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Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
Chapter 9
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  • 1. Chapter 9 The Mammalian Heart
  • 2. mammalian heart
    • The mammalian heart has a mass of about 300 g (size of fist)
      • composed of cardiac muscle
      • What’s unique about cardiac muscle?
  • 3. cardiac muscle
    • cardiac muscle made of interconnecting cells
    • plasma membranes very tight to facilitate passing of waves of electrical excitation
    • nucleated cells with striated fibers
  • 4. Heart Flow
  • 5. Heart structure
    • largest arching blood vessel – aorta
    • aorta branches, upwards towards the head and the mainflow doubling downwards to the rest of the body (descending aorta)
    • pulmonary artery – blood vessel leaving the heart with two branches leading to each lung
  • 6. Heart structure cont’d
    • pulmonary veins – bring blood from the left and right lungs
    • vena cava – two large veins merge, bringing blood downwards from the head (superior vc) and upwards (inferior vc) from the rest of the body
    • coronary arteries - branch from the aorta delivering oxygenated blood
  • 7.  
  • 8.  
  • 9. Heart structure cont’d
    • septum – wall of muscle that divides left side and right sides of the heart, blood cannot pass though the septum
    • four chambers – two on the left, two on the right
    • atrium (auricle) – upper chamber each side, both receive blood from the veins
  • 10.  
  • 11. Heart structure cont’d
    • right atrium – receive blood from the vena cavae
    • left atrium – receive blood from the pulmonary veins
    • ventricles – blood flows into the ventricles from the atria, then is squeezed out into the arteries
  • 12.  
  • 13. atrio-ventricular valves
    • mitral or bicuspid – between the left atrium and ventricle
    • tricuspid – between right atrium and ventricle
  • 14.  
  • 15. The Cardiac Cycle
    • cardiac cycle – sequence of events that makes up one heart beat
    • normal heart pulse rate – 70 beats per minute
  • 16. atrial systole
    • atrial spaces fill with blood and the muscles of the atrial walls contract
    • low pressure on this contraction
    • forces blood through the atrio-ventricular valves
    • semilunar valves prevent backflow
    • atrial muscle walls are thin
  • 17.  
  • 18. ventricular systole
    • 0.1 sec after the atria contract the ventricle contract
    • lasts about 0.3 sec
    • ventricles thick muscle
    • ventricles squeeze inward on the blood increasing the pressure, pushing it out of the heart
  • 19. ventricular systole
    • blood leaves the ventricles through the aorta and pulmonary artery
    • pressure in the ventricle becomes greater than the atria and pushes the atrio-ventricular valves shut,
    • papillary muscle – attached to the valves by tendons ( Chordae tendineae) , prevents the valves from being forced inside out
  • 20.  
  • 21. ventricular diastole
    • ventricle muscle relax
    • pressure in the ventricles drops
    • blood in the arteries puts pressure on the cusps of the semilunar valves forcing them shut preventing backflow
  • 22. diastole
    • whole of the heart muscle relaxes
    • even though the pressure of the blood in the veins is low, the blood fills the atria as their thin walls distend
  • 23. diastole
    • some blood can trickle through the atrio-ventricular valves into the ventricles
    • atrial muscle contract and the cycle begins again
  • 24. Why is the left ventricular wall thicker than the right?
    • The left ventricle must develop sufficient force to push blood around the rest of the body
    • The right ventricle pushes blood to the lungs, this requires much less pressure, therefore the right ventricle wall is thinner
  • 25. Control of the Heart Beat
    • myogenic – naturally contracts and relaxes without receiving nerve impulses
    • cardiac cells grown in oxygenated nutrient solution will rhythmically contract and relax all by themselves
    • What if all the cardiac cells of the heart contracted at their own rhythms?
  • 26. Control of the Heart Beat
    • Heart has its own built-in controlling and coordinating system
    • Sinoatrial node – SAN – pacemaker – specialized patch of muscle in the wall of the right atrium
    • Muscle cells of the SAN – set the rhythm for all the other cardiac cells
  • 27. Control of the Heart Beat
    • SAN muscles – contract slightly faster than the rest of the heart muscle
    • Set up a wave of electrical activity – wave spreads out rapidly over the whole atrial walls
    • Atrial wall cardiac muscle – responds to this excitation wave by contracting at the same rhythm as the SAN
  • 28. Control of the Heart Beat
    • Both atria – muscle cells almost contract simultaneously
    • As the wave spreads
    • Atrio-ventricular node – AVN – patch of conducting fibers in the septum
    • - the AVN picks up the excitation wave as it spreads across the atria
    • Atrioventricular fibrous tissue - Band of fibers between the atria and ventricles that do not conduct the excitation wave
  • 29. Purkyne tissue (Purkinje fibers)
    • after a delay of 0.1 s, the excitation wave is passed on to a bunch of conducting fibers that run down the septum, the Purkyne tissue
    • Purkyne tissue – transmits the excitation wave rapidly to the base of the septum where it spreads out through the ventricle walls
    • The excitation – causes the ventricle walls to contract from the bottom up, squeezing blood upwards and into the arteries
  • 30.  
  • 31. Healthy Heart
    • atria contract
    • then the ventricles, from the bottom up
    • Lub-dub
    • What if the coordination of contraction goes wrong?
  • 32.  
  • 33. Fibrillation
    • Fibrillation – heart flutters rather than contracting as a whole and relaxing as a whole
    • Must be treated instantly or could be fatal
    • Electric shock often used
  • 34. Electrocardiograms (ECG)
    • Electrocardiograms (ECG) – graph of voltage against time
    • P – represents the wave of excitation sweeping over the atrial walls
    • Q, R, & S – represent the wave of excitation in the ventricle walls
    • T – indicates the recovery of the ventricle walls
  • 35. Electrocardiograms (ECG)
  • 36. How to Read an EKG Strip
    • EKG paper is a grid where time is measured along the horizontal axis.
    • * Each small square is 1 mm in length and represents 0.04 seconds.
    • * Each larger square is 5 mm in length and represents 0.2 seconds.
  • 37.
    • Voltage is measured along the vertical axis.
    • * 10 mm is equal to 1mV in voltage.
    • * The diagram below illustrates the configuration of EKG graph paper and where to measure the components of the EKG wave form
  • 38.  
  • 39. Heart rate
    • Heart rate can be easily calculated from the EKG strip:
    • * When the rhythm is regular, the heart rate is 300 divided by the number of large squares between the QRS complexes.
      • For example, if there are 4 large squares between regular QRS complexes, the heart rate is 75 (300/4=75).
  • 40. Heart rate
    • * The second method can be used with an irregular rhythm to estimate the rate. Count the number of R waves in a 6 second strip and multiply by 10.
      • For example, if there are 7 R waves in a 6 second strip, the heart rate is 70 (7x10=70).
  • 41. This dysrhythmia results in the absence of cardiac output. Almost always occurs with serious heart disease, especially acute MI. The course of treatment for ventricular fibrillation includes: * immediate defibrillation and ACLS protocols.
  • 42. Atrial fibrillation may occur paroxysmally, but it often becomes chronic. It is usually associated with COPD, CHF or other heart disease. Treatment includes: * Digoxin, diltiazem, or other anti-dysrhythmic medications to control the AV conduction rate and assist with conversion back to normal sinus rhythm. * Cardioversion (shocking simultaneously with the QRS) may also be necessary to terminate this rhythm.