UNI101Y1 Chapter Notes - Chapter 3: Eulampis, Torpor
16 Feb 2013
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Species living in cool climates would starve overnight if they didn"t enter torpor (a voluntary, reversible condition of low body temp. and inactivity) West indian hummingbird eulampis jugularis drops it temp to 18 c-20 c when resting at night. Changes the set point to reduce diff. b/w ambient and body temp. , thereby reducing. Heat moves from warm to cool; eventually temp. equalizes & net mvmt of heat equalizes. Conduction of heat esp. from exposed extremities works against maintaining body temp. A solution is an arrangement of blood vessels in the extremities called ccoouunntteerrccuurrrreenntt cciirrccuullaattiioonn in this system, blood flowing from the body toward the extremities continuously encounters blood returning to the body. Extremities of birds would be major avenues of heat loss in cold regions were they not held at lower temp. than rest of the body. Warm blood in arteries leading to the feet cools as it passes close to veins that return cold blood to the body.
