| Describe the structure and function of the heart and | | | | delay of 0.1 seconds allows the atria to fully contract |
| explain how it responds to exercise or disease. How | | | | and force the blood into the ventricles. The AV |
| could you measure this clinically or in the laboratory? | | | | Bundle (Bundle of His), then, speeds the impulse rapidly |
| | | | | through the ventricles over the Purkinje Fibres (fibres |
| | | | | penetrating the left and right ventricles), causing |
| The heart is anchored and protected by the pericardial | | | | contraction of the ventricles. |
| sac. The pericardium has two layers; the fibrous | | | | |
| pericardium and the serous pericardium. These two | | | | Stimulation of the sympathetic cardio-accelerator |
| layers work in conjunction with each other to prevent | | | | nerves releases neural hormones, such as epinephrine |
| the heart from over-stretching, thus, preventing over | | | | and norepinephrine. These hormones increase |
| filling of the heart but also allows for rapid and vigorous | | | | myocardial contractibility by accelerating depolarization |
| contraction where required. | | | | of the SA Node, this increases the heart rate. The |
| | | | | parasympathetic nervous system releases hormones, |
| Between the two pericardial layers is the pericardial | | | | such as acetylcholine. These hormones have |
| cavity which is filled with serous fluid. This fluid | | | | opposite effect on the heart’s activity. This |
| contributes to the protection of the heart as it provides | | | | change in neural hormone release occurs when there |
| lubrication allowing the heart to contract free from | | | | is an increase or decrease in physical activity. |
| friction. | | | | |
| | | | | |
| The heart is made up of three layers; the epicardium, | | | | Cardiac output components in endurance-trained and |
| myocardium and the endocardium. | | | | untrained subjects during rest and maximal exercise |
| | | | | |
| The heart acts as a dual pump. The left side of the | | | | |
| heart pumps blood to and from the lungs, this is the | | | | Cardiac output (ml) |
| pulmonary circulation and the blood being distributed by | | | | Heart rate (b. Min-1) |
| the right side of the heart is pumped around the rest | | | | Stroke Volume (ml. B-1) |
| of the body via the systemic circulation. | | | | Untrained |
| | | | | Rest |
| Each “pump” consists of atria and ventricles. | | | | Maximal Exercise |
| The atria are located superior to the ventricles and are | | | | |
| made up of thin, smooth walls covered with | | | | 5000ml |
| endothelium. | | | | 22,000ml |
| | | | | |
| The ventricles have thicker muscles than the atria; this | | | | 70 b. Min-1 |
| allows the ventricles to provide enough force for the | | | | 195 b. Min-1 |
| blood to be pumped out of the heart to tissues and | | | | |
| organs. The walls of the left ventricle are thicker than | | | | 71 ml. B-1 |
| those of the other chambers; this is due to the greater | | | | 113 ml. B-1 |
| stress that is being applied. | | | | Endurance Trained |
| | | | | Rest |
| Between the four chambers are thin partitions held in | | | | Maximal Exercise |
| place by connective tissue, these prevent blood from | | | | |
| one chamber being contaminated with the blood from | | | | 5000ml |
| another. The interatrial septum separates the atria | | | | 35,000ml |
| and the interventricular septum separates the | | | | |
| ventricles. | | | | 50 b. Min-1 |
| Valves located in the heart play a vital role in | | | | 195 b. Min-1 |
| preventing back flow of blood. The atrioventricular | | | | |
| valve (tricuspid valve) is found between the right atrium | | | | 100 ml. B-1 |
| and the right ventricle (Fig. 3); this stops the blood being | | | | 179 ml. B-1 |
| pumped back in to the atrium as the ventricle | | | | |
| contracts. | | | | Table taken from: McArdle, W. D.et al. Essentials of |
| | | | | Exercise Physiology. 2nd Edition. 2000 |
| Between the left atrium and the left ventricle, the mitral | | | | |
| valve (bicuspid valve) is found; the role of this particular | | | | These changes are achieved as hypertrophy |
| valve is similar to that of the atrioventricular valve. | | | | (increase of muscle fibre) occurs. Echocardiography |
| This valve has two lobes; this is due to the high | | | | involves the use of sound waves to produce an image |
| pressure and force of contraction from the left | | | | showing the structure of the heart, including its four |
| ventricle. | | | | chambers and the myocardium structure. It has been |
| | | | | used to determine what training types can inflict |
| When the blood leaves the left ventricle, it enters the | | | | myocardium enlargement and whether there are |
| aorta. The aortic valve acts as a barrier and does | | | | consequences to health from hypertrophy due to |
| not allow the blood to flow back into the heart as the | | | | physical activity. |
| ventricle relaxes. | | | | |
| | | | | During exercise blood pressure and heart rate |
| It is the Sino-atrial Node (SV Node), the pace maker, | | | | increase. This is due to the demand from working |
| that intrinsically regulates the heart rate. The electric | | | | muscles to remove waste (I. e. CO2) in order to keep |
| pulse then passes across the atria, causing them to | | | | perform effectively. |
| contract, to the Atrio-ventricular Node (AV Node). A | | | | |