Summary
Low oxygen triggers erythropoietin, raising red cell count over days and weeks.
In depth
Lower partial pressure of oxygen causes hypoxia. Acclimatisation: hyperventilation, EPO release raising haematocrit, 2,3-BPG changes. Highlanders in Tibet and the Andes show genetic adaptations. Altitude sickness includes headache and, rarely, pulmonary oedema.
Acute mountain sickness is common above 2500 m. Acclimatisation takes weeks. Hypoxic ventilatory response increases breathing.
Example: Sherpas show adaptations such as efficient oxygen use.
At 5500 m, atmospheric pressure is about half of sea level, though the oxygen fraction is the same. Peripheral chemoreceptors trigger hyperventilation within minutes, producing respiratory alkalosis that kidneys compensate for over days via bicarbonate loss. Hypoxia induces HIF-1 and EPO over days, raising haematocrit, and increases capillary density and 2,3-BPG. Acute mountain sickness (headache, nausea) can progress to high-altitude pulmonary oedema or cerebral oedema, which are emergencies requiring descent.
Populations living at altitude show genetic adaptations: Tibetans have EPAS1 variants (from Denisovan ancestry) that limit haemoglobin rise; Andeans have higher haemoglobin; Ethiopians have other mechanisms. Training at altitude is used by athletes ("live high, train low"). Pilots and climbers need supplementary oxygen at extreme heights.
Example: the summit of Everest has about one third of sea-level oxygen pressure, and climbers use bottled oxygen.
Frequently asked questions
What is Altitude Physiology?
Low oxygen triggers erythropoietin, raising red cell count over days and weeks.
Which area of biology covers Altitude Physiology, and how advanced is it?
Altitude Physiology is one of the 51 topics in Human Physiology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Gas Exchange in Alveoli, Exercise Physiology, Respiratory Control.
Can you give an example of Altitude Physiology?
Climbers use acclimatisation stops.
What should I learn before Altitude Physiology?
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Altitude Physiology. Advanced topics assume the Intermediate vocabulary.
What topics are related to Altitude Physiology?
The closest topics to Altitude Physiology are Gas Exchange in Alveoli, Exercise Physiology, Respiratory Control, Acid-Base Balance. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Altitude Physiology?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Altitude Physiology. To practise the whole of Human Physiology, use the Human Physiology quiz.
How is Altitude Physiology different from Gas Exchange in Alveoli?
Altitude Physiology: Low oxygen triggers erythropoietin, raising red cell count over days and weeks. Gas Exchange in Alveoli: Oxygen and carbon dioxide diffuse across thin alveolar and capillary walls down concentration gradients. Read both side by side and note what each one explains.
How should I study Altitude Physiology step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Gas Exchange in Alveoli and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.