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The Cardiac C ycle

The Cardiac C ycle. OPTION H: Further human physiology. The cardiac cycle. R epeating sequence of actions in the heart which result in the pumping of blood to the lungs and all other parts of the body.

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The Cardiac C ycle

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  1. The Cardiac Cycle OPTION H: Further human physiology

  2. The cardiac cycle • Repeating sequence of actions in the heart which result in the pumping of blood to the lungs and all other parts of the body. • Cardiologists refer to contraction of the heart’s chambers as systole and relaxation as diastole. • There are three sequences of contraction:

  3. Atrial systole: http://img2.tfd.com/mk/C/X2604-C-74A.png

  4. Ventricular systole: http://img2.tfd.com/mk/C/X2604-C-74A.png

  5. Diastole: http://img2.tfd.com/mk/C/X2604-C-74A.png

  6. The cardiac cycle includes all the events from the beginning of one heartbeat to the beginning of the next. http://aura.edu.in/read/IB/BIOLOGY_COURSE_COMPANION_(OXFORD)/original/Page-343.html (Pearson pg 620)

  7. To start the cycle, the sinoatrial node fires an electrical signal throughout the walls of the atria. This causes the atria to undergo systole. http://aura.edu.in/read/IB/BIOLOGY_COURSE_COMPANION_(OXFORD)/original/Page-343.html

  8. The signal then reaches the atrioventricular node, from which the signal spreads throughout the heart via specialized heart muscle tissue called Purkinje fibers. • This causes the ventricles to undergo systole. http://aura.edu.in/read/IB/BIOLOGY_COURSE_COMPANION_(OXFORD)/original/Page-343.html

  9. After the ventricles are emptied, the semilunar valves close. The ventricles begin diastole, the atrioventricular valves open and ventricles start filling with blood. • When the atria are filled and the ventricles are 70 per cent filled, the cycle has ended http://aura.edu.in/read/IB/BIOLOGY_COURSE_COMPANION_(OXFORD)/original/Page-343.html

  10. Artherosclerosis and heart attacks.- • Coronary heart disease (CHD) refers to damage to the heart as a consequence of reduced blood supply. http://2.bp.blogspot.com/_4smz8ewivFs/TElpOu-gEwI/AAAAAAAAAq4/Am8Hqj4qZZs/s1600/hearth+coroner+diseases.jpeg

  11. Atherosclerosis is hardening of the arteries caused by the formation of plaques, or atheromas, on the inner lining of arteries. • Plaques are areas that are swollen and accumulate a diversity of debris composed of lipids, cholesterol, cell debris and calcium. http://t3.gstatic.com/images?q=tbn:ANd9GcTeBYa6nJyQiMc6acnSgqJw9twYVQLY1w__4Y09cswGlhgh5Dgy

  12. The plaques can reduce the speed at which blood moves through vessels. • This can trigger a clot, or thrombosis, which can block the blood flow through the artery and deny the tissue access to oxygen.

  13. http://www.texasheartinstitute.org/HIC/Topics/Cond/CoronaryArteryDisease.cfmhttp://www.texasheartinstitute.org/HIC/Topics/Cond/CoronaryArteryDisease.cfm

  14. Symptoms of coronary thrombosis include: • Pain in the chest area, often radiating out towards the left arm. • Constricting sensation in or around the throat. • Breathing difficulties • Severe dizziness, sometimes fainting. http://us.123rf.com/400wm/400/400/kmiragaya/kmiragaya1201/kmiragaya120100076/11874750-grunge-image-of-a-man-having-a-chest-pain-or-heart-attack.jpg

  15. Risk factors affecting coronary heart disease: • Old age leads to less flexible blood vessels • Heredity, having parents who have experienced heart attacks indicates a genetic precondition • Race, some ethnic groups have far higher rates of CHD than others • Gender, risk in females increases post-menopause correlated with a fall in estrogen levels; males are at greater risk compared with females correlated with lower levels of estrogen. • Hypertension/high blood pressure causes the heart to work harder. http://images.medicinenet.com/images/SlideShow/heart_disease_s6_lifestyle_risk.jpg

  16. Risk factors affecting coronary heart disease: • Smoking raises blood pressure because nicotine causes vasoconstriction • High salt diet, excessive amounts of alcohol and stress are also correlated with CHD • Eating too much saturated fat and cholesterol promotes plaque formation • Obesity strains the heart • Sedentary lifestyle, lack of exercise is correlated with obesity. • Diabetes when it is not well managed. http://www.surgical-blog.com/wp-content/uploads/2011/05/post-28-risk-factors-of-heart-disease.jpg

  17. Sources • Allot, A., & Mindorff, D. (2010). IB Biology Course Companion. New York: Oxford University Press. • Damon, A., McGonegal, R., Tosto, P., & Ward, W. (2007). Biology Higher Level. London: Pearson Baccalaureate.

  18. Questions: • Answer exercises 12, 13, and 14 from the Pearson IB Biology HL book pg 627.

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