Ch 14_lecture_presentation
Transcript of Ch 14_lecture_presentation
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14The Nervous System: The Spinal Cord and Spinal Nerves
PowerPoint® Lecture Presentations prepared bySteven BassettSoutheast Community College Lincoln, Nebraska
© 2012 Pearson Education, Inc.
Introduction
• The Central Nervous System (CNS) consists of:
• The spinal cord• Integrates and processes information• Can function with the brain• Can function independently of the brain
• The brain• Integrates and processes information• Can function with the spinal cord• Can function independently of the spinal cord
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Gross Anatomy of the Spinal Cord
• Features of the Spinal Cord• 45 cm in length• Passes through the foramen magnum
• Extends from the brain to L1
• Consists of:• Cervical region• Thoracic region• Lumbar region• Sacral region• Coccygeal region
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Figure 14.1a Gross Anatomy of the Spinal Cord
Cervical spinalnerves
Thoracicspinal
nerves
Lumbarspinal
nerves
Sacral spinalnerves
Coccygealnerve (Co1)
Filum terminale(in coccygeal ligament)
Cauda equina
Inferiortip ofspinal cord
Conusmedullaris
Lumbosacralenlargement
Posteriormedian sulcus
Cervicalenlargement
C1
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
L2
L3
L4
L5
S1
S2
S3
S4
S5
Superficial anatomy and orientation of the adult spinal cord. The numbers to the left identify the spinal nerves and indicate wherethe nerve roots leave the vertebral canal. The spinal cord, however,extends from the brain only to the level of vertebrae L1–L2.
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Gross Anatomy of the Spinal Cord
• Features of the Spinal Cord• Transverse view
• White matter• Gray matter• Central canal• Dorsal root and ventral root: merge to form a spinal
nerve• Dorsal root is sensory: axons extend from the
soma within the dorsal root ganglion• Ventral root is motor
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Figure 14.1d Gross Anatomy of the Spinal Cord
Inferior views of cross sectionsthrough representativesegments of the spinal cordshowing the arrangement ofgray and white matter
Posterior median sulcus
White matter
Graymatter
Anterior median fissure
Dorsal root
Spinalnerve
Ventralroot
Dorsal rootganglion
Centralcanal
C3
T3
L1
S2
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Gross Anatomy of the Spinal Cord
• Features of the Spinal Nerves• Consist of:
• Sensory nerves (afferent nerves): transmit impulses toward the spinal cord
• Motor nerves (efferent nerves): transmit impulses away from the spinal cord
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Spinal Meninges
Spinal meninges are specialized membranes that provide protection, physical stability, and shock absorption.Three meningeal layers:
The dura mater— tough and thickest, fibrous outermost layer The arachnoid mater— middle layer. Contains meshwork of elastic
fibers called arachnoid trabeculae. The Pia mater— innermost layer
Meningeal spaces: Epidural space: the space just outside the dura mater Subdural space: the space between dura and arachnoid layers. Subarachnoid space: the space between arachnoid and pia layers.
It contains CSF (Cerebro Spinal Fluid). This is space is used in spinal tap to obtain CSF.
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Figure 14.2c The Spinal Cord and Spinal Meninges
Posterior view of the spinal cord showing themeningeal layers, superficial landmarks, anddistribution of gray and white matter
White matter
Ventral root
Dorsal root
Pia mater
Arachnoid mater
Gray matter
Spinal nerve
Dorsal root ganglion
Dura mater
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Sectional Anatomy of the Spinal Cord
• Gray matter• Central canal• Consists of somas (cell bodies) surrounding
the central canal
• White matter• Consists of axons• Nerves are organized into tracts or columns• Located outside the gray matter area
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Sectional Anatomy of the Spinal Cord
Organization of Gray Matter Surrounds the central canal and contains cell bodies of neurons
and glial cells. This is the H shape mass in the center of spinal cord.
Groups of nuclei (sensory or motor) with specific functions Posterior gray horns contain somatic and visceral sensory
nuclei; this is the destination of dorsal root. Anterior gray horns contain somatic motor nuclei. This is the
origin of ventral root. Lateral gray horns contain visceral motor neurons. Gray commissures contain the axons of interneurons that cross
from one side of the cord to the other.
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Figure 14.4b Sectional Organization of the Spinal Cord
The left half of this sectional view shows important anatomical landmarks; the right half indicates the functional organization of the gray matter in the anterior, lateral, and posterior gray horns.
Posteriorgray horn
Posterior graycommissure
Lateralgray horn
Anteriorgray horn
Anterior graycommissure
Anterior medianfissure
To ventralroot
Posterior median sulcusFrom dorsal root
Sensorynuclei
Motornuclei
Somatic
Somatic
Visceral
Visceral
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Sectional Anatomy of the Spinal Cord
Organization of White Matter Divided into 6 columns, which contain tracts
Ascending tracts relay information from spinal cord to brain
Descending tracts carry information from brain to spinal cord
The spinal nerves that extend distal to the conus medularis are collectively referred to as the cauda equina.
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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 whitecolumn (funiculus)
Anterior whitecolumn (funiculus)
Anterior whitecommissure
FlexorsExtensors
Lateralwhite
column(funiculus)
Leg
Hip
TrunkArm
Hand
Forearm
Arm
Shoulder
Trunk
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Spinal Nerves
• There are 31 pairs of spinal nerves• 8 cervical nerves• 12 thoracic nerves• 5 lumbar nerves• 5 sacral nerves• 1 coccygeal nerve
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Figure 14.1a Gross Anatomy of the Spinal Cord
Cervical spinalnerves
Thoracicspinal
nerves
Lumbarspinal
nerves
Sacral spinalnerves
Coccygealnerve (Co1)
Filum terminale(in coccygeal ligament)
Cauda equina
Inferiortip ofspinal cord
Conusmedullaris
Lumbosacralenlargement
Posteriormedian sulcus
Cervicalenlargement
C1
C2
C3
C4
C5
C6
C7
C8
T1
T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
L2
L3
L4
L5
S1
S2
S3
S4
S5
Superficial anatomy and orientation of the adult spinal cord. The numbers to the left identify the spinal nerves and indicate wherethe nerve roots leave the vertebral canal. The spinal cord, however,extends from the brain only to the level of vertebrae L1–L2.
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Spinal Nerves
• The covering of the nerve fibers from inside out is:• Endoneurium: covers the nerve fiber.• Perineurium: covers a bundle of nerve fibers
( Fascicle)• Epinerium: covers a group of fascicles.
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Figure 14.5a Anatomy of a Peripheral Nerve
A typical peripheralnerve and its connectivetissue wrappings
Connective TissueLayers
Blood vessels
Fascicle
Schwann cell
Myelinatedaxon
Epineurium coveringperipheral nerve
Perineurium (aroundone fascicle)
Endoneurium
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Figure 14.6a Peripheral Distribution of Spinal Nerves
Motor Commands
KEY
Postganglionic fibersto smooth muscles,glands, etc., of back
To skeletalmuscles of back
To skeletalmuscles of bodywall, limbs
Postganglionic fibers tosmooth muscles, glands, etc., of body wall, limbs
Postganglionic fibersto smooth muscles,glands, visceral organsin thoracic cavity
Preganglionic fibers tosympathetic gangliainnervating abdomino-pelvic viscera
Somatic motorcommands
Visceral motorcommands
Ramicommunicantes
Gray ramus(postganglionic)
White ramus(preganglionic)
Sympathetic nerve
Sympathetic ganglion
Spinal nerve
Ventral ramus
Dorsal ramus
Dorsal root ganglionDorsal
rootVisceralmotor
Somaticmotor
Ventralroot
The distribution of motor neurons in the spinal cord and motor fibers within the spinalnerve and its branches. Although the gray ramus is typically proximal to the white ramus,this simplified diagrammatic view makes it easier to follow the relationships betweenpreganglionic and postganglionic fibers.
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Figure 14.6b Peripheral Distribution of Spinal Nerves
Sensory Information
KEY
From interoceptorsof visceral organs
From interoceptorsof back
From exteroceptors,proprioceptors of back
From exteroceptors,proprioceptors ofbody wall, limbs
From interoceptorsof body wall, limbs
Somaticsensations
Visceralsensations
Ventral ramus
Ramicommunicantes
Dorsalroot
ganglion
Dorsalroot
Somaticsensory
Visceralsensory
Ventralroot
A comparable view detailing the distribution of sensory neurons and sensory fibers
Dorsal ramus
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Nerve Plexuses
• There are four nerve plexuses• Cervical plexus• Brachial plexus• Lumbar plexus• Sacral plexus
• Sometimes the lumbar and sacral are combined to form the lumbosacral plexus
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Important brachial plexus nerves
• Musculocutaneous N.: • mainly for flexors of the arm like brachialis and brachioradialis.
• Radial N.: • mainly the extensors of the arm like triceps brachii and
ancuneous.• Ulnar N.:
• sense and motor of 5th and half of 4th finger and associated area of the hand.
• Median N.: • sense and motor of the rest of the hand and fingers.
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Important lumbosacral plexus nerves• Sciatic nerve:
• posterior muscles of the thigh.• the largest nerve of the body.
• Femoral nerve:• Anterior muscles of the thigh.
• Obturator nerve:• Adductors of the thigh.
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Figure 14.8 Peripheral Nerves and Nerve Plexuses
Lesser occipital nerveGreat auricular nerveTransverse cervical nerveSupraclavicular nerve
Phrenic nerve
Axillary nerve
Musculocutaneous nerve
Thoracic nerves
Radial nerve
Ulnar nerve
Median nerve
Iliohypogastricnerve
Ilioinguinal nerve
Genitofemoral nerve
Femoral nerve
Obturator nerve
Superior
InferiorGlutealnerves
Pudendal nerve
Sciatic nerve
Lateral femoral cutaneous nerve
Saphenous nerve
Common fibular nerve
Tibial nerve
Medial sural cutaneous nerve
Cervicalplexus
Brachialplexus
Lumbarplexus
Sacralplexus
C1C2C3C4C5C6C7C8T1T2
T3T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
L2
L3
L4
L5
S1
S2
S3
S4
S5
Co1
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Figure 14.9 The Cervical Plexus
Great auricular nerve
Geniohyoid muscle
Transversecervical nerveThyrohyoid muscleAnsa cervicalis
Omohyoid muscle
Phrenic nerve
Sternohyoid muscle
Sternothyroid muscle
Cranialnerves
Accessorynerve (N XI)
Hypoglossalnerve (N XII)
Lesser occipitalnerve
Nerve roots ofcervical plexus
Supraclavicularnerves
Clavicle
C1
C2
C3
C4
C5
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Figure 14.10b The Brachial Plexus
Anterior view of the brachial plexus and upper limbshowing the peripheral distribution of major nerves
Anterior
Distribution ofcutaneous nerves
Median nerve
Ulnar nerve
Radial nerve
Palmar digital nerves
Superficial branch of ulnar nerve
Deep branch of ulnar nerve
Anterior interosseous nerve
Median nerve
Ulnar nerve
Deep radial nerve
Radial nerve
Median nerve
Ulnar nerve
Superficial branchof radial nerve
Lateral antebrachialcutaneous nerve
Musculocutaneousnerve
BRACHIALPLEXUS
Dorsal scapular nerve
Suprascapular nerve
Superior trunkMiddle trunk
Inferior trunk
C4
C5
C6
C7
C8
T1
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Figure 14.10a The Brachial Plexus
Radial nerve
Ulnar nerve
Thoracodorsalnerve
Long thoracicnerve
INFERIORTRUNK
MIDDLETRUNK BRACHIAL
PLEXUS
The trunks and cords of the brachialplexus
KEY
Lateral cord
Posterior cord
Medial cord
C5
C6
C7
C8
T1
Median nerve
Medial antebrachialcutaneous nerve
Posterior brachialcutaneous nerve
Musculocutaneousnerve
Axillary nerve
Subscapular nerves
Medial pectoral nerve
Lateral pectoral nerve
Suprascapular nerve
SUPERIOR TRUNK
Nerve tosubclavius muscle
Dorsal scapularnerve
Firstrib
Roots (ventral rami)
Trunks
Divisions
Cords
Peripheral nerves
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Figure 14.12a The Lumbar and Sacral Plexuses, Part I
The lumbar plexus, anterior view
Lumbosacraltrunk
LUMBARPLEXUS
T12
L1
L2
L3
L4
L5
Femoral branch
Genital branch
Femoral nerveObturator nerve
Branches ofgenitofemoral
nerve
Lateral femoralcutaneous nerve
Genitofemoral nerve
Ilioinguinal nerve
Iliohypogastric nerve
T12 subcostal nerve
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Figure 14.12c The Lumbar and Sacral Plexuses, Part I
The lumbar and sacralplexuses, anterior view
Subcostal nerve
Iliohypogastric nerve
Ilioinguinal nerve
Genitofemoral nerve
Lateral femoralcutaneous nerve
Femoral nerve
Superior gluteal nerve
Inferior gluteal nerve
Pudendal nerve
Posterior femoralcutaneous nerve (cut)
Sciatic nerve
Saphenous nerve
Common fibularnerve
Superficial fibularnerve
Deep fibularnerve
Obturator nerve
Suralnerve
Suralnerve
Saphenousnerve
Saphenousnerve
Saphenousnerve
Suralnerve
Tibialnerve
Tibialnerve
Fibularnerve
Fibularnerve
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Reflexes
A reflex is an immediate involuntary response to a specific stimulus.The neural “writing” of a single reflex is referred to as a reflex arc. Reflexes are classified according to:
Their development (innate and acquired) The site where information processing occurs (spinal
and cranial) The nature of resulting motor response (somatic and
visceral or autonomic) The complexity of the neural circuit (monosynaptic and
polysynaptic)
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Figure 14.14 A Reflex Arc
Arrival of stimulus andactivation of receptor
Response by effector
Activation of asensory neuron
Activation of amotor neuron
Information processingin CNS
Stimulus
Effector
Receptor
REFLEXARC
Ventralroot
Dorsalroot
Sensationrelayed to
the brain bycollateral
KEYSensory neuron(stimulated)
Excitatoryinterneuron
Motor neuron(stimulated)
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Figure 14.15 The Classification of Reflexes
Reflexes
development response
can be classified by
complexity of circuit processing site
• Processing in the spinal cord
• Processing in the brain
• One synapse
• Multiple synapses (two to several hundred)
• Genetically determined
• Learned • Control actions of smooth and cardiac muscles, glands
• Control skeletal muscle contractions• Include superficial and stretch reflexes
Innate Reflexes
Acquired Reflexes
Somatic Reflexes
Visceral (Autonomic) Reflexes
Spinal Reflexes
Cranial Reflexes
Monosynaptic
Polysynaptic
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Reflexes
• Spinal reflexes can be:• Monosynaptic
• Involves a single segment of the spinal cord
• Polysynaptic • Integrates motor output from several spinal
segments
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Figure 14.16 Neural Organization and Simple Reflexes
CENTRALNERVOUSSYSTEM
CENTRALNERVOUSSYSTEM
Motorneuron
Ganglion
Sensoryneuron
Sensoryreceptor(musclespindle)
Skeletal muscle
Circuit 1
A monosynaptic reflex circuit involves a peripheralsensory neuron and a central motor neuron. In thisexample, stimulation of the receptor will lead to areflexive contraction in a skeletal muscle.
A polysynaptic reflex circuit involves a sensory neuron,interneurons, and motor neurons. In this example, thestimulation of the receptor leads to the coordinatedcontractions of two different skeletal muscles.
Skeletal muscle 1
Skeletal muscle 2
Motorneurons
Circuit 2
Interneurons
Ganglion
Sensory neuron
Sensoryreceptor
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Figure 14.17b Stretch Reflexes
KEY
Motor neuron(stimulated)
Sensory neuron(stimulated)
The patellar reflex is controlled by muscle spindles in the quadriceps group. Thestimulus is a reflex hammer striking the muscle tendon, stretching the spindlefibers. This results in a sudden increase in the activity of the sensory neurons,which synapse on spinal motor neurons. The response occurs upon the activationof motor units in the quadriceps group, which produces an immediate increase inmuscle tone and a reflexive kick.
Spinal cord
Stimulus
Stretch
Contraction
Effector
Receptor(musclespindle)
REFLEXARC
Response
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Terminology • Hemiplegia:
• loss of sensation and motor fonction of one side of the body.
• Paraplegia: • loss of sensation and motor function of lower
limbs.
• Quadriplegia: • loss of sensation and motor function of upper
and lower limbs.