Cardiovascular Functions

The following is a non-exhaustive discussion of various cardiovascular functions, such blood and oxygen flow through the body, cardiac output and blood pressure.

Blood Distribution

The body has a number of mechanisms for controlling its circulation of blood. For instance, blood vessels can constict and dialate as way control the quantity of blood that flows to an area. At the same time, by closing specific blood vessel pathways, the blood can be shunted, so that it is delivered to parts of the body that need it most, as seen in thermal regulation and exercise:

When cold, for example, blood is redirected away from the extremities and towards the your core, which contains the most heat and your vital organs.
In contrast, when hot, blood rises closer to the surface of the skin for evaporative cooling.
When we exercise, the blood capillaries to the muscles are all open to facilitate nutrient, oxygen and waste product exchange.

Venous Return

This is the blood that returns from the systemic veins back to the heart through the right atrium. It is de-oxygenated blood and carries carbon dioxide by-product from the body's cells to be released in the lungs.

Venous Pooling

Venous pooling occurs when blood accumulates within the systemic veins when one stands up too quickly or is inactive for long periods following exercise. The consequential lack of blood flow through your head may result in dizziness or at worse, fainting. By doing light continuous movements (ex. walking) following a workout, you can avoid this fate since the contractions of your skeletal muscles squeeze blood back to your upper body.

Blood Pressure

Skeletal muscle contractions and the pumping of the heart generates the pressure that drives blood through the circulatory system. Thus, blood pressure is greatest in the arterial system closest to the heart and gradually ebbs as the distance increases. The pressure is lowest in the capillaries, where the cross-sectional area is the greatest in the blood vessel network. The slower blood flow assists the transfer of nutrients and waste-products between the blood and body's tissues.

Heart Sounds

The "thump bump" sounds that your you hear from your heart is produced by the closing of the valves between the heart chambers in each stroke cycle. The initial "thump" is made by the valve between the atria and ventricles. The subsequent "bump" is the valves closing between the ventricles and pulmonary artery and aorta.

Coronary Arteries

The arteries that surround and provide oxygen to the heart. Blocked or constricted (hardened) coronary arteries can lead to angina pectoris or heart attack.

Ischemia

Reduced blood supply to an organ or body part. Ischemia is often accompanied by pain and/or functional loss of the affected region.

Hypoxia

A state where insufficient oxygen is delivered to the tissues, such as during anaerobic exercise. Prolonged periods of hypoxia can lead to cell death.

Heart Rate

Your heart rate is the number of time your heart beats per minute (bpm).

Stroke Volume

Stroke volume is the amount of blood that is pumped out by the left/right ventricle of the heart per cycle. For the average adult, the stroke volume would be around 75 mL at rest. This value would be greater for individuals who have trained their cardiovascular system.

Cardiac Output

Do not get this mixed up with the stroke volume. Your cardiac output is the total volume of blood that is pumped by the left/right ventricle per minute. This can be calculated by multiplying your stroke volume with your heart rate as follows:

Cardiac Output = Heart Rate x Stroke Volume At rest, the cardiac output is generally 5-6 litres per minute. In exercise however, this value can increase to 30 liters per minute.

Max VO₂

Also known as Maximal Oxygen Uptake or Maximal Aerobic Power, your Max VO₂ is the maximum volume of oxygen that can be taken in for exercise. Accordingly, your Max VO₂ is a representation of your aerobic fitness to transport oxygen in your body and use it for metabolic processes. Max VO₂ can be measured in liters per minute (absolute) or milliliters per kg body mass per minute (relative).

Hemoglobin

Hemoglobin is an iron containing protein that plays a critical role in respiration. Found in red blood cells, hemoglobin carries oxygen from the lungs to the rest of the body. At the same time, hemoglobin remove carbon dioxide, a metabolic waste, from the body's cells back to the lungs to be released.

Myoglobin

Myoglobin is a globular protein found in muscle tissues that facilitates the transport of oxygen from the capillaries to the mitochondria of muscle cells. The the red colour of slow twitch fibers is a result of the presence of myoglobin, whereas fast twitch fibers are white due to its reduced quantity.

The Cardiovascular System - Learn how your heart works to deliver blood through your body.

Cardio Fitness Training - Design an effective cardio training program based on fitness principles.

Heart Conditions and Diseases - Learn about various types of heart conditions and diseases.