1. Chapter 13: The Spinal Cord, Spinal Nerves, and Spinal Reflexes

2. Outline Introductions Syllabus, Textbooks, etc.
Gross anatomy of sensory and motor systems
Reflex anatomy and physiology
Case of autonomic regulation (handout to be used throughout term)

3. Next Time: Chapters 13 and 14
Prepare to answer the following questions:
How are somatic reflexes and autonomic reflexes different? How are they similar?
What is the connection between cranial nerves and reflexes? …between spinal nerves and reflexes?

4. Biology 232 Human Anatomy and Physiology II
Dieterich Steinmetz
(503)
Web:
Lab:

5. Separation of Structure and Function

6. General Organization of the Nervous System
Highly organized, very efficient
Figure 13–1

7. Motor-Sensory Strip of the Cerebral Cortex

8. Quick Questions What is the somatic nervous system?
What is the autonomic nervous system?
Examples:
What are receptor molecules?
What are ligands?

9. Quick Answers What is the somatic nervous system?
Voluntarily controllable (eg., skeletal muscle control)
What is the autonomic nervous system?
Sympathetic ANS  fight/flight
Parasympathetic ANS  rest/repose (or rest/digest)
What are receptor molecules?
Examples: adrenoceptors (alpha1, alpha2, beta1, or beta2), cholinergic receptors (muscarinic or nicotinic)
What are ligands?
Examples: catecholamines (adrenaline, noradrenaline), ACh, muscarine, nicotine

10. Case of the Woman with HT
Name the two parts of the ANS
Describe the two major groups of receptors and their subtypes (and their usual ligands.)
Distinguish between receptor stimulation and cell stimulation.
Explain what “specificity” means when we are referring to a ligand’s specificity for receptors.
Provide a background for studying examples of somatic and autonomic reflexes.

11. Specialization of the Human Nervous System
The CNS is not homogenous.
Review
Gray matter and white matter
CNS vs. PNS
Brain vs. Spinal Cord
Cranial Nerves vs. Spinal Nerves

12. Motor-Sensory Strip of the Cerebral Cortex

13. Motor-Sensory Strip

14. Somatosensory Map of Postcentral Gyrus
Relative sizes of cortical areas
proportional to number of sensory receptors
proportional to the sensitivity of each part of the body
Can be modified with learning

15. Primary Motor Cortex
The precentral gyrus initiates voluntary movement.
Cells are called upper motor neurons.
Muscles are represented unequally (according to the number of motor units)

18. A Somatic Reflex
Figure 13–14

19. Sectional Anatomy of the Spinal Cord
Figure 13–5a

20. Peripheral Distribution of Spinal Nerves
Sensory fibers
Figure 13–7b

21. 5 Steps in a Neural Reflex
Figure 13–14

22. Video of Human Nervous System
Meninges
Gross brain
12 cranial nerves ….. Don’t fall asleep!
Gross spinal cord
Examples spinal nerves

23. What are the basic structural and organizational characteristics of the nervous system?

24. General Organization of the Nervous System
Highly organized, very efficient
Figure 13–1

25. In lab this week: Spinal Reflexes
Rapid, automatic, predictable response triggered to a specific stimulus
Controlled by spinal cord alone; not the brain

26. What are the structures and functions of the spinal cord?

27. Spinal Cord: Gross Anatomy
Note variations in cross sections.
Figure 13-2

28. Spinal Cord Protection
the vertebral column, meninges, cerebrospinal fluid, and vertebral ligaments.

29. 1.  dura
2.  arachnoid (transparent)
3.  cerebral veins in subarachnoid space, over pia matter

30. Spinal Cord Enlarged

31. Coverings of the Spinal Cord
Three “meninges”:
Dura Mater
Arachnoid Mater
Ce re bro spi nal Flu id
Pia Mater
spinal cord (or brain)

32. The Adult Spinal Cord About 18 inches (45 cm) long
1/2 inch (14 mm) wide
Ends between vertebrae L1 and L2

33. Bilateral Symmetry Grooves divide the spinal cord into left and right
Posterior median sulcus:
on posterior side
Anterior median fissure:
deeper groove on anterior side

34. Enlargements of the Spinal Cord
Caused by:
amount of gray matter in segment
involvement with sensory and motor nerves of limbs
Cervical enlargement:
nerves of shoulders and upper limbs
Lumbar enlargement:
nerves of pelvis and lower limbs

35. Spinal Cord Cervical Enlargement Conus Medularis Cauda Equina
pia matter
Filum Terminale

36. The Distal End Conus medullaris: Filum terminale: Cauda equina:
thin, conical spinal cord below lumbar enlargement
Filum terminale:
thin thread of fibrous tissue at end of conus medullaris
Cauda equina:
nerve roots extending below conus medullaris

37. 31 Spinal Cord Segments
Based on vertebrae where spinal nerves originate
Relationships of segments to vertebrae change with age because spine grows longer than spinal cord.

38. Naming Spinal Nerves Superior SEVEN spinal nerves: All other nerves:
are named for #___ inferior vertebra
All other nerves:
are named for superior vertebra
Where is spinal nerve C8? ________

39. Roots 2 branches of spinal nerves: Dorsal root ganglia: ventral root:
contains axons of motor neurons
dorsal root:
contains axons of sensory neurons
Dorsal root ganglia:
contain cell bodies of sensory neurons

40. White Matter of the Spinal Cord
Dorsal
Ventral
Anterior median “fissure” is clearer than the Posterior median “sulcus”

41. The Spinal Nerve Each side of spine: dorsal and ventral roots join
to form a “mixed” spinal nerve

42. Mixed Nerves Carry both afferent (sensory) and efferent (motor) fibers
Spinal nerves are mixed nerves

43. What are the structures and functions of the three meningeal layers that surround the central nervous system?

44. The Meninges
Specialized membranes isolate spinal cord from surroundings
Spinal meninges:
protect spinal cord
carry blood supply
continuous with cranial meninges
Meningitis:
viral or bacterial infection of meninges

45. Spinal Meninges
Figure 13–3

46. The 3 Meningeal Layers Dura mater: Arachnoid mater: Pia mater:
outer layer of spinal cord
Arachnoid mater:
middle meningeal layer
Pia mater:
inner meningeal layer

47. The Spinal Dura Mater Are tough and fibrous Cranially: Caudally:
fuses with periosteum of occipital bone
is continuous with cranial dura mater
Caudally:
tapers to dense cord of collagen fibers
joins filum terminale in coccygeal ligament

48. The Epidural Space
Between spinal dura mater and walls of vertebral canal
Contains loose connective and adipose tissue
Anesthetic injection site

49. The Arachnoid Mater Middle meningeal layer Arachnoid membrane:
simple squamous epithelia
covers arachnoid mater

50. Inter-Layer Spaces Subdural space: Subarachnoid space:
between arachnoid mater and dura mater
Subarachnoid space:
between arachnoid mater and pia mater
contains collagen/elastin fiber network (arachnoid trabeculae attach to arachnoid membrane of arachnoid mater)
filled with cerebrospinal fluid (CSF)

51. Cerebrospinal Fluid (CSF)
Is found in subarachnoid space
Carries dissolved gases, nutrients, and wastes
Spinal tap:
withdraws CSF

52. The Pia Mater Is the innermost meningeal layer
Is a mesh of collagen and elastic fibers
Is bound to underlying neural tissue

53. Structures of the Spinal Cord
Paired denticulate ligaments (image):
extend from pia mater to dura mater
stabilize side-to-side movement
Blood vessels:
along surface of spinal pia mater
within subarachnoid space

54. The Spinal Cord
Figure 13–4

55. Gray Matter
The amount of ventral gray matter at a given level of the spinal cord is proportional to the amount of skeletal muscle innervated.

56. Gray Matter of the Spinal Cord
Note: colors in reverse due to staining of tissue
(common stains)

57. What are the roles of white matter and gray matter in processing and relaying sensory information and motor commands?

58. Sectional Anatomy of the Spinal Cord
Figure 13–5a

59. Back
Front

60. Dorsal Roots (Sensory)
Spinal Cord
Ventral Roots (Motor)
Dorsal Roots (Sensory)
Spinal Nerve (this is where sensory and motor mix)
Dorsal Ramus (mixed)
Ventral Ramus (mixed)
Rami communicantes (mixed)
Nerve Plexuses
Sympathetic ganglia

61. Sectional Anatomy of the Spinal Cord
Figure 13–5b

62. White Matter
Is superficial
Contains myelinated and unmyelinated axons

63. Gray Matter Surrounds central canal of spinal cord
Contains neuron cell bodies, neuroglia, unmyelinated axons
Has projections (gray horns)

64. The Gray Horns Posterior gray horns: Anterior gray horns:
contain somatic and visceral sensory nuclei
Anterior gray horns:
contain somatic motor nuclei
Lateral gray horns:
are in thoracic and lumbar segments
contain visceral motor nuclei

65. Gray Commissures
Axons that cross from one side of cord to the other before reaching gray matter

66. Nuclei Nuclei: Sensory nuclei: Motor nuclei:
functional groups of cell bodies
Sensory nuclei:
dorsal (posterior)
connect to peripheral receptors
Motor nuclei:
ventral (anterior)
connect to peripheral effectors

67. Posterior White Columns
Lie between posterior gray horns and posterior median sulcus

68. Anterior White Columns
Lie between anterior gray horns and anterior median fissure

69. Anterior White Commissure
Area where axons cross from 1 side of spinal cord to the other

70. Lateral White Columns Located on each side of spinal cord
Between anterior and posterior columns

71. Tracts Tracts or fasciculi: Ascending tracts: Descending tracts:
in white columns
bundles of axons
relay same information in same direction
Ascending tracts:
carry information to brain
Descending tracts:
carry motor commands to spinal cord

72. Descending Motor Tracts
Corticospinal (Pyramidal) Tract: Carry motor signals from the primary motor cortex of the brain to the skeletal muscles of the body

73. Descending Motor Tracts
Medial Pathways (vestibulospinal, tectospinal, reticulospinal):
muscle tone and gross movements of the neck, trunk and proximal limb muscles
Lateral Pathway (rubrospinal tract):
muscle tone and precise movements of the distal parts of the limbs.

75. Ascending Sensory Tracts
Anterior Spinothalamic Tract:
crude touch and pressure
sensations from the body to the thalamus
Lateral Spinothalamic Tract:
pain and temperature sensations from the body to the thalamus

76. Ascending Sensory Tracts
Posterior columns (gracile fasciculus and cuneate fasciculus)
fine touch, vibration, pressure and proprioception from the body to the thalamus

77. KEY CONCEPT (1 of 3) Spinal cord has a narrow central canal
surrounded by gray matter
containing sensory and motor nuclei
Sensory nuclei are dorsal
Motor nuclei are ventral

78. KEY CONCEPT (2 of 3) Gray matter: White matter:
is covered by a thick layer of white matter
White matter:
consists of ascending and descending axons
organized in columns
containing axon bundles with specific functions

79. KEY CONCEPT (3 of 3) Spinal cord is so highly organized:
it is possible to predict results of injuries to specific areas
More on this later…

80. continues with part 2