Please tell me which one is TRUE or FALSE for the statements below:
1. During the cardiac cycle the pressure in the left ventricle and right ventricle are approximately equal.
2. During isovolumetric contraction the left ventricular pressure continues to increase and eventually reaches a point where it exceeds the aortic pressure.
3. The aortic valve opens when left ventricular pressure equals aortic pressure.
4. In the absence of other influences the intrinsic rate of the sinoatrial node is between 80 and 85 beats per minute.
5. The QRS complex represents the wave of ventricular depolarisation that precedes the contraction of the ventricle
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To determine which statements are true or false, we can analyze each statement individually and refer to the relevant knowledge in cardiology. Here is an explanation for each statement:
1. During the cardiac cycle, the pressure in the left ventricle and right ventricle are approximately equal.
This statement is TRUE. During the cardiac cycle, the pressure in the left and right ventricles is indeed almost equal. Both ventricles pump blood simultaneously to supply oxygenated blood to the body and deoxygenated blood to the lungs, respectively.
2. During isovolumetric contraction, the left ventricular pressure continues to increase and eventually reaches a point where it exceeds the aortic pressure.
This statement is FALSE. During isovolumetric contraction, the left ventricular pressure indeed increases, but it does not exceed the aortic pressure. The aortic valve remains closed during this phase, and the ventricular pressure rises until it surpasses the pressure in the left atrium, leading to the opening of the mitral valve.
3. The aortic valve opens when left ventricular pressure equals aortic pressure.
This statement is TRUE. The aortic valve opens during the cardiac cycle when the pressure in the left ventricle exceeds the pressure in the aorta. This allows the blood to be ejected from the left ventricle into the systemic circulation.
4. In the absence of other influences, the intrinsic rate of the sinoatrial node is between 80 and 85 beats per minute.
This statement is FALSE. The intrinsic rate of the sinoatrial (SA) node, often referred to as the natural pacemaker of the heart, is around 60 to 100 beats per minute. However, it is important to note that the actual heart rate can be influenced by various factors, including nervous system stimulation and hormonal control.
5. The QRS complex represents the wave of ventricular depolarization that precedes the contraction of the ventricle.
This statement is TRUE. The QRS complex in an electrocardiogram (ECG) represents the electrical activity associated with ventricular depolarization (contraction). It is the result of the spread of the electrical impulse through the ventricles, leading to their coordinated contraction and subsequent pumping of blood.
By examining each statement and considering the knowledge from cardiology, we have determined which are true and false.