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Ch. 16 The Autonomic Nervous System and Higher-Order Functions
Martini - Fundamentals of Anatomy and Physiology 12th Edition
Martini, Nath, Bartholomew12th EditionFundamentals of Anatomy and PhysiologyISBN: 9780137854011Not the one you use?Change textbook
All textbooksMartini, Nath, Bartholomew 12th EditionCh. 16 The Autonomic Nervous System and Higher-Order FunctionsProblem 24
Chapter 16, Problem 24

Under which of the following circumstances would the diameter of peripheral blood vessels be greatest?
(a) Increased sympathetic stimulation
(b) Decreased sympathetic stimulation
(c) Increased parasympathetic stimulation
(d) Decreased parasympathetic stimulation
(e) Both increased parasympathetic and sympathetic stimulation

Verified step by step guidance
1
Understand that the diameter of peripheral blood vessels is primarily controlled by the autonomic nervous system, specifically through sympathetic stimulation, which generally causes vasoconstriction (narrowing of blood vessels).
Recognize that increased sympathetic stimulation typically causes vasoconstriction, reducing the diameter of peripheral blood vessels, while decreased sympathetic stimulation leads to vasodilation (widening of blood vessels), increasing their diameter.
Note that parasympathetic stimulation has minimal direct effect on most peripheral blood vessels, so changes in parasympathetic activity usually do not significantly alter vessel diameter.
Evaluate each option by considering whether it would increase or decrease sympathetic or parasympathetic activity and how that would affect vessel diameter:
Conclude that the greatest diameter of peripheral blood vessels would occur under conditions of decreased sympathetic stimulation, as this reduces vasoconstriction and allows vessels to dilate.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Sympathetic Nervous System and Vascular Tone

The sympathetic nervous system primarily controls the constriction of peripheral blood vessels through the release of norepinephrine, which binds to alpha-adrenergic receptors causing vasoconstriction. Increased sympathetic stimulation typically reduces vessel diameter, while decreased stimulation leads to vasodilation.
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Sympathetic Nervous System Example 3

Parasympathetic Nervous System Influence on Blood Vessels

The parasympathetic nervous system generally has minimal direct effect on peripheral blood vessel diameter, as most vessels lack significant parasympathetic innervation. Its role is more prominent in regulating heart rate and glandular secretions rather than vascular tone.
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Function of the Parasympathetic Nervous System

Vasodilation and Vasoconstriction Mechanisms

Vasodilation is the widening of blood vessels, often caused by decreased sympathetic activity or local chemical signals, increasing blood flow. Vasoconstriction is the narrowing of vessels, usually triggered by increased sympathetic stimulation, reducing blood flow. Understanding these mechanisms helps explain changes in vessel diameter.
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Related Practice
Textbook Question

A possible side effect of a drug used to open the airways of someone suffering from an asthma attack is

(a) Decreased activity of the digestive system

(b) Diarrhea

(c) Profuse urination

(d) Increased blood pressure

(e) Decreased heart rate

Textbook Question

Damage to the hippocampus, a component of the limbic system, leads to

(a) A loss of emotion due to forgetfulness

(b) A loss of consciousness

(c) A loss of long-term memory

(d) An immediate loss of short-term memory

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Textbook Question

Why does sympathetic function remain intact even when the anterior roots of the cervical spinal nerves are damaged?

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Textbook Question

You are home alone at night when you hear what sounds like breaking glass. What physiological effects would this experience probably produce, and what would be their cause?

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Textbook Question

During sympathetic stimulation, a person may begin to feel 'on edge'; this is the result of

(a) Increased energy metabolism by muscle tissue

(b) Increased cardiovascular activity

(c) Stimulation of the reticular activating system

(d) Temporary insensitivity to painful stimuli

(e) Decreased levels of epinephrine in the blood

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Textbook Question

Why is autonomic tone a significant part of ANS function?

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