Animal Size and Heart Rate
Please can you tell me why smaller animals have a faster
pulse and respiratory rate compared to larger animals?
Because the ratio of surface to volume in their large blood vessels
and airways is larger for small animals than for large animals.
At the surface of a blood vessel, blood hardly moves because it is
in contact with the wall. So the more surface you have, the harder
it is to pump blood. This means small animals have to work harder
that large animals to get blood to each of their cells.
But large animals and small animals use the same kind of pumping
machinery (i.e., muscle fibers), so the only thing small animals
can do to make up the difference is to run their pumps faster.
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Update: June 2012