Circulation and respiration - Part 1 Flashcards
Blood flow in fish is ___________.
unidirectional
Give the direction of blood flow to the heart in fish.
Heart ventral aorta afferent branchial artery gas exchange at gill lamellae efferent branchial artery dorsal aorta head and body
• Head: dorsal aorta carotid artery head anterior cardinal vein + jugular vein common cardinal vein heart
• Body: dorsal aorta caudal artery, superior mesenteric artery, coeliac artery caudal vein common cardinal vein heart
Where does oxygen exchange actually occur?
In the gill lamellae.
Lamellae are filled with ________ that are directly next to ______.
capillaries; water
Describe the counter-current exchange for gas exchange.
Blood flow through the capillaries goes in one direction while water flow over the gill lamellae goes in a different direction. This effectively concentrates oxygen into the capillaries.
At every point along the capillary flow in the lamellae, the blood PO2 is lower than that of the surrounding water.
Blood flow in fish is not _______.
Fixed
What is meant by blood flow in fish is not ‘fixed’?
Fish can control the amount of blood flowing through lamellae and can control which lamellae get blood and which ones do not.
If one of the filaments is damaged, can stop blood loss by stopping blood flow to the capillaries and send it to undamaged parts.
Describe the regulation of blood flow through the lamellae.
Part of the regulation is hormonal.
Epinephrine and Acetylcholine (Ach) act as complements.
Epinephrine in the fishes blood will increase the amount of blood flow.
Ach will decrease lamellar blood flow.
If it was nearing winter, what hormone would the fish most likely secrete regarding blood flow to the lamellae. Why?
Ach.
If the fish knows winter is coming, needs less oxygen. Uses ACh to shut blood flow down.
Lamellae are _____ cell(s) thick
1 (or two)
More active fish will have ______ filaments and ______ lamellae per filament.
More; more
One can determine the relative amount of activity of a fish based on the number of _____ and ______.
filaments; lamellae
Each gill arch has ________ filaments on them.
multiple
Within a fish, water flow across the gills can be changed. How?
Can spread filaments out, bring them back together.
If more oxygen is needed, can flare filaments, let more water pass over lamellae or can close to have less water flow.
Often, we find that more _______ fish will have thicker lamellae.
What is the trade-off for this?
Benthic
Give up efficiency in oxygen exchange to have increased durability in these lamellae.
Overall surface area for exchange is related to what?
Number of filaments
Number of lamellae
Thickness of lamellae
Active, pelagic fish will have _____ lamellae, benthic fish will have _______.
more; less
Where are pseudobranchs found?
Under the operculum
Many fishes have pseudobranchs, especially _______.
teleosts
What is a pseudobranch?
Vestigial gill arch which functions as a partial gill.
What is the main probable function of a pseudobranch?
What is another possible function?
Special gill arch for blood supply to the eye.
May also function as a pressure detector
Why is it difficult for a fish to know at what depth it’s at?
Difficult to do this without light cues.
Why does a swim bladder not work as a pressure detector?
It does, but only coarsely.
Not a precise measure, takes a large pressure change to change compression on the swim bladder.
How would a pseudobranch function as a pressure detector?
Small-scale changes in pressure might make small-scale compression changes to capillaries to determine pressure.
How does temperature affect DO concentration in the water?
DO in the water decreases as temperature increases.
Which carries more oxygen, all else being equal, freshwater or saltwater?
Freshwater
Describe how mixing affects DO content in the water.
Mixing of surface water with deeper water - upwelling
Mixing of water with air
Wave action
All increase DO
Describe the issues with Lake Erie in low oxygen content during the summer.
Low mixing in the summer for lake Erie since the winds die off.
Water also gets warmer.
Algae builds up and then gets digested by bacteria which further reduce oxygen content.
What is normoxia?
Water with normal oxygen concentrations for the fish, plenty of oxygen.
What is anoxia?
No oxygen. No fish can live in anoxic waters.
What is the range between anoxic and normoxic called?
Hypoxic zone
What is the hypoxic zone.
Where there is less oxygen than most fish need
Oxygen consumption goes _____ as body size increases.
up
Which fish would be more affected by hypoxia, an adult or juvenile fish?
Adult - due to simple metabolic needs
How do carp survive hypoxic conditions?
Take air and hold it against gills and exchange the oxygen with the blood.
Describe some behavioural modifications fish have when in hypoxic waters.
Swim less
slow down metabolism
slow down respiration
Most fish have a ________ Hb.
tetrameric
What fish have monomeric Hb?
Lampreys and hagfish
What fish, other than lampreys and hagfish, don’t have tetrameric Hb?
Antarctic icefish
How do Antarctic icefish deal with their lack of Hb?
Carry dissolved oxygen in the blood to reduce ice crystal formation.
They can do this since the water temperature is so cold that oxygen supply is very high and, the fish is not particularly active.
Describe, very briefly, the polymorphic nature of some fish in terms of their Hb.
Some fish can express different Hbs for different habitats.
These are still tetrameric but aim to optimize overall affinity of Hb to oxygen.
What is affinity for Hb?
What is high affinity?
Low?
Affinity is how tightly Hb binds to oxygen.
High affinity means it will bind tightly to oxygen.
Low affinity means it will grab oxygen but less-so.
Polymorphic Hb will ______ in ______ for oxygen.
Differ in affinity
Describe the polymorphic nature of the Goldfish Hb.
Will have different Hb at different temperatures.
At higher temperatures, will express a higher affinity Hb; at lower temperatures the fish will express lower affinity Hb.
Describe the polymorphic nature of suckers’ Hb.
When pH decreases, suckers will start expressing pH insensitive Hb.
What does decreased pH usually do to Hb?
Causes a decrease in affinity to oxygen.
Describe how a sucker stays active in a small desert lake.
Very active in these lakes.
As the lake heats up, less oxygen present but the fish stays active. Due to hypoxia, lactic acid is formed in the muscles, reducing pH. The fish gets around this by expressing pH insensitive Hb to capture the little amount of oxygen in the lake, effectively.
In general, increased temperature will ________ the affinity of Hb for oxygen.
decrease
How are the Bohr and Root shifts similar?
Both of them deal with Hb’s ability to carry oxygen as pH changes.
How are the Bohr and Root shifts different?
Bohr - deals with affinity of Hb to oxygen. As pH decreases, the affinity will decrease. i.e. at lower pH, Hb will hold oxygen less tightly
Root - deals with carrying capacity of Hb. As pH decreases, so too does the amount of oxygens that can be carried by Hb.
The ______ shift is more extreme while the ______ shift is more gradual.
Root
Bohr
Why are the Bohr and root shifts a good thing?
They are necessary for exchange of oxygen and carbon dioxide at the tissues and lungs.
Describe how the Bohr and Root shifts work at the tissues and lungs.
When blood goes to the gills or lungs, pH is high so affinity is high for oxygen, all four sites bound.
Then, as get to the muscles and tissues, pH goes down causing a decrease in cooperativity and affinity for oxygen, allowing oxygen to diffuse into the tissues.
This allows Hb to exchange oxygen for carbon dioxide and carry it to the lungs, to then perform the same exchange in reverse.
How is most of the CO2 in a fish’s body carried?
As bicarbonate.
Other than as bicarb, how else can CO2 be carried in the blood?
As CO2
What is the Haldane shift?
As blood oxygen decreases, Hb scavenges protons.
This takes away protons forcing the equilibrium equation (CO2 + H20 H+ + HCO3-) to make more bicarb.
i.e. More carbon dioxide is carried as the bicarbonate ion since Hb scavenges protons when reaching the low pH of the tissues, shifting the eqb. equation to make more bicarb, which is dissolved in solution
