The Mammalian The Mammalian HeartHeart

External and Internal External and Internal StructureStructureMass = 300 gMass = 300 g

Muscle = Cardiac muscleMuscle = Cardiac muscleALBIO9700/2006JK

ALBIO9700/2006JK

Cardiac muscleCardiac muscle

A mammalian heart seen from A mammalian heart seen from the front (External)the 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 Difference in thickness of the walls of different the walls of different chambers and their chambers and their

functions?functions?

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Closed double circulation

Mammalian circulatory Mammalian circulatory systemsystem

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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 – naturally contracts and relaxes, not

needing to receive impulses from a nerve to make needing to receive impulses from a nerve to make it contractit contract

Important components:Important components:i) sinoatrial node (SAN/pacemaker) – sets the i) sinoatrial node (SAN/pacemaker) – sets the rhythm of contraction for all other cardiac muscle rhythm of contraction for all other cardiac muscle cellscellsii) atrio-ventricular node (AVN) – picks up the ii) atrio-ventricular node (AVN) – picks up the excitation wave as it spreads across the atria and excitation wave as it spreads across the atria and passes it on to Purkyne tissuepasses it on to Purkyne tissueiii) Purkyne tissue – conducting fibres that iii) Purkyne tissue – conducting fibres that transmits excitation wave through ventrical wallstransmits excitation wave through ventrical walls

Fibrillation Fibrillation – heart wall flutters rather than – heart wall flutters rather than contracting as a whole and then relaxing as a contracting as a whole and then relaxing as a whole (started by electric shock or by damage to whole (started by electric shock or by damage to large areas of muscle in the walls of the heart)large areas of muscle in 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

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ALBIO9700/2006JK

ALBIO9700/2006JK