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

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Chapter 13: The Spinal Cord, Spinal Nerves, and Spinal Reflexes Outline Introductions Syllabus, Textbooks, etc. Gross anatomy of sensory and motor systems Reflex ... – PowerPoint PPT presentation

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Title: Chapter 13: The Spinal Cord, Spinal Nerves, and Spinal Reflexes


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 232Human Anatomy and Physiology II
  • Dieterich Steinmetz
  • (503)977-4226
  • E-mail dsteinme_at_pcc.edu
  • Web http//my.pcc.edu
  • Lab http//www.spot.pcc.edu/anatomy/lab.htm

5
Separation of Structure and Function
6
General Organization of the Nervous System
  • Highly organized, very efficient

Figure 131
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?
  • Examples
  • What are ligands?
  • Examples

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 ligands 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)

16
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17
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18
A Somatic Reflex
Figure 1314
19
Sectional Anatomy of the Spinal Cord
Figure 135a
20
Peripheral Distribution of Spinal Nerves
  • Sensory fibers

Figure 137b
21
5 Steps in a Neural Reflex
Figure 1314
22
Video of Human Nervous System
  • Meninges
  • Gross brain
  • 12 cranial nerves .. Dont 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 131
25
In lab this weekSpinal 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
  • 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
  • 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
  • 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 133
46
The 3 Meningeal Layers
  • Dura 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
  • 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
  • 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 134
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 135a
59
Back
Front
60
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 135b
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
  • 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
  • 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
  • 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.

74
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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
  • 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
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