9.23.13 Kin 272 class notes- Cardiac Cycleo 1. Passive filling (heart is accidentally filling the ventricle – trying to fill atria) Av valve is open SL valve is closedo Analogy: Pint glass – top is always wide open Think about atria… Right: vena cava Pulmonary veins… They are wide open Blood is always constantly returning into the heart Double floored glass…- Can’t fill the top completely because there is a hole in the bottomo 2. Atrial contraction Ejection of blood to ventricle Takes all blood and pushes it to ventricle After that happens, AV valve will close, pins blood down (creates pressure because its jammed in there) SL valve is still closedo 3. Isovolumic contraction Iso – means same Volumic – means volume “Same volume” AV valve is closed Semilunar valve is also closed Volume in ventricle doesn’t change! Muscle in ventricle starts to contract (not fully – doesn’t want to explode) Fluid in the ventricle wants to go out the semilunar valveo 4. Ejection AV valve closed SL valve open “Overcome of pressure” Need to move blood from the ventricle to the aorta Pressure needs to be larger in the cup than in the tube! Aorta has a lot of pressure- Ventricle needs to have more pressure than aorta- Only way you are going to eject is when the pressure in ventricle is higher than pressure in aorta Minimal pressure needed to get from right side to lefto 5. Isovolumic Relaxation AV valve closed SL valve closed Need to return to step 1 End of the cardiac cycle How to get AV valve open again?- Pressure in atria is higher than in ventricle- Cardiac cycle- Preloado Alters contractilityo What are you putting into the heart before it contractso Passive fillingo Atrial contraction (?)o Venous return (?) All blood volume returning to the heart in veins Could be told in quantity amount – could be figured out Speed of return a little more difficult…- HEART RATE affects rate at which blood is returning- Corresponds to speed- Heart rate goes up; speed of return goes up as well- Heart rate- beats per minute- Stroke volume – volume ejected per beat- Cardiac outputo Volume ejected per minuteo Math problem can be used to calculate Cardiac output = stroke volume * heart rate Q (with a dot over the top) = SV * HR (science people)- Dot indicates per minute- Q = flow- “flow per minute” CO = SV * HR (nursing majors) Q = Flow VO2- After loado Alters contractilityo- Contractility strength of contractiono What is contractility of heart? Efficiency of one strong contractiono Has a strong contraction due to quantity of fluid moving Small amount from one contraction doesn’t benefit the rest of the system Volume related- Pulse pressureo Estimate!o SV estimateo SBP-DBPo SBP = 120o DBP = AROUND 80o STROKE VOLUME = mLo Cardiac output usually in
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