Cardiorespiratory Physiology
Supporting Metabolism
Why do We Need a Cardiorespiratory System?
• Provides oxygen for oxidative phosphorylation (aerobic respiration), to produce
sufficient amounts of ATP required for cellular processes.
• Metabolism requires O2.
• CO2 is a product of the TCA cycle, therefore metabolism produces CO2.
• The uptake of O2, and the outtake of CO2 can be a measure of metabolism.
• The use of O2 and production of CO2 in oxidative phosphorylation metabolism, occurs
within mitochondria.
• We can define and quantity metabolism at the mitochondrial level, but we can also take
into account the whole body (how much oxygen are all the mitochondria in all my cells
taking up per minute?).
• This is known as whole body VO2 consumption, which is 250ml/min at rest.
• We can also look at the whole body VCO2 production, which is 200ml/min at rest.
• Where the symbol V = air flow.
• When we are thinking about how the cardiorespiratory systems supports metabolism,
we tend to consider conditions during exercise…
- How will the system deliver extra oxygen for mass ATP generation in skeletal
muscles?
- How will the system remove the excess CO2 created during oxidative
phosphorylation in skeletal muscles?
Metabolism Uses O2 and Produces CO2
• We add a substrate (e.g. glucose, fatty acids… etc) and oxygen, oxidising the substrate.
• At the mitochondrial level…
- Fats for example, complete oxidation/combustion of Palmitic Acid:
* C16H32O2 + 23O2 → 16CO2 + 16H2O.
- Proteins for example, complete oxidation/combustion of Albumin:
* C72H112N18O22S + 77O2 → 63CO2 + 38H2O + SO3 + 9CO(NH2)2.
- Carbohydrates for example, complete oxidation/combustion of Glucose:
* C6H12O6 + 6O2 → 6CO2 + 6H2O.
• We can see that in the reaction of each of the substrates, oxygen is always used and
carbon dioxide is always produced.
• The respiratory quotient (RQ) is the ratio between CO2 production and O2
intake…
- Fats RQ = 16/23 = 0.696.
- Proteins RQ = 65/77 = 0.818.
- Carbohydrates RQ = 6/6 = 1.0.
• We can also use this to calculate the RQ of the body…
- RQ = 200/250 = 0.8.
- Whilst it may seem from this value that proteins are our main metabolite fuel, they are
important and required for other processes in the body, and only metabolised when
in starvation mode.
- At rest, 70% of energy is released by fats.
- At rest, 30% of energy is released by carbohydrates.
- This is true when considering the ‘whole’ body, different tissues will utilise these
substrates in metabolism differently.
, - As our metabolism changes, whether between rest, exercise and starvation, our
‘whole’ body’s fuel consumption composition changes (no longer just 70% fats, 30%
carbohydrates).
- We know that ATP can be generated anaerobically by glycolysis, using
carbohydrates, it is a fast process and occurs primarily in exercise.
- As a result, this will input more substrates into the TCA cycle for oxidative
phosphorylation, and our metabolism begins to rely more on carbohydrates as a fuel
during exercise.
- Therefore, during exercise, percentage of energy being released by carbohydrates
increases, and percentage of energy being released by fats decreases.
- RQ is based on our dietary intake, and the calculated RQs above are based on a
mixed diet.
- If we want to take an instantaneous measurement of carbon dioxide production (at a
certain point in time), and want to discuss how it may change throughout exercise,
we use the symbol R instead of RQ.
- R (known as RQ if measured over time) will increase above 1.0 as we begin to rely on
anaerobic respiration (glycolysis) as observed during exercise.
* This is because we continue to produce CO2, whereas we do not take up any O2.
Functions of the Respiratory System
Actions of the Cardiorespiratory System
• Functions relate to the anatomy/structure of the system.
• Blood from the left side/ventricle of the heart will be pumped around
the entire body.
• Once the oxygenated blood reaches capillaries within certain
tissues, oxygen will be delivered to these cells to support their
metabolism.
• Carbon dioxide then produced at these tissues, will be picked up by
the venous circulation and enter the right side of the heart.
Deoxygenated blood at this right side will be pumped around the
pulmonary circulation.
• As the blood enters the capillaries of the lungs, CO2 is lost and O2 is
picked up, where this now oxygenated blood will return back into
the left side of the heart, ready to be pumped around the entire
body.
• All cardiac output (amount of blood pumped out of the heart per
minute, cardiac output of the systemic circulation is that of the left side of the heart
which will then return to the right side, and become the cardiac output of the right side
which will be that of the pulmonary circulation) flows through the pulmonary circulation.
• Normally, the cardiac output of the left side of the heart, is the same as the right side.
Functions
• Gas exchange…
- Oxygen input and carbon dioxide output in the lungs.
- Oxygen is circulated around tissues and taken-up, whilst carbon dioxide is picked-up
into the blood and transported away to the lungs.
• Blood pH control…
- Carbon dioxide is an acidic gas, metabolism also produces acidic hydrogen ions.
Supporting Metabolism
Why do We Need a Cardiorespiratory System?
• Provides oxygen for oxidative phosphorylation (aerobic respiration), to produce
sufficient amounts of ATP required for cellular processes.
• Metabolism requires O2.
• CO2 is a product of the TCA cycle, therefore metabolism produces CO2.
• The uptake of O2, and the outtake of CO2 can be a measure of metabolism.
• The use of O2 and production of CO2 in oxidative phosphorylation metabolism, occurs
within mitochondria.
• We can define and quantity metabolism at the mitochondrial level, but we can also take
into account the whole body (how much oxygen are all the mitochondria in all my cells
taking up per minute?).
• This is known as whole body VO2 consumption, which is 250ml/min at rest.
• We can also look at the whole body VCO2 production, which is 200ml/min at rest.
• Where the symbol V = air flow.
• When we are thinking about how the cardiorespiratory systems supports metabolism,
we tend to consider conditions during exercise…
- How will the system deliver extra oxygen for mass ATP generation in skeletal
muscles?
- How will the system remove the excess CO2 created during oxidative
phosphorylation in skeletal muscles?
Metabolism Uses O2 and Produces CO2
• We add a substrate (e.g. glucose, fatty acids… etc) and oxygen, oxidising the substrate.
• At the mitochondrial level…
- Fats for example, complete oxidation/combustion of Palmitic Acid:
* C16H32O2 + 23O2 → 16CO2 + 16H2O.
- Proteins for example, complete oxidation/combustion of Albumin:
* C72H112N18O22S + 77O2 → 63CO2 + 38H2O + SO3 + 9CO(NH2)2.
- Carbohydrates for example, complete oxidation/combustion of Glucose:
* C6H12O6 + 6O2 → 6CO2 + 6H2O.
• We can see that in the reaction of each of the substrates, oxygen is always used and
carbon dioxide is always produced.
• The respiratory quotient (RQ) is the ratio between CO2 production and O2
intake…
- Fats RQ = 16/23 = 0.696.
- Proteins RQ = 65/77 = 0.818.
- Carbohydrates RQ = 6/6 = 1.0.
• We can also use this to calculate the RQ of the body…
- RQ = 200/250 = 0.8.
- Whilst it may seem from this value that proteins are our main metabolite fuel, they are
important and required for other processes in the body, and only metabolised when
in starvation mode.
- At rest, 70% of energy is released by fats.
- At rest, 30% of energy is released by carbohydrates.
- This is true when considering the ‘whole’ body, different tissues will utilise these
substrates in metabolism differently.
, - As our metabolism changes, whether between rest, exercise and starvation, our
‘whole’ body’s fuel consumption composition changes (no longer just 70% fats, 30%
carbohydrates).
- We know that ATP can be generated anaerobically by glycolysis, using
carbohydrates, it is a fast process and occurs primarily in exercise.
- As a result, this will input more substrates into the TCA cycle for oxidative
phosphorylation, and our metabolism begins to rely more on carbohydrates as a fuel
during exercise.
- Therefore, during exercise, percentage of energy being released by carbohydrates
increases, and percentage of energy being released by fats decreases.
- RQ is based on our dietary intake, and the calculated RQs above are based on a
mixed diet.
- If we want to take an instantaneous measurement of carbon dioxide production (at a
certain point in time), and want to discuss how it may change throughout exercise,
we use the symbol R instead of RQ.
- R (known as RQ if measured over time) will increase above 1.0 as we begin to rely on
anaerobic respiration (glycolysis) as observed during exercise.
* This is because we continue to produce CO2, whereas we do not take up any O2.
Functions of the Respiratory System
Actions of the Cardiorespiratory System
• Functions relate to the anatomy/structure of the system.
• Blood from the left side/ventricle of the heart will be pumped around
the entire body.
• Once the oxygenated blood reaches capillaries within certain
tissues, oxygen will be delivered to these cells to support their
metabolism.
• Carbon dioxide then produced at these tissues, will be picked up by
the venous circulation and enter the right side of the heart.
Deoxygenated blood at this right side will be pumped around the
pulmonary circulation.
• As the blood enters the capillaries of the lungs, CO2 is lost and O2 is
picked up, where this now oxygenated blood will return back into
the left side of the heart, ready to be pumped around the entire
body.
• All cardiac output (amount of blood pumped out of the heart per
minute, cardiac output of the systemic circulation is that of the left side of the heart
which will then return to the right side, and become the cardiac output of the right side
which will be that of the pulmonary circulation) flows through the pulmonary circulation.
• Normally, the cardiac output of the left side of the heart, is the same as the right side.
Functions
• Gas exchange…
- Oxygen input and carbon dioxide output in the lungs.
- Oxygen is circulated around tissues and taken-up, whilst carbon dioxide is picked-up
into the blood and transported away to the lungs.
• Blood pH control…
- Carbon dioxide is an acidic gas, metabolism also produces acidic hydrogen ions.
