Textbook Question
Central pattern generators (CPGs) are found at the segmental level of motor control.
a. What is the job of the CPGs?
b. What controls them, and where is this control localized?
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Ch. 13 The Peripheral Nervous System and Reflex Activity
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732
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Table of contents
- Ch. 1 The Human Body: An Orientation25
- Ch. 2 Chemistry Comes Alive24
- Ch. 3 Cells: The Living Units24
- Ch. 4 Tissue: The Living Fabric19
- Ch. 5 The Integumentary System12
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System25
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue23
- Ch. 12 The Central Nervous System25
- Ch. 13 The Peripheral Nervous System and Reflex Activity30
- Ch. 14 The Autonomic Nervous System16
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System26
- Ch. 17 Blood27
- Ch. 18 The Cardiovascular System: The Heart25
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues16
- 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
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
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Hoehn, Haynes, Abbott 12th EditionCh. 13 The Peripheral Nervous System and Reflex ActivityProblem 20
Hoehn, Haynes, Abbott 12th EditionCh. 13 The Peripheral Nervous System and Reflex ActivityProblem 20Chapter 13, Problem 20
(a) Describe the formation and composition of a spinal nerve.
(b) Name the branches of a spinal nerve (other than the rami communicantes), and indicate their distribution.
Verified step by step guidance1
(a) Begin by explaining that a spinal nerve is formed by the union of two roots: the dorsal (posterior) root and the ventral (anterior) root. The dorsal root contains sensory (afferent) fibers, while the ventral root contains motor (efferent) fibers. These roots merge to form a mixed spinal nerve that carries both sensory and motor information.
Next, describe the composition of the spinal nerve, emphasizing that it contains both sensory and motor neurons, as well as autonomic fibers. The nerve is surrounded by connective tissue layers: the endoneurium around individual axons, the perineurium around fascicles (bundles of axons), and the epineurium surrounding the entire nerve.
(b) Identify the main branches of a spinal nerve after it forms, excluding the rami communicantes. These branches include the dorsal (posterior) ramus and the ventral (anterior) ramus.
Explain the distribution of the dorsal ramus, which innervates the muscles and skin of the back (the deep muscles of the back and the overlying skin).
Then, describe the ventral ramus, which is larger and innervates the anterior and lateral parts of the trunk and the limbs. It also contributes to the formation of nerve plexuses such as the cervical, brachial, lumbar, and sacral plexuses.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Formation of a Spinal Nerve
A spinal nerve is formed by the union of two roots: the dorsal (posterior) root, which carries sensory fibers, and the ventral (anterior) root, which carries motor fibers. These roots emerge from the spinal cord and combine to form a mixed nerve that transmits both sensory and motor signals.
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Composition of a Spinal Nerve
Spinal nerves are mixed nerves containing both afferent (sensory) and efferent (motor) fibers. They include somatic and autonomic fibers, allowing communication between the central nervous system and the body’s muscles, skin, and organs.
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Branches of a Spinal Nerve and Their Distribution
After formation, a spinal nerve divides into several branches: the dorsal ramus (innervates muscles and skin of the back), the ventral ramus (innervates limbs and anterior body wall), and meningeal branches (supply spinal cord coverings). Rami communicantes connect to the sympathetic trunk but are excluded here.
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