Radiotelemetry of cardiovascular responses to exercise and diving in penguins.
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Animals↗
Biomedical subjects
W K Milsom
Publications and source records attributed to W K Milsom.
Effects of changing ambient temperature on metabolic, heart, and ventilation rates during steady state hibernation in golden-mantled ground squirrels (Spermophilus lateralis).
To determine whether metabolic rate is suppressed in a temperature-independent fashion in the golden-mantled ground squirrel during steady state hibernation, we measured body temperature and metabolic rate in ground squirrels during hibernation at different T(a)'s. In addition, we attempted to determine whether heart rate, ventilation rate, and breathing patterns changed as a function of body temperature or metabolic rate. We found that metabolic rate changed with T(a) as it was raised from 5 degrees to 14 degrees C, which supports the theory that different species sustain falls in metabolic rate during hibernation in different ways. Heart rate and breathing pattern also changed with changing T(a), while breathing frequency did not. That the total breathing frequency did not correlate closely with oxygen consumption or body temperature, while the breathing pattern did, raises important questions regarding the mechanisms controlling ventilation during hibernation.
Adaptation, Physiological↗
The role of CO2/pH chemoreceptors in ventilatory control.
It now appears that at least some members of all classes of vertebrates exhibit ventilatory responses to changes in CO2/pH per se, including fishes. With the transition from aquatic to aerial respiration, there is an increase in the sensitivity of animals to this complex of stimuli, an increase in the variety of putative receptors possibly involved in eliciting ventilatory responses and an increase in the relative importance of this complex of stimuli in the genesis of resting ventilation. The variety of CO2-sensitive chemoreceptors present in air-breathing lower vertebrates adds considerable complexity to experimental studies of ventilatory responses to CO2/pH. Because of the locations, discharge characteristics and reflex effects of the different receptor groups, most air-breathing lower vertebrates show different responses to increases in CO2/[H+] due to cerebral ischemia, anoxia, metabolic acidosis and environmental hypercarbia. In some cases the differences are only quantitative, while in other cases the responses are qualitatively very different. These differences appear to reflect differences in the relative strength of the reflexes elicited by the various receptor groups and the net sum of their modulating influences when CO2/pH are altered via different routes. Although the situation is simpler in the higher vertebrates, in all cases the input from all of the CO2/[H+]-sensitive receptors appears to act as a biasing input which summates with other afferent information to modulate respiratory motor output, even in those species that breathe intermittently.
Acidosis, Respiratory↗