increased resistance. means that RV will increase and VC will decrease, bc not expiring as much. FEV1 is less than 80% VC. 2. Restrictive disorders - scoliosis, pneumothorax. restrict lung expansion, which affects inspiration bc lung vol cant increase therefore lung pressure cant decrease to allow air to move in. IC is low, VC is low, FEV1 is low but FEV1 = 80% VC (bc theyre both lower).

Question 25

What is external respiration and what is it aided by?

Answer 25

O2 from alveoli to blood and co2 from blood to alveoli. aided by; 1. thin respiratory membrane. 2. large surface area - caps and alveoli. rbcs move single file through caps, so get max rbc exposure to gases. 3. bl velocity is slow compared to gas diffusion rates so rbcs have time to pick up/release gases.

Question 26

What is internal respiration?

Answer 26

involves diffusion of O2 from blood to ISF then cells, and diffusion of CO2 from cells to ISF then blood.

Question 27

What is the partial pressure of gases?

Answer 27

the pressure exerted by a single gas in a mixture of gases. ex. O2 is 21% of air so Po2 is 0.21 x 760 = 160mmHg. pressure gradients promote gas mvmts, gases move from high p to low p.

Question 28

What are the 2 ways O2 is carried (list)?

Answer 28

1. dissolved in plasma and carried through caps. (1.5%) 2. bound to Hb and carried through caps

Question 29

How is O2 dissolved in plasma at lung capillaries (ext resp)?

Answer 29

O2 moves from high P 105mmHg in lungs alveoli to low P 40mmHg in cap.

Question 30

How is O2 dissolved in plasma at tissue capillaries (int resp)?

Answer 30

O2 moves from high P in arterial cap at 95 mmHg to low P in ISF at 40 mmHg and then cells at less than 40 mmHg. when O2 leaves cap the resting venous Po2 changes to 40 mmHg (bc O2 leaving).

Question 31

How is O2 bound to Hb?

Answer 31

each Hb has 4 Fe which each bind 1 mol of O2, so each Hb can have 4 O2. Hb is deoxygenated Hb, add o2 and becomes HbO2 which is oxygenated Hb.

Question 32

What does the O2-Hb dissociation curve show?

Answer 32

relationship btwn Po2 (amount of O2) and saturation of Hb with O2 (Hb%). so shows how much O2 is on Hb for a given amount of dissolved O2.

Question 33

What does the plateau on the O2-Hb dissociation curve signify?

Answer 33

range of P02 at the lungs where Hb picks up O2 , so btwn 60 and 100 mmHg Po2. Hb is 97% saturated. if alveolar Po2 decreases slightly below normal there would be little change to Hb%. at high altitudes if alveolar Po2 is above 60 mmHg Hb carries normal amount of O2.

Question 34

What does the steep portion of the O2-Hb dissociation curve signify?

Answer 34

range of Po2 at the tissues where O2 is unloaded from Hb. at rest; ISF Po2 is 40 mmHg and Hb is 75% saturated. (97 - 75 = 22% O2 unloaded to cells), so most of the Hbs are still oxygenated. high metabolism/exercise; ISF P02 is 20 mmHg and Hb is 40% saturated. 97 - 40 = 57% of O2 unloaded to cells, so much less oxygenated Hb in blood.

Question 35

What happens when the dissociation curve shifts to the right?

Answer 35

for a given Po2 (amount of O2) get less Hb saturation. so O2 either unloads more easily or loads less easily.

Question 36

Why does the shift to the right happen?

Answer 36

increase in Pco2, decrease in pH which is related to Pco2 increase and lactic acid, means decreased ability for o2 to bind to Hb when H+ is bound to globin (Bohr effect). increased temp. all occur when cell metabolism increases (ie exercise - Hb releases more O2).

Question 37

What happens when the dissociation curve shifts to the left?

Answer 37

for a given Po2/amount of o2, get more Hb saturation. so O2 loads more easily or unloads less easily.

Question 38

Why does the shift to the left happen?

Answer 38

decrease in Pco2, increase in pH, decrease in temp. all conditions at the lung (decreased temp due to evaporative cooling).

Question 39

What are the ways that CO2 is carried?

Answer 39

1. dissolved in plasma (8%) 2. bound to Hb (20%) 3. As bicarbonate ions HCO3- (72%)

Question 40

How is CO2 dissolved on the plasma at the lungs during external respiration?

Answer 40

Pathway: blood/capillary --> lungs/alveoli. resting arterial Pco2= 45 mmHg. alveolar Pco2= 40 mmHg (Co2 goes down P grad from bl to alveoli). venous Pco2= 40 mmHg (bc CO2 unloading into lungs so there is less afterwards)

Question 41

How is CO2 dissolved in the plasma at the tissues during internal respiration?

Answer 41

Pathway: cell --> ISF --> capillary/blood. arterial Pco2= 40mmHg (before co2 loaded fro mtissues). ICF Pco2= more than 40 mmHg. ISF Pco2= 40 mmHg. (co2 goes down P grad). venous Pco2= 45mmHg (after co2 loaded into capillary).

Question 42

How is CO2 bound to Hb?

Answer 42

carbamino Hb, CO2 binds to globin. CO2 binds to deoxy Hb better than oxyHb. so at tissues where Hb has been deoxygetnated, CO2 binds readily.

Question 43

How is CO2 transported as bicarbonate ions (HCO3-) inside the RBCs at the tissues?

Answer 43

Rxn to become bicarbonate ion: CO2 + H2O --carbonic anhydrase in rbc--> H2CO3 --> H + HCO3-. H + Hb --> HbH (Hb is a buffer). HCO3- transported out of the RBC in exchange for Cl-, so venous blood rbcs have more Cl-.

Question 44

What is the chloride shift?

Answer 44

when HCO3- leaves the rbc, Cl- comes in to replace it to keep the cell neg. this allows for more HCO3- to be made.

Question 45

How is CO2 transported as bicarbonate ions (HCO3-) inside the RBCs at the lungs?

Answer 45

1. O2 + deoxyHb --> oxyHb/HbO2. so deoxygenated Hb becomes oxygenated. deoxyHb= HbH or HbCO2. since HbO2 binds CO2 and H poorly, CO2 is released (haldane effect) and H is released. so CO2 and H are kicked off Hb bc HbO2 doesnt bind well to them like Hb does. So at lungs Hb becomes oxygenated, letting CO2 loose 2. H + HCO3- --> H2CO3 --carbonic anhydrase--> Co2 + H2O. therefore HCO3- decreases in rbc, so HCO3- that was outside moves into the rbc (down grad) and exchanges with Cl- (reverse chloride shift). CO2 then moves from rbc --> plasma --> alveolar air --> out.

Question 46

What controls respiration? (list)

Answer 46

1. respiratory centres in medulla 2. pontine respiratory centres 3. other factors a. lung stretch receptors b. voluntary control c. chemical control d. other.

Question 47

How do the respiratory centres in the medulla control respiration?

Answer 47

set the rate, depth and rhythm of breathing. 2 groups of neurons. has inspiratory and expiratory neurons.

Question 48

What are the 2 groups of neurons in the respiratory centres in the medulla and what do they do?

Answer 48

1. VRG= ventral respiratory group - generates rate, expiratory and inspiratory neurons. 2. DRG= dorsal respiratory group - receives chemoreceptor input and modifies VRG output.

Question 49

What are the inspiratory neurons and what do they do?

Answer 49

impulses are sent down SC to; a. phrenic nerve which innervates the diaphragm b. thoracic nerves which innervate the external intercostal mms.

Question 50

What are the expiratory neurons and what do they do?

Answer 50

fire to inhibit the inspiratory neurons and expiration occurs passively. (so stop inhalation by turning off inspiratory neurons)

Question 51

How does the medulla affect quiet breathing? What happens if the VRG is damaged?

Answer 51

inspiratory neurons active for around 2 sec = inspiration. expiratory neurons inhibit inspiratory neurons output for around 3 sec = expiration. VRG also active for forced inspiration and expiration to recruit more mms. respiration may cease of VRG damaged or suppressed (ie alc or morphine).

Question 52

What do the pontine respiratory centres do?

Answer 52

work with medulla centres to make breathing smooth. damage= gasping, irregular breathing.

Question 53

How do lung stretch receptors affect breathing?

Answer 53

in smooth mm of bronchi and bronchioles. Hering-Breuer Reflex.

Question 54

What is the Hering-Breuer reflex?

Answer 54

receptors are overstretched on inspiration --> impulses via vagus nerve --> inhibit inspiratory neurons --> relaxes mms (expiration - prevents over inflation).

Question 55

How does voluntary control affect breathing?

Answer 55

primary motor cortex signals to skel mms involved in breathing (via corticospinal pathway) so bypasses medulla. if the medulla is damaged a person must consciously remember to breathe. if a person holds their breath - Pco2 increases and eventually he medulla will override voluntary control and the person iwll inspire.

Question 56

What are the types of chemoreceptors (list)?

Answer 56

1. peripheral chemoreceptors - carotid and aortic bodies 2. central chemoreceptors - medulla oblongata (dominant control)

Question 57

How do the peripheral chemoreceptors affect breathing?

Answer 57

weakly sensitive to Pco2, but very sensitive to H+. so if bl H+ increases which means pH decreased, the ventilation rate will increase and vice versa (ie. H+ decreases= vent rate decrease). since bl is buffered it takes a large change in H+ to change the pH. Po2 - stimulates receptors when Po2 reaches around 50-60 mmHg (end of plateau) which is an emergency situation. Po2 decreases due to lung disease or low atm Po2

Question 58

How do central chemoreceptors affect breathing?

Answer 58

respond indirectly to arterial Pco2. resting arterial Pco2 = 40 mmHg. CO2 crosses the bl brain barrier easily, but H+ and HCO3- do not. in cerebrospinal fluid - CO2 + H2O --carbonic anhydrase--> H2CO3 --> H + HCO3-. so H is detected. CSF is poorly buffered so small change will stimulate a response. so will know that theres too much CO2 if theres lots of H bc CO2 is being converted.

Question 59

What are other factors that affect ventilation?

Answer 59

1. increased temp --> increased vent. 2. decreased temp --> decreased vent. 3. increased emotion --> increased vent 4. increased proprioceptor discharge --> increased vent. 5. sudden increase BP --> decreased vent 6. sudden decrease in BP --> increase vent 7. sudden pain --> stops vent 8. chronic pain --> increased vent 9. sudden cold --> stops temporarily 10. stretching anal sphincter --> increased vent.

Question 60

What is hyperventilation?

Answer 60

too much CO2 released. decreases arterial Pco2 which causes cerebral vasocon (intrinsic metabolic response). vasocon reduces Po2 in brain (bc less bl and O2 to brain) and get dizziness.

Question 61

What is hypoventilation?

Answer 61

not enough Co2 released. increases arterial Pco2 which results inmore free H in blood leads to acidosis (decrease in pH)

Question 62

What is carbon monoxide?

Answer 62

produced by the incomplete burning of gas. (cars, furnaces).

Question 63

What is carbon monoxide poisoning?

Answer 63

CO binds 210x more strongly to Fe in Hb compared to O2. Hb with CO bound to it is carboxyhemoglobin (HbCO). so what happens is the total O2 carries by Hb decreases (bc its taken up by CO). but theres no change in the Po2 or Pco2, so vent rate doesnt change. the body is suffocating but the NS doesnt detect a change in amount of O2 carries on Hb, it can only detect changes to Po2 and Pco2. Summary: less HbO2, bc of more HbCO, so not enough O2 getting to tissues, but body doesnt know bc amount of O2 in the plasma is the same.