physiological thermoregulation few fishes--tunas & lamnid sharks fish are active --generate heat...
TRANSCRIPT
Physiological Thermoregulation
• few fishes--tunas & lamnid sharks
• fish are active --generate heat
• rete mirabile for heat exchange & conserv.
• fish are large--low surface area to mass ratio– body surf. area increases as square of length– body mass increases as cube of length
end
Physiological Thermoregulation
body
skin
skingills
heat
rete mirabile
end
Counter-current blood flow
Distance along capillaries (rete)
Tem
pera
ture
low
high
arterial blood
venous blood
heat
from gills
from body
end
Counter Current flow:
• fluid flowing in opposite directions
• exchange of heat or gas perpendicular to flow
• efficiency versus speed
end
Distance along capillaries (rete)
Tem
pera
ture
low
high
Hypothetical Co-current blood flow:
from gills
from body
arterial blood
venous bloodcounter-current
heat
end
Hypothetical Co-Current flow:
• fluid flowing in same direction
• exchange of heat or gas perpendicular to flow
• speed versus efficiency
end
Hydromineral Balance: Life in a solvent
Environmental forces cause movement of water and dissolved substances
versus
Homeostasis--the need to maintain balance of water and dissolved substances in cells and body fluids of organisms
-constant internal environment
end
Environmental forces:• heat--(movement of molecules) energy for
movement
• diffusion--net movement of molecules
• pressure--density of molecules – difference causes or blocks movement
• osmosis--movement of water
• electrochemical forces--attraction & repulsion of molecules based on charge
end
• Environmental forces work together toward equilibrium
• equilibrium-no net movement of molecules
end
Diffusion:
water
substance
diffusion
end
water
end
substance
water
end
substance
end
Osmosis:
water
substance
semipermeable membrane
osmosis
end
substance
water
end
substance
water
end
substance
water
end
• Diffusion--Net movement of molecules from an area of high concentration to an area of low concentration
• Osmosis--Net movement of water across a semipermeable membrane from an area of high concentration to an area of low concentration
end
Electrochemical forces:
• Movement of ions (charged molecules) due to charge
• likes repel--opposites attract
end
Passive processes:
• Diffusion, osmosis & molecular movement from electrochem. Forces are passive processes – require no energy from organism
• Active Processes-those that require organism to expend energy.– needed for homeostasis; to counter some
passive processes
end
Definitions:
• Ionic Regulation: maintenance of concentrations of specific ions
• Osmoregulation: maintenance of constant concentrations of total dissolved substances in extracellular fluids
end
end
Four osmoregulatory strategies in fishes:
1. Isosmotic (nearly isoionic)– essentially no regulation– body fluids same osmotic conc. as environment
advantages and disadvantages?
Examples: many inverts. Hagfishes; only marine spp.
end
Four osmoregulatory strategies in fishes continued:
2. Isosmotic with regulation of specific ions– organic salts stored in extracellular fluids (prim. urea)– Inorganic salt conc. approx. 1/3 seawater– rectal gland secretes Na+ and Cl- in conc close to that of
seawater (active process)
advantages and disadvantages?
Examples: elasmobranchs, coelacanth (marine)
end
Four osmoregulatory strategies in fishes continued:
3. Osmotic & ionic regulation by marine teleosts– ionic conc. Approx 1/3 of seawater– drink copiously to gain water– Chloride cells eliminate Na+ and Cl-
– kidneys eliminate Mg++ and SO4=
advantages and disadvantages?
Examples: saltwater teleosts
end
Saltwater teleosts:
drink
active
passive
Na+, Cl-
Mg++, SO4=
H2O
Na+, Cl-
Na+, Cl-
chloride cells
Mg++, SO4=
kidneys
end
Chloride Cell fig 6.2:
pavementcell PCPC
active
passive
chloride cell
accessory cell
sea water
internalmitochondria
tubular system
Na+
K+ Na+ K+ ATPase
Na+, Cl-
Na+
Cl-
Cl-
Cl-Cl-
gut
carrier
Na+
Na+
Na+
pump
+
end
Four osmoregulatory strategies in fishes continued:
4. Osmotic & ionic regulation by FW teleosts– ionic conc. Approx 1/3 of seawater– don’t drink– Chloride cells fewer, work in reverse – kidneys eliminate excess water; ion loss– ammonia & bicarbonate ion exchange mechanisms
advantages and disadvantages?
Examples: FW teleosts; FW elasmobranchs
end
Freshwater teleosts: active
passive
H2O
Na+, Cl-
Na+, Cl-
don’tdrink
waterkidneys
Ion exchangepumps; beta chloride cells
end
Ion Exchange Mechanisms
gill membrane
freshwater interior
active
pump
active
pump
Na+
Cl-
NH+ or H+
HCO3-
ATP
ATP
end
end
end
end
pO2
Distance along capillaries
efferent
Counter-current flow
afferent
O2
end
Four osmoregulatory strategies in fishes continued:
1. Isosmotic (nearly isoionic)
2. Isosmotic with regulation of specific ions
3. Osmotic & ionic regulation by marine teleosts (continued)
Summary of previously covered strategies:
end
• The following slides are animated with a feature that does not work on powerpoint2000. save for use when 105 gets ppxp
• These will replace the diffusion and osmosis slides above.
end
water
substanceend
water
substanceend
substance
water
end
substance
water
end