Respiratory systems

Question 1

factors on rate of diffusion

Answer 1

• partial pressure gradient
• size of gas molecules
• temperature
• solubility of gas in liquid
• thickness of gas exchange surface
• surface area of gas exchange surface

Question 2

fick’s law

Answer 2

Q = D A (Pe-Pi) / L

Q= rate of diffusion
D= diffusion coefficient
A= surface area
P-P= partial pressure difference
L= thickness of barrier

Question 3

o2 availability

Answer 3

air is a better respiratory medium than water
-more o2 per unit volume
-o2 diffuses faster
higher temps reduce o2 solubility
o2 availability decreases with altitude

Question 4

gas exchange (intro)

Answer 4

external respiration = delivery + removal of gases to and from tissues and cells. intake of atmospheric o2 for cellular metabolism
passive, governed by diffusion
driven by partial pressure membranes
primary role to meet metabolic demands of organism - via specialised body surfaces + mechanisms for ventilation + perfusion

Question 5

liquid environments

Answer 5

gills - highly branched + folded extensions (evaginations, delicate and vunerable)
maximise SA
thin tissue - minimise diffusion pathway length
new medium flows continuously over suface

Question 6

gaseous environments

Answer 6

internal respiratory organs (invaginations, protected)
thin tissue
branching - maximise internal SA
lungs elastic- increase capacity

Question 7

mammalian airways

Answer 7

trachea-bronchi-bronchioles-alveolar ducts- alveolar sacs

trachea contains cartilaginous rings to hold open
23 generations of airway divisions
alveoli- specialised surfaces where gas exchange takes place (respiratory zone)
rest of lung facilitates (dead space)
warm + humidify air, remove foreign material, transfer gases+ filtrate

Question 8

tidal ventilation

Answer 8

incoming air mixes with ‘used’ gas
alveoli provide reservoir of o2 (2L after expiration)

vital capacity = maximum
tidal volume = normal amount

Question 9

alveolar ventilation rate

Answer 9

ventilates both dead space + alveoli

Ve = Vd + Va

Ve = minute ventilation of entire lung
Vd = ventilation of dead space
Va = amount of fresh air available for gas exchange

Va = (TV - dead space) X breathing rate
can be increased by ^TV or ^respiratory frequency

Question 10

respiratory system at rest

Answer 10

lungs dont empty entirely
lungs encased in 2 pleural membranes
intrapleural space - fluid filled
-pressure lower than atmospheric pressure
-pressure gradient across alveoli to prevent collapse
lungs expans to fill thoracic cavity + maintain functional residual capacity

Question 11

inspiration

Answer 11

active process
1) volume of thorax increases
-diaphragm contracts + flattens
-external intercostal muscles contract, move ribcage up +out
2) pressure in interpleural space falls (boyle’s law p1v1=p2v2)
3) alveoli expand
-pressure drops
-alveolar pressire<atmospheric
4) air flows into lungs until alveoli = atmospheric pressure

Question 12

expiration

Answer 12

largely passive process
1) elastic recoil of lungs + chest wall reduces volume of thorax
2) intrapleural pressure rises
3) alveoli recoils
4) alveolar pressure> atmospheric
5) air expelled from lungs

can be active during forced expiration
internal intercostals and abdominal muscles contract (accessory muscles)

Question 13

compliance

Answer 13

how effective lungs are
C = change in volume/change in pressure
2 rest points -FRC and peak of inspiration

reduced when surface tension increased (lack surfactant) or elasticity impaired

Question 14

deviation in compliance slope

Answer 14

during inspiration - curves right as resistive forces oppose airflow (airway resistance, pulmonary tissue resistance (friction miminised by pleural fluid), intertia of air + tissues)

during expiration- curves left as resistive forces assist airflow
(elastic recoil, alveolar surface tension)

Question 15

ventilation in birds

Answer 15

posterior + anterior air sace
lung volume changes less than mammals
moves through lungs from interconnected air sacs (do not participate in gas exchange)
unilateral air flow
higher ppO2 than mammalian

Question 16

ventilation in frogs

Answer 16

breathe in and fill glottis with air
air forced into lungs
some circulation of air to promote
lungs emptied by abdominal contraction

Question 17

ventilation in insects

Answer 17

airwars penetrate each body segment (spiracles), allow diffusion
abdominal muscles ‘pump’ air through tracheae
relatively low pressure gradient

Question 18

water movement across gills

Answer 18

energy required to pump water across gills
water ‘pulled# across gills when opercular cavity expands + opercular flaps open
water ‘pushed’ over gills when fish opens mouth

Question 19

airflow through tubes

Answer 19

laminar flow : slow flow rate and parallel stream lines
turbulent flow: high flow rate, disorganised stream lines but net movement still forward
transitional flow: intermediate flow rate, eddy cuurents

flow rate (V) = pressure gradient / airway resistance

Question 20

poiseuille’s law

Answer 20

resistance directly proportional to 1/r^4

small changes in radius have drastic effect on resistance

Question 21

airway resistance

Answer 21

70% in trachea + bronchial tree
30% in upper airways (nose, larynx, pharynx)

airway resistance decreases with increasing lung volume

most of the work done in inspiration is overcoming R
greater R = slower PEFR

Question 22

factors affecting airway resistance
(radical traction, dynamic compression, bronchial smooth muscle tone, inflammation+mucus)

Answer 22

radical traction : as lung expands, connective tissue pulls on bronchioles = diameter expands = resistance falls

dynamic compression : occurs at low lung volume or forced expiration, airways compressed + may close

bronchial smooth muscle : affected by NS/hormones/external factors
bronchioconstriction = increases R(aw)
bronchiodilation = lowers R(aw)

inflammation + mucus : signifinantly increase resistance as airways narrowed and mucus can accumulate

Question 23

elastic properties of lung

Answer 23

tendency to recoil back to resting volume
elastin + collagen fibres in alveolar wall, around vessels + bronchi
-allow distension but recovers

Question 24

surface tension in alveoli

Answer 24

lined with fluid - air-fluid interface created potential problems
-attractive forces oppose expansion + promotes collapse of smaller alveoli = reduced SA

Question 25

surfactant

Answer 25

lowers surface tension phospholipoprotein secreted by type 2 alveolar cells prevents collapse at low pressure present in all air breathing animals

Question 26

specialisation of pulmonary circulation

Answer 26

gas composition of blood vessels opposite (pulmonary vein oxygenated and artery deoxy) lungs recieve all blood pressures very low arterial walls thin + little smooth muscle vascular resistance very low -vascular resistance = (input - output pressure) / blood flow

Question 27

influence of gravity

Answer 27

as move from base to apex: decreasing perfusion (blood flow) decreasing ventilation (air flow) alveoli at base smaller at FRC - better air flow as can expand more blood pressure greater at base - more powerful effect as low pressure system affected by posture, excersise + disease

Question 28

Va : Q

Answer 28

ventilation to perfusion ratio changes across lung local blood flow falls 3x faster than ventilation (as go base -> apex) ideal Va:Q = 1 (most efficient gas exchange in middle of lung) can vary 0-infinity (0= blood passing through lungs + not coming into contact with alveolar air)

Question 29

Va:Q matching

Answer 29

important to optimise gas exchange modulation of blood flow rather than ventilation -vasoconstriction by low pO2 (hypoxia) = blood directed away from poorly ventilated areas to prevent wasted perfusion

Question 30

avian lung

Answer 30

unidirectional, no tidal flow (lung itself doesn't expand + recoil) air move into parabronchi + driven through capillary beds between vessels - cross current flow (40% O2 extraction)

Question 31

fish gills

Answer 31

countercurrent flow to maximise gas exchange -water moves in opposite direction to blood flow -maintains gradient - driving force for O2 uptake across entire length (90% O2 uptake)

Question 32

O2 uptake - red blood cells and haemoglobin

Answer 32

o2 diffuse across erythrocyte (RBC) membrane O2 + Hb -> HbO2 : increases o2 carrying capacity of blood RBC has high surface area : biconcave shape, no nucleus Hb has 4 iron containing haem subgroups (binding sites), one o2 binding encourages another molecule

Question 33

Hb dissociation curve

Answer 33

Hb will give up oxygen to metabolising cells, but not all of it Bohr shift: increase in pCO2 pushes curve right as more O2 given up to working cells (also caused by increasing H+ conc, temp and 2-3 BPG as promotes O2 release)

Question 34

respiratory pigments

Answer 34

increase O2 carrying capacity -haemoglobin -myoglobin (similar to single Hb subunit) -foetal Hb (much higher affinity for O2) -haemocyanin - crustaceans, contains Cu, not in blood cells

Question 35

CO2 carried in chemical combination

Answer 35

CO2 + H2O -> H2CO3 -> H+ + HCO3- -> H+ + CO3- reversible H+ ions alter pH combines in plasma can form carbamino compounds on Hb - force O2 off

Question 36

control of breathing

Answer 36

central controller = brainstem effectors = respiratory muscles sensors = receptors (lung, peripheral, chemo) electrical activity drives pattern (pacemaker) arises in medulla - specialised neurones phrenic nerve PONS refines pattern (limbic system + hypothallamus send signals + alter rhythm) cortex - voluntarily control breathing sensory receptors in PNS detecy changes + relay to medulla higher centres can override brainstem

Question 37

reflex modification - lung receptors

Answer 37

indicate when enough inspiration - relay to relax juxta-pulmonary "J" receptors = respond to changes in pulmonary circulation irritant receptors = eject air, protective proprioreceptors = changes in movement of rib cage other receptors can have influence eg nociceptors (pain) + chemoreceptors

Question 38

central chemoreceptors

Answer 38

sensitive to changes in pH of cerebrospinal fluid (CSF) located in medulla CO2 can freely diffuse across BBB to CSF increased pCO2 from metabolism causes acidification (H+) buffered in blood plasma however cannot be buffered in CSF as no plasma proteins H+ directly stimulates, increases ventilatio by increasing tidal volume and frequency relatively slow response time insensitive to pO2

Question 39

peripheral chemoreceptors

Answer 39

located in carotid + aortic bodies (high blood flow) decrease in pO2 leads to increased firing also increase in H+ or pCO2 responds rapidly (breath to breath)

Question 40

response to changes in blood chemistry

Answer 40

increase in pCO2 increases minute ventilation not as sensitive to reduced pO2 increased CO2 main drive to breathe ^pCO2 and reduced pO2 act synergistically

Question 41

diving reflex

Answer 41

triggered by cold water on face reduced heart rate increase peripheral vasoconstriction lactate accumulates in muscle energy conservation (delay ^pCO2)