Control of Breathing in Birds: Implications for High-Altitude Flight

Scott, Graham R.; Milsom, William K.

doi:10.1007/978-3-540-93985-6_17

Cited by 13 publications

(15 citation statements)

References 73 publications

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“…Because CO 2 and H + normally stimulate breathing via central and peripheral chemoreceptors, secondary hypocapnia and alkalosis restrain the ventilatory response. The net effect is an increase in ventilation that is dependent on the severity of hypoxia, but the magnitude of this increase is less than if blood CO 2 levels had remained constant (Fig.2) (Scott and Milsom, 2009). The magnitude of the hypoxic ventilatory response is also dependent on the duration of hypoxia (Powell et al, 1998).…”

Section: The Nature Of Physiological Adaptation To High-altitude Hypoxiamentioning

confidence: 98%

“…The most important factors affecting ventilation at high altitude are the partial pressures of O 2 and CO 2 and the pH of arterial blood (Scott and Milsom, 2009). Breathing is stimulated when a decline in arterial P O2 (Pa O2 ; hypoxemia) is sensed by chemoreceptors in the carotid bodies.…”

Section: The Nature Of Physiological Adaptation To High-altitude Hypoxiamentioning

confidence: 99%

“…The underlying chemoreceptive mechanisms are not necessarily convergent at the cellular level. For example, the enhanced ventilatory response to acute hypoxia in the high-altitude bar-headed goose (Anser indicus) is partly due to an insensitivity to hypocapnia (Fig.2) (Scott and Milsom, 2007;Scott and Milsom, 2009), whereas responses of high-altitude humans generally involve changes in O 2 sensitivity (Brutsaert, 2007). Other highland species or populations exhibit a blunted ventilatory response to acute hypoxia (Blake and Banchero, 1985;Brutsaert et al, 2005), which would be maladaptive at high altitudes without compensatory changes at other steps in the O 2 transport pathway that maintain peripheral O 2 supply.…”

Section: The Nature Of Physiological Adaptation To High-altitude Hypoxiamentioning

confidence: 99%

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Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates

Storz

Scott

Cheviron

2010

Journal of Experimental Biology

353

343

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SummaryHigh-altitude environments provide ideal testing grounds for investigations of mechanism and process in physiological adaptation. In vertebrates, much of our understanding of the acclimatization response to high-altitude hypoxia derives from studies of animal species that are native to lowland environments. Such studies can indicate whether phenotypic plasticity will generally facilitate or impede adaptation to high altitude. Here, we review general mechanisms of physiological acclimatization and genetic adaptation to high-altitude hypoxia in birds and mammals. We evaluate whether the acclimatization response to environmental hypoxia can be regarded generally as a mechanism of adaptive phenotypic plasticity, or whether it might sometimes represent a misdirected response that acts as a hindrance to genetic adaptation. In cases in which the acclimatization response to hypoxia is maladaptive, selection will favor an attenuation of the induced phenotypic change. This can result in a form of cryptic adaptive evolution in which phenotypic similarity between high-and low-altitude populations is attributable to directional selection on genetically based trait variation that offsets environmentally induced changes. The blunted erythropoietic and pulmonary vasoconstriction responses to hypoxia in Tibetan humans and numerous high-altitude birds and mammals provide possible examples of this phenomenon. When lowland animals colonize high-altitude environments, adaptive phenotypic plasticity can mitigate the costs of selection, thereby enhancing prospects for population establishment and persistence. By contrast, maladaptive plasticity has the opposite effect. Thus, insights into the acclimatization response of lowland animals to high-altitude hypoxia can provide a basis for predicting how altitudinal range limits might shift in response to climate change.

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Section: The Nature Of Physiological Adaptation To High-altitude Hypoxiamentioning

confidence: 98%

Section: The Nature Of Physiological Adaptation To High-altitude Hypoxiamentioning

confidence: 99%

Section: The Nature Of Physiological Adaptation To High-altitude Hypoxiamentioning

confidence: 99%

See 1 more Smart Citation

Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates

Storz

Scott

Cheviron

2010

Journal of Experimental Biology

353

343

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“…We have assessed this issue in waterfowl using theoretical modeling to calculate the physiological control coefficient for each step in the pathway (Fig.4) (Scott and Milsom, 2006;Scott and Milsom, 2009). This approach allows physiological traits to be altered individually so that their influence on the whole O 2 pathway can be assessed without compensatory changes in other traits.…”

Section: The Unique Attributes Of High Fliersmentioning

confidence: 99%

“…Increases in breathing (i.e. ventilation) are an important response of the respiratory system to hypoxia, and the magnitude of this response is dictated primarily by the partial pressures of O 2 and CO 2 and the pH of arterial blood (Scott and Milsom, 2009). The decline in arterial O 2 tension (hypoxaemia) drives the increase in ventilation, whose secondary consequence is an amplification of CO 2 loss to the environment.…”

Section: Introductionmentioning

confidence: 99%

Elevated performance: the unique physiology of birds that fly at high altitudes

Scott

2011

Journal of Experimental Biology

139

113

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Summary Birds that fly at high altitudes must support vigorous exercise in oxygen-thin environments. Here I discuss the characteristics that help high fliers sustain the high rates of metabolism needed for flight at elevation. Many traits in the O2 transport pathway distinguish birds in general from other vertebrates. These include enhanced gas-exchange efficiency in the lungs, maintenance of O2 delivery and oxygenation in the brain during hypoxia, augmented O2 diffusion capacity in peripheral tissues and a high aerobic capacity. These traits are not high-altitude adaptations, because they are also characteristic of lowland birds, but are nonetheless important for hypoxia tolerance and exercise capacity. However, unique specializations also appear to have arisen, presumably by high-altitude adaptation, at every step in the O2 pathway of highland species. The distinctive features of high fliers include an enhanced hypoxic ventilatory response, an effective breathing pattern, larger lungs, haemoglobin with a higher O2 affinity, further augmentation of O2 diffusion capacity in the periphery and multiple alterations in the metabolic properties of cardiac and skeletal muscle. These unique specializations improve the uptake, circulation and efficient utilization of O2 during high-altitude hypoxia. High-altitude birds also have larger wings than their lowland relatives to reduce the metabolic costs of staying aloft in low-density air. High fliers are therefore unique in many ways, but the relative roles of adaptation and plasticity (acclimatization) in high-altitude flight are still unclear. Disentangling these roles will be instrumental if we are to understand the physiological basis of altitudinal range limits and how they might shift in response to climate change.

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Ritchison

2023

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Control of Breathing in Birds: Implications for High-Altitude Flight

Cited by 13 publications

References 73 publications

Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates

Phenotypic plasticity and genetic adaptation to high-altitude hypoxia in vertebrates

Elevated performance: the unique physiology of birds that fly at high altitudes

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