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HUMAN CIRCULATORY SYSTEM - Coggle Diagram
HUMAN CIRCULATORY SYSTEM
Heart
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Protected by Pericardium, encloses the pericardial fluid
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Semilunar Valves
Guards the opening of pulmonary artery and aorta into the right and right & left ventricle respectively
Cardiac Cycle
Sino-Atrial Node (SAN)
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Natural Pacemaker
Generates 70-75 action potential per minute which is responsible for initiating & maintaining rhythmic contractile activity of the heart
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The nodal musculature is auto-excitable, i.e., it generates action potential without any external stimuli
1. Joint Diastole
- All chambers are in relaxed state
- As the mitral & tricuspid valves open, venous blood flows from anterior & posterior vena cava & pulmonary artery to the right & left atrium respectively
- The semilunar valves are closed at this stage
2. Atrial Systole
- Flow of blood into the atria increases the pressure
- SAN generates action potential and stimulates atria to undergo systole
- The semilunar valves open while the mitral and tricuspid valves close
- Simultaneously, the ventricles undergo diastole
3. Ventricular Systole
- Blood flows into ventricles, increasing the pressure
- Semilunar valves open due to the increase in pressure
- Mitral and tricuspid valves close to prevent backflow of blood to atria
- The action potential generated by SAN is transmitted through AVN and AV Bundle through the Purkinje Fibres, reaching the ventricles & stimulate them to undergo systole
- Then, the ventricular pressure decreases, opening the mitral and tricuspid valves
- Simultaneously, the atria undergo diastole
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Stroke Volume: Volume of blood pumped out by each ventricle during a cardiac cycle. It is approx. 70mL of blood
Cardiac Output: Volume of blood pumped put by each ventricle per minute and averages 5L in a healthy individual
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Electrocardiograph (ECG)
- P-wave: Represents depolarisation or electrical excitation of atria which leads to contraction of atria
- QRS complex: Represents depolarisation of ventricles which initiates ventricular contraction
- T-wave: Represents repolarisation of ventricles marking the end of systole
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