respiration

Question 1

what is cellular respiration

Answer 1

The chemical process by which cells obtain energy from molecules such as glucose

Question 2

what is physiological respiration

Answer 2

Uptake of oxygen from the environment and its distribution to the tissues of the body

Question 3

what is the biggest respiratory challenge fish face compared to humans

Answer 3

obtaining sufficient oxygen to fuel metabolism - 200 ml O2 L-1 air , 0.04 - 12 ml O2 L-1 water

Question 4

what happens to O2 conc as Temperature or Salinity increases

Answer 4

decreases

Question 5

what are the 2 problems face fish during respiration

Answer 5

1. Get water to the gills (ventilation)
2. Extract oxygen from the water

Question 6

how do fish Extract oxygen from the water

Answer 6

by using their gills (multipurpose organs)

Question 7

what 4 things are gills used for

Answer 7

Aquatic gas exchange
Osmotic and ionic regulation
Acid-base regulation
Excretion of nitrogenous waste

Question 8

how do the gills mainly function

Answer 8

via diffusion (although some specialised mechanisms also exist, e.g. for osmoregulation).

Question 9

how many gill arches do teleosts and elasmobranchs have

Answer 9

• Normally 4 gill arches on either side of head in teleosts
• 5 in elasmobranchs (more variable)

Question 10

what are gill arches

Answer 10

Bony – each one carries 2 rows of filaments

Question 11

what are gill rakers

Answer 11

Projections that act like a siv – stop damage to the filaments

Question 12

what are gill filaments

Answer 12

Sight of gaseous exchange – filled with blood, water runs across them – stiffened with internal bony ray
- each filament carries leaf-like lamellae positioned parallel to water flow - maximises surface area

Question 13

what is counter current flow

Answer 13

Maintains diffusion gradient for entire length of blood vessel – 100% transfer efficiency – blood always encounters water with higher O2 concentration
- Venous blood (entering) encounters water that has had most of the O2 taken out of it by the gills, but NOT all of it – still has more O2 than the blood

Question 14

what is Concurrent flow

Answer 14

blood and water go in same direction – 50% transfer efficiency

Question 15

2 things that maximise gas transfer

Answer 15

• Lamellae interleaved with adjacent filaments – maxamises surface area
• thin lamellae epithelium wall (2-4um) - short distance to maximise transfer

Question 16

what kind of circulatory system do fish have

Answer 16

Single circulatory system - Venous blood comes into the heart, gets pumped to gill, around the body, then back to heart

Question 17

function of the bulbus Arteriosus

Answer 17

where blood pumps out of the heart
Evens out the flow – allows consistant pressure

Question 18

what part of the heart collects the blood

Answer 18

sinus venosus

Question 19

why is getting water into the gills a problem

Answer 19

water = more viscous

Question 20

what are the 2 types of ventilation

Answer 20

Ram ventilation (passive)
Buccal ventilation (active)

Question 21

what is ram ventilation

Answer 21

• Forward swimming that forces water through the mouth, exits at operculum (gill-slits in sharks) - Usually for fish that swim all the time
• Creates some drag, otherwise doesn’t require any muscular work (passive)
• Superb mechanism – the faster you go, the greater your oxygen demand but the more efficient you are at extraction

Question 22

what is Buccal ventilation

Answer 22

• Actively pumping water over the gills – muscular contraction costs energy
• Sharks can use this method of ventilation
• Some fish ram ventilate AND buccal ventilate (many sharks and some larger teleosts e.g. mackeral)

Question 23

explain the buccal ventilation process

Answer 23

1. Buccal cavity (BC) increases, water drawn in through mouth
2. Fraction later opercular cavity (OC) increases but opercular valve (OV) stays closed, so OC acts like suction pump and draws water across gill
3. Mouth closes, buccal cavity (BC) contracts and acts like pressure pump forcing water over gills
4. Fraction later opercular cavity (OC) contracts forcing water out of opercular valve (OV) (or gill slits in sharks)
5. Cycle starts again
   **A pressure gradient is maintained across gills, keeping a UNIDIRECTIONAL flow of water aka there is no backflow of water across the gills

Question 24

explain Aerial respiration (air breathing)

Answer 24

• Done by lots of freshwater fish
• Use an accessory organ – can be many different things e.g. modified gills/stomach (catfish), cheek (electric eel), rectum (loach)
• A lot of primitive fishes that gulp air use a modified swim bladder e.g. lungfish, bowfin
• Allow fish to leave water or live in hypoxic environments

Question 25

how does More activity ensure they require more oxygen

Answer 25

Increasing stroke volume (more water per pump) Increasing stroke rate (more pumps per minute) **this decreases time water in contact with gill (from 250ms at rest to 30ms at speed)

Question 26

what is the Short-term control of gill area affected by

Answer 26

release of adrenalin to accommodate different activity levels

Question 27

what long term / evolutionary physiological and morphological adaptations can highly active fish show

Answer 27

- most obvious = dramatically increased gill surface area - Also can reduce thickness barrier between blood and water – faster diffusion - ram ventilate – the faster you go, the more contact time reduces between lamellae and a “unit” of water aka the quicker the water goes in and out of the gills – means a larger concentration gradient -> higher diffusion (rate of diffusion depends on difference in concentration)

Question 28

Adaptation for ram ventilation in teleosts

Answer 28

- Contains filament fusions too – enhances strength - Also decreases surface area – used by really fast fish - don’t need the large surface area as thy rely on ram ventilation completely

Question 29

respiration features for low aerobic fish

Answer 29

- thick blood barrier - small gill SA - buccal ventilation

Question 30

heat characteristics of fish

Answer 30

- Ectothermic - rely on external heat source - Poikilothermic - variable body temperature - but regional ENDOthermy has evolved independently in several lineages of marine fishes, including lamnid sharks, tunas and billfishes

Question 31

heat characteristics of mammals

Answer 31

- Endothermic use an internal heat source - Homiothermic maintain a constant body temperature

Question 32

what is The rete mirabile

Answer 32

- “Wonderful net” - Based on principal of maintaining the concentration gradient between contents of adjacent capillaries (arterioles and venules) - It utilises principal of countercurrent flow - Gills are NOT a rete mirabile

Question 33

what does A rete mirabile rely on

Answer 33

Small diameter capillaries, with very thin walls, all packed tightly together, with arterioles and venules adjacent to one another - There may be over 200,000 capillaries in a rete mirabile - That’s equivalent to 1,000 m2 diffusional area (17 times larger diffusional area than in a human lung)

Question 34

what does Retia mirabilia in fish entail

Answer 34

- Oxygen multiplication in the retina + swimbladder - Heat multiplication in scombrid + lamnid shark muscle - Fish can't be truly endothermic – can't control heat loss across gills – but can keep the heat somewhere

Question 35

explain Retia mirabilia in fish

Answer 35

1. Blood going across the gills gets cooled by water around it 2. Blood goes across postcardinal vein – makes whole body cold 3. Endothermic fish also have lateral blood vessels (on the side) - these run through retina mirabilia before getting to the swimming muscles 4. Warm blood going into swimming muscles runs next to the cold blood running in, warming the blood up – maintains a warm part of the body - need to move the swimming muscle for this to work – swimming muscles are moved into the body away from the surrounding water in endotherms e.g. all tuna

Question 36

examples of what Retia mirabilia is used for in other animals

Answer 36

- To reduce heat loss in legs of wading birds, arctic wolves, caribou and other cold climate homiotherms - Reduce heat loss in flippers of marine mammals - Prevent overheating in brain of some hoofed mammals and small carnivores (e.g. cats and dogs) - Prevent overheating in mammalian testes (used as cooling device rather than heating)

Question 37

Advantages of endothermy

Answer 37

- Mammal like muscle power - red muscle of tuna is stenothermic (better stamina + strength) - Increased digestive efficiency (enzyme activity dependent on temperature) - Increased ability to see in the deep-dark ocean (Orbital rete miribile e.g. big-eye thresher, swordfish - Allow niche expansion