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Cardiac Cycle

Cardiac Cycle . Circuits of the heart. Systemic circuit- the left side of the heart pumps to the body (Contains oxygenated blood) Pulmonary circuit- the right side of the heart pumps to the lungs to oxygenate blood. The heart….

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Cardiac Cycle

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  1. Cardiac Cycle

  2. Circuits of the heart • Systemic circuit- the left side of the heart pumps to the body (Contains oxygenated blood) • Pulmonary circuit- the right side of the heart pumps to the lungs to oxygenate blood

  3. The heart…. • Location- in the middle of the chest directly below the sternum (breastbone) • Structure- the heart is enclosed in a sac, the pericardium, is a two layered wall. The space between the walls is filled with a lubricating fluid that allows the walls of the heart to slide over one another as the heart beats without friction • Comprised of cardiac muscle (myogenic muscle)- a type of muscle that is exclusive to the heart. It spontaneously contracts and relaxes quickly and without nervous system control • Supplied with blood by the coronary blood vessels • Requires over 10% of total O2 load of blood. This is greater than any other muscle of its size

  4. The heart

  5. Atria • Are known as the collection chambers • Receive blood passively and pump to the ventricles • Right Atria- receives blood from the body • Left Atria- receives blood from the lungs • The cardiac muscle that lines the walls of the atria are thin compared to the rest of the heart. • This is because the atria only need to pump the blood a short distance to the ventricles

  6. Ventricles • Ventricles have a larger space and have thicker walls that are much more powerful than the atria. These thicker walls (especially the left ventricle) pump blood out to all the body organs. • Left is thicker because it pumps blood out to the whole body via the systemic circuit and the right is less thick because it pumps the shorter distance to the lungs

  7. The two sides of the heart are separated by the septum. A thick muscular wall. • The pumping action of the heart is synchronized. The left and right atria pump together and the left and right ventricles pump together • Blood flows in one direction, with the help of valves 1) Atrioventricular valves (AV valves) • Separate atria and ventricles • Prevents blood from flowing from the ventricles back to the atria 2) Semilunar Valves (SL valves) • Separate ventricles from arteries • Prevent blood from flowing from the arteries back into the ventricles

  8. Chordae Tendineae: White fibres that support the AV valves Mitral- Left AV Tricuspid- right AV Pulmonary -right SL Aortic – Left SL Heart murmur- unusual heart sound as a result of a leaky valve

  9. SL valve https://www.youtube.com/watch?v=gSNty0jz0BU

  10. Heart rate • Heart rate- the number of times a heart beats each minute (measured by taking your pulse) • Pulse- the dilation of arteries resulting from increased pressure from the heart contraction. Arteries close to the surface and backed by bone are ideal locations for taking pulse (Carotid, brachial, radial, femoral)

  11. Heart beat • 1 complete heart beat is equivalent to 2 contractions of the heart (1 atrial and 1 ventricular contraction)- approx 0.8sec • Recall: the heart is made of cardiac muscle which is myogenic (beats without control from the brain) • If taken out of the heart the cells will continue to beat

  12. Diastole vs. Systole • Diastole- the relaxation phase of the heart “ Filling of the heart” • Can be broken down into atrial and ventricular diastole • Systole- when the heart is contracting “emptying of the heart” • Can be broken down into atrial and ventricular systole

  13. Cardiac Cycle • As the atria relax the passively fill with blood (atrial diastole)- the ventricles are also relaxed at this point • As the atria fill, pressure builds and the atria contract (systole), opening the AV valves, allowing blood to move into the ventricles • As the ventricles fill, the AV valves close, and the ventricles contract forcing the semilunar valves to open and blood rushes out into the arteries https://www.youtube.com/watch?v=jLTdgrhpDCg

  14. Cardiac Cycle and Electrical Impulses • The nerve impulses that generate the heart contraction originate from a specific region of the right atrium: the sino-atrial node (SA node) • The SA node sends out an “electrical signal” to both atria causing them to contract simultaneously. This causes blood to be pushed out of the atria into the ventricles.

  15. Cardiac Cycle and Electrical Impulses • The right atrium contains another node, near the bottom called the atrioventricular node (AV node) • Once the signal is sent from the SA node it is relayed to the AV node • After 0.1 s, the AV node then sends its signal • The impulse is sent to the bundle of His and then down the Purkinje fibres; special conducting fibres that run down the septum of the heart • The ventricles then contract simultaneously from the apex (tip) of the heart to the top of the heart http://media.pearsoncmg.com/bc/bc_marieb_ehap_8/activities/chapter11/Act11C.html

  16. Heart Sounds • Using a stethoscope, you can hear the characteristic sounds “lub-dub, lub-dub” • The “lub” sound is made by the closing of the AV valves • The “dub” is the sound made by the closing of the SL valves http://depts.washington.edu/physdx/heart/demo.html

  17. Control of Heart Rate • The heart mainly controls itself, however, the brain and hormones can influence the frequency of heart beats • Controlled by the sympathetic (activating; increases HR) or the parasympathetic nervous system (deactivating; decreases HR) • Hormones, exercise, drugs all affect the frequency of heart rate

  18. Vagus nerve= parasympathetic

  19. Stroke volume: the amount of blood per heart beat (increased adrenalin and increased venous return increase stroke volume)

  20. Analysing Heart Rate • The cardiac cycle can be measured using an electrocardiograph which measures electrical signals and produces an electrocardiogram (ECG)

  21. Electrocardiogram • P= SA signals to contract atria • QRS= signal moves via purkinje fibres initiating a ventricular contraction • T = recovery period (repolarization)

  22. Coronary Circulation • Coronary arteries –supply heart muscles with blood and oxygen • They have a small diameter, they can become blocked, producing a heart attack

  23. Blood Pressure • Blood in under pressure in the blood vessels because of the pumping of the heart. • The overall volume is significant factor in determining blood pressure • If the volume of blood increase, then blood pressure increases • If the size of the blood vessels decrease and volume stays the same, then blood pressure increases

  24. Blood pressure is the measure of how much pressure is exerted by the blood on the vessel walls of the circulatory system

  25. Measuring Blood Pressure With an instrument called a sphygmomanometer (sphyg·mo·ma·nom·e·ter) The cuff is inflated until blood flow to the brachial artery is stopped. When the cuff deflates, sensors detect vibrations of the blood flowing through the artery

  26. Measuring Blood Pressure The first reading is the systolic pressure (pressure when the heart contracts) The second reading is the diastolic pressure (pressure when the heart is relaxed)

  27. Systolic Diastolic • Normal blood pressure is 120/80 (“120 over 80”) • The normal range is: • Systolic: 110-130 • Diastolic: 75-85 • Blood pressure decreases as it flows away from the heart

  28. Factors that affect Blood Pressure • Diameter of blood vessels- dilated decreases bp • Level of physical activity- exercise constricts blood vessels therefore bp increases • Temperature-hotter • Body position- standing has higher bp than other body positions • Diet – high sodium dietsresults in more fluid retention to balance solute concentrations, thus increasing blood pressure • Stress- increases bp • Age – old vessels lose elasticity with age • Medications-can increase or decrease depending • Smoking-constricts blood vessels therefore increase bp • Inherited Conditions • Kidney disease: can cause more fluid to be retained, thus increasing blood pressure • Age: vessels lose elasticity and cannot stretch as much to compensate for increased pressure resulting in higher blood pressure

  29. HYPERTENSION • = consistently high blood pressure • Can be caused by a variety of factors (as mentioned) • Ex: Diet – high in sodium • Excess sodium (salt) in your diet means more salt in your blood stream. This causes water excess water to enter your blood stream (water retention) to dilute the salt concentration. This also increases blood volume and therefore blood pressure

  30. Hypertension • Ex: Smoking • Cigarettes can cause a build up of tar on alveolar surfaces, reducing gas exchange. To compensate for this, the heart rate and blood pressure increase to pump more blood to the lungs so to pick up oxygen.

  31. Hypertension Hypertension is dangerous because it forces the heart to work harder to pump blood around the body. It can result in ruptured blood vessels in organs It can be reduced by adjusting one’s lifestyle (proper diet, losing weight, regular exercise) Medications work by dilating blood vessels or by reducing water retention

  32. Arteriosclerosis = the hardening of the arteries Over time, too much pressure can cause the arteries to lose elasticity and harden Can happen in any artery Sometimes, bacteria can cause damage to the artery walls and cause deposition of calcium on the walls which harden them

  33. Since arteriosclerosis occurs within the body where it cannot be seen, it is not always recognized early or easily. • Some signs and symptoms: • high blood pressure – as arteries harden • Poor circulation in fingers and toes • Recurrent kidney infections • Heart attacks (in advanced cases)

  34. Arteriosclerosis actually describes several diseases of the cardiovascular system: • Atherosclerosis: the condition resulting from the hardening of arteries by plaque build-up. Most common form of arteriosclerosis • Coronary Artery Disease(CAD):the narrowing or blockage of the coronary arteries, usually caused by atherosclerosis

  35. Atherosclerosis Hardening of the artery walls caused by a build up of plaque (fat, cholesterol, calcium) in the artery walls

  36. Atherosclerosis The plaque narrows the passage of blood- creates a clog! Dangerous because it can cut off blood flow to an organ Atherosclerosis can occur in any artery in the body

  37. ANGINA Chest/neck pain or discomfort due to CAD or any prolonged reduction of blood supply to the heart Low blood flow to the cardiac muscles Pain is created when the heart muscle doesn’t get as much blood as it needs because of a blockage in a coronary artery Attacks often triggered by physical activity Treated with nitroglycerin: causes vasodilation to increase blood flow.

  38. Heart Attack / Myocardial Infarction = death of an area of the heart muscle due to oxygen deprivation If the plaque that builds up in a coronary artery ruptures, a blood clot will form at the rupture site The clot reduces blood flow, causing the coronary arteries to narrow and less blood and O2 to reach the heart

  39. Heart Attack After 20-40 minutes, heart cells will start dying (b/c of oxygen deprivation) and will continue to die for the next few hours if not treated Can be fatal if a large area of the heart is affected or if it interferes with the cardiac cycle

  40. Heart Attack After 20-40 minutes, heart cells will start dying (b/c of oxygen deprivation) and will continue to die for the next few hours if not treated Can be fatal if a large area of the heart is affected or if it interferes with the cardiac cycle

  41. Heart Attack: SYMPTOMS • Usually occurs suddenly but there are warning symptoms: • Chest pain • Difficulty breathing • Pain in the arm, back , jaw • Nausea and vomiting • Tingling in the left arm • Heartburn and indigestion • Dizziness • Often, these symptoms are confused with digestive problems

  42. Factors that influence the occurance of coronary heart disease • See H.5.5 page 367 • Genetics, age gender, smoking obesity, diet, exercise

  43. Treatments • Angioplasty: involves opening blocked artery by inflating a small balloon at the point of blockage • Coronary Bypass: a surgery that re-routes or bypasses blood around a blockage by grafting on a new vessel (most commonly an existing vein from leg)

  44. Imagery and Prevention • Cardiac Catherization: or cardiac angiography. Involves moving a catheter camera into blood vessel or heart • CT and PET: produces a 2D image of a 3D object with “x-ray slices”. PET with gamma rays • MRI: magnetic resonance imaging. Uses magnets and radio waves to produce still or video images

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