Lecture 34: Altitude Flashcards
What are the effects of increased altitude on sprinting and long-distance exercise?
Sprint times increase as there is less air resistance to high-speed movements
Long-distance times worsen as there is less oxygen delivery to muscles
Describe Boyle’s Law.
The volume of gas is inversely proportional to the partial pressure
What happens to O2 content and O2 pressure with increasing altitude?
O2 content remains at the same percentage
Pressure decreases with altitude
How do high altitudes lead to physiological responses?
Hypoxia –> lower PO2 in alveoli –> lower PO2 in arteries –> disrupted homeostasis –> Cardiac, respiratory and neuroendocrine changes are made
What are the physiological areas that are affected by altitude?
Lungs Haemoglobin Cardiac Output Muscle blood flow Oxygen extraction Cellular metabolism
Which physiological factor is significantly higher at sea level compared to high altitude?
Oxygen extraction
What immediate responses occur to high altitude?
Peripheral chemoreceptors detect PO2 fall, therefore ventilation increases
Causes increased O2 in the alveolar, less CO2 and more alkalotic conditions
Also an increase in heart rate and CO
What are the effects of increasing altitude on exercise performance?
Decreased VO2 max performance
Increased oxygen consumption at every intensity
What are the short term responses to altitude?
Increased:
SaO2
PAO2
Alkalosis (slows down)
Ventilation
Decreased:
PCO2
What causes the increased HR & cardiac output during sub-max exercise at high altitude?
Increased sympathetic nerve activity
What happens to maximum heart rate at high altitudes?
It decreases
What does the injection of glycopyrolate show about the why max HR is attenuated at high altitudes?
Glycopyrolate blocks the parasympathetic nervous system
When using glycopyrolate, the maximum heart rate increased to the same amount as sea level, when at a high altitude
Shows that parasympathetic nervous system is lowering maximum heart rate
This is due to the increased O2 demand of the heart during exercise
Atmospheric PO2 is very low therefore this increase in demand has to be prevented
Give a summary of the short term effects of altitude on the physiological responses to exercise.
Increased HR and CO at submax Decreased maximum HR Increased ventilation Decreased VO2 max A-VO2 difference decreases massively
What is the effect of altitude acclimitisation on O2 consumption?
Decreases it
What are the physiological responses to altitude acclimitisation?
Greater ventilation (sensitisation of chemoreceptors)
Decreased SV and therefore CO
Increased RBC mass and decreased plasma volume
Increased capillarisation due to muscular atrophy
Increased oxidative enzyme activity
Increased myoglobin
Increased SNA (chemoreceptors more sensitive to PO2; also more noradrenaline)
