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Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology Frederic H. Martini Lecture 9: Chapter 13.

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Presentation on theme: "Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology Frederic H. Martini Lecture 9: Chapter 13."— Presentation transcript:

1 Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings Fundamentals of Anatomy & Physiology Frederic H. Martini Lecture 9: Chapter 13 The Spinal Cord and Spinal Nerves Pages : 421- 450 Lecturer: Dr. Barjis Room: P313 Phone: (718) 260-5285 E-Mail: ibarjis@citytech.cuny.edu

2 Learning Objectives Discuss the structure and functions of the spinal cord. Describe the three meningeal layers that surround the CNS. Describe the major components of a spinal nerve and relate their distribution to their regions of innervation. Discuss the significance of neuronal pools. Describe the steps in a neural reflex. Explain how reflexes interact to produce complicated behaviors.

3 CNS Brain and spinal cord In the white matter, axons arranged in tracts and columns PNS Remainder of nervous tissue General Organization of the Nervous System Divisions of the Nervous System

4 An Introduction to the Anatomical Organization of the Nervous System

5 Localized enlargements provide innervation to limbs 31 segments each segment has a pair of dorsal roots and a pair of ventral roots Filum terminale Conus medularis Spinal nerves extend off cord Mixed nerves Gross Anatomy of the Spinal Cord Adult spinal cord

6 Gross Anatomy of the Adult Spinal Cord

7 Spinal meninges Provide physical stability and shock absorption Three layers Dura mater Arachnoid Pia mater

8 Covers spinal cord Tapers to coccygeal ligament Epidural space separates dura mater from walls of vertebral canal Dura mater

9 The Spinal Cord and Spinal Meninges

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11 Arachnoid Interior to dura mater are the subdural space, the arachnoid and the subarachnoid space Subarachnoid space contains CSF

12 Pia mater Meshwork of elastin and collagen fibers Innermost meningeal layer Denticulate ligaments extend from pia mater to dura mater

13 The Cervical Spinal Cord

14 Sectional anatomy of the spinal cord White matter is myelinated and unmyelinated axons Gray matter is cell bodies, unmyelinated axons and neuroglia Projections of gray matter toward outer surface of cord are horns

15 The Sectional Organization of the Spinal Cord

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17 Posterior gray horn contains somatic and visceral sensory nuclei Anterior gray horns deal with somatic motor control Lateral gray horns contain visceral motor neurons Gray commissures contain axons that cross from one side to the other Horns of spinal cord

18 White matter Divided into six columns (funiculi) containing tracts Ascending tracts relay information from the spinal cord to the brain Descending tracts carry information from the brain to the spinal cord Animation: Spinal cord dissections (see tutorial)

19 Nerves consist of: Epineurium Perineurium Endoneurium 31 pairs of spinal nerves

20 A Peripheral Nerve

21 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

22 Peripheral Distribution of Spinal Nerves

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24 Dermatomes

25 Complex interwoven network of nerves Four large plexuses Cervical plexus Brachial plexus Lumbar plexus Sacral plexus Nerve plexus

26 Peripheral Nerves and Nerve Plexus

27 The Brachial Plexus

28 The Branchial Plexus

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30 The Lumbar and Sacral Plexuses

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32 Sensory neurons Deliver information to CNS Motor neurons Distribute commands to peripheral effectors Interneurons Interpret information and coordinate responses Principles of Functional Organization General organization

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

34 The Organization of Neuronal Pools

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

36 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

37 Components of a Reflex Arc

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

39 Methods of Classifying Reflexes

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

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

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

43 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

44 Neural Organization and Simple Reflexes

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

46 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

47 Components of the Stretch Reflex

48 The Patellar Reflex

49 Intrafusal Fibers

50 Produce more complicated responses Tendon reflex Withdrawal reflexes Flexor reflex Crossed extensor reflex Polysynaptic reflexes

51 The Flexor and Crossed Extensor Reflexes

52 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

53 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

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

55 The Babinski Reflexes

56 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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