Choose the correct statement regarding Alpha-1 receptor.
These are ligand gated ionotropic channels.
These are cholinergic receptors and their activation causes relaxation.
These are mostly located in brain.
These are adrenergic receptors and their activation causes constriction.
The Correct Answer is D
Alpha-1 receptors are a subtype of adrenergic receptors that play a vital role in the sympathetic nervous system's "fight or flight" response. They are primarily located on vascular smooth muscle and utilize the G-protein coupled signaling pathway. Activation leads to an increase in intracellular calcium, resulting in muscle contraction. Pharmacological agonists are used to increase blood pressure, while antagonists are used to treat hypertension and prostatic hypertrophy.
Rationale:
A. Alpha-1 receptors are not ligand-gated ionotropic channels; they are G-protein coupled receptors (GPCRs). Ionotropic channels allow for the rapid flow of ions like sodium or chloride directly through a pore. Alpha-1 receptors work through a second messenger system involving phospholipase C and inositol trisphosphate (IP3). This metabolic pathway results in a slower but sustained cellular response.
B. Alpha-1 receptors are adrenergic, meaning they respond to norepinephrine and epinephrine, not acetylcholine. Cholinergic receptors are part of the parasympathetic system and include nicotinic and muscarinic types. Furthermore, activation of alpha-1 receptors causes contraction, not relaxation, of smooth muscle. Activation of certain cholinergic receptors would typically promote secretions or bradycardia instead.
C. While some alpha-1 receptors exist in the central nervous system, they are predominantly located in the peripheral vasculature and smooth muscle organs. Their most significant clinical effects are observed in the systemic arteries, where they regulate total peripheral resistance. They are also found in the radial muscle of the eye and the sphincters of the urinary tract.
D. These are adrenergic receptors and their activation causes constriction is the correct statement. As part of the sympathetic system, they bind to catecholamines to trigger vasoconstriction of the arterioles. This increases blood pressure and diverts flow to essential organs. In the eye, they cause mydriasis (pupillary dilation) by constricting the pupillary dilator muscle, facilitating improved vision in low light.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
Step 1. Set up alligation.
17.5% (High)
5% (Low)
15% (Target)
Step 2. Determine parts.
Parts of 17.5% = 15 - 5 = 10 parts
Parts of 5% = 17.5 - 15 = 2.5 parts
Total parts = 10 + 2.5 = 12.5 parts
Step 3. Calculate the volume of 17.5% solution needed for 360 mL.
Volume = (10 / 12.5) x 360 = 288 mL
Correct Answer is ["A","C"]
Explanation
Valacyclovir is an L-valyl ester prodrug of the purine nucleoside analogue acyclovir, utilized for the inhibition of viral DNA polymerase. It exhibits high oral bioavailability and is converted in the liver to acyclovir, which competes with deoxyguanosine triphosphate. It is primarily indicated for DNA viruses such as Varicella-Zoster and Herpes Simplex. Side effects include headache and nausea, while severe cases may involve thrombotic thrombocytopenic purpura.
Rationale:
A. Herpes zoster, commonly known as shingles, is a primary FDA-approved indication for valacyclovir. The drug accelerates the resolution of lesions and reduces the duration of postherpetic neuralgia by inhibiting viral replication. Treatment is most effective when initiated within 72 hours of rash onset to limit neuralgic damage. Its high plasma concentration facilitates effective suppression of the Varicella-Zoster virus.
B. Tinea pedis is a fungal infection of the feet caused by dermatophytes, such as Trichophyton rubrum. Valacyclovir is strictly an antiviral agent and possesses no pharmacological activity against fungal organisms. Fungal cell walls contain ergosterol, whereas valacyclovir targets viral DNA synthesis. Consequently, this medication is completely ineffective for treating athlete's foot or any other mycotic infection.
C. Genital herpes is a major FDA-approved indication for valacyclovir, used for both acute outbreaks and long-term suppressive therapy. By decreasing viral shedding, the medication reduces the risk of transmission to seronegative partners. It is effective against both Herpes Simplex Virus type 1 and type 2. Suppression protocols typically involve daily dosing to maintain adequate virological control in the host.
D. Infections caused by Methicillin-Resistant Staphylococcus aureus (MRSA) require bactericidal or bacteriostatic antibiotics like vancomycin or daptomycin. Valacyclovir has no effect on bacterial cell wall synthesis or protein synthesis. Bacteria are prokaryotic organisms, while valacyclovir is specifically designed to interfere with viral replication machinery. Using an antiviral for a bacterial pathogen like MRSA would result in treatment failure.
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