BIOC32H3 : Cardiac Control (Myogenic hearts) summary

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7 Mar 2011
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The spontaneous rhythmic beating of the heart is the result of electrical activity that originates from a pacemaker. This electrical activity spreads throughout the heart causing it to contract. In vertebrates, the pacemaker cells are located in the sinoatrial (sa) node in the upper region of the right atria. The pacemaker cells spontaneously depolarise and generate action potentials (ap) that then spread throughout the heart. Although the activity of the pacemaker can be influenced by nervous input, it does not need any input in order to depolarise. A myogenic heart is one in which the pacemaker cells are specialised muscle cells. The electrical activity (action potential) generated in the sa node spreads in an orderly fashion throughout the heart. First, the wave of depolarisation (action potentials) spreads throughout both atria. The cells in the atria are large and therefore have a low resistance to the flow of electrical current.