lecture 11-12

Question 1

Why do we need respiratory gases ?

Answer 1

animals must exchange respiratory gases -O2 &CO2
-cell needs O2 from environment for cellualr respiration –>to prod ATP
-No O2 :Pyruvate oxidation ,citric acid cyle and oxidative phosphorylation do not function
-Anaerobic function is much less efficient than aerobic respiration as less ATP is made

Question 2

Define External respiration ?

Answer 2

Process by which O2 needed for energy metabolism is obtained CO2 is eliminated
-gas exchanfe pf O2 & CO2 between pumonary blood (mammals)

Question 3

What does gas exchange of animals consist of ?

Answer 3

1.Specialised body surface areas where gases can move between the body internal and external environment
2.Mechanisms that ventilate the environmental/external side of surfaces with air/water
3.Mechanisms that circulate ECF on internal sides

No active transport mechanisms to move respiratory gases across biologic

No active transport mechanisms to move respiratory gases across biological membranes –>gas exchange bwteen an animals internal body fluids and outside medium occurs by diffusion

Question 4

Define solute ?

Answer 4

Solute diffuses from regions of a solution where it is high in concentration to where it is low

Rate of solute diffusion is proportional to its difference in concentration between regions

Question 5

Define Chemical potential ?

Answer 5

strength of the tendancy of a chemical substance to undergo a physical/chemical change study of chemical diffusion

Question 6

Define diffusion

Answer 6

with a single aqeous solution the concentration of a solute is a usefull surrogate for chemical potential)
-However O2 & CO2 exist in both gas mictures and aqeous solutions they diffuse between them
so partial pressure is used to express chemical potential in the study of gases

Question 7

Define universal law

Answer 7

PV=nRT

Question 8

Define Daltons law of partial pressure ?

Answer 8

:The total pressure exerte by mixture of gases is = to the sum of the partial pressures of all the gases of the mixture

Question 9

Define partial pressure ?

Answer 9

the individual pressure exerted by any given gas in gas mixture

Partial pressure of each indivisual gas in a mixture can be calculated from the universal gas law

Question 10

Define Henrys law ?

Answer 10

amount of gas dissolved in a given volume of liquid is proportional to the partial pressure in the gas phase .Proportionally constant is called -solubility coefficient

relates PP and conc in aqeous solutions
-can use absorption coefficient :dissolved concentration of a gas when partial pressure is 1 atm

Question 11

What is solubility of gases ?

Answer 11

amount of O2 that is dissolved is proportional to its partial pressure in the gas phase

Question 12

Diffusion of gases :partial pressure

Answer 12

gas in aqeous solution :not equal to partial pressure but the latter drives diffusion

Ficks law applies to all systems of gas exchange

Question 13

What does Ficks law apply to all ?

Answer 13

all systems of gas exchange :whether in air or water diffusion rates of respiratory gases depend on partial pressure gradients & other factors

Question 14

What is Ficks law ?

Answer 14

rate at which a gas diffuses between 2 locations (Q) depends on
1.diffusion coefficient (D); incorporating temp ,diffusiing substances;medium
2.Area(A) over which gas is diffusing
3.Difference between the gas partial pressure (P1-P2) at 2 locations ;
4.Distance(L) between 2 locations

all tissues ,Ficks law applies to rate of diffusion of any substance in the interstitial fluid
substance moves from plasma to tissue->passive molecules

Question 15

Animal adaptations to rate at which gas diffuses between 2 locations ?

Answer 15

Sponges-body walls contain many channels –>waterr flows into central cavity

Question 16

Specialised respiratory systems

Answer 16

in organs specalised for external respiration thr gas exchange membrane typically has extensive invaginations/evaginations to increase A(influence SA or pressure gradient

Question 17

Brief overview of insect respiratory system ?

Answer 17

Consist of branched air tubes-trachea &tracheoles that end in air capillaries
-insect tracheal systems brings air to all tissues /cells in the body :
-spiracles :enable communication between an insects internal and external environment
spiracles–>trachea,tracheoles–>air capillaries

Question 18

Where does Ventilation & Perfusion occur ?

Answer 18

Venti=(occurs on environmental side)Maintains high PO2 and low PCO2
Perf=(occurs on the internal side ;tissues/fluid)Maintains a low PO2 and high PCO2

Question 19

Define Ventilation ?

Answer 19

Bulk flow of air and water to and from the gas exchange membrane during breathing
-not all animals use ventilation ;breathing can occur by diffusion
active ventilation constantly moves external medium over gas exchange surfaces–>fresh supply of O2 and CO2

may be unidirectional,non or tidal

Question 20

Define Perfusion ?

Answer 20

Actively moves internal medium (blood) side of exchanged surfaces –>CO2 brought to these surfaces exchanged for O2

Question 21

Breathing by Fish ?

Answer 21

Teolasts buccal cavity communicates with environment via mouth and gilll slits
internal gils are supported by gill arches ;opperculum covers gills
4 gill arches :provides structuaral support for gills ;each arch bears 2 rows of gill filaments

gill are composed of gill filaments ;rows of gill filaments seperate the buccal cavity from opperculum cavity

Question 22

Breathing by fish ?

Answer 22

Each gill filament vears a series of folds:secondary lamallae –>richly perfused with blood ;thin welled
lamallae are principle sites of gas exchange in teleosts
gills–>enormous SA for gas exchange highly subdivided
water flows unidirectionally into mouth across gills out opperculum flaps -flow is either :
1.constant swimming wiht mouth open (tuna,sharks) some must to avoid suffocation
2.most fish ventilate their gills via 2 -pump mechanism
-buccal -opperculum pumping :mouth cavity closes& contracts

Question 23

How does countercurrent gas exchange occurs in lamallae of fish ?

Answer 23

Blood flows in via the afferent vessels (deoxy),across lamllae & out via the efferent vessels .
-Blood flows is also unidirectional ;but in the opposite direction to water low –>countercurrent

gas exchange rate is maximised by maintaining the PO2 gradient between water and blood using countercurrent system

Question 24

What is the difference between unidirectional ventilation :concurrent and countercurrent ?

Answer 24

figure show flow of medium and flow of blood along gas exchange membranes
concurrent/cocurrent~:flow of medium and blood occurs in same direction
countercurrent:medium and blood flow in opposite directions
acheives more complete transfer of O2 from medium to blood than ccurrent exchange :thus is more efficient /effective

Question 25

What are adaptations of fish for respiration ?

Answer 25

Fish maximise gas exchange rate (Q) -highly subdivided and folded SA --> maximise A -very thin surface -maintain high P1 through an almost constant unidirectional water flow and low PO2 through constant blood flow countercurrent system maintains PO2 gradient -->enables fish to obtain adequate O2 supply from meagre sources

Question 26

Any problems that may affect fish and their respiratory adaptations ?

Answer 26

high temperature : casue respiratory problems for aquatic animals -fishy -rising water temp increaes the animals metabolic rate thus needs more O2 but warmer water holds less O2Needs to move more water across gas exchange surface → uses more energy… Recap: air is a better respiratory medium than water (slide 17). Animal needs more O2, but less is available

Question 27

Breathing by birds ?

Answer 27

allows air to flow unidirectionally:very little dead space freshair does not mix with stale air -->maintains high PO2 -air sacs :part of breathing system but are located outside of the lungs in thoracic cavity usually 9,2 groups anterior and posterior

Question 28

What are birds air sacs connected with ?

Answer 28

interconnected with each with the lungs and with air spaces in some of ther bones -non-respiratory :are not gas exchange surfaces -act as bellows:maintains unidirectional flow of air through lungs ## Footnote air in through trachea →primary bronchi→secondary bronchi→parabronchu

Question 29

what are parabronchi and what do the do ?

Answer 29

tertiary bronchi air diffuses into tiny air capillaries which are the gas exchange surfaces air capillaries: surrounded by blood capillaries air flows out of lungs to anterior air sacs and finally out of bird via trachea

Question 30

How much breath remains in birds respiratoy system ?

Answer 30

single breath for 2 cycles of inhalation and exhalation lungs ventilated by bellows action -generated by action,expansion and compressionof air sacs

Question 31

What happens in cycle 1 of bird breathing ?

Answer 31

Inhalation:air enters via trachea and drawn into posterior air sacs as they expand During exhalation this air is then pushed into lungs Cycle 2 during next inhalation -lungs is displaced into anterior sacs during exhalation-air forced out via trachea ## Footnote Avian lungs are compact, rigid structures: undergo minimal change in volume during a breathing cycle.

Question 32

The cross-current gas exchange occurs in air capillaries in birds ?

Answer 32

cross current (unidirectional) pattern relative to air flow afferent blood vessel breaks into many vessels that 'cross' the path followed by medium merging to form a single efferent blood vessel

Question 33

What are birds respiratory adaptations ?

Answer 33

minimise gas exchange rate many air capillaries- large SA Air & blood capillaries -thin walls maintain high P1-almost unidirectionally air flow through constant blood flow maintains PO2 gradient-enabling birds to maintain blood PO2 slightly below of environmental air even at high altitude

Question 34

What is tidal ventilation ?

Answer 34

bidirectional so air flows to and from the gas exchange membranes via the same passages Mixing with stale airs lowers PO2 grad ## Footnote not as efficient as unidirectional ventilation

Question 35

Breathing by mammals ?

Answer 35

have elaborate animal lungs densly filled with branching & rebranching :lungs=High gas exchange SA barrie thickness between blood & environmental medium very thin

Question 36

2 major functions of mamalian areas ?

Answer 36

1.Conducting zone :moving gases to and from the atmosphere and lungs including trachea,bronchi & bronchioles 2.Respiratory zone :where gases are exchanged ->Alveoli are sites of gas exchange across alveolar capillary membrane

Question 37

What do mammals lungs end up in ?

Answer 37

dead end sacs Trachea,bronchi &bronchioles constitute dead space Respiratory bronchioles end blindly i alveolar ducts & sacs Gas occupying final respiratory airways almost motionless -->O2 and CO2 transport must occur by diffusion

Question 38

What is the role of surfactant ?

Answer 38

In alveolar epithelial type 2 cells = prod surfactant =reduce surface tension of alveoli and prevent alveoli from collapsing during exhalation compensation for tidal ventilation =adaptations 1. large SA 2. short diffusion pathway