Control Of Heart Beat

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  • 1. Control of heart beat Please hand in your homework
  • 2. What is wrong?
  • 3. Starter question 1 square = 1mm
  • 4.
    • Cardiac muscle is myogenic
    • It does not need nerve impulses to contract
    • These contractions must be controlled so that cells work in unison
  • 5. SAN
    • Sino atrial node
    • Small patch of muscle in right atrium wall
    • Pacemaker
    • Their contractions spread a wave of electrical activity in the atrial walls
    • Cardiac muscle responds, making the atria contract in time with the SAN
  • 6.
    • Both atria contract together
    • The excitation wave is briefly delayed by a bunch of fibres which do not conduct the electrical activity
    • This delay is to ensure that the ventricles contract after the atria
  • 7. AVN
    • Atrio ventricular node
    • Small patch of conducting fibres high up in septum
    • Allows the electrical activity to spread slowly from the atria to the ventricles
    • Passes on to the purkyne tissue
  • 8. Purkyne tissue
    • Fibres in septum
    • Cause contractions in ventricle walls from bottom up
    • Squeezing blood upwards
  • 9. Diagram of heart showing SAN, AVN and purkyne tissue
  • 10. Summary diagram
  • 11. Blood vessels
    • We will examine and draw some prepared slides
    • Extension – if you would like to examine your own blood under the microscope you may do so, using a lancet
    • Homework to hand in next thurs– read about the 3 types of blood vessels – make a labelled diagram of each and describe the differences.