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Chapter 13, part 2

Chapter 13, part 2. The Spinal Cord and Spinal Nerves. 31 pairs of spinal nerves. Nerves consist of: Epineurium Perineurium Endoneurium. Figure 13.8 A Peripheral Nerve. Figure 13.8. Spinal nerves. White ramus (myelinated axons)

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Chapter 13, part 2

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  1. Chapter 13, part 2 The Spinal Cord and Spinal Nerves

  2. 31 pairs of spinal nerves • Nerves consist of: • Epineurium • Perineurium • Endoneurium

  3. Figure 13.8 A Peripheral Nerve Figure 13.8

  4. Spinal nerves • 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

  5. Figure 13.9 Peripheral Distribution of Spinal Nerves Figure 13.9a

  6. Figure 13.9 Peripheral Distribution of Spinal Nerves Figure 13.9b

  7. Figure 13.10 Dermatomes Figure 13.10

  8. Nerve plexus • Complex interwoven network of nerves • Four large plexuses • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus

  9. Figure 13.11 Peripheral Nerves and Nerve Plexus Figure 13.11

  10. SECTION 13-4Principles of Functional Organization

  11. General organization • Sensory neurons • Deliver information to CNS • Motor neurons • Distribute commands to peripheral effectors • Interneurons • Interpret information and coordinate responses

  12. Neuronal pools • Functional group of interconnected neurons • Neural circuit patterns • Divergence • Convergence • Serial processing • Parallel processing • Reverberation

  13. Figure 13.15 The Organization of Neuronal Pools Figure 13.15

  14. An introduction to reflexes • Reflexes are rapid automatic responses to stimuli • Neural reflex involves sensory fibers to CNS and motor fibers to effectors

  15. 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

  16. Figure 13.16 Components of a Reflex Arc Figure 13.16

  17. Reflex classification • According to • development • Site of information processing • Nature of resulting motor response • Complexity of neural circuit

  18. Figure 13.17 Methods of Classifying Reflexes Figure 13.17

  19. reflex classifications • Innate reflexes • Result from connections that form between neurons during development • Acquired reflexes • Learned, and typically more complex

  20. More reflex classifications • Cranial reflexes • Reflexes processed in the brain • Spinal reflexes • Interconnections and processing events occur in the spinal cord

  21. still more reflex classifications • Somatic reflexes • Control skeletal muscle • Visceral reflexes (autonomic reflexes) • Control activities of other systems

  22. 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

  23. Figure 13.18 Neural Organization and Simple Reflexes Figure 13.18

  24. SECTION 13-5Spinal Reflexes

  25. Spinal Reflexes • Range from simple monosynaptic to complex polysynaptic and intersegmental • Many segments interact to form complex response

  26. 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

  27. Figure 13.19 Components of the Stretch Reflex Figure 13.19

  28. Figure 13.20 The Patellar Reflex Figure 13.20

  29. Figure 13.21 Intrafusal Fibers Figure 13.21

  30. Polysynaptic reflexes • Produce more complicated responses • Tendon reflex • Withdrawal reflexes • Flexor reflex • Crossed extensor reflex

  31. Figure 13.22 The Flexor and Crossed Extensor Reflexes Figure 13.22

  32. 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

  33. SECTION 13-6Integration and Control of Spinal Reflexes

  34. 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

  35. Reinforcement and inhibition • Reinforcement = facilitation that enhances spinal reflexes • Spinal reflexes can also be inhibited • Babinski reflex replaced by planter reflex

  36. Figure 13.23 The Babinski Reflexes Figure 13.23

  37. 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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