Chapter 4 - Blood and the cardiovascular system. This chapter commences with an overview of basic cardiovascular function, identifying the main anatomy and physiological functions of this system. Common diseases that affect the ability of the system to function will be explored, illustrating how an individual’s ability to perform the basic functions of life can be compromised; ultimately these diseases can result in the individual’s lifespan being shortened. | Chapter 4 Blood and the Cardiovascular System The Heart Provides the pump that ejects both deoxygenated blood to the lung and simultaneously oxygenated blood to the systemic circulation Weighs around 300grams Is positioned in the thoracic cavity in the mediastinum, resting between the right and left lungs. Figure The heart and its relationship with the blood and the lymphatic system Cardiovascular Function Figure demonstrates an overall picture of the function of the cardiovascular system. Optimum function requires several key components working in unison. The heart is an extremely muscular organ necessary for its principle action of providing the individual with a lifetimes supply of blood. Identifying the Apex Anatomy & Physiology in Action The cardiac cycle reflects the flow of blood through the heart during one heartbeat Depolarisation = discharging Repolarisation = recharging Systole = the contraction phase Diastole = the relaxation phase (filling) phase The atria contract and force blood down into the ventricles, in contrast the ventricles need to exert a pumping force to reach their targets. The contraction of the atria can result in between 20-30% more blood entering the ventricles, in disease states such as atrial fibrillation where the atria fail to adequately contract the individual can lose this amount of their cardiac output resulting in haemodynamic collapse. What Makes the Heart Pump? A combination of internal components result in the rate, force of contraction and rhythm of each heart beat (know as the rate, rhythm & depth). These are the: Mechanics Nervous stimulation Electrical activation Neurologic (involuntary control over the heart) Various neurologic factors regulate heart function; the most predominant is the autonomic nervous system. The heart is innervated via the cardiac centres in the brain by both sympathetic and parasympathetic fibres. Electrophysiological (the conduction system) The cardiac conduction system controls the . | Chapter 4 Blood and the Cardiovascular System The Heart Provides the pump that ejects both deoxygenated blood to the lung and simultaneously oxygenated blood to the systemic circulation Weighs around 300grams Is positioned in the thoracic cavity in the mediastinum, resting between the right and left lungs. Figure The heart and its relationship with the blood and the lymphatic system Cardiovascular Function Figure demonstrates an overall picture of the function of the cardiovascular system. Optimum function requires several key components working in unison. The heart is an extremely muscular organ necessary for its principle action of providing the individual with a lifetimes supply of blood. Identifying the Apex Anatomy & Physiology in Action The cardiac cycle reflects the flow of blood through the heart during one heartbeat Depolarisation = discharging Repolarisation = recharging Systole = the contraction phase Diastole = the relaxation phase (filling) phase The atria .
