Which of the following heart valves lies between the left atrium and left ventricle and prevents the regurgitation of blood from the ventricle back into the atrium?
Mitral valve.
Tricuspid valve.
Pulmonary valve.
Aortic valve.
The Correct Answer is A
The mitral valve lies between the left atrium and left ventricle and prevents the regurgitation of blood from the ventricle back into the atrium.
It has two leaflets that open and close to allow blood to flow from the lungs into the left atrium and then to the left ventricle.
Choice B is wrong because the tricuspid valve lies between the right atrium and right ventricle and prevents the regurgitation of blood from the ventricle back into the atrium.
It has three leaflets that open and close to allow blood to flow from the body into the right atrium and then to the right ventricle.
Choice C is wrong because the pulmonary valve lies between the right ventricle and the pulmonary artery and prevents the regurgitation of blood from the artery back into the ventricle.
It has three leaflets that open and close to allow blood to flow from the right ventricle to the lungs, where it picks up oxygen.
Choice D is wrong because the aortic valve lies between the left ventricle and the aorta and prevents the regurgitation of blood from the aorta back into the ventricle.
It has three leaflets that open and close to allow blood to flow from the left ventricle to the rest of the body.
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Related Questions
Correct Answer is B
Explanation
Cardiac output is calculated by multiplying the stroke volume by the heart rate, not by the systolic blood pressure.
Stroke volume is the amount of blood circulated by the heart with each beat. Heart rate is the number of beats per minute.
Systolic blood pressure is the pressure in the arteries when the heart contracts. Choice A is wrong because it confuses systolic blood pressure with heart rate.
Systolic blood pressure is not directly related to cardiac output, although it can be affected by it.
1: Cardiac Output- Definition, Factors Affecting, Cardiac Index - BYJU’S 2: Cardiac Output (Fick’s Formula) - MDCalc 3: Calculating how much blood is pumped by the heart - Cellular respiration and transport - Edexcel - GCSE Biology (Single Science) Revision - Edexcel - BBC Bitesize 4: Cardiac output - Structure and function of the heart - Higher Human Biology Revision - BBC Bitesize : Blood Pressure: What Is Normal? How To Measure Blood Pressure (healthline.com)
Correct Answer is C
Explanation
Uterine contractions during childbirth illustrate a positive feedback mechanism.
A positive feedback mechanism is a process in which the end products of an action cause more of that action to occur in a feedback loop.
This amplifies the original action.
For example, when a woman goes into labor, the pressure of the baby’s head on the cervix stimulates nerve impulses that travel to the brain and trigger the release of oxytocin, a hormone that causes the uterus to contract.
The contractions increase the pressure on the cervix, which stimulates more nerve impulses, more oxytocin, and more contractions.
This cycle continues until the baby is delivered.
Choice A is wrong because body temperature control is an example of a negative feedback mechanism, which is when the end results of an action inhibit that action from continuing to occur.
For example, when the body temperature rises above normal, the skin sweats, and blood vessels dilate to release heat.
This lowers the body temperature back to normal and stops sweating and dilation.
Choice B is wrong because control of blood sugar is also an example of a negative feedback mechanism.
For example, when the blood sugar level rises after a meal, the pancreas secretes insulin, a hormone that helps cells take up glucose from the blood.
This lowers the blood sugar level back to normal and stops the insulin secretion.
Choice D is wrong because maintaining blood pressure is another example of a negative feedback mechanism.
For example, when the blood pressure drops due to blood loss or dehydration, the heart beats faster and stronger, and the blood vessels constrict to increase the blood pressure.
This restores the blood pressure back to normal and stops the heart rate and vessel constriction.
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