Oscillating Heat Flow From the Pinna of the Ear of the Rabbit (Oryctolagus Cuniculus)
Mohler, Forrest Scott
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https://hdl.handle.net/2142/71448
Description
Title
Oscillating Heat Flow From the Pinna of the Ear of the Rabbit (Oryctolagus Cuniculus)
Author(s)
Mohler, Forrest Scott
Issue Date
1987
Department of Study
Physiology and Biophysics
Discipline
Physiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Abstract
Heat flow from the pinna of the ear of New Zealand White rabbits (Oryctolagus cuniculus) was studied using infrared (IR) thermography, which measures the thermal characteristics of the pinna more accurately than the standard method of measuring pinna temperature with a thermocouple. Heat flow from the pinna was found to oscillate.
Thermal pulsing is obvious on the IR thermograms of the pinnae of normothermic rabbits at a neutral ambient temperature (20(DEGREES)C). Characteristics of the thermal pulsing were measured using video frame analysis of the thermograms. At 20(DEGREES)C ambient, the pulsing occurred at an oscillatory frequency of about 0.025 Hz and an amplitude of 0.36(DEGREES)C.
Ambient temperature affected both the gross vasomotor state and the thermal pulsing of the pinnae. A warm environment (25(DEGREES)C) resulted in a general vasodilation of the pinnae. Superimposed on the vasodilation, the thermal pulsing continued with an increased frequency of around 0.027 Hz and a decreased amplitude of 0.27(DEGREES)C. A cool environment (15(DEGREES)C) led to a general vasoconstriction, but the thermal pulsing continued superimposed on the constriction. Cooling increased the frequency of thermal pulsing to 0.031 Hz and decreased the amplitude to 0.17(DEGREES)C.
Preoptic area (PO/AH) temperature also had an effect on both the gross vasomotor state and thermal pulsing of the pinnae. Warming the PO/AH by 1(DEGREES)C caused a distinct vasodilation; and the thermal pulsing continued with no change in frequency but an increase in amplitude to 0.44(DEGREES)C. Cooling the PO/AH by 1(DEGREES)C caused a distinct vasoconstriction, and the thermal pulsing continued with an increased frequency around 0.033 Hz and a decreased amplitude of 0.10(DEGREES)C.
Under all experimental conditions, the thermal pulsing was synchronous in the two pinnae of individual rabbits.
It has been proposed that an oscillatory motor output could function, in the thermoregulatory system, to temporally dissociate the thermomotor role from the thermosensory role of cutaneous areas. The thermal pulsing observed in the pinna of the ear of the rabbit has many of the characteristics necessary to serve such a function.
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