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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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Frederic H. Martini Fundamentals of SECTION 13-4 Principles of Functional Organization Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings General organization • Sensory neurons • Deliver information to CNS • Motor neurons • Distribute commands to peripheral effectors • Interneurons • Interpret information and coordinate responses Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Neuronal pools • Functional group of interconnected neurons • Neural circuit patterns • Divergence • Convergence • Serial processing • Parallel processing • Reverberation Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.15 The Organization of Neuronal Pools Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.16 Components of a Reflex Arc Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.16 Reflex classification • According to • development • Site of information processing • Nature of resulting motor response • Complexity of neural circuit Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.17 Methods of Classifying Reflexes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.17 reflex classifications • Innate reflexes • Result from connections that form between neurons during development • Acquired reflexes • Learned, and typically more complex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings More reflex classifications • Cranial reflexes • Reflexes processed in the brain • Spinal reflexes • Interconnections and processing events occur in the spinal cord Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings still more reflex classifications • Somatic reflexes • Control skeletal muscle • Visceral reflexes (autonomic reflexes) • Control activities of other systems Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.18 Neural Organization and Simple Reflexes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.18 SECTION 13-5 Spinal Reflexes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Spinal Reflexes • Range from simple monosynaptic to complex polysynaptic and intersegmental • Many segments interact to form complex response Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.19 Components of the Stretch Reflex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.19 Figure 13.20 The Patellar Reflex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.20 Figure 13.21 Intrafusal Fibers Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.21 Polysynaptic reflexes • Produce more complicated responses • Tendon reflex • Withdrawal reflexes • Flexor reflex • Crossed extensor reflex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.22 The Flexor and Crossed Extensor Reflexes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 13-6 Integration and Control of Spinal Reflexes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Reinforcement and inhibition • Reinforcement = facilitation that enhances spinal reflexes • Spinal reflexes can also be inhibited • Babinski reflex replaced by planter reflex Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.23 The Babinski Reflexes Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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. Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings