1. General information about the nervous system.

2. Structure of the Spinal Cord
Extends from the foramen magnum to the first or second lumbar vertebra.
Ends in the conus medullaris
Filum terminale
Extends from conus medullaris to sacral vertebrae
Cauda equina
= filum terminale + dorsal & ventral roots from spinal nerves that extend below conus medularis
Human Anatomy, 3rd edition
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3. Coverings of the Spinal Cord
3 layers called meninges
Dura mater
Outer layer
Arachnoid
Middle layer
Pia mater
Adheres tightly to the surface of the spinal cord
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4. Meninges of the Spinal Cord
FG14_02.JPG
Title: The Spinal Cord and Spinal Meninges
Notes: (a) Anterior view of spinal cord showing meninges and spinal nerves. (b) MRI scan of inferior portion of spinal cord. (c) Posterior view of spinal cord; meningeal layers, superficial landmarks, distribution of gray and white matter. (d) Sectional view throu
Keywords: spinal cord, meninges, spinal nerves, anterior median fissure, pia mater, denticulate ligaments, arachnoid mater, dura mater, cervical nerve, rami communicantes, autonomic ganglion, ventral ramus
Human Anatomy, 3rd edition
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5. Meninges of the Spinal Cord
Human Anatomy, 3rd edition
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6. Sectional Anatomy of the Spinal Cord
Inner part consists of gray matter
Unmyelinated cell bodies, neuroglia, & dendrites
Organized into “horns”
Outer part consists of white matter
Tracts of myelinated fibers
Ascending tracts are sensory
Descending tracts are motor
Human Anatomy, 3rd edition
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7. Example of Ascending Nerve Tracts
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8. Human Anatomy, 3rd edition
Spinal Nerves
Connect to the spinal cord via a dorsal and a ventral root
Dorsal root is sensory
Contains a dorsal root ganglion
Ventral root is motor
Human Anatomy, 3rd edition
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9. Human Anatomy, 3rd edition
Spinal Nerves
The roots unite into the spinal nerve
Spinal nerves exit through intervertebral foramen
Split into branches, or rami.
Dorsal ramus
Ventral ramus
Regions of skin supplied by a spinal nerve = dermatomes (“skin slices”)
Human Anatomy, 3rd edition
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10. Human Anatomy, 3rd edition
Dermatomes
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Title: Dermatomes
Notes: Anterior and posterior distribution of dermatomes; the related spinal nerves are indicated for each dermatome.
Keywords: dermatomes, anterior, posterior
Human Anatomy, 3rd edition
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11. Human Anatomy, 3rd edition
Nerve Plexuses
Plexus = “braid”
Nerves supplying the limbs form plexuses when they leave the spinal cord
Cervical plexus
Brachial plexus
Lumbosacral plexus
Lumbar plexus
Sacral plexus
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12. Human Anatomy, 3rd edition
Cervical Plexus
Formed by spinal nerves C1 – C5
Nerves innervate the neck and shoulder region
Phrenic nerve to the diaphragm
Human Anatomy, 3rd edition
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13. Human Anatomy, 3rd edition
Brachial Plexus
Formed by spinal nerves C5 – C8 and T1
Nerves innervate the arm and shoulder
Radial nerve
Ulnar nerve
Median nerve
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14. Human Anatomy, 3rd edition
Brachial Plexus
FG14_11A.JPG
Title: The Brachial Plexus
Notes: (a) The trunks and cords of the brachial plexus.
Keywords: brachial plexus, superior trunk, middle trunk, inferior trunk, medial cord, lateral cord, posterior cord, musculocutaneous, median, radial, ulnar, axillary
Human Anatomy, 3rd edition
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15. Human Anatomy, 3rd edition
Lumbosacral Plexus
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Title: The Lumbosacral Plexus, Part I
Notes: (a) Anterior view of the lumbar plexus; origins and major brances. (b) Anterior view of sacral plexus; origins and major branches. (c) Anterior view of the lumbrosacral plexus and innervation of lower limb. (d) Posterior view of sacral plexus and associat
Keywords: lumbosacral plexus, lumbar plexus, sacral plexus, lumbosacral trunk, iliohypogastric nerve, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, tibial, peroneal, medial plantar, pudendal, gluteal, sciatic, saphenous
Human Anatomy, 3rd edition
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16. Human Anatomy, 3rd edition
Lumbar Plexus
Formed by spinal nerves T12 and L1 – L4.
Innervates the medial and anterior portions of the thigh and lower abdominal regions
Lateral femoral cutaneous nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001

17. Human Anatomy, 3rd edition
Sacral Plexus
Formed by spinal nerves L4 and L5, and S1 and S2
Innervates the posterior portion of the hip, thigh, and leg, and the genital region
Sciatic nerve
Human Anatomy, 3rd edition
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18. Human Anatomy, 3rd edition
Sacral Plexus
FG14_13B.JPG
Title: The Lumbosacral Plexus, Part I
Notes: (a) Anterior view of the lumbar plexus; origins and major brances. (b) Anterior view of sacral plexus; origins and major branches. (c) Anterior view of the lumbrosacral plexus and innervation of lower limb. (d) Posterior view of sacral plexus and associat
Keywords: lumbosacral plexus, lumbar plexus, sacral plexus, lumbosacral trunk, iliohypogastric nerve, ilioinguinal, genitofemoral, lateral femoral cutaneous, femoral, obturator, tibial, peroneal, medial plantar, pudendal, gluteal, sciatic, saphenous
Human Anatomy, 3rd edition
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19. Human Anatomy, 3rd edition
Spinal Reflexes
Reflexes are automatic responses to stimuli
Spinal reflexes result from the stimulation of a spinal reflex arc.
Human Anatomy, 3rd edition
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20. Basic Elements of a Reflex Arc
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21. Human Anatomy, 3rd edition
Located btwn the diencephalon and the pons.
2 bulging cerebral peduncles on the ventral side. These contain:
Descending fibers that go to the cerebellum via the pons
Descending pyramidal tracts
Running thru the midbrain is the hollow cerebral aqueduct which connects the 3rd and 4th ventricles of the brain.
The roof of the aqueduct ( the tectum) contains the corpora quadrigemina
2 superior colliculi that control reflex movements of the eyes, head and neck in response to visual stimuli
2 inferior colliculi that control reflex movements of the head, neck, and trunk in response to auditory stimuli
Midbrain
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22. Human Anatomy, 3rd edition
Cranial nerves 3&4 (oculomotor and trochlear) exit from the midbrain
Midbrain also contains the headquarters of the reticular activating system
Human Anatomy, 3rd edition
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23. Human Anatomy, 3rd edition
Medulla Oblongata
Nuclei in the medulla are associated w/ autonomic control, cranial nerves, and motor/sensory relay.
Autonomic nuclei:
Cardiovascular centers
Cardioinhibitory/cardioacceleratory centers alter the rate and force of cardiac contractions
Vasomotor center alters the tone of vascular smooth muscle
Respiratory rhythmicity centers
Receive input from the pons
Additional Centers
Emesis, deglutition, coughing, hiccupping, and sneezing
Human Anatomy, 3rd edition
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24. Human Anatomy, 3rd edition
Medulla Oblongata
Sensory & motor nuclei of 5 cranial nerves:
Auditory/Vestibular (8), Glossopharyngeal (9), Vagus (10), Accessory (11), and Hypoglossal (12)
Relay nuclei
Nucleus gracilis and nucleus cuneatus pass somatic sensory information to the thalamus
Olivary nuclei relay info from the spinal cord, cerebral cortex, and the brainstem to the cerebellar cortex.
Human Anatomy, 3rd edition
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25. Human Anatomy, 3rd edition
Spinal Cord
Functions to transmit messages to and from the brain (white matter) and to serve as a reflex center (gray matter).
Tube of neural tissue continuous w/ the medulla at the base of the brain and extends about 17” to just below the last rib. (Ends at L1)
Majority of the SC has the diameter of your thumb
Thicker at the neck and end of the cord (cervical and lumbar enlargements) b/c of the large group of nerves connecting these regions of the cord w/ the arms and legs.
Human Anatomy, 3rd edition
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26. Human Anatomy, 3rd edition
Spinal Cord
Surrounded by a single
layered dura mater
and arachnoid and pia mater.
Terminates in cone shaped
structure called the conus medullaris.
The filum terminale, a fibrous extension of the pia mater, extends to the posterior surface of the coccyx to anchor the spinal cord.
The cord does not extend the entire length of the vertebral column – so a group of nerves leaves the inferior spinal cord and extends downward. It resembles a horses tail and is called the cauda equina.
Human Anatomy, 3rd edition
Prentice Hall, © 2001

27. Cross Sectional Anatomy of the Spinal Cord
Flattened from front to back.
Anterior median fissure and posterior median sulcus partially divide it into left and right halves.
Gray matter is in the core of the cord and surrounded by white matter.
Human Anatomy, 3rd edition
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28. Human Anatomy, 3rd edition
Resembles a butterfly.
2 lateral gray masses connected by the gray
commissure.
Posterior projections are the posterior or dorsal horns.
Anterior projections are the anterior or ventral horns.
In the thoracic and lumbar cord, there also exist lateral horns.
Human Anatomy, 3rd edition
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29. Human Anatomy, 3rd edition
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30. Spinal Cord & Spinal Nerves
Truly the pathway between body and mind
Conducts impulses to and from the brain
Carries out spinal reflexes
Spinal nerves
31 pairs
All are mixed nerves

31. Human Anatomy, 3rd edition
Spinal Cord Injuries
Can affect sensory perception; motor paralysis
Location affects severity of the injury
Spinal compression results from squeezing the spinal cord within the vertebral canal
Spinal transection is the severing of the spinal cord
Human Anatomy, 3rd edition
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32. Spinal Cord Injuries Quadriplegia Paraplegia

33. Spinal ganglia, their structure and functional importance.

44. Part I: Spinal cord 1. Organization 2. Structure 3. Blood supply
- General
- Cauda equina
- Meninges
2. Structure
Grey matter
White matter
3. Blood supply
4. Spinal nerves
Typical n.
Components

45. 1. Organization
Cauda equina
Meninges

46. 2. Structure: Grey matter
Components: Nerve cells, Processes, Neuroglia, Blood vessels
Grey columns: Anterior, Posterior, Transverse, Lateral

47. Posterior horns contain interneurons. Anterior horns contain some
Gray Matter
Posterior horns contain
interneurons.
Anterior horns contain some
interneurons as well as the cell
bodies of motor neurons.
These cell bodies project their axons via the ventral roots of the spinal cord to the skeletal muscles.
The amount of ventral gray matter at a given level of the spinal cord is proportional to the amount of skeletal muscle innervated.

48. Gray Matter
Lateral horn neurons are sympathetic motor neurons serving visceral organs.
Their axons also exit via the ventral root.
Afferent sensory fibers carrying info from peripheral receptors form the dorsal roots of the spinal cord. The somata of these sensory fibers are found in an enlargement known as a dorsal root ganglion.
The dorsal and ventral roots fuse to form spinal nerves.

49. Grey columns: Anterior: Posterior:
Medial group: skeletal muscles of the neck and trunk
Central group: cervical and lumbosacral segments & contains the phrenic, asccessory and lumbosacral nuclei
Lateral group: cervical and lumbosacral areas innervating skeletal muscles of the limbs
Posterior:
Substantia gelatinosa: concerned with pain, temperature and touch
Nucleus proprius: fibers from white posterior column associated with proprioception, 2-piont discrimination and vibration
Nucleus dorsalis (Clark’s column) from C8 – L3/4 proprioceptive endings in spindles
Visceral afferent nucleus from T1– L3 receives visceral afferent information

50. Grey columns (cont.) Transverse: Lateral:
Contains central canal that starts in the MO,
Inferiorly expands in the conus medullaris as the terminal ventricle: CSF & ependyma
Lateral:
From T1–L2/3
Give rise to preganglionic sympathetic fibers
Similar group in S2-4 give rise to preganglionic parasympathtic fibres

51. 2. Structure: White matter
Mixture of myelinated nerve fibers, neuroglia and blood vessels
Ascending tracts
Descending tracts
Ascending and descending tracts with the same origin, course and termination: Fasciculus
Intersegmental tracts

52. Myelinated nerve fibers.
White Matter
Myelinated nerve fibers.
Allows for communication btwn the brain and spinal cord or btwn different regions of the spinal cord.
White matter on each side of the cord is divided into columns or funiculi.
Typically, they are ascending or descending.
What does that mean?

54. Ascending tracts: Sensory, contain 1st, 2nd and 3rd order neurons
Pathways for temperature, pain, proprioception
Examples: Spinothalamic tract (lateral & anterior, fasciculus gracilis and cuneatus); Spinocerebellar tract (anterior & posterior); Cuneocerebellat tract.
Other: Spinotectal, spinoreticular, spino-olivary, visceral sensory

55. Descending tracts:
White matter from the supraspinal centers with 1st, 2nd and 3rd order motor neurons
Examples: Corticospinal, reticularspinal, tectospinal, rubrospinal, vestibulospinal, olivospinal, descending autonomic

56. 3. Blood supply: Spinal arteries
From vertebral, posterior intercostal, lumbar, lateral sacral, ascending cervical, deep cervical, iliolumbar aa.
Posterior spinal a. in close association to posterior spinal roots, but is insufficient to supply the spinal cord alone
Anterior spinal a. unite to for a single artery on the median fissure of the spinal cord.

57. Spinal arteries (cont.)
Radicular a. reinforce the spinal arteries by entering through the intervertebral foramina
Larger anterior radicular arteries: A. radicularis magna (artery of Adamkiewicz) from the left an intersegmental branch of the descending aorta, that supplies 2/3rds of the spinal cord

58. 3. Blood supply: Venous drainage
Internal (anterior & posterior) venous plexus
External venous plexus (anterior & posterior)
Basivertebral and intervertebral veins.

59. 4. Typical spinal nerve
Posterior (dorsal) root: Supplies synovial joints of the vertebral column, deep muscles of the back & overlying skin. Posterior root ganglia: Sensory, unipolar with satellite cells.
Anterior (ventral) root: Supplies the remaining areas: anterior & lateral regions of the trunk and limbs

60. What brainstem structures are visible here?

61. Reticular Formation
Extensive network of neurons that runs thru the medulla and projects to thalamic nuclei that influence large areas of the cerebral cortex.
Midbrain portion of RAS most likely is its center
Functions as a net or filter for sensory input.
Filter out repetitive stimuli. Such as?
Allows passage of infrequent or important stimuli to reach the cerebral cortex.
Unless inhibited by other brain regions, it activates the cerebral cortex – keeping it alert and awake.
How might the “sleep centers” of your brain work? Why does alcohol make you tired?

62. Cover and protect the CNS Protect blood vessels
Protection
What is the major protection for the brain?
There are also 3 connective tissue membranes called the meninges:
Cover and protect the CNS
Protect blood vessels
Contain cerebrospinal fluid
The 3 meninges from superficial to deep:
Dura mater
Arachnoid mater
Pia mater

63. Skin
Galea Aponeurotica
Connective Tissue
Bone
Dura Mater
Arachnoid mater

64. Spinal Cord
Functions to transmit messages to and from the brain (white matter) and to serve as a reflex center (gray matter).
Tube of neural tissue continuous w/ the medulla at the base of the brain and extends about 17” to just below the last rib. (Ends at L1)
Majority of the SC has the diameter of your thumb
Thicker at the neck and end of the cord (cervical and lumbar enlargements) b/c of the large group of nerves connecting these regions of the cord w/ the arms and legs.

65. Spinal Cord Surrounded by a single layered dura mater
and arachnoid and pia mater.
Terminates in cone shaped
structure called the conus medullaris.
The filum terminale, a fibrous extension of the pia mater, extends to the posterior surface of the coccyx to anchor the spinal cord.
The cord does not extend the entire length of the vertebral column – so a group of nerves leaves the inferior spinal cord and extends downward. It resembles a horses tail and is called the cauda equina.

66. Spinal Cord Notice the gross features of the spinal cord on the right.
31 pairs of spinal nerves attach to the cord by paired roots and exit from the vertebral canal via the intervertebral foramina.

67. Resembles a butterfly.
2 lateral gray masses connected by the gray
commissure.
Posterior projections are the posterior or dorsal horns.
Anterior projections are the anterior or ventral horns.
In the thoracic and lumbar cord, there also exist lateral horns.

69. Spinal Nerves 8 paired cervical nerves 12 paired thoracic nerves
31 nerves connecting the spinal cord and various body regions.
8 paired cervical nerves
12 paired thoracic nerves
5 paired lumbar nerves
5 paired sacral nerves
1 pair of coccygeal nerves

70. Spinal Nerves
Each connects to the spinal cord by 2 roots – dorsal and ventral.
Each root forms from a series of rootlets that attach along the whole length of the spinal cord segment.
Ventral roots are motor while dorsal roots are sensory.

71. Spinal Nerves
The 2 roots join to form a spinal nerve prior to exiting the vertebral column.
Roots are short and horizontal in the cervical and thoracic regions while they are longer and more horizontal in the sacral and lumbar regions.
Almost immediately after emerging from its intervertebral foramen, a spinal nerve will divide into a dorsal ramus, a ventral ramus, and a meningeal branch that reenters and innervates the meninges and associated blood vessels.

72. Each ramus is mixed.
Joined to the base of the ventral rami of spinal nerves in the thoracic region are the rami communicantes. These are sympathetic fibers that we’ll deal with shortly.
Dorsal rami supply the posterior body trunk whereas the thicker ventral rami supply the rest of the body trunk and the limbs.

74. Thank you for attention !