i am in zoology class plz someone help me with this homework question:
Question: Sequence the following event during the cardiac cycle, in right order.
1. AV valves open; aortic valve closed;ventricular filling occuring.
2. Blood ejected from the ventricle
3. atrial contraction
4. aortic valves open
5. sa node discharges
6. ventruclar filling complete
7. second heart sound
8. aortic valve closes
9. ventricular contraction begins. AV valve closes
10. Isovolumetric ventricular relaxation
11. Isovolumetric ventricular contraction.
12. First heart sound
Please don't post the same question twice within a few minutes.
This site may help you.
http://www.google.com/search?hl=en&ie=ISO-8859-1&q=cardiac+cycle
that wasn't much of help. i aint stupid to not search for it. Can u plz answer my question
If you post what you do know about the order of the cardiac cycle, we'll be glad to help you from there.
To sequence the events during the cardiac cycle in the right order, let's break down and analyze each event. This will help us understand the order in which they occur:
1. Ventricular filling begins - AV valves open; aortic valve closed; ventricular filling occurring: During this stage, the atria contract, and the AV valves open, allowing blood to flow from the atria into the ventricles. The aortic valve is closed at this point.
2. Atrial contraction: After the ventricles have filled with blood, the atria contract, further forcing blood into the ventricles.
3. SA node discharges: The SA (sinoatrial) node, also known as the natural pacemaker of the heart, sends an electrical signal, causing the atria to contract. This event occurs after the atrial contraction.
4. Ventricular filling complete: After the atrial contraction and the SA node discharging, the ventricles are filled to their maximum capacity with blood.
5. AV valve closes; ventricular contraction begins: As the ventricles are filled, the AV (atrioventricular) valves close to prevent backflow of blood into the atria. This marks the beginning of ventricular contraction.
6. Isovolumetric ventricular contraction: During this stage, the ventricles contract, building pressure. However, no blood is ejected yet since both the aortic valve and the pulmonary valve, situated between the right ventricle and the pulmonary artery, are closed.
7. First heart sound: The closure of the AV valves, known as the first heart sound or "Lub," can be heard during this stage. It signifies the beginning of ventricular contraction.
8. Aortic valve opens: The pressure generated by the contracting ventricles exceeds the pressure in the aorta, causing the aortic valve to open. This allows blood to be ejected from the left ventricle into the aorta.
9. Blood ejected from the ventricle: As the aortic valve opens, blood is propelled into the aorta, supplying the body with oxygenated blood.
10. Isovolumetric ventricular relaxation: Following the ejection of blood, the ventricles start to relax, resulting in a decrease in pressure. However, both the aortic valve and the AV valves remain closed during this phase, keeping the blood volume constant.
11. Second heart sound: The closure of the aortic valve, also known as the second heart sound or "Dub," occurs during this stage. It indicates the end of systole (contraction) and the beginning of diastole (relaxation).
12. Aortic valve closes: As ventricular relaxation continues, the pressure in the aorta drops below the pressure in the left ventricle. This causes the aortic valve to close, preventing blood from flowing back into the ventricle.
So, the correct sequence of events during the cardiac cycle is as follows:
5. SA node discharges
3. Atrial contraction
1. AV valves open; aortic valve closed; ventricular filling occurring
4. Ventricular filling complete
9. AV valve closes; ventricular contraction begins
11. Isovolumetric ventricular contraction
12. First heart sound
8. Aortic valve opens
2. Blood ejected from the ventricle
10. Isovolumetric ventricular relaxation
7. Second heart sound
6. Aortic valve closes
Please note that some minor variations and additional stages may exist depending on the source or textbook being referenced.