Transcript AP Oct 20 and 21 2016x

Hearts in Different Vertebrate Groups
Obj 11
The challenge of multicellularity
• Being >2 cells thick creates problems for those on
the inside
• How to breath? Eat? Get rid of waste?
• Exchange calls for lots of surface area
• many tiny vessels
• need a major mover
Functions of the circulatory system
• Supply metabolically active cells with food
• Glucose, fats, amino acids
• O2
• Remove wastes
• Nitrogenous wastes
• Metabolic H2O
• CO2
• Others (homeostasis, immune response)
Planaria
• Aquatic, small, and high surface area
• Receives O2 and releases CO2 by diffusion
• No true circulatory system
Terrestriality and larger body size selected for
adaptations for nutrient and gas transport
http://designmatrix.wordpress.com/2010/02/25/circulatory-systems/
Universal solutions
• Move stuff from where it is to where it isn’t
• Circulatory system is transit
• Respiratory system provides gas exchange
Fish:
Simple Heart
Under Pressure?
This and following heart figures (unless otherwise noted) from http://bio1151.nicerweb.com/doc/class/bio1151/
Lungfish
A ‘sometimes’ circuit useful when no water
Lungfish photo credit: http://animals.howstuffworks.com/fish/lungfish-info.htm
from Sadava, Life, pp. 1048-9
Amphibian:
Increased Separation
A commitment to lungs comes
with a dedicated circuit
Reptiles: Bypass
Periods of low
metabolism (no need to
maintain constant body
temp!!); option to skip
the lungs
Two aortas for a
stop-and-go
metabolism
Crocodilians:
Better bypass
Croc valves ‘actively
controlled’: not just resistive
to backflow, can be ‘set’ open
or closed.
Why send blood to the lungs
when there’s no air there?
The underwater option: 4 chambers, lung-skipping
http://www.iucncsg.org/pages/The-Crocodilian-Body.html
http://media.web.britannica.com/eb-media/62/117362-004-C401D1FD.gif
Why might hearts get fancier?
“Four-fifths of a mammal’s food consumption
is invested in keeping it warm. A reptile has
much lower running costs – about one-tenth of
the food needed by an endotherm of the same
size”
The Book of Life, Stephen Jay Gould, ed. p. 129
Mammals, birds:
Closed circuit
• Flight and body temp maintenance place
huge metabolic demands on the system.
• Blocking all possibility of leakage (assuming
development went well) means max delivery
of deoxy blood to lungs; oxy blood to
tissues.
Full-blown compartmentalization
Do the 4-chambered hearts of birds and mammals
most likely represent common ancestry or convergent
evolution?
Hearts…
• Fish – 2-chambered. Why is this ‘okay’?
• Amphibians – 3-chambered. Why is this okay?
• Reptiles – 3-4-chambered; pretty well developed septum
keeps blood separate.
• “Warm Bloods” – 4-chambered hearts
Objective 8
• GET IT DONE!!!!
• Due tomorrow
Objectives 15 & 16
with background on 14, 18, and 19
• rbc – “no” organelles: nucleus, mitochondria,
ribosomes!, etc.
• Can’t divide and “make new cells”
• Yet, you produce over 2 million NEW rbc’s per
second!!!
• “Short” life span ~ 100 days
• Takes about 30 seconds to circulate
HEMOGLOBIN!!
Hemoglobin
• 250-300 MILLION per rbc
• Made of four subunits (2 and 2)
Hemoglobin
• 250-300 MILLION per rbc
• Made of four subunits (2 and 2)
• Hb in blood, MYOglobin in muscles
• VERY similar molecules
• Myoglobin binds
oxygen ‘better’
Hemoglobin vs Myoglobin
• Myoglobin binds oxygen ‘better’
• Why hemoglobin?
• Let’s see what you remember…
• Gaseous oxygen is O=O; chemically what does
this mean?
• What is MOST of your blood?
• Hb binds O2 so it can be carried
• Carbon dioxide is O=C=O; same thing
• Hb doesn’t bind CO2 as well
• But it combines with water (with enzymes
from rbc) to form carbonic acid
• This WILL dissolve in blood
• Lower pH DECREASES Hb’s ability to
bind O2!
Blood and your Brain
• Your ‘brain’ monitors blood pH
• When it drops, respiration increases
• Hyperventilation?
Back to Fetal Circulation…
• If Hb binds oxygen, why would the mother’s
Hb give it up AT THE SAME POINT the fetus
binds it?
• Different Hb!
• Fetal Hb has a higher affinity for oxygen!
Back to Fetal Circulation…
Your turn
• Obj 19 & 20
• Obj 23 due Wed
• Find diseases that are interesting to YOU!!!