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 D
Explanation
It is measured as part of a blood test and depends on the number and size of red blood cells. It is normally 40.7–50.3% for males and 36.1–44.3% for females.
Red blood cells contain hemoglobin, which transports oxygen and nutrients to the cells and tissues of the body.
Choice A is wrong because the color of plasma is not hematocrit.
Plasma is the liquid part of blood that carries blood cells and other substances.
Choice B is wrong because hematocrit is not a disease.
It is a test that can indicate conditions such as anemia or polycythemia.
Choice C is wrong because hematocrit is not a clotting factor.
Clotting factors are proteins that help the blood to clot and prevent bleeding.
Correct Answer is A
Explanation
It is a major component of the lymphatic system and contains T and B lymphocytes.
Choice B is wrong because the spleen does not produce T lymphocytes, but rather stores them.
T lymphocytes are produced in the thymus.
Choice C is wrong because the spleen does not filter lymph, but rather blood. It traps bloodborne microbes and produces an immune response to them.
Choice D is wrong because the spleen consists of one lobe and is located in the upper left abdomen below the diaphragm.
The description in choice D matches the thymus, not the spleen.
The normal size of the spleen in adults is about 12 cm long, 8 cm broad, and 3-4 cm thick, weighing about 200 g.
The normal range of splenic index (the product of length, width, and thickness) is 120-480 cm.
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