1. Chapter 14 Spinal Cord & Spinal Nerves

2. The Spine The spinal cord is a hiway, sensory impulses going up to the brain and motor impulses going down from the brain. The exceptions are reflexes which are local. The spinal cord begins at the foramen magnum of this skull and continues down to L1 or L2

3. Figure 14.1a Gross Anatomy of the Spinal Cord © 2015 Pearson Education, Inc. Cervical spinal nerves Cervical enlargement C1C1 C2C2 C3C3 C4C4 C5C5 C6C6 C7C7 C8C8 T1T1 T2T2 T3T3 T4T4 T5T5 T6T6 T7T7 T8T8 T9T9 T 10 T 11 T 12 Thoracic spinal nerves Posterior median sulcus Lumbosacral enlargement Conus medullaris L1L1 L2L2 L3L3 L4L4 L5L5 Inferior tip of spinal cord Cauda equina Lumbar spinal nerves S1S1 S2S2 S3S3 S4S4 S5S5 Sacral spinal nerves Filum terminale (in coccygeal ligament) Coccygeal nerve (Co 1 ) Superficial anatomy and orientation of the adult spinal cord. The numbers to the left identify the spinal nerves and indicate where the nerve roots leave the vertebral canal. The spinal cord, however, extends from the brain only to the level of vertebrae L 1 –L 2. a Conus medullaris: the tapered end of the spinal cord forming a long filament called the filum terminale which will become the coccygeal ligamentwhich anchors the spinal cord in place so to prevent upward movement Cauda equina: a collection of nerve roots at the inferior and of the vertebral column. Lumbar and sacral nerve roots must descend before exiting the proper inter- vertebral foramen or sacral foramen Cervical and lumbar enlargements: nerves for arms and legs

4. Fiber Types: © 2015 Pearson Education, Inc. Nervous Conduction Fiber Types: ascending carry sensory toward brain descending fibers: motor information to muscles and glands commissural fibers: reflex arc fibers within the CNS Column: (funiculus) dorsal, ventral and lateral Tract: (fasiculus) separate areas within colums either motor or sensory Dorsal Root: sensory only. Impulses enter the dorsal root and extends to the gray dorsal horn. The cell bodies form the dorsal root ganglion. (ganglion = a group of cell bodies in the PNS) Ventral Root: motor nerves only. Impulses leave the anterior root and ends in muscles or glands. No ganglion.

5. Spinal cord Spinal cords are about 16”-18” long.

6. Figure 14.2a The Spinal Cord and Spinal Meninges © 2015 Pearson Education, Inc. Gray matter Dorsal root ganglion Spinal nerve White matter Ventral root Dorsal root Meninges Pia mater Arachnoid mater Dura mater a Posterior view of the spinal cord shows the meningeal layers, superficial landmarks, and distribution of gray and white matter. White matter is composed of axons while gray matter is composed of cell bodies of neurons, short un myelinated axons, dendrites and neuroglia The meninges are coverings over the brain and spinal cord composed of the Dura mater which is most exterior, the arachnoidid mater, and the pia mater which is in close in proximity to the brain and spinal cord

7. Figure 14.2b The Spinal Cord and Spinal Meninges © 2015 Pearson Education, Inc. ANTERIOR POSTERIOR Meninges Dura mater Arachnoid mater Pia mater Rami communicantes Vertebral body Subarachnoid space Autonomic (sympathetic) ganglion Ventral root of spinal nerve Ventral ramus Dorsal ramus Dorsal root ganglion Denticulate ligament Spinal cord Adipose tissue in epidural space Sectional view through the spinal cord and meninges shows the peripheral distribution of the spinal nerves. b Ant median fissure Post. Medial sulcus

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9. Figure 14.2c The Spinal Cord and Spinal Meninges © 2015 Pearson Education, Inc. Spinal cord Anterior median fissure Pia mater Denticulate ligaments Arachnoid mater (reflected) Dura mater (reflected) Spinal blood vessel Dorsal root of sixth cervical nerve Ventral root of sixth cervical nerve Anterior view of spinal cord shows meninges and spinal nerves. For this view, the dura and arachnoid membranes have been cut longitudinally and retracted (pulled aside); notice the blood vessels that run in the subarachnoid space bound to the outer surface of the delicate pia mater. c

10. a. in the subarachnoid space b. in the subdural space c. in the epidural space d. within the pia mater Where is cerebrospinal fluid found?

11. Clinical Note 14.1 Spinal Taps and Spinal Anesthesia (Part 1 of 2) Dura mater Epidural space Body of third lumbar vertebra Interspinous ligament Lumbar puncture needle Cauda equina in subarachnoid space Filum terminale The position of the lumbar puncture needle is in the subarachnoid space, near the nerves of the cauda equina. The needle has been inserted in the midline between the third and fourth lumbar vertebral spines, pointing at a superior angle toward the umbilicus. Once the needle correctly punctures the dura and enters the subarachnoid space, a sample of CSF may be obtained.

12. Spinal Cord Structures

14. Figure 14.4c Sectional Organization of the Spinal Cord The left half of this sectional view shows the major columns of white matter. The right half indicates the anatomical organization of sensory tracts in the posterior white column for comparison with the organization of motor nuclei in the anterior gray horn. Note that both sensory and motor components of the spinal cord have a definite regional organization. Posterior white column (funiculus) Anterior white column (funiculus) Anterior white commissure Flexors Extensors Lateral white column (funiculus) Leg Hip Trunk Arm Hand Forearm Arm Shoulder Trunk Within columns are tracts

16. Figure 14.6b Peripheral Distribution of Spinal Nerves © 2015 Pearson Education, Inc. Sensory Information From interoceptors of back From exteroceptors, proprioceptors of back Dorsal ramus Ventral ramus Dorsal root ganglion From exteroceptors, proprioceptors of body wall, limbs From interoceptors of body wall, limbs Rami communicantes Ventral root From interoceptors of visceral organs Somatic sensations Visceral sensations KEY b A comparable view detailing the distribution of sensory neurons and sensory fibers Dorsal root Somatic sensory Visceral sensory

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18. Figure 14.6a Peripheral Distribution of Spinal Nerves © 2015 Pearson Education, Inc. Postganglionic fibers to smooth muscles, glands, etc., of back To skeletal muscles of back Dorsal ramus Ventral ramus Ventral root Dorsal root ganglion Dorsal root Visceral motor Somatic motor Spinal nerve Sympathetic ganglion Sympathetic nerve Gray ramus (postganglionic) White ramus (preganglionic) To skeletal muscles of body wall, limbs Postganglionic fibers to smooth muscles, glands, etc., of body wall, limbs Postganglionic fibers to smooth muscles, glands, visceral organs in thoracic cavity Preganglionic fibers to sympathetic ganglia innervating aboomino- pelvic viscera Somatic motor commands Visceral motor commands KEY The distribution of motor neurons in the spinal cord and motor fibers within the spinal nerve and its branches a Motor Commands Rami communicantes

19. Figure 14.13 A Reflex Arc © 2015 Pearson Education, Inc. Arrival of stimulus and activation of receptor Activation of a sensory neuron 1 Activation of a sensory neuron 2 Dorsal root Sensation relayed to the brain by collateral REFLEX ARC Receptor Stimulus Effector Ventral root Information processing in CNS Activation of a motor neuron Response by effector 3 4 5 Sensory neuron (stimulated) Excitatory interneuron Motor neuron (stimulated) KEY

20. Figure 14.16 Neural Organization and Simple Reflexes CENTRAL NERVOUS SYSTEM Motor neuron Ganglion Sensory neuron Sensory receptor (muscle spindle) Skeletal muscle Circuit 1 A monosynaptic reflex circuit involves a peripheral sensory neuron and a central motor neuron. In this example, stimulation of the receptor will lead to a reflexive contraction in a skeletal muscle. A polysynaptic reflex circuit involves a sensory neuron, interneurons, and motor neurons. In this example, the stimulation of the receptor leads to the coordinated contractions of two different skeletal muscles. Skeletal muscle 1 Skeletal muscle 2 Motor neurons Circuit 2 Interneurons Ganglion Sensory neuron Sensory receptor

21. Figure 14.16 Stretch Reflexes © 2015 Pearson Education, Inc. Stimulus. Stretching of muscle stimulates muscle spindles 1 Activation of a sensory neuron 2 Information processing at motor neuron 3 Activation of motor neuron 4 Response. Contraction of muscle 5 Stimulus Stretch Receptor (muscle spindle) Spinal cord REFLEX ARC Effector Contraction Response Sensory neuron (stimulated) Motor neuron (stimulated) The patellar reflex is controlled by muscle spindles in the quadriceps muscle group.The stimulus is a reflex hammer striking the muscle tendon, stretching the spindle fibers. This results in a sudden increase in the activity of the sensory neurons, which synapse on spinal motor neurons.The response occurs upon the activation of motor units in the quadriceps group, which produces an immediate increase in muscle tone and a reflexive kick. b a Steps 1- 5 are common to all stretch reflexes.

22. 1.Destruction of ventral horn cells of spinal cord result in a loss of : a) association areas b) all sensation c) pain d) motor control

23. Paired structures that contain cell bodies of sensory neurons are: a) Dorsal rami b) ventral rami c) dorsal root ganglion d) ventral root ganglion

24. Spinal nerves are mixed nerves because: a) They contain sensory and motor fibers b) They exit at intervertebral foramina c) Associate with dorsal root ganglia d) Associated with ventral and dorsal roots

25. II. Spinal Nerves

26. Roots (either sensory or motor) Rami (mixed, spinal nerve split)

27. Spinal Nerves can be motor, sensory or mixed (both) On the next slide, be able to identify the endoneurium, perineurium and epineurium We have 8 pair of cervical nerves exiting through intervertebral foramina and are named C1-C8 12 pair of thoracic nerves 5 pair of lumbar nerves 5 pair sacral nerves 1 coccygeal nerve Plexus: A network of nerves – Cervical, brachial, lumbar and Sacral plexuses Connections to head, arms, legs, addominal wall, pelvis

28. Figure 14.5a Anatomy of a Peripheral Nerve © 2015 Pearson Education, Inc. Blood vessels Epineurium covering peripheral nerve Perineurium (around one fascicle) Endoneurium Schwann cell Myelinated axon Fascicle A typical peripheral nerve and its connective tissue wrappings a Connective Tissue Layers

29. Figure 14.5b Anatomy of a Peripheral Nerve © 2015 Pearson Education, Inc. Blood vessels Epineurium covering peripheral nerve Perineurium (around one fascicle) Endoneurium Connective Tissue Layers A scanning electron micrograph showing the various layers in great detail b

30. Define: Neuron Nerve fiber Nerve:

31. Spinal Nerves

32. Figure 14.9 The Cervical Plexus Geniohyoid muscle Thyrohyoid muscle Phrenic nerve Sternohyoid muscle Sternothyroid muscle Nerve roots of cervical plexus Supraclavicular nerves Clavicle C1C1 C2C2 C3C3 C4C4 C5C5

34. Figure 14.10b The Brachial Plexus Anterior view of the brachial plexus and upper limb showing the peripheral distribution of major nerves Anterior Distribution of cutaneous nerves Median nerve Ulnar nerve Radial nerve Palmar digital nerves Superficial branch of ulnar nerve Deep branch of ulnar nerve Median nerve Ulnar nerve Deep radial nerve Radial nerve Median nerve Ulnar nerve Superficial branch of radial nerve Musculocutaneous nerve BRACHIAL PLEXUS Superior trunk Middle trunk Inferior trunk C4C4 C5C5 C6C6 C7C7 C8C8 T1T1

35. Figure 14.10c The Brachial Plexus (Part 1 of 2) Posterior view of the brachial plexus and the innervation of the upper limb Musculocutaneous nerve Axillary nerve Branches of axillary nerve Radial nerve Ulnar nerve Median nerve

36. Figure 14.10b The Brachial Plexus © 2015 Pearson Education, Inc. Deep branch of radial nerve Superficial branch of radial nerve Dorsal digital nerves Radial nerve Ulnar nerve Median nerve Posterior Posterior antebrachial cutaneous nerve Median nerve Ulnar nerve Radial nerve Branches of axillary nerve Axillary nerve Musculocutaneous nerve b This posterior view of the brachial plexus shows the location and distribution of the nerves.

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38. Radial Nerve Palsy Wrist drop, Saturday night palsy Pressure on back of the arm interrupts function of radial nerve.

39. Figure 14.11 The Cervical and Brachial Plexuses Cervical plexus Right common carotid artery Sternocleido- mastoid muscle, sternal head Sternocleido- mastoid muscle, clavicular head Right subclavian artery Retractor holding pectoralis major muscle (cut and reflected) Brachial plexus (C 5 –T 1 ) Median nerve Radial nerve Ulnar nerve Median nerve Right brachial artery Coracobrachialis muscle Biceps brachii, long and short heads Right axillary artery over axillary nerve Musculocutaneous nerve Clavicle, cut and removed Deltoid muscle Skin

40. Nerves to thorax & abdomen: don’t form a plexus T2-T12 innervate intercostal & abdominal muscles, as well as sensory for skin on thorax & abdomen.

41. Figure 14.12a The Lumbar and Sacral Plexuses, Part I The lumbar plexus, anterior view Lumbosacral trunk LUMBAR PLEXUS T 12 L1L1 L2L2 L3L3 L4L4 L5L5 Femoral branch Genital branch Femoral nerve Obturator nerve Branches of genitofemoral nerve Lateral femoral cutaneous nerve Genitofemoral nerve Ilioinguinal nerve Iliohypogastric nerve T 12 subcostal nerve

42. Figure 14.12a Peripheral Nerves Originating from the Lumbar and Sacral Plexuses © 2015 Pearson Education, Inc. Iliohypogastric nerve Illioinguinal nerve Genitofemoral nerve Lateral femoral cutaneous nerve Femoral nerve Obturator nerve Superior gluteal nerve Inferior gluteal nerve Posterior femoral cutaneous nerve Pudendal nerve Sciatic nerve Nerves Originating from the Sacral Plexus Subcostal nerve Saphenous nerve Common Fibular Nerve and Its Branches Common fibular nerve Nerves Originating from the Lumbar Plexus Superficial fibular nerve Deep fibular nerve The lumbar and sacral plexuses, anterior view a

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44. Figure 14.12b Peripheral Nerves Originating from the Lumbar and Sacral Plexuses © 2015 Pearson Education, Inc. Superior gluteal nerve Inferior gluteal nerve Posterior femoral cutaneous nerve Pudendal nerve Sciatic nerve Nerves Originating from the Sacral Plexus Branches of the Sciatic Nerve Tibial nerve Common fibular nerve Medial sural cutaneous nerve Lateral sural cutaneous nerve Sural nerve Medial plantar nerve Lateral plantar nerve The sacral plexus, posterior view b

45. Figure 14.13c The Lumbar and Sacral Plexuses, Part II A diagrammatic posterior view of the right hip and lower limb detailing the distribution of peripheral nerves Gluteus maximus (cut) Inferior gluteal nerve Pudendal nerve Perineal branch Hemorrhoidal branch Perineal branches Descending cutaneous branch Semitendinosus Tibial nerve Popliteal artery and vein Gluteus medius (cut) Gluteus minimus Superior gluteal nerve Piriformis Posterior femoral cutaneous nerve Sciatic nerve Biceps femoris (cut) Common fibular nerve Lateral sural cutaneous nerve Sural nerve Medial sural cutaneous nerve Gastrocnemius Small saphenous vein Calcaneal tendon Tibial nerve (medial calcaneal branch)

46. Figure 14.12d Peripheral Nerves Originating from the Lumbar and Sacral Plexuses © 2015 Pearson Education, Inc. Gluteus maximus (cut) Superior gluteal artery and nerve Gluteus medius Inferior gluteal nerve Piriformis Sciatic nerve Posterior femoral cutaneous nerve Gluteus maximus Nerve to gemellus and obturator internus Pudendal nerve Internal pudendal artery A dissection of the right gluteal region d

47. Figure 14.7 Dermatomes ANTERIORPOSTERIOR S1S1 L5L5 L4L4 L3L3 L2L2 L1L1 L4L4 L3L3 L2L2 L1L1 L5L5 S2S2 S1S1 S5S5 S2S2 S3S3 S4S4 T1T1 C7C7 C8C8 C6C6 C6C6 C7C7 C8C8 T1T1 T2T2 T2T2 C5C5 C4C4 C3C3 C2C2 C3C3 C 2 –C 3 NV C4C4 C5C5 T1T1 T2T2 T2T2 T3T3 T3T3 T4T4 T4T4 T5T5 T5T5 T6T6 T6T6 T7T7 T7T7 T8T8 T8T8 T9T9 T9T9 T 10 T 11 T 12 L1L1 L2L2 L3L3 L4L4 L5L5 Dermatomes: is an area of skin that is mainly supplied by a sensory neurons of one spinal nerve. Loss of sensation to a particular area tells you there may be damage to that spinal nerve.