High-altitude adaptation in humans is an instance of evolutionary modification in certain human populations, including those of Tibet in Asia, the Andes of the Americas, and Ethiopia in Africa, who have acquired the ability to survive at altitudes above 2,500 meters. This adaptation means irreversible, long-term physiological responses to high-altitude environments, associated with heritable behavioural and genetic changes. While the rest of the human population would suffer serious health consequences, the indigenous inhabitants of these regions thrive well in the highest parts of the world. These people have undergone extensive physiological and genetic changes, particularly in the regulatory systems of oxygen respiration and blood circulation, when compared to the general lowland population. Around 81.6 million people, approximately 1.1% of the world's human population, live permanently at altitudes above 2,500 metres (8,200 ft)[4] putting these populations at risk for chronic mountain sickness (CMS). However, the high-altitude populations in South America, East Africa, and South Asia have done so for millennia without apparent complications. This special adaptation is now recognised as an example of natural selection in action. The adaptation of the Tibetans is the fastest known example of human evolution, as it is estimated to have occurred any time around 1,000 B.C.E. to 7,000 B.C.E.

1. HIGH
ALTITUDE
ADAPTATI
ONS
(In Homo sapiens)
14TH April, 2019
Guided By,
Sadashivaiah
Asst. Professor
Department of Molecular Biology
Yuvaraja’s College (Autonomous), Mysore
Presented By,
Shryli K S
4th Semester
Molecular Biology
Yuvaraja’s College (Autonomous), Mysore
1

2. INTRODUCTION
Fig 1: Tibetan high
altitude
natives.
Fig 2: American Andes
natives.
Fig 3: African Ethiopian
natives.
Graph 1: Marginal
frequency histograms
(filled bars) of number
of people by elevation
(a); occupied land area
by elevation (b);
number of people by
population density
( According to 1979-1994
census range)
2

3. CONTENTS
• Introduction
• Hypoxia
• Acclimatization to low Po2
• Reduced work capacity at high altitude
• Acute mountain sickness
• Chronic mountain sickness
• Natural Adaptations
• Death Zone
• Summary
• References
• Acknowledgement
3

4. HYPOXIA
Fig 4: Effects of hypoxia 4
Drowsiness Mental Fatigue Muscle fatigue Headache
Nausea Euphorbia Seizures Coma

5. 5

6. • Mental proficiency decreases.
• Decreases Judgment, memory & performance of discrete motor movements.
6
Table 1: Effects of Acute Exposure to Low Atmospheric Pressures on
Alveolar Gas Concentrations

7. ACCLIMATIZATION TO LOW PO2
The principle means by which acclimatization occurs are,
• Great increase in pulmonary ventilation.
• Increased number of red blood cells.
• Increased diffusing capacity of lungs.
• Increased Vascularity of peripheral tissue.
• Increased ability of tissue cells to use oxygen despite of low Po2
7

8. INCREASED PULMONARY VENTILATION
• Stimulates arterial chemoreceptors.
• Alveolar ventilation increases up to 1.65 of normal.
• Compensation occurs within seconds.
• It alone allows the person to rise several thousand feet above the sea-level.
• Further increases the ventilation up to 5 times.
8

9. INCREASED RED BLOOD CELLS (&
HEMOGLOBIN DURING
ACCLIMATIZATION)
9
Fig 5: Increase in RBC count during hypoxia.

10. INCREASED DIFFUSING CAPACITY
10
Fig 6: Diffusion of
respiratory gases
at the respiratory
membrane.
Fig 7: Increase in lung air
volume.

11. INCREASED VASCULARITY OF
PERIPHERAL TISSUES
11
Fig 8: Cardiac output increases 30% the
normal.
• Cardiac output increases.
• Increase tissue capillarity.
• High capillarity density in the right
ventricle.

12. CELLULAR ACCLIMATIZATION
12
Fig 9: Mitochondria

13. REDUCED WORK CAPACITY AT HIGH
ALTITUDE
13
Table 2: Work capacity of different type of people.

14. ACUTE MOUNTAIN SICKNESS
• High Altitude Cerebral Edema.
14
A
Fig 10: A) Normal human brain MRI scan. B) MRI scan of the
brain

15. • High Altitude Pulmonary Edema.
15
Fig 11: A) Scanned image of affected individuals lungs. B) Scanned
image of
HAPE unaffected lungs.

16. CHRONIC MOUNTAIN SICKNESS
• Red cell mass becomes high.
• Hematocrit increases.
• Pulmonary arterial becomes elevated.
• Right side of the heart becomes enlarged.
• Peripheral arterial pressure begins to fall.
• Congestive heart failure.
• Death often follows unless the person is removed to a lower altitude.
16

17. NATURAL ADAPTATIONS
17
Graph 2: Oxygen-hemoglobin dissociation curves
for blood of high-altitude residents (red curve) and
sea-level residents (blue curve), showing the
respective arterial and venous PO2 levels and
oxygen contents as recorded in their native
surroundings. (Data from
Oxygen-dissociation curves for bloods of high-
altitude and sea-level residents. PAHO Scientific
Publication No. 140, Life at High Altitudes, 1966.)

18. DEATH ZONE
18
Fig 12: The Eight Thousanders.

19. 19
SUMMARY

20. REFERENCES
• Textbook of medical Physiology, 11th edition. Guyton and Hall. Elsevier Inc. 1600 John
F. Kennedy Blvd., Suite 1800 Philadelphia, Pennsylvania 19103-2899. 1152 pages, 2006.
• Hypsographic demography: The distribution of human population by altitude Joel
Cohen and Christopher Small PNAS November 24, 1998 95 (24) 14009-
14014; https://doi.org/10.1073/pnas.95.24.14009 Contributed by Joel E. Cohen.
• Clin Endocrinol (Oxf). 1995 Jul;43(1):11-8. The effects of high altitude on
hypothalamic-pituitary secretory dynamics in men. Ramirez G1, Herrera R, Pineda D.
• High-altitude adaptations s14 THE LANCET Extreme medicine ■ Vol 362 ■ December
2003 ■ www.thelancet.com Cynthia Beall at the Department of Anthropology, Case
Western Reserve University, 238 Mather Memorial Building, 11220 Bellflower Road,
Cleveland, OH 44106-7125, USA.
• https://en.wikipedia.org/wiki/High-altitude_adaptation_in_humans
20

21. ACKNOWLEDGEMENT
I thank the department of Molecular Biology for giving me an opportunity to present my
seminar. I would also like to thank my guide Mr Sadashiviah for his valuable guidance
and support.
Thank you all.
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