Basic Physiology of the Cardiorespiratory System

• Cardiorespiratory system: system that circulates blood through the body; consists of the heart, blood vessels, and respiratory system (the lungs).

The Heart

• The heart is a four chambered, fist sized muscle located under our sternum (breast bone), just slightly off center to the left side of the chest.
• It pumps oxygen poor blood to the lungs and delivers oxygen rich blood to the rest of the body. There are 2 circulatory systems that accomplish these tasks.
  • Pulmonary circulation: circulatory system that moves blood between the heart and the lungs; controlled by the right side of the heart
  • Systemic circulation: circulatory system that moves blood between the heart and the rest of the body; controlled by the left side of the heart
• The heart has four valves that prevent blood flow to move backwards. They keep blood flowing in the correct direction.  Think of them as one-way doors that keep things moving correctly and efficiently.
  • Tricuspid-between the right atrium and right ventricle
  • Pulmonary-between the right ventricle and pulmonary artery
  • Mitral-between the left atrium and left ventricle
  • Aortic-between the left ventricle and aorta.

The Heart-Pathway of Blood Flow

1. Oxygen-poor blood travels through the venae cavae into the heart’s right upper chamber, or atrium.
2. After the right atrium fills, it contracts and pumps blood into the heart’s right lower chamber, or ventricle.
3. After the right ventricle is full, it contracts and pumps blood through the pulmonary artery, into the lungs.
4. Once in the lungs, blood picks up oxygen and discards carbon dioxide through the process of diffusion.
5. The clean, O2 rich blood flows from the lungs back to the heart through the pulmonary veins.
6. The blood collects in the left atrium and is then pumped to the left ventricle.
7. Finally it’s pumped to the aorta so it can be dispersed to the rest of the body.

Blood Pressure

The force exerted by blood on the walls of the blood vessels, is known as blood pressure.  During systole, or the period when the heart is contracting, blood pressure is greater.  During diastole, or the period when the heart is relaxing, blood pressure is lower.

Blood Pressure Recommendations

• Normal: Less than 120/80 mm Hg
• Elevated: Systolic between 120-129 and diastolic less than 80
• Stage 1 Hypertension: Systolic between 130-139 or diastolic between 80-89
• Stage 2 Hypertension: Systolic at least 140 or diastolic at least 90

Blood Vessels

• Veins: vessels that carry blood to the heart
• Arteries: vessels that carry blood away from the heart
• Capillaries: very small blood vessels that distribute blood to all parts of the body
• Coronary arteries: pair of large blood vessels that branch off the aorta and supply the heart muscle with oxygenated blood

The Respiratory System

The respiratory system supplies oxygen to the body and also rids the body of carbon dioxide.  Carbon dioxide is a waste product of body processes.  The respiratory system includes the lungs, air passages, and the muscles that help us breathe.

Air Flow and Exchange

• Air flows in and out of the lungs as a result of pressure changes.
• As the diaphragm muscle contracts and relaxes, air is drawn in and out of the lungs.
• As air is breathed in, it passes through the nasal passages, throat, larynx, trachea, and bronchi in the lungs.
• The lungs contain alveoli, tiny air sacs that allow the exchange of oxygen and carbon dioxide between the lungs and the blood.
• Carbon dioxide passes from blood cells into the alveoli, where it is carried out of the lungs during exhalation
• Oxygen from inhaled air is passed from the alveoli into blood cells; the oxygen rich blood cells are then returned to the heart and pumped out to the rest of the body.

The Cardiorespiratory System at Rest and During Exercise

Energy Production

The sum of all the bodies chemical processes necessary to maintain life is known as metabolism.  Energy is required to fuel bodily functions-build and break down tissue, contract muscles, conduct nerve impulses, regulate body temperature, etc.  Metabolic rate is the rate at which your body uses energy.  At rest, you have a low metabolic rate.  As you increase your activity level and movement in general, your metabolic rate increases.

Energy From Food

The body converts chemical energy from food into substances that the cells can use as fuel.  Fuels can be used immediately or stored for later use.  The three classes of energy-containing nutrients are: carbohydrates, fats, and proteins.  Carbohydrates are broken down into the simple sugar, glucose.  Some glucose circulates in the blood and some is converted to glycogen, where it’s stored (mainly in the liver and muscles) for later use.

Physical Fitness and Energy Production

Metabolic rate is increased substantially through movement, generating the energy needed for powerful or sustained exercise.  When we first begin a cardiorespiratory training program, we may find we are fatigued more rapidly, we have lower body soreness, and breathe heavily during the training.  These are normal occurrences for people who are just getting started with a program!  As you train and move more regularly, this will improve.  Your body’s ability to produce energy and meet the challenges of increased physical activity will become easier.

Benefits of Cardiorespiratory Endurance Exercise

Cardiorespiratory endurance exercise helps the body become overall more efficient.  We are more easily able to overcome physical challenges in our daily lives.  Lastly, cardiorespiratory endurance exercise lowers risk for many chronic diseases.  These are explained further below.

Improved Cardiorespiratory Functioning

Performing cardiovascular exercise leads to increases in cardiac output and blood pressure, breathing rate, and blood flow to skeletal muscles.  All of these elements help body respond to the challenge of physical activity.  When performed regularly, permanent adaptations in our bodies occur, making everyday tasks and physically challenging tasks, easier to perform.  This is what it means to be physically fit.

Improved Cellular Metabolism

Regular endurance exercise enhances your ability to produce and use energy efficiently.  Cardiorespiratory training improves metabolism by:

• Increasing the number of capillaries in the muscles. This supplies the muscles with more fuel and oxygen and allows them to more efficiently eliminate waste products. More capillaries also positively impacts injury healing rates.
• Training muscles to make the most of oxygen and fuel so they work more efficiently.
• Increasing the amount of mitochondria in muscle and brain cells, thereby increasing the cells’ capacity for energy.
• Preventing glycogen depletion
• Increases the ability of the cells to work effectively, preventing fatigue and abnormal heart rhythms.

Reduced Risk of Chronic Disease

Regular endurance exercise lowers your risk of many chronic, disabling diseases.  It can also help people with those diseases improve their health and quality of life.  These diseases include cardiovascular disease, cancer, type 2 diabetes, and osteoporosis.

Improved Immune Function

Moderate endurance exercise boosts immune function, whereas overtraining (excessive training) depresses it.  Physically fit people get fewer colds and upper respiratory infections.  Exercise affects immune function by influencing levels of specialized cells and chemicals involved in the immune response.

Improved Psychological and Emotional Well-Being

Most people who engage in regular exercise, experience social, psychological, and emotional benefits.  Recreational sports provide a means of socializing, and having fun!  When we master a new physical skill or reach a new goal, we feel good about ourselves which leads to more self-efficacy and desire to keep going with our movement activities.  Endurance activities lessen anxiety, depression, stress, and anger, thereby improving mood.

How to Assess Your Cardiorespiratory Fitness

There are several ways to measure your current state as it relates to your level of cardiorespiratory fitness.  Consult with your FTWL 106 lecture or activity instructor if you’d like to do a self-assessment.  Each link also shows how to do the respective test if you’d like to do an assessment on your own.

• 1 mile walk test
• 3 minute step test
• 1.5 mile run/walk test
• PACER or Beep test

Monitoring Your Heart Rate

It’s important to monitor your heart rate if your personal fitness goals include making improvements in cardiovascular fitness.

References

Khanacademymedicine. (2012, Oct 10). Flow through the heart-Circulatory system physiology-NCLEX-RN-Khan Academy [Video]. YouTube. https://www.youtube.com/watch?v=7XaftdE_h60

Mayo Clinic. (2013, Jun 19). The heart and circulatory system-how they work [Video]. YouTube. https://www.youtube.com/watch?v=CWFyxn0qDEU&t=180s

American College of Cardiology. (2017). New ACC/AHA High Blood Pressure Guidelines Lower Definition of Hypertension. https://www.acc.org/latest-in-cardiology/articles/2017/11/08/11/47/mon-5pm-bp-guideline-aha-2017

What’s Up Dude. (2020, Sept 7). What is heart rate zones training-how to do heart rate zone training-calculate max heart rate [Video]. YouTube. https://www.youtube.com/watch?v=2MvZ_7401aI

Salisbury University FTWL 106 Course-Module 3 Power Point