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Biology 10

Biology 10. Heart Beat Heart Sounds Heart Rate Blood Pressure. Initiating the Heart Beat. Cardiac muscle contracts without external nervous stimulation Sino-Atrial Node ( SA Node ) Pacemaker Coordinates contractions Special muscle and nerves located in the right atrium

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Biology 10

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  1. Biology 10 Heart Beat Heart Sounds Heart Rate Blood Pressure

  2. Initiating the Heart Beat • Cardiac muscle contracts without external nervous stimulation • Sino-Atrial Node (SA Node) • Pacemaker • Coordinates contractions • Special muscle and nerves located in the right atrium • 70 beats/minute

  3. S-A Node

  4. Initiating the Heart Beat • The SA node sends nerve impulses: • that cause atria to contract • across the atria to the second node, the antrioventricular node

  5. S-A Node A-V Node

  6. Initiating the Heart Beat • AV node • mass of nerve tissue between right atrium and right ventricle • passes nerve impulse through septum to the bottom of ventricles • Impulse conducted upwards through nerves in the ventricles • Contraction of ventricles begins • Contraction begins at apex • Bottom to top contraction • Result… • Atria contract followed by the ventricles.

  7. Setting the Heart’s Rate • Autonomic Nervous System in charge! • Sympathetic nerves • stimulated during times of stress • Increases heart rate • Parasympathetic nerves • stimulated during times of non-stress • returns heart to slow rate

  8. Setting the Heart’s Rate • Problem: • SA node malfunction • Ventricular fibrillation • disorganized and random contraction of heart cells • no longer pumps blood • death • Solution: • First -- Electro shock to halt the “short circuit” • Then -- installation of an artificial pacemaker

  9. Electrocardiogram • Electrodes are placed on the body surface • Connected to a recording device • Electrical impulses from heart are displayed on a screen. • P wave • atrial contraction • QRS wave • ventricular contraction • Used to diagnose heart problems • more evident during heavy exercise • Doctors identify dead patches of heart muscle which will not conduct impulses.

  10. Heart Murmurs • An improper seal in the valves of the heart allow for a backflow of blood. • The heart compensates for decreased oxygen deliver by increasing heart rate.

  11. Cardiac Cycle • One heart beat has both: • Systole • ventricles contract • Diastole • ventricles relax • 70 - 75 beats/min • two sides of heart beat in unison • first the atria then the ventricles • pulse- the movement of blood through the body resulting from the contraction of the ventricles

  12. Stages of the Cardiac Cycle • 1) Heart relaxed -- atria filling • Right Atrium • blood from Superior & Inferior Vena Cava • Left Atrium • blood returning from lungs via 4 pulmonary veins • 2) Atria Contract • Ventricular diastole (relaxed) • Ventricles fill up • blood pushed from atria into ventricles past the AV valves

  13. Stages of the Cardiac Cycle 3) Ventricles Contract • ventricular systole • AV valves close • Semilunar valves open • Right ventricle • blood through pulmonary artery to lungs • Left Ventricle • blood through aorta to rest of body

  14. Heart Sounds • “lubb dubb” • Systole (lubb) • longest and loudest • ventricles contract • caused by AV valves closing • Diastole (dubb) • caused by semilunar valves closing • ventricles relaxing

  15. Cardiac Output • Cardiac Output- amount of blood that flows from each side of the heart per minute. Unless there is a malfunction this amount should be the same on both sides. • Two parts: • Stroke volume: quantity of blood pumped with each beat of the heart. Normally 70 ml/beat • Heart rate: number of times the heart beats per minute. Normally 70 times /minute. • 70 *70 = 4900 ml/ min or 5 L per minute • Think back to heart murmur.

  16. Blood Pressure • Measures amount of pressure in artery • Two parts (120/80) • Systolic pressure • high number (120) • pressure in artery when ventricles contract • Diastolic pressure • low number (80) • pressure in artery when ventricles relax • Most important in diagnosis of heart health. • Measured using a sphygmomanometer!!

  17. Comparing Pressure in Glood Vessels • Arteries > arterioles > capillaries > venules> veins

  18. Problems / Diseases • Hypertension • high blood pressure • 140/90 • can lead to heart attack, stroke, kidney damage • Caused by: • high blood volume : water • the constriction of blood vessels • stress

  19. Problems / Diseases • Hypotension • low blood pressure • often associated with bleeding • external or internal • body compensates by • increasing cardiac output • increasing peripheral resistances • arteriolar constriction

  20. Regulation of Blood Pressure • Negative Feedback Loop • Monitor: • Baroreceptors (blood pressure receptors) • in walls of aorta and carotid arteries • measures blood pressure • Control Center: • Medulla Oblongata • Blood pressure regulator in the brain stem

  21. Regulation of Blood Pressure • Regulators: • Sympathetic Nerve Stimulation • arterioles constrict • cardiac output increases • stroke volume & stroke rate • increases blood pressure • Parasympathetic Nerve Stimulation • arterioles dilate • decreased cardiac output • decrease blood pressure

  22. Regulation of Blood Pressure • Example: • M. Oblongata processes info from baroreceptors • BLOOD PRESSURE TOO HIGH • decrease sympathetic nerve stimulation • increase parasympathetic nerve stimulation • sends message to slow heart rate and dilate arterioles • BLOOD PRESSURE TOO LOW • decrease parasympathetic nerve stimulation • increase sympathetic nerve stimulation • increase heart rate • constricts blood flow

  23. 5 factors that affect blood pressure • Epinephrine- arteriolar constriction (except heart, muscles and skin) • Sympathetic nerve stimulation- arteriolar constriction (except cardiac and skeletal muscle) • Acid accumulation- arteriolar dilation • Carbon dioxide- arteriolar dilation • Lactic Acid- arteriolar dilation Arteriolar Dilation Metabolic Products Increase Increased Blood Flow

  24. Steps in finding Blood Pressure 1) Inflate cuff beyond normal pressure • this squeezes the artery closed 2) Leak, Look and Listen • release pressure slowly • listen to stethoscope for thump • blood forcing its way through the cuff • read the number on the dial at that point • this is systolic pressure 3) Wait and Listen • When thumping stops, blood is moving unrestricted • this is diastolic pressure

  25. Do the Blood Pressure Lab Procedure can be found on page 263 of Nelson Biology

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