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Re: rearing up (long)



>3.  In terms of the sauropod rearing question, with their small brains
>and presumably small-diametered cerebral arteries I have been under the
>impression they would not require that much of an increase in blood
>pressure to perfuse their brains. 

This is going to sound like an extraordinarily silly question, but here
goes.  I am not sure I quite understand why rearing would cause additional
blood-pressure problems (barring the increase in activity rate).  As the
heart is in the anterior half of the body, rearing does not necessarily
raise the head higher relative to the heart, because the heart is elevated
too.  If the rearing animal then bent its head well forward to reach
branches on the far side of the tree it might even come level with the
heart.  If pooling in the posterior extremities is the problem, surely
either constricting the posterior vessels or using muscle activity to
"pump" the blood back to the anterior end could solve this problem (this is
akin to what diving whales do).  Am I missing something?
--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court                 
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@home.com