Metabolic effect of thyroid hormone is
Increased BMR
Increased protein synthesis
Increased glycolysis
Increased heat production
All the above
The Correct Answer is E
Thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3), act as the primary regulators of metabolic rate in almost all nucleated cells. By binding to nuclear receptors, they modulate gene expression to enhance mitochondrial activity and fuel utilization. These hormones are essential for growth, development, and the maintenance of body temperature. They influence the turnover of carbohydrates, lipids, and proteins to sustain systemic energy requirements.
Rationale:
A. Increased BMR is a hallmark effect of thyroid hormones, achieved through the up-regulation of the Na+/K+-ATPase pump. This energy-intensive process consumes high amounts of ATP, thereby increasing the basal rate of oxygen consumption. A higher basal metabolic rate ensures that the body maintains the necessary kinetic energy for vital cellular functions.
B. Increased protein synthesis occurs as T3 stimulates the transcription of numerous structural and functional proteins. In a physiological state, thyroid hormones promote a positive nitrogen balance essential for growth and tissue repair. However, it is important to note that at pathological, thyrotoxic levels, the effect may shift toward protein catabolism and muscle wasting.
C. Increased glycolysis is part of the hormone's role in enhancing glucose turnover to provide immediate fuel for mitochondria. T3 increases the expression of glycolytic enzymes and facilitates glucose uptake in peripheral tissues. By accelerating the breakdown of glucose, the hormone ensures a steady supply of substrates for oxidative phosphorylation and energy production.
D. Increased heat production, or thermogenesis, is a direct consequence of increased metabolic activity and uncoupled respiration. Thyroid hormones stimulate the expression of uncoupling proteins (UCPs) in mitochondria, which dissipate energy as heat. This effect is crucial for maintaining homeothermy and explains why patients with hyperthyroidism often exhibit significant heat intolerance.
E. All the above is correct because thyroid hormones exert a pleiotropic effect on metabolism that encompasses all these actions. They simultaneously increase the basal metabolic rate, stimulate the production of new proteins, and accelerate carbohydrate catabolism. This integrated response ensures that the body’s energy production and heat generation are appropriately matched to physiological demands.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is E
Explanation
Parasympathetic innervation of the heart is primarily mediated through the vagus nerve, which releases acetylcholine (ACh) onto the sinoatrial (SA) node. This chemical signal binds to muscarinic M2 receptors, triggering G-protein mediated changes in membrane potential. The resulting negative chronotropic effect slows the heart rate to maintain resting homeostasis and cardiac output efficiency during periods of low activity.
Rationale:
A. Decreasing permeability to potassium would lead to a buildup of positive charge inside the cell, causing depolarization rather than slowing the heart. This would make the cell more excitable and increase the heart rate. Acetylcholine acts to stabilize the membrane, not to make it more prone to reaching the threshold potential quickly.
B. While sodium channels are involved in the initial "funny" current of the pacemaker potential, closing them is not the primary mechanism of vagal hyperpolarization. The main inhibitory effect of acetylcholine relies on the movement of potassium ions out of the cell. Sodium channel modulation is a secondary effect compared to the direct potassium conductance increase.
C. Opening calcium channels would actually increase the rate of depolarization and strengthen muscular contraction. Acetylcholine actually inhibits the L-type calcium current in the nodal tissue to help slow the rate of firing. This choice incorrectly describes the ion flow and the resulting effect on the cardiac cycle timing.
D. Closing sodium channels would not lead to hypopolarization (becoming less negative). Furthermore, the vagus nerve's primary inhibitory action is not centered on simple sodium channel closure. The heart's response to acetylcholine is characterized by a significant membrane shift toward a more negative, stable state, which is the opposite of hypopolarization or depolarization.
E. Acetylcholine increases permeability to potassium in the sinus node by opening specialized GIRK (G-protein coupled inwardly rectifying potassium) channels. As potassium exits the cell, the membrane potential becomes more negative, a state called hyperpolarization. This moves the resting potential further from the threshold, effectively slowing the rate of pacemaker firing and heart rate.
Correct Answer is B
Explanation
Intranasal administration of corticosteroids or decongestants requires specific techniques to maximize mucosal absorption and minimize systemic ingestion. Proper positioning and preparation ensure the drug reaches the turbinates rather than the pharynx. Effective delivery relies on the medication remaining in contact with the nasal mucosa for a sufficient duration. Errors in technique, such as improper sniffing or nose blowing, can significantly reduce the therapeutic efficacy of the treatment.
Rationale:
A. True is incorrect because blowing the nose after administration would mechanically remove the medication from the nasal cavity. The goal of the spray is to facilitate local absorption through the respiratory epithelium. If the patient clears their nose immediately after spraying, the active ingredients are expelled, resulting in a sub-therapeutic dose and poor symptom control for the patient.
B. False is the correct answer because while patients should blow their nose before administration to clear mucus, they must avoid doing so afterward. Clearing the passages initially allows for better surface contact with the medication. However, after the dose is given, the patient should avoid blowing their nose for at least 15 minutes to ensure the drug is fully absorbed.
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