The Cardiovascular and Respiratory System

Every cell in the human body needs oxygen. Whether it’s the muscle cells in your baby toe helping you balance, or the cells in your temporal lobe of your brain bringing back memories of the smell of cookies baking in the oven, oxygen (O2), carbon dioxide (CO2) and several nutrients are the key ingredients to life.

There are 2 main systems responsible for the delivery of these “goods” (O2 + nutrients) to our bodies. The first system is responsible for bringing gases to and from the outside environment (The Respiratory System) and the other has the important role of the delivery system within our bodies (The Cardiovascular System). Both of these systems attempt to maintain “normal” function at times of rest or at low activity, and amazingly enough, can adapt to increases in physical activity both in the short term (acute) and in the long term (chronic). Let’s have a closer look at both systems.

The Cardiovascular System:

The Cardiovascular system or CV system for short is the internal delivery system. Keep in mind that it is equally important to remove waste products from the body as it is to bring in new "goods" for cellular processes.

The Cardiovascular system has 4 major roles:

1. to transport oxygen from the lungs to the tissues;
2. to transport carbon dioxide from the tissues to the lungs;
3. to transport nutrients from the digestive system to other areas in the body;
4. to transport waste products from sites of production to sites of excretion.

Long Description

Heart Dynamics

Now that you have learned about the three main components of the cardiovascular system, it’s time to examine the relationship between the three as a response to activity and as reflection of overall health.

Cardiac Output (Q)

Imagine the engine car on a train is at the back of a long train, which is on a circular track. As the engine pushes the train forward it moves the first car around the circular track right back to where it started (the station). This is very similar to what the heart does to blood. Your heart constantly pumps (Heart Rate or HR), moving blood around your body with each contraction (Stroke Volume or SV); this relationship is known as the Cardiac Output (Q).

Mathematically, cardiac output can be calculated by the following equation:

"Resistance to work" - Blood Pressure

As the contraction of the ventricles forces blood out of the heart into the aorta it is pushing the blood throughout the system forward and eventually back to the heart. Now the easier it is to push the blood through the overall system, the less work there is for the heart. The resistance to flow both during the contraction phase (systole) or the when the heart is relaxed (diastole) is what we call blood pressure and it is affected by a number of different variables.

The reading of blood pressure is done with 2 numbers. The first number is the systolic pressure followed by the diastolic pressure to give you a reading in mmHg (millimeters of mercury). Doctors have prescribed the average blood pressure to be approximately 110/80 mmHg. Readings above and below the average are reflective of the overall health of the cardiovascular system and may be warning signs of other health related issues.

The following infograph includes risk factors and causes of high blood pressure:

You can see a larger version of the infographic above .

Actute versus Chronic Blood Pressure Changes

Acute blood pressure changes can occur in the simplest ways. Have you ever been dizzy after standing up first thing in the morning after a long sleep? That’s called postural hypotension, or low blood pressure due to change in body position. One way to help out in that situation is using what is called the "Valsalva technique". This is what you do when you go to lift something heavy and you hold your breathe and contract your abdominal muscles to create a stronger core from which to lift.

This is the same technique pilots use when trying to keep blood in their brains during G-Force (gravitational force) testing to become fighter pilots. They do this so that they don’t pass out as blood is being forced down into their bodies away from their brains as they spin in large centrifuges.

The Respiratory System

Long Description

The following video reviews the components involved in taking a breath:

So what does smoking do to the respiratory system?

When you inhale smoke from a cigarette you damage the very tissues that connect the outside world to the internal workings of the human body with respects to gas exchange.

The microscopic air sacs of the lungs, called the alveoli, are particularly sensitive to the effects of cigarette smoke. When these alveoli are damaged, the exchange of oxygen and carbon dioxide can not occur as efficiently.

The damage from cigarette smoke to the alveoli of the lungs can cause symptoms such as shortness of breath after activity, coughing and hacking and susceptibility to lung infections such as pneumonia. These symptoms get worse over time as you continue to smoke. Eventually, this may develop into chronic obstructive pulmonary disease, or COPD, which can develop into respiratory failure. COPD encompasses emphysema and chronic bronchitis, both of which make it hard for a person to get enough oxygen.

When we exercise, working muscles require a significant response from the body with respects to the need for oxygen and removal of carbon dioxide. It is also extremely important as the movement of these gases help in the regulation of blood pH levels.

As discussed previously in the activity on the 3 main energy systems, you may recall how during glycolysis, lactic acid is produced. The increase in the movement of CO2 aids in the buffering of this and other acids to maintain proper blood pH and functioning of the muscular system during exercise.

Taking it to the max!

In order to fully see the effects of the gas exchange requirements during exercise it is interesting to measure the amount of oxygen going into the "battle" and compare it to the amount of oxygen coming back out (not being used). This is an extremely important measurement when examining the efficiency of the cardiovascular system and can be used to as a means of testing the training effects on individuals with respects to their exercise capabilities.

The comparison of the amount of oxygen inspired compared to the amount expired is referred to as VO₂ or ventilatory oxygen. It reflects the efficiency of the overall cardiovascular system in bringing in oxygen, transporting it to working muscles, and how well the muscles use the O₂ in cellular respiration.

In terms of testing an individual’s capacity to adapt to the demands of exercise, it is best to observe the body’s ability during maximal testing of VO₂, known as the VO₂ max test. The VO₂ max test is one of the most grueling and painful exercise tests that can be done. Often performed on a stationary bicycle (although there are others such as treadmill, and rowing tests), a subject is asked to perform the activity as the intensity is programmed to increase at set intervals.

Heart rate and ventilation are measured to determine if the test subject has reached their VO₂ max as reflected in combination with reaching a maximum heart rate, stroke volume and VO₂ difference. The amazing part of this test is that the data recorded can indicate whether or not the subject has actually reached their maximal oxygen uptake or if they have just succumbed to the negative "feeling" associated with pushing their bodies to high intensity exercise.

The following video does a good job of demonstrating and reviewing VO₂ Max testing: