5106349
Description
Flashcards by Danielle Cope, updated more than 1 year ago
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Created by Danielle Cope
over 8 years ago
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| Question | Answer |
| the events in one complete heart beat are known as the cardiac cycle | three main stages (atrial systole, ventricular systole and diastole.) -the heart beats MYOGENICALLY (meaning that the events initiated within the heart muscle) |
| Atrial Systole | the SINO-ATRIAL NODE located in the RIGHT atrium initiates a wave of excitation (electrical impulses) across BOTH atria. - this causes the cardiac muscle in the ATRIA to CONTRACT and the volume of the artia reduces so the pressure INCREASES pushing blood into the ventricles through the ATRIO-VENTRICULAR VALVES |
| semi-lunar valves | 1- Atrial systole: semi-lunar valves are CLOSED (as the pressure in the arteries is higher than that in the ventricles, which are RELAXED) 2-Ventricular systole: contraction continues>pressure in ventricles exceeds that of the arteries and blood exists the heart by OPENING and pushing through the semi-lunar valves (VENTRICULAR EJECTION) 3- Diastole: VENTRICLES relax 1ST > pressure in ventricles FALL below that of the ARTERIES and the semi-lunar valves CLOSE |
| Atrioventricular valves (tripcuspid) | 1- Atrial systole: Atrioventricular valves are OPEN allowing blood to pass into the ventricles 2- Ventricular systole: as ventricles contract the atria RELAX (ATRIAL DIASTOLE). The CONTRACTION of the ventricles RAISES pressure of the blood in the ventricle chamber and pushes the atrio-ventricular valves SHUT as the pressure rises above that of the atria (ISOVOLUMETRIC CONTRACTION) 3- Diastole: muscles continue to relax, the pressure FALLS below that of the ATRIA and the atrio-ventricular valves OPEN. |
| Ventricular systole | 1- wave of excitation collects at the ATRIO-VENTRICULAR NODE (located in the septum - junction of atria and ventricles) >electrical contraction DELAYED here for a short period of time (allowing atria to complete contraction and ventricles to fill) > ventricles ALWAYS contract AFTER atria 2- impulse is passed to APEX (heart peak at base) through a bundle of fibres (BUNDLE OF HIS) > heart contracts from the BOTTOM and squeezes blood upwards to arteries 3- impulse spreads through cardiac muscle of the ventricles through branches (PURKINJE FIBRES) 4- as ventricles contract the atria RELAX (ATRIAL DIASTOLE). The CONTRACTION of the ventricles RAISES pressure of the blood in the ventricle chamber and pushes the atrio-ventricular valves SHUT as the pressure rises above that of the atria (ISOVOLUMETRIC CONTRACTION) >contraction continues>pressure in ventricles exceeds that of the arteries and blood exists the heart by OPENING and pushing through the semi-lunar valves (VENTRICULAR EJECTION) |
| Diastole | - following ventricular systole ALL cardiac muscles RELAX (both atria and ventricles). 1-VENTRICLES relax 1ST > pressure in ventricles FALL below that of the ARTERIES and the semi-lunar valves CLOSE, as the muscles continue to relax the pressure FALLS below that of the ATRIA and the atrio-ventricular valves OPEN. 2- blood flows from veins through the relaxed atria, through the atrio-ventricular valves and into the ventricles |
| Atria | - only have to move blood into ventricles so has a thin layer of muscle |
| RIGHT ventricle | -RIGHT ventricle moves the blood to the LUNGS and has a THICKER muscle layer than the atria |
| LEFT ventricle | -LEFT VENTRICLE have a very THICK layer of muscle as blood must be moved around the WHOLE BODY |
| CALCULATING HEART RATE | one cardiac cycle = 0.8 seconds - heart rate is expressed in beats per minute so convert it 0.8/60= 75 beats per minute |
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