Textbook Question
Side-to-side movements of the spinal cord are prevented by the:
(a) Filum terminale
(b) Denticulate ligaments
(c) Dura mater
(d) Pia mater
(e) Arachnoid mater
Ch. 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089
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Table of contents
- Ch. 1 An Introduction to Anatomy and Physiology26
- Ch. 2 The Chemical Level of Organization34
- Ch. 3 The Cellular Level of Organization30
- Ch. 4 The Tissue Level of Organization24
- Ch. 5 The Integumentary System17
- Ch. 6 Bones and Bone Structure36
- Ch. 7 The Axial Skeleton11
- Ch. 8 The Appendicular Skeleton17
- Ch. 9 Joints13
- Ch. 10 Muscle Tissue12
- Ch. 11 The Muscular System28
- Ch. 12 Nervous Tissue18
- Ch. 13 The Spinal Cord, Spinal Nerves, and Spinal Reflexes22
- Ch. 14 The Brain and Cranial Nerves20
- Ch. 15 Sensory Pathways and the Somatic Nervous System17
- Ch. 16 The Autonomic Nervous System and Higher-Order Functions30
- Ch. 17 The Special Senses16
- Ch. 18 The Endocrine System20
- Ch. 19 Blood31
- Ch. 20 The Heart31
- Ch. 21 Blood Vessels and Circulation29
- Ch. 22 The Lymphatic System and Immunity31
- Ch. 23 The Respiratory System12
- Ch. 24 The Digestive System18
- Ch. 26 The Urinary System31
- Ch. 27 Fluids & Electrolytes32
- Ch. 28 The Reproductive System12
- Ch. 29 Development and Inheritance23
Martini, Nath, Bartholomew11th EditionFundamentals of Anatomy & PhysiologyISBN: 9780136874089Not the one you use?Change textbook
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Martini, Nath, Bartholomew 11th EditionCh. 13 The Spinal Cord, Spinal Nerves, and Spinal ReflexesProblem 27
Martini, Nath, Bartholomew 11th EditionCh. 13 The Spinal Cord, Spinal Nerves, and Spinal ReflexesProblem 27Chapter 13, Problem 27
What effect does the stimulation of a sensory neuron that innervates an intrafusal muscle fiber have on muscle tone?
Verified step by step guidance1
Step 1: Understand the components involved. Sensory neurons that innervate intrafusal muscle fibers are part of the muscle spindle, which is a sensory receptor within the muscle that detects changes in muscle length.
Step 2: Recognize the role of intrafusal fibers. These fibers are specialized muscle fibers inside the muscle spindle that respond to stretch and send information via sensory neurons to the central nervous system.
Step 3: Identify what happens when the sensory neuron is stimulated. When the intrafusal fibers are stretched, the sensory neuron increases its firing rate, sending signals to the spinal cord.
Step 4: Connect sensory neuron stimulation to the reflex arc. The sensory input activates alpha motor neurons that innervate the extrafusal muscle fibers, causing them to contract.
Step 5: Conclude the effect on muscle tone. This reflex contraction increases muscle tone, which is the muscle's resistance to passive stretch, helping maintain posture and muscle readiness.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Intrafusal Muscle Fibers
Intrafusal muscle fibers are specialized muscle fibers located within muscle spindles that detect changes in muscle length. They play a key role in proprioception by sensing stretch and relaying this information to the central nervous system to help regulate muscle activity.
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The Muscle Fiber
Sensory Neurons Innervating Intrafusal Fibers
Sensory neurons, particularly type Ia and II afferents, innervate intrafusal fibers and transmit information about muscle stretch to the spinal cord. Their stimulation signals changes in muscle length, which is essential for initiating reflexes that adjust muscle contraction and maintain posture.
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Muscle Tone and Reflex Regulation
Muscle tone refers to the continuous, passive partial contraction of muscles, maintained by reflex arcs involving sensory input from muscle spindles. Stimulation of sensory neurons from intrafusal fibers triggers reflexive activation of alpha motor neurons, increasing muscle contraction and thus enhancing muscle tone.
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Related Practice
Textbook Question
Mary complains that when she wakes up in the morning, her thumb and forefinger are always “asleep.” She mentions this condition to her physician, who asks Mary whether she sleeps with her wrists flexed. She replies that she does. The physician tells Mary that sleeping in that position may compress a portion of one of her peripheral nerves, producing her symptoms. Which nerve is involved?
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Textbook Question
Ascending tracts
(a) Carry sensory information to the brain,
(b) Carry motor information to the brain
(c) Carry sensory information from the brain
(d) Carry motor information from the brain
(e) Connect perceptive areas with the brain
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Textbook Question
Bowel and urinary bladder control involve spinal reflex arcs that are located in the sacral region of the spinal cord. In both instances, two sphincter muscles—an inner sphincter of smooth muscle and an outer sphincter of skeletal muscle—control the passage of wastes (feces and urine) out of the body. How would a transection of the spinal cord at the L1 segment level affect an individual's bowel and bladder control?
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Textbook Question
The subarachnoid space contains:
(a) cerebrospinal fluid
(b) lymph
(c) air,
(d) connective tissue and blood vessels
(e) denticulate ligaments.