Spinal nerves and Guillain-Barre syndrome
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- Spinal nerves and Guillain-Barre syndrome
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Spinal nerves and Guillain-Barre syndrome
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[ID] => 559683
[post_author] => 12815
[post_date] => 2024-12-28 16:40:04
[post_date_gmt] => 2024-12-28 21:40:04
[post_content] => Practice Passage (Question 1-5)
*This passage is the property of Khan Academy and has been reformatted into an AAMC-style interface in their entirety by MedLife Mastery. MedLife Mastery does not endorse and is not an affiliate of Khan Academy.
Unlike many better-known nervous system disorders, Guillain-Barre syndrome (GBS) is a polyneuropathy that affects only the peripheral nervous system (PNS). GBS is an autoimmune disease, most often triggered by a specific bacterial infection whose surface proteins mimic the cell surface molecules of the nervous system. This tricks the immune system into attacking host cells in addition to the bacteria. Patients present with progressive weakness or numbness in their limbs, and symptoms often progress very quickly. Left untreated, GBS can lead to paralysis or death.
The PNS is composed of the nerves and ganglia found outside the brain and spinal cord. It is the PNS that innervates the body and transmits messages to and from the brain. The point of contact between the PNS and the central nervous system (CNS) is the spinal cord from which exit the spinal nerves (Figure 1).
There are two major nerve classifications – somatic or visceral, and afferent or efferent. The word “somatic” shares a root with the word “soma”, which means cell bodies. Somatic refers to nerves that go to the body wall and limbs. “Visceral” is the terms used for nerves that innervate the organs, or viscera.
Afferent nerves bring signals from the body to the CNS. These nerves connect to the spinal cord at the dorsal root. Efferent nerves, on the other hand, send signals from the CNS to the rest of the body. They exit the spinal column at the ventral root, and meet with the afferent nerves to create a spinal nerve.
Figure 1. Spinal nerve. Attribution: adapted from Tristanb, CC-BY-SA 3.0.
[post_title] => Spinal nerves and Guillain-Barre syndrome
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[questions] => Array
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[question] => Which of the following signals would be transmitted through a visceral efferent nerve?
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[answer] => 3
[description] => Reason for the Correct Answer:
Peristalsis is the contraction of smooth muscle tissue in the GI tract
Visceral nerves innervate the organs.
A visceral efferent nerve sends a motor signal to the viscera, e.g., signaling the esophagus to contract during peristalsis.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Moving your finger away from a hot plate
)
[1] => Array
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[each_answer] => B. The signal that the stomach is full
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[2] => Array
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[each_answer] => C. The signal to induce peristalsis
)
[3] => Array
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[each_answer] => D. The sensation of burning your finger on a hot plate
)
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[1] => Array
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[quiz_unique_key] => 3873426850
[question] => If a person can move their fingers, but cannot feel a needle prick, which type of nerve is most likely affected?
[value] => Array
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[answer] => 3
[description] => Reason for the Correct Answer:
Motor signals travel through efferent nerves.
Skeletal muscles are innervated with somatic nerves, while smooth muscle is innervated with visceral nerves.
Somatic afferent nerves send sensory information from the body wall and limbs. Afferent nerves travel through the dorsal root to reach the spinal cord. If a patient cannot feel pain in their hand, it is these nerves that are affected.
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[answers] => Array
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[0] => Array
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[each_answer] => A. Visceral nerves from the dorsal root
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[1] => Array
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[each_answer] => B. Somatic nerves from the ventral root
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[2] => Array
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[each_answer] => C. Somatic nerves from the dorsal root
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[3] => Array
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[each_answer] => D. Visceral nerves from the ventral root
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[2] => Array
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[quiz_unique_key] => 83407773
[question] => In patients with GBS, there is particular concern for the autonomic nervous system. Which nerves are a part of this system?
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[answer] => 1
[description] => Reason for the Correct Answer:
The autonomic nervous system is responsible for the “fight or flight” instinct.
The autonomic nervous system regulates heart rate, digestion, and salivation.
Both visceral efferent and visceral afferent nerves must be part of the autonomic nervous system such that it can both affect change and monitor the effects of those changes.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Visceral efferent and afferent
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[1] => Array
(
[each_answer] => B. Somatic efferent only
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[2] => Array
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[each_answer] => C. Somatic efferent and afferent
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[3] => Array
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[each_answer] => D. Visceral efferent only
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[3] => Array
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[quiz_unique_key] => 2261298308
[question] => Which of the following would indicate that a patient has something other than GBS?
[value] => Array
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[answer] => 2
[description] => Reason for the Correct Answer:
Cranial nerves are a part of the peripheral nervous system alongside spinal nerves.
As nerves degrade, they can begin to send even more signals, causing pain.
Guillain-Barre syndrome is an autoimmune disorder, and should be systemic. Weakness localized to only one part of the body indicates that the patient does not have GBS.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Pain due to increased firing of afferent nerves
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[1] => Array
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[each_answer] => B. Weakness in only one side of the body
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[2] => Array
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[each_answer] => C. Facial muscle weakness
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[3] => Array
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[each_answer] => D. Decreased tendon reflexes
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[quiz_unique_key] => 574431310
[question] => A scientist studying Guillain-Barre wants to determine if the dorsal root is more affected than the ventral root. Which of the following tests should they perform?
[value] => Array
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[answer] => 1
[description] => Reason for the Correct Answer:
Efferent nerves travel through the ventral root.
The autonomic response involves both afferent and efferent nerve fibers.
The immune system would most likely attack more where there are more surface markers. To compare dorsal and ventral roots, it is necessary to compare efferent and afferent nerve fibers.
)
[answers] => Array
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[0] => Array
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[each_answer] => A. Compare the distribution of the cell surface marker between somatic efferent and somatic afferent nerves
)
[1] => Array
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[each_answer] => B. Measure loss of motor function vs loss of autonomic function
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[2] => Array
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[each_answer] => C. Compare the distribution of the cell surface marker between somatic efferent and visceral efferent nerves
)
[3] => Array
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[each_answer] => D. Measure loss of pain sensation in the trunk vs loss of pain sensation in the gut
)
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[559683|1] => C
[559683|2] => C
[559683|3] => A
[559683|4] => B
[559683|5] => A
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Figure 1