Multiple Choice
A recording of the electrical activity of a patient's heart shows that the atria are contracting regularly and normally, but every few beats the ventricles fail to contract. Which of the following is probably functioning improperly?
40. Circulatory System
Heart Physiology
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A mutation that results in a nonfunctioning nitric oxide receptor would cause __________.
A
increased vasoconstriction
B
decreased vasoconstriction
C
decreased blood pressure
D
increased vasodilation
E
decreased vasodilation
Verified step by step guidance1
Understand the role of nitric oxide (NO) in the body: Nitric oxide is a signaling molecule that plays a crucial role in the cardiovascular system by promoting vasodilation, which is the widening of blood vessels.
Recognize the function of the nitric oxide receptor: The NO receptor, often a guanylate cyclase, is activated by nitric oxide. This activation leads to the production of cyclic GMP (cGMP), which causes smooth muscle relaxation and vasodilation.
Consider the impact of a nonfunctioning NO receptor: If the receptor is nonfunctional, it cannot respond to nitric oxide, leading to reduced production of cGMP.
Analyze the physiological outcome: With decreased cGMP levels, smooth muscle relaxation is impaired, resulting in reduced vasodilation.
Conclude the effect on vasodilation: Since the receptor is nonfunctional, the expected outcome is decreased vasodilation, as the signaling pathway for vessel widening is disrupted.
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