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 C
Explanation
This sequence ensures that the atria contract before the ventricles and that the ventricles contract from the bottom up.
Choice A is wrong because it reverses the order of the SA node and the AV node. The SA node is the pacemaker of the heart and initiates the cardiac impulses.
Choice B is wrong because it places the Purkinje fibers before the AV node.
The Purkinje fibers are the last part of the conduction system and stimulate the ventricular muscle fibers.
Choice D is wrong because it reverses the order of the entire sequence.
The AV node is not the pacemaker of the heart and does not initiate cardiac impulses.
Correct Answer is B
Explanation
The hypothalamus is the part of the brain that produces hormones that control the pituitary gland.
The pituitary gland then releases hormones that target other endocrine glands, such as the thyroid, adrenal, and gonads.
Therefore, the hypothalamus is the source of releasing hormones for target cells in the anterior pituitary gland.
Choice A is wrong because the anterior pituitary gland does not produce releasing hormones, but responds to them by secreting other hormones.
Choice C is wrong because the thyroid gland does not produce releasing hormones, but responds to them by secreting thyroid hormones.
Choice D is wrong because the posterior pituitary gland does not produce releasing hormones, but stores and releases hormones made by the hypothalamus, such as oxytocin and antidiuretic hormone.
Whether you are a student looking to ace your exams or a practicing nurse seeking to enhance your expertise , our nursing education contents will empower you with the confidence and competence to make a difference in the lives of patients and become a respected leader in the healthcare field.
Visit Naxlex, invest in your future and unlock endless possibilities with our unparalleled nursing education contents today