1) When people engage in strenuous physical activity like mountain climbing, their bodies increase oxygen consumption and energy demands. 2) In response, the circulatory and respiratory systems work to increase oxygen delivery and carbon dioxide removal. The heart rate and stroke volume increase to pump more blood. Arterioles dilate to direct blood flow to active muscles. Breathing rate and depth increase through the respiratory centers in the brain. 3) At high altitudes where oxygen is low, the body responds to hypoxia through increased ventilation and other mechanisms like raising red blood cell count. However, this can lead to issues like hypocapnia, respiratory alkalosis, and pulmonary edema. Oxygen treatment is the most

1. LIU KUNPENG
117797

2. Circulatory system and respiratory system
response to strenuous activity
When people is climbing the mountain, they are in a
high intensity and high duration physical exercises.
Normally we all will feel our breath is deeper, our heart
is bumping faster. This is because our body cells are
in high metabolic condition which need consume
more energy and oxygen.
Increasing blood flow to certain part of our body can
supply the energy and oxygen. This is increased by
both a rise in heart rate and the stroke volume. A
more forcible systolic contraction can help increase
empty the heart.

3. The increase in heart rate is mediated by noradrenergic
sympathetic nervous system, vagal inhibition and is
sustained by autonomic sympathetic responses and
carbon dioxide acting on the medulla. Thus the heart
rate and stroke volume can increase to about 90% of
their maximum value.
Increasing heart rate and stroke volume can increase
the blood carry material more efficiently, but when
people in strenuous activity, some of their organ like
stomach and gut do not need much energy. So there
are some mechanism can increase the blood volume
in some particular organs and tissue.
The vascular smooth muscle cells surrounding the
arterioles are sensitive to the concentration of
substances such as oxygen and carbon dioxide.

4. Decreasing in oxygen or increasing in oxygen
tend to cause vasodilation
Vasodilation can increase the blood flow to the
certain tissue where lack of oxygen and
energy. Not only supply oxygen and
energy, the increasing in blood volume can
also carry more waste like carbon dioxide
away from the body.
Further more, the vascular muscle cells can
release a small amount of nitric oxide all the
time which helps to keep the arterioles
dilated.

5. When body in high consumption of oxygen and
energy, the nitric oxide can also be released in
the arterioles of skeletal muscles which result
in vasodilation so that increase in supplying
the oxygen and blood meanwhile carrying
away carbon dioxide.
The arterioles can also respond to the extrinsic
controller such as nervous and endocrine
system. The smooth muscle can also be
controlled by the sympathetic nervous system.

6. The adrenergic receptors can bind to the
norepinephrine released by sympathetic
neurons, can cause vasoconstriction. During
strenuous activity, the norepinephrine
released because of the increasing in
sympathetic activity can cause the vascular
smooth muscle on the arterioles leading the
gut and kidney to contract.
This vasoconstriction can result in blood flow
away the organs which do not need much
energy but focusing on supplying energy to
necessary organs and tissues.

7. The increasing in oxygen supply need the help of
respiratory system. This can be done by increasing
the pulmonary ventilation. When we breathe faster
is to increase the respiratory rate. When we breathe
deeper is to increase the tidal volume.
Human body have internal CO2/pH chemoreceptors
that monitor the CO2 and pH of the blood.
The central chemoreceptors respond to pH change in
blood. Because there of the carbonic anhydrase
equilibrium, these chemoreceotors can also sense
the carbon dioxide level in the blood.

8. The peripheral chemoreceptors are the carotid
body chemoreceptor which monitor the
composition of blood going to the brain and
the aortic body chemoreceptor which monitor
the composition of blood going to the body.
These receptors can detect the oxygen level in
blood and transmit the signals via afferent
sensory neurons.
All those signals will be transmitted to the
central pattern generators within the medulla
of the brain.

9. Finally, the respiratory pattern generators send
signals to the somatic motor neurons which
control the skeletal muscles involving in
Breathing. So rate and depth of ventilation is
increased.

10. Circulatory system and respiratory
system response to hypoxia
When people climb the mountain and reach a
high altitude where the air in atmosphere is
subtle, Their body may show different kinds of
symptoms by the decreasing of blood oxygen
level.
The drop in blood oxygen level can be detected
by arterial chemoreceptors, then those
receptors will send a signal to the medulla in
order to increase the rate and depth of
breathing.

11. The first symptom hypocapnia may be shown
due to the increasing ventilation rate. Because
the more oxygen are absorbed, the more
carbon dioxide are released at the same time.
People that may feel hard to breathe is mostly
because of the low carbon dioxide level in
blood because the carbon dioxide can also
drive the oxygen to be absorbed.
Low carbon dioxide lead to low proton level
[H+ ]in blood , which will cause respiratory
alkalosis. This symptom will also trigger the
kidney to excrete HCO3− in to the blood.

12. High attitude hypoxia can result in increasing
the number of the red blood cell, the
erythrocyte. This increase the viscosity of
blood which can impair blood flow through
the capillaries and interfere with gas exchange
at the tissue.
Hypoxia can also increase the level of 2.3-DPG in
the red blood cell. This can decrease the
oxygen affinity.

13. The low oxygen level cause the pulmonary
arterioles to vasoconstrict and reduce
perfusion of the lungs. Then the input oxygen
will decrease and the blood pressure within
lungs will increase. This can cause a dangerous
symptom which called pulmonary edema.
Other symptoms such as headache, fatigue,
numbness and nausea are also common.

14. The treatment of hypoxia is trying to put the
oxygen level in blood return to normal.
The most effective and directly treatment is to
supply enough oxygen to patients. For
example use the oxygen concentrator to
accumulate oxygen and provide them with
patients.
There may not have many differences between
male and female in facing the problem of
hypoxia. But differences between different
individuals may are existing.