The basic event in the formation of a blood clot is the change of:
Thrombin to prothrombin.
Fibrinogen to fibrin.
Vitamin K to prothrombin.
Fibrin to fibrinogen.
The Correct Answer is B
This is because fibrinogen is a soluble protein in the blood plasma that is converted to insoluble fibrin strands by the enzyme thrombin during blood clotting. Fibrin forms a mesh-like network that traps platelets and other blood cells to form a clot.
Choice A is wrong because thrombin is not converted to prothrombin, but rather prothrombin is converted to thrombin by another enzyme called prothrombinase.
Choice C is wrong because vitamin K is not converted to prothrombin, but rather vitamin K is required for the synthesis of prothrombin and other clotting factors in the liver.
Choice D is wrong because fibrin is not converted to fibrinogen, but rather fibrinogen is converted to fibrin as explained above.
Normal ranges of fibrinogen in the blood are 200 to 400 mg/dL.
Normal ranges of prothrombin time (a measure of how long it takes blood to clot) are 11 to
13.5 seconds.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
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.
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.
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