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An in-depth analysis of thermoregulation in animals, specifically focusing on ectotherms and endotherms. It explains the concept of energy generation and heat loss, the differences between ectotherms and endotherms, and the strategies used by each group to regulate body temperature. The document also covers the mechanisms of freeze tolerance and avoidance in ectotherms, and the characteristics of endothermy. useful for students studying animal physiology, particularly those focusing on thermoregulation and metabolism.
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In the process of creating energy
for an animal, heat is generated.
Why and How????Why and How????
Second Law of Thermodynamics
75% of the total potential energy
derived from breaking covalent
bbonds in molecules is ultimately d i l l i lti t l
lost as heat.
Two categories describe how
animals use heat in their bodies
Energy input and output
The internal body temperatures of both ectotherms and endotherms depend simply on the difference between heat input and heat output.
Strategies to regulate heat in
ectotherms
Some ectotherms can
metabolically compensate for
changes in body temperatures
How do ectotherms survive
extreme cold?
When water freezes on the peeper frog's outer skin, a signal is sent to the liver to trigger a massive breakdown of glycogen in the liver.
As a result, a flood of glucose molecules enter the circulatory system raising blood sugar over 450 fold above normal.
The increase of blood sugar acts as an antifreeze by lowering the freezing point due to simple colligative properties.
Glucose molecules are transported into cells and act as a cryoprotectant to help keep the cells in osmotic balance with the increasing osmotic pressure in the ECF caused by ice crystals.
When the animal finally thaws, it has lots of glucose to generate lots of ATP.
Mechanism of Freeze Avoidance
Mechanisms used by endotherms
to maintain a stable core
temperature
Gaining external heat/avoiding
loss to cold environments
a) Vasoconstriction in the blood vessels to the skin to reduce heat loss.
b) Anatomic insulation
c) Behavioral insulationc) Behavioral insulation
d) Larger body size in colder climates will generate more heat than smaller bodies.
e) Countercurrent exchangers: Blood flow can be used to retain core heat using a countercurrent exchanger. Typically found between the core body and exposed peripheral organs that could lose heat rapidly
What coordinates all the
behaviors and physiological
responses to heat or cold?
Characteristics of hypothalamus
as a thermoregulator
Function of Hypothalamus in
Thermoregulation
