Cardiovascular Physiology

LECTURE OUTLINE (CHAPTER 14)

LECTURE OBJECTIVES

1. Introduce the functional anatomy of the heart and the circulatory system.
2. Explain the physiological basis for a heartbeat and its relationship to the ECG.
3. Establish how the heart is responsible for blood pressure and blood flow.
4. Compare the action potentials of the heart's autorhythmic and contractile cells.
5. Define cardiac output and discuss the factors that regulate it.

LECTURE OUTLINE

I. INTRODUCTION:  FUNCTIONS OF CIRCULATORY SYSTEM 

  A. Circulatory system has a number of functions
     1. Transport of nutrients, wastes, essential gases
     2. Buffers body pH
     3. Transports hormones
     4. Assists in temperature regulation
     5. Urine formation
     6. Assists in response to infections 
  B. Heart and vessels
     1. Closed circulatory cycle
          a. Advantages
     2. Details on human circulatory cycle

II. MAMMALIAN CIRCULATORY CYCLE

  A. The human circulatory cycle
     1. Functional anatomy of the heart 
          a. Characteristics of cardiac muscle
     2. Coronary arteries and the heart's blood supply

III. PHYSIOLOGY OF THE HEART 

  A. The heart beat 
  B. Characteristics of the myogenic heart
     1. Cardiac cycle  (S-A node, A-V node, Bundle of His, Purkinje fibers)
          a. At rest, parasympathetic tone slows heart rate to 70 beats/min
          b. Timing of the cycle
          c. Delay at the AV Node?
          d. Animation of cardiac cycle
     2. Why do the autorhythmic (=pacemaker) cells fire first?
          a. AP's of autorhythmic and contractile cardiac cells 

IV  THE ELECTROCARDIOGRAM (ECG or EKG)

  A. What is an ECG?
     1. ECG is used as a diagnostic tool 
     2. Components of the ECG (P, Q, R, S, and T)
          a. Their relationship to the heart beat 
     3. ECG abnormalities
 
V.  CARDIAC OUTPUT AND ITS CONTROL

  A. Characteristics of Cardiac Output (CO)
  B. Autonomic Nervous System regulates CO
     1. Sympathetic -- increases heart rate and stroke volume
          a.  Sympathetic tone determines CO
     2. Parasympathetic -- decreases heart rate
     3. Functional effects on the autorhythmic cells 
  C. Starling (aka Franck-Starling) law of the heart
     1. Starling curve
          a. Relationship between sacromere length and stroke volume
  D. Summary: Cardiac Output is regulated by multiple factors

VI. MEDICAL IMPLICATIONS (if time permits)

  A. Myocardial infarction (Image of infarcted heart)
     1. Examples of myocardial infarction 
     2. Premature ventricular contractions
     3. Development of atherosclerotic plaques
          a. Roles of Cholesterol, LDL, and HDL
  B. Congestive heart failure due to decreased cardiac output  
     1. Effect on Starling curve
Reading Assignment. For the next lecture, please read Chapter 15.



STUDY QUESTIONS ON CARDIAC PHYSIOLOGY (CHAPTER 14)
  1. Review heart anatomy with respect to chambers, valves, etc. Starting at the vena cava (=sinus), trace the path that a red blood cell would take to get to the aorta. At each point is red blood cell oxygenated or deoxygenate Draw a normal ECG. Relate each point of the ECG to the events occurring within the heart.

  2. Review Figure 14-26 in the text, but don't memorize it. Read about this figure in the text for general points.

  3. Define and give the physiological significance (how or why it is important) for the following terms:
    • Chordae tendineae
    • Heart attack
    • Bundle of His
    • Purkinge fiber
    • Desmosome (See page 470)
    • Gap junction
    • Stroke volume
    • S-A node
    • A-V node
    • Papillary muscle
    • Valvular stenosis (See page 486)
    • Heart murmur
    • End diastolic volume (EDV)
    • End systolic volume (ESV)
    • Low- and High-density lipoproteins (LDL and HDL)

  4. What is meant by "closed circulatory system?" What are the advantages of having closed circulation?

  5. Contrast the action potential of a skeletal muscle cell and the pacemaker potential of the heart. What is the physiological basis for muscle pacemaker activity in the S-A node?

  6. What is the physiological basis for a heart attack? What factors enhance the chance of a heart attack? Explain.

  7. Describe the many factors that control cardiac output (CO). How do neural and hormonal components influence cardiac output?

  8. By what signal transduction pathway does norepinephrine and epinephrine affect heart function? Acetylcholine?

  9. Is the molecular mechanism for contraction of cardiac muscle unique or is it more like either 1) smooth muscle or 2) skeletal muscle? Explain your answer.


    CONCEPTS

  10. What is the physiological basis for the AV Delay in the heart? How is the AV Delay important to heart function?

  11. In the figure below, identify the problem with the ECG. Explain what must have happened to the heart at the arrow. Review other ECG abnormalities.

  12. Define Cardiac Output. In what units is it measured? What factors influence cardiac output? During strenuous excercise your cardiac input increases 2-4 fold. What underlying physiological factors contribute to that increase (there are at least three correct answers)? How is cardiac output important to the regulation of blood pressure?

  13. What causes heart failure? How does the Starling curve change during heart failure? What are the effects of that change on cardiac function?

  14. Contrast the physiology of pacemaker (=autorhythmic) cells in the S-A node with the contractile cardiac cells in the rest of the heart. For example, how do they differ with respect to ion flux and the properties of their "resting" membrane?

  15. Why is tetanus of cardiac muscle impossible in a healthy heart? Why is this advantageous?

  16. What is the Starling law of the heart. How is it important for regulating cardiac output? What is the Starling curve?

  17. How does Cholesterol encourage the formation of arteriosclerotic plaques? What is the role of LDL in this process? Why is it advantageous to have a high HDL?

  18. What is a pressure-volume curve? How would the presure-volume curve for the right ventricle differ from that of the left ventricle (See Figure 14-25 in Silverthorn)? Draw a pressure-volume curve for the right ventricle. Keep in mind that the right ventricle's blood pressure is lower than the left.


    REASONING AND PROBLEM SOLVING

  19. Given the following pacemaker potential as a reference, draw the changes that would occur in it's structure following 1) sympathetic stimulation and 2) parasympathetic stimulation. Explain these changes? Given your knowledge of the ion fluxes responsible for generating an action potential in the pacemaker cells, propose how the neurotransmitters of the ANS influence ion flux to bring about these regulatory effects.

  20. If you tie off both atria from the ventricles so that there is no electrical communication between the atria and ventricles, the ventricles will still spontaneously contract, but at a slower rate than the atria. Given your understanding of the properties of cardiac muscle, provide a physiological explanation for this slower ventricular rhythmicity.
  21. What is the physiological basis for angina pectoralis? Why is pain often felt in the left arm or shoulder, not in the heart?

  22. Bill is a marathon runner who has been in training since last September. He has a resting heart rate of 50 beats per minute and a blood pressure of 105/75. His brother, Bob, has no regular exercise routine and has a resting heart rate of 85 beats/minute and a blood pressure of 130/85. Both men have the same cardiac output of about 5.0 liters/minute. What is the stroke volume at rest for each brother? Explain the physiological basis for their difference in heart rate.




Last revised: February 26, 2008