Textbook Question
Mark the following statements as true or false. If a statement is false, correct it to make a true statement.
b. Sympathetic stimulation increases sweat secretion.
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14. The Autonomic Nervous System
Sympathetic Nervous System
Problem L3.A3
Textbook Question
Mr. Chevalier has been diagnosed with Horner syndrome, which is caused by dysfunction of the sympathetic neurons in the superior cervical ganglion that innervate structures of the head, face, and neck. What symptoms is Mr. Chevalier likely to face due to his disease? Explain.
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Understand the role of the sympathetic nervous system in the superior cervical ganglion. The superior cervical ganglion is part of the sympathetic nervous system and provides innervation to structures in the head, face, and neck, including the eyes, sweat glands, and blood vessels.
Recognize the symptoms associated with Horner syndrome. Horner syndrome results from disruption of sympathetic innervation, leading to characteristic symptoms such as ptosis (drooping of the upper eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side of the face.
Explain the mechanism behind ptosis. Ptosis occurs because the sympathetic nerves normally stimulate the superior tarsal muscle, which helps elevate the upper eyelid. Dysfunction of these nerves leads to drooping of the eyelid.
Describe the cause of miosis. Miosis happens because the sympathetic nerves are responsible for dilating the pupil. When these nerves are impaired, the parasympathetic system dominates, causing the pupil to remain constricted.
Discuss the reason for anhidrosis. Anhidrosis occurs due to the loss of sympathetic stimulation to the sweat glands on the affected side of the face, resulting in reduced or absent sweating.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Horner Syndrome
Horner syndrome is a neurological condition resulting from disruption of sympathetic nerve pathways, particularly affecting the eye and surrounding structures. It is characterized by a triad of symptoms: ptosis (drooping of the upper eyelid), miosis (constricted pupil), and anhidrosis (lack of sweating) on the affected side of the face. Understanding this syndrome is crucial for recognizing its clinical manifestations and underlying causes.
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Sympathetic Nervous System
The sympathetic nervous system is part of the autonomic nervous system responsible for the body's 'fight or flight' response. It prepares the body for stressful situations by increasing heart rate, dilating pupils, and inhibiting digestion. Dysfunction in this system, particularly in the superior cervical ganglion, can lead to the symptoms observed in Horner syndrome, highlighting the importance of sympathetic pathways in regulating facial and ocular functions.
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Superior Cervical Ganglion
The superior cervical ganglion is the largest of the sympathetic ganglia and is located in the neck. It plays a critical role in innervating structures in the head and neck, including the eyes, salivary glands, and sweat glands. Damage or dysfunction in this ganglion can lead to the characteristic symptoms of Horner syndrome, making it essential to understand its anatomy and function in relation to sympathetic nervous system disorders.
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