basic bio- altitude sickness- spectrum of disorders that occur at high altitudes
- three major clinical syndromes: acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE), and high-altitude cerebral edema (HACE); these are on a continuum of severity, all caused by decrease in oxygen
- occurs because partial pressure of oxygen in atmosphere is too low at high altitudes
- driver of oxygen delivery to mitochondria is the pressure difference
- what counts as “high altitude” varies from person to person for unknown reasons; scientists use ~2,500m as a working definition
- hypoxia and hypoxemia cause hyperventilation (acclimatization)
adaptation to altitude- there is a genetic basis to adaptive phenotype. important genes and proteins include:
- EGLN1 encodes oxygen sensor PHD2
- EPAS1 encodes transcription factor subunit HIF-2α
- hypoxia inducible factors are a family of transcription factors that regulate response to oxygen levels
- continuously made and degraded depending on PHD levels
- Allele frequencies for EGLN1 and EPAS1 provide the strongest evidence for natural selection and association with adaptive phenotypes
- dampened hemoglobin phenotype beneficial because maintaining high hemoglobin levels is:
- costly in terms of fitness
- shown to have side effects such as higher risk of complications during pregnancy or Chronic Mountain Sickness
primary sources:
- Beall, Cynthia M. “Adaptations to High Altitude: Phenotypes and Genotypes”. Annual Review of Anthropology 43 (2014): 251-272. Web.
- Beall, Cynthia M. “Adaptations to Altitude: A Current Assessment”. Annual Review of Anthropology 30 (2001): 423–456. Web.
secondary source:
- Gupta, Kapil. "Altitude Sickness." The Gale Encyclopedia of Medicine. Ed. Deirdre S. Blanchfield and Jacqueline L. Longe. 2nd ed. Vol. 1. Detroit: Gale, 2002. 132-134. Gale Virtual Reference Library. Web. 29 Feb. 2016.