Cardiorespiratory Performance (Human Biology III)

Students will cover a variety of related topics in order to learn how the cardiovascular and respiratory systems function cooperatively to keep the body alive.  Monitoring and regulatory mechanisms governing cardiorespiratory functions are investigated, along with the physical laws and biochemical processes that explain how and why the cardiorespiratory system works in the way it does.  From gas exchange, cellular energy production, cardiomyocyte contraction, alveolar structure and function, gas laws, blood physiology and cellular oxygen demand, students will develop a sound understanding of breathing and blood flow.

Lesson Structure

There are 7 lessons in this course:

1. The Science of Blood
2. Blood Pressure
3. Pulmonary Ventilation
4. Gas Exchange & Transport
5. Blood Flow & Gas Transport
6. Cardio Respiratory Control
7. Cardio Respiratory Disease

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.

What You Will Do

• Apply physical formulas to explain movement of gases in the body
• Understand the cellular need for oxygen
• Investigate removal of carbon dioxide from the body
• Learn the importance of carbon dioxide in blood chemistry
• Understand how cells produce energy aerobically and anaerobically, and how the body cardiorespiratory system deals with the waste products of these processes
• Develop their understanding of homeostasis and equilibrium, diffusion and osmosis and the importance of each to gas exhange
• Test concepts practically using common household items
• Analyse data from basic experiments to develop their knowledge of lesson topics
• Examine the role of fitness and exercise in cardiorespiratory health and function
• Interpret electrocardiograms
• Discover the impact of different conditions, illnesses and disease processes on cardiorespiratory performance

Sinoatrial Node (SA Node)

The sinoatrial node is found right at the top of the wall of the right atrium, near where the superior vena cava enters.  It is composed of modified cardiomyocytes that do not contract but transit electrical impulses much more rapidly than normal cardiomyocytes.  The cells of the sinoatrial node initiate the action potential that triggers cardiac muscle contraction.  It triggers action potentials without influence from the nervous system; however, the rate and strength of contractions are influenced by feedback from the nervous system and brain.  The sinoatrial node is essential the hearts natural pacemaker.  How often the cells of the sinoatrial node depolarise and trigger an action potential determines how often your heart will beat. 

The electrical impulses (action potentials) from the sinoatrial node trigger co-ordinated contraction of both atria by causing depolarisation of the cardiomyocytes in that area.  The impulse travels on to the atrioventricular node.

Atrioventricular Node (AV Node)

The atrioventricular node is found on the bottom wall of the right atrium, along the wall of cardiac tissue that divides the two atria.  It is also comprised of modified, non-contractile cardiomyocytes.  Its function is to hold up the electrical impulse from the sinoatrial node.  This provides a delay that allows the atria to fully contract before the cardiomyocytes of the ventricles are stimulated to contract.  This ensures that the ventricles are full of blood before they contract.  The electrical impulse then travels on to the bundle of His, also known as the atrioventricular bundle.  When the sinoatrial node is damaged, the atrioventricular node can take over as the primary pacemaker for the heart.

Bundle of His (Atrioventricular bundle)

The bundle of His is located immediately inferior to the AV node; in the wall (septum) that divides the ventricles.  It branches as it travels down the septum and functions to provide very rapid transmission of the electrical impulse from the AV node to the Purkinje fibres.  This function is due to the bundle also being composed of the modified non-contractile cardiomyocytes.

Purkinje Fibres

These are the terminal end of the electrical conduction system of the heart.  They run from the base of the septum up and around the outer walls of both ventricles.  Like the rest of the conduction system, they are made up of modified cardiomyocytes.  (The term fibre here refers to muscle fibres, or cells, not to nerve fibres). 

Credentials

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