Respiratory system

Question 1

external respiration:

Answer 1

pulmonary ventilation + pulmonary diffusion

Question 2

internal respiration:

Answer 2

transport to and from tissue + capillary diffusion and exchange

Question 3

pleural membrane:

Answer 3

makes the lungs ‘stick’ to the inside of the rib cage - the lungs are inflated and compressed with each breath (ventilatory cycle)

fluid filled space between lungs and ribs prevents the lungs collapsing

Question 4

inspiration / inhalation:

Answer 4

active process:

1. external intercostal muscles contract to raise the rib cage and move it outwards - increases thorax volume
2. diaphragm contracts to becomes flatter - increases thorax volume
3. Boyle’s law: if volume increases, pressure must decrease = pressure in chest cavity falls below atmospheric pressure
4. air flows into the lungs down pressure gradient

Question 5

pressure change during inhalation:

Answer 5

at rest: 2-3mmHg

during heavy exercise: 80-100 mmHg

Question 6

expiration / exhalation:

Answer 6

passive process:

1. diaphragm and intercostal muscles relax and ribs fall
2. volume of the chest cavity decreases
3. Boyle’s law: pressure in lungs increases above atmospheric pressure
4. air flows out of lungs down a pressure gradient

Question 7

forced exhalation - during exercise:

Answer 7

active process: quicker than natural expiration

1. contraction of the intercostal muscles cause the rib cage to move down and inwards
2. volume of the chest cavity decreases
3. increased pressure in lungs - air flows out of lungs
4. diaphragm muscles relax and contraction of the abdominal wall raises the diaphragm

Question 8

tidal volume =

Answer 8

volume moving in and out of lungs during each breath

Question 9

vital capacity =

Answer 9

the greatest amount of air that can be expired after maximal inspiration

Question 10

residual volume =

Answer 10

amount of air remaining in lungs after maximal expiration

Question 11

total lung capacity =

Answer 11

sum of vital capacity and residual volume

average = 4-6L of air

Question 12

bronchoconstriction can be caused by…

Answer 12

cold, allergens, parasympathetic activity

Question 13

bronchodilation can be caused by…

Answer 13

sympathetic activity, exercise, beta2-adrenoceptor agonists (salbutamol)

Question 14

Dalton’s law =

Answer 14

total pressure of a mixture of gases equals the sum of the partial pressure og the individu gases in that mixture

Question 15

partial pressure =

Answer 15

contribution of individual gas to the total pressure

Question 16

gaseous exchange at the alveoli:

Answer 16

gases move down their pressure gradient

PO2 in pulmonary arterial blood is lower than in the alveoli = O2 diffuses into blood

opposite for CO2

Question 17

volume of gas transferred =

Answer 17

proportional to the (area over the thickness), multiplied by the (diffusion constant) and multiplied by the (difference in partial pressure)

Question 18

transport of O2 in the blood:

Answer 18

2% dissolved in the blood

98% combined with haemoglobin (oxyhaemoglobin)

Question 19

oxyhaemoglobin saturation curve:

Answer 19

oxygen loading at vessels near lungs - saturation stays high due to high O2 conc.

oxygen unloads at tissue - saturation changes quickly with even small changes in PO2

as PO2 increases, haemoglobin collects more O2 = higher saturation

Question 20

transport of CO2 in the blood:

Answer 20

7-10% dissolved in plasma
10-20% combined with haemoglobin (carbaminohaemoglobin)
70-80% dissolved in blood as bicarbonate ions (hydrogencarbonate ions)

Question 21

CO2 in blood as bicarbonate ions:

Answer 21

CO2 + H2O -> H2CO3 -> H+ + HCO3-

CO2 in plasma diffuses into rbc - combines with H20 to form carbonic acid catalysed by carbonic anhyrdase - this dissociates to form hydrogen ions and hydrogencarbonate ions - hydorgencarbonate ions diffuse into plasma (charge is maintained by chloride shift)

Question 22

O2 within the muscles saturation curve:

Answer 22

steep saturation curve for myoglobin means that there is a very efficient delivery of O2 to the mitochondria

myoglobin has a higher affinity for O2 than haemoglobin - haemogloin passes O2 to myoglobin in the muscle

Question 23

regulation of pulmonary ventilation:

Answer 23

mostly neuronal control but can also be voluntary control (e.g. holding breath)

respiratory control centres located in medulla oblongata and pons

Question 24

regulation of inspiration:

Answer 24

stimulus = chemoreceptors detect changes in PO2, PCO2 and pH + signals from active muscles stimulate the inspiratory centre

response = external intercostal muscles contract to increase thoracic volume

Question 25

regulation of expiration:

Answer 25

stimulus = the stretching of the lungs triggers the expiratory centre

response = intercostal and abdominal muscles relax or contract to decrease thoracic volume

Question 26

pulmonary ventilation increases on exercise to match changing O2 demand:

Answer 26

• the initial change in ventilation rate is due to neural sympathetic drive
• later changes occur due to changes in chemical composition of the blood gases/pH = breath more
• ventialtion response may also increse in anticipation of exercise (try to control breathing) = overcompensation
• as soon as respiratory rate increases lactate forms

Question 27

overcompensation leads to…

Answer 27

hyperventilation (breathing too much)

Question 28

ventilatory equivalent for oxygen:

Answer 28

volume of air expired divided by volume of O2 consumed

varies little over a range of exercise = ventilation and O2 demand are well matched

Question 29

respiratory quotient (RQ values)/ respiratoy exchange ratio (RER):

Answer 29

RQ = VCO2 (eliminated)/VO2 (consumed)

values of oxidation:

• carbohydrate = 1.0
• fat = 0.7
• protein = inbetween (0.8/0.9)

Question 30

ventilatory threshold:

Answer 30

ventilation increases disproportionately to O2 consumption = ventilatory threshold

initially believed to be due to increase in blood lactate stimulating ventilation centres in brain

now believed to be due to needing to remove excess O2

could be due to overcompensation of breathing during exercise

Question 31

respiratory limitations to performance:

Answer 31

as rate and depth of ventilation increases so does energy consumption of the muscles involved

use of energy for breathing doesn’t slow down exercise - respiratory muscles have high aerobic capacity

Question 32

respiratory disorders that may limit the ability to exercise:

Answer 32

asthma

fibrosis

chronic obstructive pulmonary disease

Question 33

asthma =

Answer 33

constriction of airways due to allergens or exercise

Question 34

fibrosis =

Answer 34

lungs have fibrous tissue laid down - stiffer lungs, less elastic = difficulty breathing

Question 35

vascular disorders that may limit the ability to exercise:

Answer 35

pulmonary hypertension

clots/thrombosis = ischemia

arterial occlusion

Question 36

pulmonary hypertension =

Answer 36

high blood pressure in arteries in lungs

poor gaseous exchange

thickenning of pulmoanry arteris = become less compliant so cannot stretch as easily during systole

• reduce blood flow
• more work for right side of heart = heart failure

Question 37

arterial occlusion =

Answer 37

caused by atherosclerosis - reduced blood flow to a limb (ischemia) = reduced metabolites/O2

can cause claudication (ischemic muscle pain) during exercise amd is relieved after rest

can result in gangrene if ischemia is prolonged = amputation of limb is needed

Question 38

ischemia =

Answer 38

inadequate blood supply to a part of the body