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
Kidneys are not part of the lymphatic system.
The lymphatic system is a network of vessels and organs that drain excess fluid from the tissues, transport fats and immune cells, and protect the body from infections.
Kidneys are part of the urinary system, which filters blood, regulates fluid and electrolyte balance, and produces urine.
Choice A is wrong because kidneys do not have a direct connection to the lymphatic system.
Although kidneys have lymphatic vessels in their cortex, they do not originate from the lymphatic system.
Kidneys receive blood from the renal arteries and return it to the renal veins.
The lymphatic vessels in the kidney cortex drain interstitial fluid and immune cells from the kidney tissue to the regional lymph nodes.
Some additional sentences are:
Choice B is right because kidneys are part of the urinary system, not the lymphatic system.
The urinary system and the lymphatic system have different functions and structures in the body.
Normal ranges for kidney function tests include blood urea nitrogen (BUN) of 7 to 20 mg/dL, serum creatinine of 0.6 to 1.2 mg/dL, and glomerular filtration rate (GFR) of more than 90 mL/min/1.73 m.
Normal ranges for lymphatic system tests include white blood cell (WBC) count of 4,000 to 11,000 cells per microliter, lymphocyte count of 1,000 to 4,800 cells per microliter, and immunoglobulin levels of IgG (700 to 1,600 mg/dL), IgA (70 to 400 mg/dL), IgM (40 to 230
mg/dL), IgE (0 to 100 IU/mL), and IgD (0.5 to 5 mg/dL).
Correct Answer is A
Explanation
Calcitonin is a hormone that protects against excessive blood calcium levels by inhibiting bone turnover and decreasing reabsorption.
It is produced by the thyroid gland and acts on both osteoclasts and osteoblasts.
Choice B is wrong because parathyroid hormone (PTH) stimulates both resorption and formation of bone, and controls the level of calcium in the blood.
Choice C is wrong because thyroxine is a thyroid hormone that is required for skeletal maturation and influences adult bone maintenance but does not directly affect calcium deposition into bone.
Choice D is wrong because insulin is a hormone that regulates both bone formation and bone resorption but does not specifically stimulate calcium deposition into bone.
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