The changes in your circulatory and respiratory system while climbing a mountain.

1. Climbing a mountain
Climbing a mountain is a strenous activity
which increases the metabolic demand of the
muscle cells. This causes the ventilation rate
and breathing frequency to increase as a
response to supply he muscles with oxygen.

2. High altitudes
At high altitudes the atmospheric pressure is
lower which lowers the partial pressure on
oxygen. This in turn decreases the density of
oxygen in the air. Thus the air that is delivered
to the lungs and into the alveolus has a lower
density of oxygen which affects the uptake of
oxygen negatively. This can cause
environmental hypoxia.

3. In the next slides I will explain the changes in
the respiratory and circulatory system for a
person at a high altitude. The changes that
occur can be a step towards acclimatization but
some can also be pathological.

5. When less oxygen is delivered through the
arteries this causes two things to happen.
First, the amount of oxygen delivered to the
tissues decreases which cause capillary density
and concentration of myoglobin to increase.
This act as a negative feedback loop on the
oxygen delivery to the tissues as it works to
increase the efficiency of the oxygen delivery.

6. The low amount of oxygen delivered to the
tissues also signals to the kidneys to synthesize
more erythropoietin – a glycoprotein
hormone that controls the synthesis of red
blood cells by promoting the survival of red
blood cell precursors in the bone marrow.
The increase in erythropoietin also act as a
negative feedback as it acts to the delivery of
oxygen to the tissues more efficient.

7. Lastly the low O2 delivered to tissues act to raise
the levels of 2,3-Disphosphoglycerate (2,3DPG).
The 2,3-DPG is present in human erythrocytes
(red blood cells). It has a chemical conformation
that gives it greater affinity for deoxygenated than
oxygenated hemoglobin. When it binds to the
deoxygenated hemoglobin it interacts with the
hemoglobins beta subunits and decreases their
affinity for oxygen.
This makes the hemoglobin release remaining
oxygen and thus increasing the efficiency of the
oxygen delivery.

8. The second effect of low amounts of oxygen in
the arteries is that it increases the peripheral
chemoreceptor firing rate which in turn signals
to the medullary central pattern generators in
that area to increase the rate of ventilation –
you start to hyperventilate.
This aims to increase the amount of air flowing
in and out of the lungs and thus act as a
negative feedback loop, but if the air is very
low in oxygen that alone is not enough.

9. If the hyperventilation continues without
generating enough oxygen it can result in a
condition called “respiratory alkalosis”.
In this condition the amount of CO2 is too low
in the blood (due to the intense breathing) and
the blood gets too alkaline, >7.45. This
condition raises the hemoglobins affinity for
oxygen, which counteracts the effects of the
2,3-DPG.

10. Also, even before the actual alkalosis, the CO2
in the blood is the primary trigger for the
breathing reflex. Thus low CO2 in the blood
may cause difficulties in breathing.

11. Symptoms of hypoxia:
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Fatigue
Lack of cognition
Lethargic
Headaches
State of euphoria
Shortness of breath
Loss of Consciousness
Pins and needles
High pulse rate
Deterioration of vision
Blue lips and fingernails
Moodiness
Drowsiness

12. Remedies for hypoxia
The primary remedy is supplying oxygen
through oxygen mask. If the cause is altitude it
is also (naturally) recommended not to
continue ascending. That goes for as long as
the symptoms do not worsen, if they do it is
highly recommended to descend to lower
altitudes.

13. For reasons that still remain to be found high
altitude sickness have been observed to affect
men more than women.
Being a woman does not however prevent you
from getting the sickness, it only lowers your risk.
The same goes for being in good physique and
health and not diving before ascending to high
altitudes.