Flow of Electrical Currents in the Chest Around the Heart

Figure 11-5 shows the ventricular muscle lying within the chest. Even the lungs, although mostly filled with air, conduct electricity to a surprising extent, and fluids in other tissues surrounding the heart conduct electricity even more easily. Therefore, the heart is actually suspended in a conductive medium. When one portion of the ventricles depolarizes and therefore becomes electronegative with respect to the

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Flow of current in the chest around partially depolarized ventricles.

remainder, electrical current flows from the depolarized area to the polarized area in large circuitous routes, as noted in the figure.

It should be recalled from the discussion of the Purkinje system in Chapter 10 that the cardiac impulse first arrives in the ventricles in the septum and shortly thereafter spreads to the inside surfaces of the remainder of the ventricles, as shown by the red areas and the negative signs in Figure 11-5. This provides electronegativity on the insides of the ventricles and elec-tropositivity on the outer walls of the ventricles, with electrical current flowing through the fluids surrounding the ventricles along elliptical paths, as demonstrated by the curving arrows in the figure. If one algebraically averages all the lines of current flow (the elliptical lines), one finds that the average current flow occurs with negativity toward the base of the heart and with positivity toward the apex.

During most of the remainder of the depolarization process, current also continues to flow in this same direction, while depolarization spreads from the endo-cardial surface outward through the ventricular muscle mass. Then, immediately before depolarization has completed its course through the ventricles, the average direction of current flow reverses for about 0.01 second, flowing from the ventricular apex toward the base, because the last part of the heart to become depolarized is the outer walls of the ventricles near the base of the heart.

Depolarized Heart

Figure 11-6

Conventional arrangement of electrodes for recording the standard electrocardiographic leads. Einthoven's triangle is superimposed on the chest.

Figure 11-6

Conventional arrangement of electrodes for recording the standard electrocardiographic leads. Einthoven's triangle is superimposed on the chest.

Thus, in normal heart ventricles, current flows from negative to positive primarily in the direction from the base of the heart toward the apex during almost the entire cycle of depolarization, except at the very end. And if a meter is connected to electrodes on the surface of the body as shown in Figure 11-5, the electrode nearer the base will be negative, whereas the electrode nearer the apex will be positive, and the recording meter will show positive recording in the electrocardiogram.

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Responses

  • Barry
    Does current flow from apex to base of the heart?
    4 years ago
  • habaccuc gaukrogers
    Why average current flow occurs with negativity towards base of heart?
    4 years ago
  • ambessa
    How outer wall of the ventricle near base is depolarize?
    4 years ago
  • iole
    Why is base of heart negative while apex positive?
    4 years ago
  • MARIGOLD
    Why ventricles become electronegative when depolarize?
    4 years ago
  • sharon
    Why electrical currebt flows from base to apex in heart?
    4 years ago
  • Rosa
    Why base of heart is electronegative to the apex?
    4 years ago
  • alice
    How when one portion of ventricle is depolirized becomes more electronegative than the remainder?
    4 years ago
  • Pamphila Tunnelly
    How heart polarises and depolarises and its relation with flow of current in heart?
    4 years ago
  • eglantine
    Why the portion of heart becums electronegatve when it depolarises?
    3 years ago
  • nicole
    Why ventricle become electronegative when one portion of ventricle depolirize?
    3 years ago
  • christian
    How an electric current flows in the heart?
    3 years ago
  • jeanie
    Why base of heart is electronegative and apex is electropositive?
    3 years ago
  • mackenzie
    Why is base of the heart last to depolarise?
    3 years ago
  • robert
    Why direcn of current reverses in last part of ventrucular depolarization?
    3 years ago
  • DINA
    What can electric current flowing do to the heart and the lungs?
    3 years ago
  • ALEANDRO LUCCHESE
    When one part of the heart is electronegative?
    3 years ago
  • mehari
    What does it mean for one side of the heart to be electro negative?
    3 years ago
  • Alice Mazzanti
    Does electricity in heart flow from a negative to a positive lead?
    1 year ago
  • toby gamgee
    What is the normal electrical activity flow across the myocardium?
    5 months ago
  • sol hamilton
    Does the electrical current of the heart move towards the leg?
    1 month ago
  • DAISY
    What is the direction of electrical current going through the heart?
    25 days ago
  • jan
    What do electric currents do to heart and lungs?
    7 days ago

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