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0:00
My name is John Torday.
I'm a Professor of
evolutionary medicine at UCLA.
This lecture is entitled
"The Evolutionary Origin
of Endothermy"
as Integrated Physiology.
0:11
The evolution of endothermy
is considered to be
a watershed
in vertebrate history,
yet it is poorly understood
at best.
It has arisen in mammals
and birds
and is conventionally thought of
as having occurred
as a consequence
of muscle generating heat.
The aerobic capacity model
has gained acceptance,
according to which selection
for metabolic demand
has led to increased metabolism
and accidentally, to endothermy
as a consequence.
However, the cellular
molecular approach
to the evolution
of visceral organs
in adaptation to land,
provides a mechanistic continuum
of adaptive events,
both ontogenetically
and phylogenetically,
offering a novel testable
and refutable approach
to how and why
endothermy evolved.
0:56
It should be kept in mind
that birds and mammals
are both endothermic
and share a number of
physiologic characteristics.
Highly specialized lungs
with expanded
pulmonary capacities
and ventilation rates.
Fully separated pulmonary
and systemic circulatory
systems,
expanded cardiac output.
The last two traits
of the direct result
is the duplication
of the beta-adrenergic receptor
during the water land
transition.
These physiologic traits
fostered the highly
specialized lungs.
1:27
Based on the cellular molecular
approach to endothermy,
phylogenetically,
ontogenetically,
and functionally,
endothermy can be understood
as a consequence of interactions
between the respiratory,
neuroendocrine
and metabolic systems
during the water to land
transition.
The effect of adrenaline
on endothermy
is consistent
with the duplication
of the beta-adrenergic receptor
during the water-land transition
fostering
the independent regulation
of blood pressure in the lung
and non-lung circulations.
Independent regulation
of blood pressure in the lung
and non-lung circulation,
complimented by the role
of the beta-adrenergic receptor
in adrenaline stimulated
fatty acid release
from fat pads causing
increased metabolic rate.
