Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology SIXTH EDITION Chapter 13, part 2 The Spinal Cord and Spinal Nerves
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Nerves consist of: Epineurium Perineurium Endoneurium 31 pairs of spinal nerves
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.8 A Peripheral Nerve Figure 13.8
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings White ramus (myelinated axons) Gray ramus (unmyelinated axons that innervate glands and smooth muscle) Dorsal ramus (sensory and motor innervation to the skin and muscles of the back) Ventral ramus (supplying ventrolateral body surface, body wall and limbs) Each pair of nerves monitors one dermatome Spinal nerves
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.9a Figure 13.9 Peripheral Distribution of Spinal Nerves
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure 13.9b Figure 13.9 Peripheral Distribution of Spinal Nerves
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Dermatomes Figure 13.10
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Complex interwoven network of nerves Four large plexuses Cervical plexus Brachial plexus Lumbar plexus Sacral plexus Nerve plexus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure Peripheral Nerves and Nerve Plexus
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 13-4 Principles of Functional Organization
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Sensory neurons Deliver information to CNS Motor neurons Distribute commands to peripheral effectors Interneurons Interpret information and coordinate responses General organization
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Functional group of interconnected neurons Neural circuit patterns Divergence Convergence Serial processing Parallel processing Reverberation Neuronal pools
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Figure The Organization of Neuronal Pools
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Reflexes are rapid automatic responses to stimuli Neural reflex involves sensory fibers to CNS and motor fibers to effectors An introduction to reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Reflex arc
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Components of a Reflex Arc Figure 13.16
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings According to development Site of information processing Nature of resulting motor response Complexity of neural circuit Reflex classification
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Methods of Classifying Reflexes Figure 13.17
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Innate reflexes Result from connections that form between neurons during development Acquired reflexes Learned, and typically more complex reflex classifications
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Cranial reflexes Reflexes processed in the brain Spinal reflexes Interconnections and processing events occur in the spinal cord More reflex classifications
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Somatic reflexes Control skeletal muscle Visceral reflexes (autonomic reflexes) Control activities of other systems still more reflex classifications
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 and more reflex classifications
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Neural Organization and Simple Reflexes Figure 13.18
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings SECTION 13-5 Spinal Reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Range from simple monosynaptic to complex polysynaptic and intersegmental Many segments interact to form complex response Spinal Reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Stretch reflex automatically monitors skeletal muscle length and tone Patellar (knee jerk) reflex Sensory receptors are muscle spindles Postural reflex maintains upright position Monosynaptic Reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Components of the Stretch Reflex Figure 13.19
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure The Patellar Reflex Figure 13.20
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure Intrafusal Fibers Figure 13.21
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Produce more complicated responses Tendon reflex Withdrawal reflexes Flexor reflex Crossed extensor reflex Polysynaptic reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure The Flexor and Crossed Extensor Reflexes Figure 13.22
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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 Polysynaptic reflexes
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 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 Control of spinal reflexes
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Reinforcement = facilitation that enhances spinal reflexes Spinal reflexes can also be inhibited Babinski reflex replaced by planter reflex Reinforcement and inhibition
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Figure The Babinski Reflexes Figure 13.23
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings 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.