| 1.
The heart is a muscular pump whose periodic contraction (beat) causes blood to
flow through the circulatory system
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| 2.
Within the circulatory system, blood carries oxygen O2 and carbon dioxide CO2
(the respiratory gases), nutrients, waste products, and hormones to and from
every cell in the body
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| 3.
The respiratory gases are exchanged (uptake of oxygen, release of carbon dioxide)
within the lungs
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| 4.
Vertebrates have a closed circulatory system, consisting of a heart, arteries,
capillaries and veins
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| 5.
The amount of blood leaving the heart each minute (cardiac output) is the product
of the heart rate (number of beats/minute) and the amount of blood pumped with
each beat (ml/beat)
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| 6.
The pressure in the aorta (just outside the heart) is determined by the product
of the cardiac output and the total peripheral resistance
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| 7.
Peripheral resistance is a function of arterial diameter which can be controlled
by smooth muscle cells that surround these vessels; their state of contraction
is controlled by the autonomic nervous system
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| 8.
The pressure at any point in the circulatory loop is determined by the volume
of blood that is contained there and the compliance at
that point
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| 9.
The pressure gradient across an organ or tissue and the resistance to flow (a
function of vessel diameter) determines the flow/minute through the organ or
tissue (the perfusion rate)
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| 10. The
cardiovascular system is homeostatic. It acts to
hold constant the pressure in the aorta (mean arterial
pressure) by controlling the function of the heart (heart
beat rate, contraction strength) and the circulatory
resistance . |
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| 11.
The resistance to blood flow in an organ or tissue is determined by the local
metabolic activity and blood vessel diameter; signals from the autonomic
nervous system regulate blood vessel diameter . |
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| 12.
Most animals are aerobic. To survive they require molecular oxygen (O2),
which they use as an electron acceptor (producing water) during respiration. O2
is obtained from the atmosphere. Its presence in the atmosphere is due
to its release as a waste product during photosynthesis . |
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| 13.
Aerobic organisms produce carbon dioxide as a waste product, it must be disposed
of into the atmosphere
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| 13.
O2 is captured from the atmosphere in the lungs and carried to the tissues (where
it is used by the cells). Carbon dioxide (produced in the cells) is carried
from the tissues to the lungs, where it is released, by the circulatory system . |
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| 14.
Air, which consists of ~20% O2 and little (~0.035%) carbon dioxide, is brought
into the lungs by the contraction of the inspiratory muscles (define?). This
leads to a sub-atmospheric pressure in the lungs. Air flows in through
the respiratory tree driven by the resulting pressure gradient . |
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| 15.
Air leaves the lungs (containing much less O2 and significantly higher levels
carbon dioxide) when the inspiratory muscles relax; elastic recoil of the lungs
creates a pressure greater than atmospheric and the resulting pressure gradient
drives flow
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| 16.
O2 diffuses from the air in the lungs into the blood, carbon dioxide diffuses
from the blood into the air in the lungs, both gases move down their respective
partial pressure gradients
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| 17.
The partial pressure of O2 in the lungs is directly determined by alveolar ventilation
and inversely determined by the rate of O2 consumption. The partial pressure
of carbon dioxide in the lungs is inversely determined by alveolar ventilation . |
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| 18.
O2 is transported in the blood bound to the protein hemoglobin, which is present
within red blood cells. Carbon dioxide is transported predominately as
bicarbonate ions |
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| 19.
The respiratory system is homeostatic. It regulates the partial pressure
of O2 and carbon dioxide in arterial blood . |
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