Textbook Question
The parasympathetic nervous system influences digestion by:
a. Relaxing smooth muscle
b. Stimulating peristalsis and secretory activity
c. Constricting sphincters
d. None of these
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14. The Autonomic Nervous System
Sympathetic Nervous System
2:42 minutesProblem 15
Textbook Question
Describe the neural mechanisms responsible for controlling blood pressure.
Verified step by step guidance1
Understand that blood pressure is regulated by the autonomic nervous system (ANS), which includes the sympathetic and parasympathetic divisions. These systems work together to maintain homeostasis.
Recognize the role of baroreceptors, which are specialized stretch-sensitive receptors located in the walls of the carotid sinus and aortic arch. These receptors detect changes in blood pressure and send signals to the brainstem.
Identify the medulla oblongata as the control center for blood pressure regulation. Specifically, the cardiovascular center in the medulla integrates input from baroreceptors and adjusts autonomic output accordingly.
Learn how the sympathetic nervous system increases blood pressure by stimulating vasoconstriction (narrowing of blood vessels) and increasing heart rate and contractility. This is mediated by the release of norepinephrine, which binds to adrenergic receptors on blood vessels and the heart.
Understand how the parasympathetic nervous system decreases blood pressure by promoting vasodilation (widening of blood vessels) and reducing heart rate. This is mediated by the release of acetylcholine, which acts on muscarinic receptors in the heart.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Autonomic Nervous System
The autonomic nervous system (ANS) regulates involuntary bodily functions, including heart rate and blood pressure. It consists of the sympathetic and parasympathetic branches, which work together to maintain homeostasis. The sympathetic nervous system increases heart rate and constricts blood vessels, raising blood pressure, while the parasympathetic system promotes relaxation and lowers blood pressure.
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Baroreceptors
Baroreceptors are specialized sensory nerve endings located in the walls of blood vessels, particularly in the carotid arteries and aorta. They detect changes in blood pressure by sensing the stretch of the vessel walls. When blood pressure rises, baroreceptors send signals to the brain to initiate responses that lower blood pressure, and vice versa when pressure drops.
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Renin-Angiotensin-Aldosterone System (RAAS)
The renin-angiotensin-aldosterone system (RAAS) is a hormone system that regulates blood pressure and fluid balance. When blood pressure falls, the kidneys release renin, which converts angiotensinogen to angiotensin I, later converted to angiotensin II. This potent vasoconstrictor increases blood pressure by narrowing blood vessels and stimulating aldosterone release, promoting sodium and water retention.
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