Transcript Chapter 13, part 3

Anatomy & Physiology
SIXTH EDITION
Chapter 13, part 3
The Spinal Cord and Spinal
Nerves
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
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Frederic H. Martini
Fundamentals of
SECTION 13-4
Principles of Functional Organization
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General organization
• Sensory neurons
• Deliver information to CNS
• Motor neurons
• Distribute commands to peripheral effectors
• Interneurons
• Interpret information and coordinate
responses
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Neuronal pools
• Functional group of interconnected neurons
• Neural circuit patterns
• Divergence
• Convergence
• Serial processing
• Parallel processing
• Reverberation
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Figure 13.15 The Organization of Neuronal
Pools
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Figure 13.15
An introduction to reflexes
• Reflexes are rapid automatic responses to stimuli
• Neural reflex involves sensory fibers to CNS and
motor fibers to effectors
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Reflex arc
• Wiring of a neural reflex
• Five steps
• Arrival of stimulus and activation of receptor
• Activation of sensory neuron
• Information processing
• Activation of motor neuron
• Response by effector
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Figure 13.16 Components of a Reflex Arc
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Figure 13.16
Reflex classification
• According to
• development
• Site of information processing
• Nature of resulting motor response
• Complexity of neural circuit
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Figure 13.17 Methods of Classifying Reflexes
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Figure 13.17
reflex classifications
• Innate reflexes
• Result from connections that form between
neurons during development
• Acquired reflexes
• Learned, and typically more complex
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More reflex classifications
• Cranial reflexes
• Reflexes processed in the brain
• Spinal reflexes
• Interconnections and processing events occur
in the spinal cord
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still more reflex classifications
• Somatic reflexes
• Control skeletal muscle
• Visceral reflexes (autonomic reflexes)
• Control activities of other systems
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and more reflex classifications
• Monosynaptic reflex
• Sensory neuron synapses directly on a motor
neuron
• Polysynaptic reflex
• At least one interneuron between sensory
afferent and motor efferent
• Longer delay between stimulus and response
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Figure 13.18 Neural Organization and Simple
Reflexes
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Figure 13.18
SECTION 13-5
Spinal Reflexes
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Spinal Reflexes
• Range from simple monosynaptic to complex
polysynaptic and intersegmental
• Many segments interact to form complex
response
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Monosynaptic Reflexes
• Stretch reflex automatically monitors skeletal
muscle length and tone
• Patellar (knee jerk) reflex
• Sensory receptors are muscle spindles
• Postural reflex maintains upright position
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Figure 13.19 Components of the Stretch Reflex
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Figure 13.19
Figure 13.20 The Patellar Reflex
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Figure 13.20
Figure 13.21 Intrafusal Fibers
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Figure 13.21
Polysynaptic reflexes
• Produce more complicated responses
• Tendon reflex
• Withdrawal reflexes
• Flexor reflex
• Crossed extensor reflex
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Figure 13.22 The Flexor and Crossed Extensor
Reflexes
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Figure 13.22
Polysynaptic reflexes
• Involve pools of interneurons
• Are intersegmental in distribution
• Involve reciprocal inhibition
• Have reverberating circuits to prolong the motor
response
• Several reflexes may cooperate to produce a
coordinated response
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SECTION 13-6
Integration and Control of Spinal Reflexes
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Control of spinal reflexes
• Brain can facilitate or inhibit motor patterns
based in spinal cord
• Motor control involves a series of interacting
levels
• Monosynaptic reflexes are the lowest level
• Brain centers that modulate or build on motor
patterns are the highest
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Reinforcement and inhibition
• Reinforcement = facilitation that enhances spinal
reflexes
• Spinal reflexes can also be inhibited
• Babinski reflex replaced by planter reflex
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Figure 13.23 The Babinski Reflexes
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Figure 13.23
You should now be familiar with:
• The structure and functions of the spinal cord.
• The three meningeal layers that surround the
CNS.
• The major components of a spinal nerve and their
distribution in relation to their regions of
innervation.
• The significance of neuronal pools.
• The steps in a neural reflex.
• How reflexes interact to produce complicated
behaviors.
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