Textbook Question
Compare and contrast flexor and crossed-extensor reflexes.
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Ch. 13 The Peripheral Nervous System and Reflex Activity
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034
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Table of contents
- Ch. 1 The Human Body: An Orientation24
- Ch. 2 Chemistry Comes Alive25
- Ch. 3 Cells: The Living Units21
- Ch. 4 Tissue: The Living Fabric20
- Ch. 5 The Integumentary System11
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System26
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue19
- Ch. 12 The Central Nervous System26
- Ch. 13 The Peripheral Nervous System and Reflex Activity32
- Ch. 14 The Autonomic Nervous System19
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System23
- Ch. 17 Blood25
- Ch. 18 The Cardiovascular System: The Heart24
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues14
- Ch. 21 The Immune System: Innate and Adaptive Body Defenses27
- Ch. 22 The Respiratory System21
- Ch. 23 The Digestive System31
- Ch. 24 Nutrition, Metabolism, and Energy Balance26
- Ch. 25 The Urinary System26
- Ch. 26 Fluid, Electrolyte, and Acid-Base Balance24
- Ch. 27 The Reproductive System24
- Ch. 28 Pregnancy and Human Development25
- Ch. 29 Heredity11
Marieb, Hoehn11th EditionHuman Anatomy & PhysiologyISBN: 9780136874034Not the one you use?Change textbook
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Marieb, Hoehn 11th EditionCh. 13 The Peripheral Nervous System and Reflex ActivityProblem 23
Marieb, Hoehn 11th EditionCh. 13 The Peripheral Nervous System and Reflex ActivityProblem 23Chapter 13, Problem 23
As Luke fell off a ladder, he grabbed a tree branch with his right hand, but unfortunately lost his grip and fell heavily to the ground. Days later, Luke complained that his right upper limb was numb. What was damaged in his fall?
Verified step by step guidance1
Step 1: Identify the anatomical structures involved in the sensation and motor function of the right upper limb, focusing on the nerves that could be affected by trauma from a fall.
Step 2: Understand that numbness in the upper limb typically indicates damage to peripheral nerves or nerve roots that carry sensory information from the limb to the central nervous system.
Step 3: Consider the brachial plexus, a network of nerves originating from the spinal cord segments C5 to T1, which innervates the upper limb both motorically and sensorily.
Step 4: Analyze the mechanism of injury—falling and grabbing a branch could stretch or compress the brachial plexus or its branches, leading to numbness in the limb.
Step 5: Conclude that the most likely damaged structure causing numbness in the right upper limb after such a fall is the brachial plexus or one of its major nerves (such as the radial, median, or ulnar nerve).
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Brachial Plexus Anatomy
The brachial plexus is a network of nerves originating from the spinal cord segments C5 to T1, responsible for motor and sensory innervation of the upper limb. Damage to this plexus can cause numbness, weakness, or paralysis in the arm. Understanding its anatomy helps localize nerve injuries after trauma.
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Mechanism of Nerve Injury in Falls
During a fall, sudden stretching or compression of nerves can occur, especially if the arm is forcibly pulled or extended, leading to nerve damage. Grabbing a branch and losing grip can cause traction injuries to the nerves supplying the upper limb, resulting in sensory deficits like numbness.
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Clinical Presentation of Upper Limb Nerve Damage
Numbness in the upper limb after trauma suggests sensory nerve involvement, often linked to peripheral nerve or brachial plexus injury. Recognizing symptoms such as numbness, weakness, or pain helps in diagnosing the specific nerve or nerve group affected and guides further management.
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