Disruption of which neurotransmitter is involved in Parkinson's disease?
Acetylcholine.
Dopamine.
Serotonin.
Norepinephrine.
The Correct Answer is B
Choice A rationale
Acetylcholine is an excitatory neurotransmitter in the basal ganglia. In Parkinson's disease, there is a relative overactivity of acetylcholine because there is not enough dopamine to inhibit it. While the imbalance between acetylcholine and dopamine is crucial to the disease's symptoms, the primary disruption and the root cause of the pathology is the loss of dopamine. Anticholinergic medications are sometimes used to restore balance, but they do not address the primary neurochemical deficit.
Choice B rationale
Parkinson's disease is directly caused by the progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta. Dopamine is essential for the smooth, coordinated regulation of muscle movement via the basal ganglia. When dopamine levels fall by approximately 60 to 80 percent, the classic motor symptoms emerge. Most pharmacological treatments, such as Levodopa, aim to increase dopamine levels or mimic its action at the receptor site to alleviate bradykinesia, tremors, and muscle rigidity.
Choice C rationale
Serotonin is involved in mood, sleep, and appetite regulation. While patients with Parkinson's disease often suffer from depression and sleep disturbances due to secondary changes in serotonergic pathways, serotonin is not the primary neurotransmitter responsible for the motor dysfunction that defines the disease. The loss of serotonin-producing neurons may occur as the disease spreads to other brain regions, but it is considered a non-motor complication rather than the central cause of the disorder's hallmark signs.
Choice D rationale
Norepinephrine is produced by neurons that are also affected in Parkinson's disease, particularly in the locus coeruleus. This loss contributes to non-motor symptoms like orthostatic hypotension and fatigue. However, the cardinal motor features like bradykinesia and rigidity are specifically linked to the dopamine deficit. While norepinephrine plays a role in the overall clinical picture of autonomic dysfunction in Parkinson's, it is not the primary neurotransmitter whose disruption characterizes the core movement disorder.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Choice A rationale
This sequence incorrectly places the bicuspid valve between the right atrium and right ventricle. In the human heart, the tricuspid valve is the structure that separates the right-sided chambers, while the bicuspid or mitral valve is strictly located on the left side. Furthermore, this choice suggests the tricuspid valve is on the left, which reverses the actual anatomical and physiological flow required for effective pulmonary and systemic circulation through the four cardiac chambers.
Choice B rationale
This pathway is incorrect because it suggests that venous blood from the vena cavae enters the left atrium. Deoxygenated blood from the systemic circulation must enter the right atrium first. Additionally, it lists the tricuspid valve on the left side and the bicuspid valve on the right side. This reverses the entire cardiac anatomy, which would prevent the separation of oxygenated and deoxygenated blood, leading to a total failure of the respiratory and circulatory systems.
Choice C rationale
This description is physiologically impossible as it starts by sending systemic venous blood to the left atrium. The left side of the heart is responsible for receiving oxygenated blood from the lungs via the pulmonary veins, not deoxygenated blood from the vena cavae. It also incorrectly lists the aortic valve before the pulmonary artery and the pulmonic valve before the aorta. This sequence ignores the pressure gradients and valve functions necessary for maintaining unidirectional blood flow.
Choice D rationale
This sequence correctly follows the physiological path of blood. Deoxygenated blood enters the right atrium from the body, passes through the tricuspid valve into the right ventricle, and is pumped through the pulmonic valve to the lungs. After gas exchange, oxygenated blood returns via pulmonary veins to the left atrium, moves through the bicuspid valve to the left ventricle, and is ejected through the aortic valve into the aorta for systemic distribution. This represents the accurate anatomical circuit.
Correct Answer is ["A","B","C","E"]
Explanation
Choice A rationale
The liver is the primary organ responsible for the metabolism and detoxification of exogenous substances, including medications and alcohol. Through various enzymatic pathways, such as the cytochrome P450 system, the liver chemically modifies drugs to make them more water soluble for excretion by the kidneys. This prevents the accumulation of toxic levels of substances in the bloodstream. Impaired liver function can lead to prolonged drug half lives and increased risk of drug toxicity in patients.
Choice B rationale
Bile production is a vital exocrine function of the liver. Hepatocytes synthesize bile, which is composed of water, electrolytes, bile salts, and bilirubin. Bile is essential for the emulsification and absorption of dietary fats and fat soluble vitamins in the small intestine. It also serves as a vehicle for the excretion of waste products like bilirubin and excess cholesterol. Without adequate bile production, patients experience malabsorption and steatorrhea, which is characterized by fatty stools.
Choice C rationale
The liver plays a central role in carbohydrate metabolism and blood glucose regulation. It stores excess glucose in the form of glycogen through a process called glycogenesis. When blood glucose levels drop, the liver performs glycogenolysis, breaking down stored glycogen into glucose to be released into the circulation. Additionally, the liver can create new glucose from non carbohydrate sources via gluconeogenesis. These processes ensure that the body maintains a stable blood glucose level, typically 70 to 100 mg/dL.
Choice D rationale
The liver is responsible for the synthesis, not the destruction, of most clotting factors, including fibrinogen, prothrombin, and factors VII, IX, and X. These proteins are essential for the coagulation cascade and the prevention of excessive bleeding. In liver failure, the production of these factors decreases, leading to an increased prothrombin time and a higher risk of hemorrhage. The destruction of clotting factors is generally associated with consumptive coagulopathies like disseminated intravascular coagulation, not normal liver function.
Choice E rationale
The liver is the major site of cholesterol synthesis in the body. It produces cholesterol to be used in the formation of cell membranes, the synthesis of steroid hormones, and the production of bile acids. The liver also regulates cholesterol levels by exporting it to other tissues via lipoproteins and removing it from the blood. While dietary intake contributes to cholesterol levels, endogenous production by the liver accounts for a significant portion of the total cholesterol found in the human body.
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