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The Mammalian HeartThe Mammalian Heart
External and Internal StructureExternal and Internal StructureMass = 300 gMass = 300 g
Muscle = Cardiac muscleMuscle = Cardiac muscleALBIO9700/2006JK
A mammalian heart seen from the A mammalian heart seen from the front (External)front (External)
ALBIO9700/2006JK
Vertical section through a Vertical section through a mammalian heart (Internal) mammalian heart (Internal)
ALBIO9700/2006JK
Vertical section through a Vertical section through a mammalian heart (Internal)mammalian heart (Internal)
• septum
• papillary muscle
ALBIO9700/2006JK
(mitral)
Difference in thickness of the Difference in thickness of the walls of different chambers and walls of different chambers and
their functions?their functions?
ALBIO9700/2006JK
Heart action controlHeart action control MyogenicMyogenic – naturally contracts and relaxes, not needing – naturally contracts and relaxes, not needing
to receive impulses from a nerve to make it contractto receive impulses from a nerve to make it contract Important components:Important components:
i) sinoatrial node (SAN/pacemaker) – sets the rhythm of i) sinoatrial node (SAN/pacemaker) – sets the rhythm of contraction for all other cardiac muscle cellscontraction for all other cardiac muscle cellsii) atrio-ventricular node (AVN) – picks up the excitation ii) atrio-ventricular node (AVN) – picks up the excitation wave as it spreads across the atria and passes it on to wave as it spreads across the atria and passes it on to Purkyne tissuePurkyne tissueiii) Purkyne tissue – conducting fibres that transmits iii) Purkyne tissue – conducting fibres that transmits excitation wave through ventrical wallsexcitation wave through ventrical walls
Fibrillation Fibrillation – heart wall flutters rather than contracting – heart wall flutters rather than contracting as a whole and then relaxing as a whole (started by as a whole and then relaxing as a whole (started by electric shock or by damage to large areas of muscle in electric shock or by damage to large areas of muscle in the walls of the heart)the walls of the heart)
ALBIO9700/2006JK
ALBIO9700/2006JK
Electrocardiogram (ECG)Electrocardiogram (ECG)
Electrodes placed over opposite sides of Electrodes placed over opposite sides of the heart and the electrical potentials the heart and the electrical potentials generated recorded with timegenerated recorded with time
ECG – graph of voltage against timeECG – graph of voltage against time