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it actively pump h+ ions from gastric mucosa to lumen to maintain low pH
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Physiology
17 Nov, 18:09
The correct answer here is:
D. Increases depolarization-activated L_K in the SA node
Explanation:
Sympathetic stimulation of the heart, primarily through the action of norepinephrine on Γ1-adrenergic receptors, leads to increased heart rate and contractility. This activation does the following at the cellular level:
1. Increases Adenylyl Cyclase Activity - Activation of B1 receptors increases cAMP production via adenylyl cyclase, not decreases it (eliminating choice A)
2. Increases Ca2+ Pump Activity - Sympathetic stimulation enhances Ca2+ handling in the sarcoplasarcoplasmic reticulum by increasing Ca2+ pump (SERCA) activity, facilitating faster relaxation, rather than decreasing it (eliminating choice B)
3. Increases Ca2+ Current (I_Ca) in the AV Node-This enhances conduction through the AV node, not decreases it (eliminating choice C).
4. Increases I_K and Hyperpolarization-Activated Current- Sympathetic stimulation leads to increased depolarization-activated potassium currents in pacemaker cells, including the SA node, helping in repolarization and increasing heart rate.
Thus, option D
D. Increases depolarization-activated L_K in the SA node
Explanation:
Sympathetic stimulation of the heart, primarily through the action of norepinephrine on Γ1-adrenergic receptors, leads to increased heart rate and contractility. This activation does the following at the cellular level:
1. Increases Adenylyl Cyclase Activity - Activation of B1 receptors increases cAMP production via adenylyl cyclase, not decreases it (eliminating choice A)
2. Increases Ca2+ Pump Activity - Sympathetic stimulation enhances Ca2+ handling in the sarcoplasarcoplasmic reticulum by increasing Ca2+ pump (SERCA) activity, facilitating faster relaxation, rather than decreasing it (eliminating choice B)
3. Increases Ca2+ Current (I_Ca) in the AV Node-This enhances conduction through the AV node, not decreases it (eliminating choice C).
4. Increases I_K and Hyperpolarization-Activated Current- Sympathetic stimulation leads to increased depolarization-activated potassium currents in pacemaker cells, including the SA node, helping in repolarization and increasing heart rate.
Thus, option D
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