After the effector cell has being stimulated by acetylcholine (ACh), what enzyme stop the stimulation and allows the effector membrane to repolarize?
Norepinephrine
Decarboxylase
Catecholamine
Acetylcholinesterase
The Correct Answer is D
A) Norepinephrine: Norepinephrine is a neurotransmitter primarily involved in the sympathetic nervous system. It is not involved in terminating the stimulation caused by acetylcholine. Norepinephrine acts on adrenergic receptors, whereas acetylcholine primarily acts on cholinergic receptors.
B) Decarboxylase: Decarboxylase is an enzyme that plays a role in the synthesis of certain neurotransmitters, including dopamine, but it does not have a role in terminating the action of acetylcholine at the effector cell. It is unrelated to the termination of acetylcholine signaling.
C) Catecholamine: Catecholamines (such as dopamine, norepinephrine, and epinephrine) are a group of neurotransmitters involved in the sympathetic nervous system. While they play a role in synaptic transmission, they are not responsible for breaking down acetylcholine or terminating its effects. Their primary function is in adrenergic signaling.
D) Acetylcholinesterase: Acetylcholinesterase is the correct enzyme. It is responsible for breaking down acetylcholine (ACh) in the synaptic cleft after it has stimulated the effector cell. By hydrolyzing acetylcholine into acetate and choline, acetylcholinesterase effectively terminates the signal and allows the effector cell's membrane to repolarize. This action prevents continuous stimulation and ensures proper function of the cholinergic system.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
A) Proteins:
Proteins are generally too large to diffuse freely across the cell membrane. They require specific transport mechanisms, such as endocytosis or transport proteins, to move in and out of cells. The hydrophilic nature of most proteins further complicates their passage across the lipid bilayer.
B) Enzymes:
Like proteins, enzymes are large molecules that do not freely diffuse across cell membranes. Enzymes, being proteins, also need specialized transport mechanisms or need to be secreted or endocytosed to enter or exit cells.
C) Hormones:
Many hormones, particularly lipid-soluble ones like steroid hormones, can diffuse freely across the cell membrane. These hormones pass through the lipid bilayer due to their hydrophobic nature and bind to intracellular receptors, initiating cellular responses. However, water-soluble hormones (e.g., insulin) typically do not diffuse freely but interact with receptors on the cell surface.
D) Electrolytes:
Electrolytes (such as sodium, potassium, calcium, and chloride ions) are charged particles that cannot pass freely through the lipid bilayer due to the hydrophobic interior of the cell membrane. They require specific ion channels or transporters to move in and out of the cell. Diffusion of electrolytes is facilitated through these channels, but it is not a simple diffusion process as seen with small, uncharged molecules.
Correct Answer is D
Explanation
A) A patient with hypotension:
Patients with hypotension may have reduced blood flow to organs, which could potentially decrease the absorption and effectiveness of many medications, including opioids. As a result, the need for a higher dose is not typical. Instead, careful dosing and monitoring are required to avoid further lowering blood pressure, which could lead to more complications.
B) A patient with a concussion:
Concussions affect the brain and can lead to symptoms like dizziness, confusion, or nausea, which may alter how medications are metabolized or tolerated. However, a concussion does not typically require higher opioid doses. In fact, opioids should be used cautiously in such patients due to the risk of exacerbating neurological symptoms or respiratory depression.
C) A patient 3 days after surgery:
Patients recovering from surgery may require pain management, but the opioid dose typically adjusts based on their pain levels and recovery stage. While some patients may still need opioids for pain control, they may not require higher-than-expected doses. Over time, doses are often tapered as healing progresses, and pain lessens.
D) A patient with cancer:
Cancer patients, particularly those with advanced stages or chronic pain, may develop increased opioid tolerance. This means that over time, they may require higher doses to achieve the same level of pain relief. This phenomenon is known as "opioid tolerance," where the body becomes less responsive to the drug, necessitating dose adjustments.
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