Which of the following illustrates a positive feedback mechanism?
Body temperature control.
Control of blood sugar.
Uterine contractions during childbirth.
Maintaining blood pressure.
The Correct Answer is C
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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
The correct answer is choice B. False.
Arteries are strong, elastic vessels that carry blood away from the heart, except for the coronary arteries that supply blood to the heart muscle.
These are the first arteries to branch off the aorta, which is the main artery that takes blood to the body from the left ventricle.
Choice A is wrong because it contradicts the definition of arteries. Arteries carry blood away from the heart, not to the heart.
Correct Answer is B
Explanation
The aorta is the largest artery in the human body, as well as the main artery in the circulatory system.
It originates from the left ventricle of the heart and extends down to the abdomen, where it splits into two smaller arteries (the common iliac arteries).
The aorta distributes oxygenated blood to all parts of the body through the systemic circulation.
Choice A. Carotid is wrong because the carotid artery is not the largest artery in the body, but one of the main arteries that pumps blood from the heart to the brain and the rest of the head.
It has a diameter of 4.3 mm-7.7 mm and a blood flow of 350-550 milliliters per minute.
Choice C. Celiac is wrong because the celiac artery is not the largest artery in the body, but a major branch of the abdominal aorta that supplies oxygenated blood to the liver, stomach, spleen, pancreas, and duodenum.
Choice D. Femoral is wrong because the femoral artery is not the largest artery in the body, but the largest artery found in the leg region.
It runs down the inner thigh and carries out the important role of supplying blood to the lower body.
It has a diameter of 6.6 mm and a blood flow of 284 milliliters per minute.
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