The Mammalian HeartThe Mammalian Heart

External and Internal StructureExternal and Internal StructureMass = 300 gMass = 300 g

Muscle = Cardiac muscleMuscle = Cardiac muscleALBIO9700/2006JK

ALBIO9700/2006JK

Cardiac muscleCardiac muscle

A mammalian heart seen from the A mammalian heart seen from the front (External)front (External)

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ALBIO9700/2006JK

Coronary arteriesCoronary arteries

Vertical section through a Vertical section through a mammalian heart (Internal) mammalian heart (Internal)

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Vertical section through a Vertical section through a mammalian heart (Internal)mammalian heart (Internal)

• septum

• papillary muscle

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(mitral)

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Atrio-ventricular valvesAtrio-ventricular valves

Difference in thickness of the Difference in thickness of the walls of different chambers and walls of different chambers and

their functions?their functions?

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Closed double circulation

Mammalian circulatory systemMammalian circulatory system

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Cardiac cycleCardiac cycle

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* Sequence of events which makes up one heart beat

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

FibrillationFibrillation

Heart action controlHeart action control

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Purkyne tissue

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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

ALBIO9700/2006JK

ALBIO9700/2006JK