The Tell Tale Heart ( ANNOTATED )

Product Information

The cardiac cycle is regulated by continuous electrical signals produced by the sinoatrial node, which pass on to the ventricles by the atrioventricular node. References The right atrium contracts pushing blood through the right atrioventricular valve into the right ventricle. The right ventricle then contracts passing the blood into the pulmonary trunk via the pulmonary valve to reach the lungs o Look at the right-hand diagram. Cut carefully upwards into the left atrium along the line shown in the diagram. This is a short 3-D animation of the heart in action, showing the detailed movement of the valve flaps and the heart muscle. The commentary has an American accent, but is quite clear. There are a number of different protocols based on patient presentation that can be broken into prospective and retrospective based:

The sino-atrial node sends impulses over the two atria which are then stimulated to contract. When the electrical impulses reach the atrioventricular node (at the junction between the atria and the ventricles), the impulses will spread rapidly through special fibers from the inter-ventricular septum to the walls of both ventricles, where the muscles are stimulated to contract. valve is open unless pressure inside the ventricle pushes it closed; papillary muscles and chordae tendineae prevent the valves from flipping open during ventricular systole (prolapse) m Look at the left-hand diagram. Make a long cut down through the aorta and the left ventricle to the tip of the heart (‘apex’), as shown in the diagram. The position of the blood vessels on the surface will help you to make this cut in the right place. Identify the coronary artery that supplies the heart muscle itself with blood.At this point, you may want to use your colored pencils to mark these vessels so that you don't get them confused when you are searching for the other two openings that top of the heart. The cardiac cycle is a series of physiological, mechanical and electrical events comprising one heartbeat. What are the different stages of the cardiac cycle?

Pulmonary veins (-> left atrium), superior and inferior vena cavae (-> right atrium), aorta (left ventricle ->), pulmonary artery (right ventricle ->) Deoxygenated blood returning from the body first enters the heart from the superior and inferior vena cava. The blood enters the right atrium and is pumped through the tricuspid valve into the right ventricle. From the right ventricle, the blood is pumped through the pulmonary semilunar valve into the pulmonary trunk.

Sign up now to get access to the entire library of A Level Biology resources for all exam boards

A normal healthy ECG trace shows what is known as the “PQRST shape” (Figure 5). Wave P is the stage that corresponds to atrial systole, excitation and contraction of the atria. Ventricular systole forms the “QRS” complex and the start of ventricular diastole corresponds to the “T” wave. Figure 5: The start is diastole where both the atria and ventricles are relaxed. The P wave shows the depolarisation of the atria and is followed by atrial systole (contraction). Atrial systole continues to the end of the QRS complex and the point where the atria relax. The QRS complex shows the relaxation of the ventricles and is followed by ventricular systole (contraction). The T wave represents a further depolarization (re- polarization) and marks the start of ventricular relaxation. The atrial pressure shown in Figure 2 (yellow line) has the least changes in the pressure. The pressure is always relatively low due to the thin walls of the atrium and therefore, cannot create a force to increase the pressure. The atria fill up with blood that leads to a slight increase in blood however, there is drop again when the left AV valve opens allowing some of the blood to enter the ventricles.

O'Brien JP, Srichai MB, Hecht EM et-al. Anatomy of the heart at multidetector CT: what the radiologist needs to know. Radiographics. 2007;27 (6): 1569-82. Radiographics (full text) - doi:10.1148/rg.276065747 - Pubmed citation

Sources

Sometimes, the pacemaker of the heart stops functioning properly (this can cause an irregular heartbeat) The heart has a somewhat pyramidal form and is enclosed by the pericardium. Its base (roughly square-shaped) points posterior while its apex points to the left and inferiorly 7. It is positioned posteriorly to the body of the sternum with one-third situated on the right and two-thirds on the left of the midline. Its left-sided orientation is formally known as levocardia (cf. dextrocardia). I had my passage on a little sea-going steamer. Her captain was a Swede, and knowing me for a seaman, invited me on the bridge. He was a young man, lean, fair, and morose, with lanky hair and a shuffling gait. As we left the miserable little wharf, he tossed his head contemptuously at the shore. 'Been living there?' he asked. I said, 'Yes.''Fine lot these government chaps -- are they not?' he went on, speaking English with great precision and considerable bitterness. 'It is funny what some people will do for a few francs a month. I wonder what becomes of that kind when it goes upcountry?' I said to him I expected to see that soon. 'So-o-o!' he exclaimed. He shuffled athwart, keeping one eye ahead vigilantly. 'Don't be too sure,' he continued. ' The other day I took up a man who hanged himself on the road. He was a Swede, too. ''Hanged himself! Why, in God's name?' I cried. He kept on looking out watchfully. 'Who knows? The sun too much for him, or the country perhaps.' The ventricles are separated by two grooves, one of which, the anterior longitudinal sulcus, is situated on the sternocostal surface of the heart, close to its left margin, the other posterior longitudinal sulcus, on the diaphragmatic surface near the right margin; these grooves extend from the base of the ventricular portion to a notch, the incisura apicis cordis, on the acute margin of the heart just to the right of the apex. Cardiac wall Some students may be sensitive to the use of any animal product in this way, or to the very existence of animals bred and raised for human consumption.

Leipsic J, Abbara S, Achenbach S et al. SCCT Guidelines for the Interpretation and Reporting of Coronary CT Angiography: A Report of the Society of Cardiovascular Computed Tomography Guidelines Committee. J Cardiovasc Comput Tomogr. 2014;8(5):342-58. doi:10.1016/j.jcct.2014.07.003 - Pubmed The sinoatrial node (SAN) is of a group of cells found high up in the right atrium close to its junction with the superior vena cava. 1,4,5 When evaluating the heart for potential CAD, usually a nonenhanced calcium scoring sequence is first performed to assess for coronary artery calcification. This low-dose technique allows for the detection of calcifications of the coronary arteries. Although this technique does not give any information about potential hemodynamically relevant stenoses, an Agatston score can be calculated based on that data. The calculated Agatston score allows for an early risk stratification of patients with a high Agatston score (>160) who have an increased risk for a major adverse cardiac event (MACE) 4. Post-processing An echocardiogram (or echo) is an ultrasound of the heart. During an echo, we record short videos of the heart as it beats, and from these videos we can learn about the structure and function of the heart. The left ventricle is the main pumping chamber of your heart – it is the one where blood leaves your heart to be pumped around your body. Because it is doing all this work, it is the largest and most muscular of the four chambers of your heart.

Or try a sample...

He broke off. Flames glided in the river, small green flames, red flames, white flames, pursuing, overtaking, joining, crossing each other -- then separating slowly or hastily. The traffic of the great city went on in the deepening night upon the sleepless river. We looked on, waiting patiently -- there was nothing else to do till the end of the flood; but it was only after a long silence, when he said, in a hesitating voice, "I suppose you fellows remember I did once turn fresh-water sailor for a bit," that we knew we were fated, before the ebb began to run, to hear about one of Marlow's inconclusive experiences