The Heart part 4

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The Heart part 4
2013-04-15 11:18:06
Heart part

The Heart part 4
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  1. cardiac output
    is the volume of blood ejected from the left ventricle (or right ventricle) into the aorta (or pulmonary trunk) each minute
  2. stroke volume
    the volume of blood ejected by the ventricle during each contraction multiplied by the heart rate beats per minute
  3. cardiac reserve
    is the difference between a person's maximum cardiac output and cardiac output at rest.  The average person has a cardiac reserve of four or five times the resting value
  4. preload
    the degree of stretch on the heart before it contracts
  5. contractility
    the forcefulness of contraction of individual ventricular muscle fibers
  6. afterload
    the pressure that must be exceeded before ejection of blood from the ventricles occurs
  7. Frank-starling law of the heart
    the more the heart fils with blood during diastole the greater the force of contraction during systole.
  8. positive inotropic agents
    substances that increase contractibility
  9. negative inotropic agents
    those that decrease contractibility
  10. cardiovascular centre
    nervous system regulation of the heart originates here in the medulla oblongata
  11. proprioceptors
    monitor the position of the limbs and muscles, send nerve impulses at increased frequencies to the cardiovascular centre once activity begins
  12. chemoreceptors
    offer sensory input to the cardiovascular centre, which monitors chemical changes in the blood
  13. baroreceptors
    which monitor the stretching of major arteries and veins caused by the pressure of the blood flowing through them
  14. cardiac accelerator nerves
    these sympathetic nerves extend out to the SA nodes, AV nodes and most portions of the myocardium.  These nerves trigger the release of norepinephrine which binds to beta-1 receptors on cardiac muscle.  This increases contractibility
  15. vagus X nerve
    parasympathetic nerve impulses reach the heart via these right and left nerves. Their axons terminate in SA nodes, AV nodes and myocardium.  They release Ach, which decreases heart rate by slowing the rate of spontaneous depolarization in autorhythmic fibers
  16. Hormones: Epinephrine and norepinephrine
    enhance the hearts pumping effectiveness.  They increase both the heart rate and contractility
  17. Tachycardia
    an elevated resting heart rate
  18. cations
    Ionic imbalances in the intracellular and extracellular fluids can quickly compromise the pumping effectiveness of the heart
  19. Bradycardia
    a resting heart rate under 50 beats/min.  This is a beneficial effect of endurance-type training because a slowly beating heart is more energy efficient.
  20. arteriosclerosis
    thickening of the walls of the arteries and loss of elasticity are the main characteristics of this group of diseases
  21. ventricular fibrillation
    is the most deadly arrhythmia, in which contractions of the ventricular fibers are completely asynchronous so that the ventricles quiver rather than contract in coordinated ways.  During this time the ECG has no P-waves, QRS complexes or T-waves
  22. cardiac arrest
    a Clinical term meaning cessation of an effective heartbeat.  The heart may be completely stopped or in ventricular fibrillation
  23. palpitation
    a fluttering of the heart or an abnormal rate or rhythm of the heart about which an individual is aware
  24. atherosclerosis
    a progressive disease characterized by the formation of lesions in the walls of large and medium sized arteries.