0-1 Chapter 13 the Spinal Cord Flashcards

1
Q

paraplegia

A

paralysis of lower limbs

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2
Q

quadriplegia

A

paralysis of all four limbs

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3
Q

hemiplegia

A

paralysis of one side of the body only

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4
Q

Functions of the Spinal Cord

A

conduction
locomotion
reflexes

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5
Q

central pattern generators

A

are pools of neurons providing control of flexors and extensors that cause alternating movements of the lower limbs

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6
Q

spinal cord

A

cylinder of nervous tissue that arises from the brainstem at the foramen magnum of the skull

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7
Q

Number of Spinal Nerves

A

31 pair of spinal nerves
•first pair passes between the skull and C1
•rest pass through intervertebral foramina

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8
Q

spinal cord ends at

A

inferior margin ends at L1 or a little beyond

occupies the upper two-thirds of the vertebral canal

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9
Q

segment

A

part of the spinal cord supplied by each pair of spinal nerves

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10
Q

spinal cord divided into the

A

cervical, thoracic ,lumbar, and sacral regions

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11
Q

two areas of the cord are thicker than elsewhere

A
  • cervical enlargement –nerves to upper limb

* lumbar enlargement –nerves to pelvic region and lower limbs

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12
Q

medullary cone (conus medullaris)

A

cord tapers to a point inferior to lumbar enlargement

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13
Q

cauda equina

A

bundle of nerve roots that occupy the vertebral canal from L2 to S5

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14
Q

meninges

A

three fibrous connective tissue membranes that enclose the brain and spinal cord
–separate soft tissue of central nervous system from bones of cranium and vertebral canal

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15
Q

Meninges of the Spinal Cord

from superficial to deep

A

dura mater, arachnoid mater, and pia mater

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16
Q

dura mater

A

–forms loose-fitting sleeve around spinal cord –dural sheath

–tough, collagenous membrane surrounded by

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17
Q

arachnoid mater

A

arachnoid membrane

subarachnoid space

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18
Q

arachnoid membrane

A

layer of simple squamous epithelium lining dura mater and a loose mesh of collagenous and elastic fibersspanning the gap between the arachnoid membrane and the pia mater

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19
Q

subarachnoid space

A

gap between arachnoid membrane and the pia mater

•filled with cerebrospinal fluid (CSF)

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20
Q

lumbar cistern

A

subarachnoid space inferior to medullary cone that contains cauda equina and CSF

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21
Q

pia mater

A

–delicate, translucent membrane that follows the contours of the spinal cord

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22
Q

terminal filum

A

fibrous strand of pia mater that extends beyond the medullary cone within the lumbar cistern

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23
Q

coccygeal ligament

A

formed from fusion of terminal filum and dura mater

•anchors the cord and meninges to vertebra Co1

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24
Q

denticulate ligaments

A

extend through the arachnoid to the dura

•anchors spinal cord to limit side to side movement

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25
Q

spina bifida

A

congenital defect in which one or more vertebrae fail to form a complete vertebral arch for enclosure of the spinal cord
–in 1 baby out of 1000
–common in lumbosacral region

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26
Q

folic acid

A

(a B vitamin) as part of a healthy diet for all women of childbearing age reduces risk

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27
Q

gray matter

A

neuron cell bodies with little myelin

–site of information processing –synaptic integration

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28
Q

white matter –

A

abundantly myelinated axons

–carry signals from one part of the CNS to another

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29
Q

Gray Matter in the Spinal Cord

A

spinal cord has a central core of gray matter that looks like a butterfly-or H-shaped in cross section

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30
Q

posterior (dorsal) root of spinal nerve carries only

A

sensory fibers

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31
Q

anterior (ventral) root of spinal nerve carries only

A

motor fibers

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32
Q

gray commissure

A

connects right and left sides

•punctured by a central canal lined with ependymal cells and filled with CSF

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33
Q

lateral horn

A

visible from T2 through L1

•contains neurons of sympathetic nervous system

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34
Q

White Matter in the Spinal Cord

A

white matter of the spinal cord surrounds the gray matter
•consists of bundles of axons that course up and down the cord
–provide avenues of communication between different levels of the CNS

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35
Q

columns or funiculi

A

three pair of these white matter bundles

–posterior(dorsal), lateral, and anterior(ventral) columns on each side

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36
Q

tracts or fasciculi

A

subdivisions of each column

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37
Q

ascending tracts

A

carry sensory information up the spinal cord

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38
Q

descending tracts

A

carry motor information down the spinal cord

–all nerve fibers in a given tract have a similar origin, destination, and function

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39
Q

decussation

A

as the fibers pass up or down the brainstem and spinal cord they cross over from the left to the right side and vice versa

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40
Q

contralateral

A

when the origin and destination of a tract are on opposite sides of the body

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41
Q

ipsilateral

A

when the origin and destination of a tract are on the same side of the body
–does not decussate

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42
Q

Ascending Tracts

A
  • ascending tracts carry sensory signals up the spinal cord
  • sensory signals travel across three neurons from origin in receptors to the destination in the sensory areas of the brain
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43
Q

sensory signals travel across three neurons

A

first order neurons
second order neurons
third order neurons

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44
Q

first order neurons

A

detect stimulus and transmit signal to spinal cord or brainstem

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45
Q

second order neurons

A

continues to the thalamus at the upper end of the brainstem

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46
Q

Ascending tracts decussates at

A

Second order neuron

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46
Q

third order neurons

A

carries the signal the rest of the way to the sensory region of the cerebral cortex

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47
Q

Major Ascending Tracts

A
  • gracile fasciculus
  • cuneate fasciculus
  • spinothalamic tract
  • spinoreticular tract
  • posterior (dorsal) and anterior (ventral) spinocerebellar tracts
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48
Q

Gracile fasciculus

A

Three neuron pathway
CONTRALATERAL
Carries touch and vibration from lower part of body (below t6)
First order neuron - unipolar - sensor to brainstem - cell body posterior root ganglion
Second order neuron - multipolar - begins with cell body in brainstem - crosses over at brainstem and continues contra laterally to thalamus
Third order neuron - multipolar - cell body in thalamus and axon goes to cortex

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49
Q

Cuneate fasciculus

A

Three neuron pathway
CONTRALATERAL
Carries touch and vibration from upper part of body (above t6)
First order neuron - unipolar - sensor to brainstem - cell body posterior root ganglion
Second order neuron - multipolar - begins with cell body in brainstem - crosses over at brainstem and continues contra laterally to thalamus
Third order neuron - multipolar - cell body in thalamus and axon goes to cortex

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50
Q

Spinothalamic tract

A

Three neuron pathway
Carries pain and temperature
First - unipolar- ends in posterior horn of spinal cord at level it enters -
Second - multipolar - cell body in posterior horn at spinal cord level where first entered - decussates at level of spinal cord and ascends CONTRALATERAL to the thalamus
Third order - multipolar - thalamus to cortex

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51
Q

Spinorecticular

A

Four neuron pathway
Carry pain
First - unipolar- ends in posterior horn of spinal cord at level it enters -
Second - multipolar - cell body in posterior horn at spinal cord level where first entered - decussates at level of spinal cord and ascends CONTRALATERAL to the brainstem (reticular formation)
Third order - multipolar- from brainstem (reticular formation) to the thalamus
Fourth order - multipolar - thalamus to cortex

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52
Q

Spinocerebellar tracts

A

Two neuron
Ipsilateral
Carry proprioceptive signals
First order - unipolar - end in posterior horn of spinal cord
Second order neuron - begins in posterior horn of spinal cord

Anterior tract—posterior horn, decussates at level, ascends to cerebellum and decussates again

Posterior tract–posterior horn, ascends to cerebellum

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53
Q

proprioception

A

nonvisual sense of the position and movements of the body

54
Q

medial lemniscus

A

formed from the second-order neurons of gracile and cuneate systems that decussate in the medulla
–tracts of these nerve fibers lead the rest of the way to the thalamus

55
Q

descending tracts

A

carry motor signals down the brainstem and spinal cord

56
Q

descending tracts

involves two neurons

A

upper motor neuron

lower motor neuron

57
Q

two neuron pathway

A

–upper motor neuron in cerebral cortex

–lower motor neuron in spinal cord

58
Q

upper motor neuron

A

originate in cerebral cortex or brainstem and terminates on a lower motor neuron

59
Q

lower motor neuron

A

in brainstem or spinal cord

60
Q

Lower motor neuron

A

Alpha motor neuron

61
Q

axon of lower motor neuron

A

leads the rest of the way to the muscle or other target organ

62
Q

Corticospinal tracts

A

Carry motor information for precise movements

Anterior and lateral

63
Q

Corticospinal tracts lateral

A

Two neuron
CONTRALATERAL
Multipolar
Cell body upper motor neuron in cortex - axon decussates in medulla and descends in lateral corticospinal tract and stops in anterior horn of spinal cord at level it needs to exit
Lower motor neuron exits through anterior root, joins spinal nerve and goes to muscle forming neuromuscular junction

64
Q

Anterior corticospinal tract

A

Two neuron
CONTRALATERAL
Multipolar
Cell body upper motor neuron in cortex - axon descends to exit level and decussates and stops in anterior horn of spinal cord at level it needs to exit
Lower motor neuron exits through anterior root, joins spinal nerve and goes to muscle forming neuromuscular junction

65
Q

pyramids

A

ridges on anterior surface of the medulla oblongata formed from fibers of this system

66
Q

tectum

A

midbrain region

67
Q

Poliomyelitis and ALS

A

both diseases cause destruction of motor neurons and production of skeletal muscle atrophy from lack of innervation

68
Q

poliomyelitis

A

–caused by the poliovirus
–destroys motor neurons in brainstem and anterior horn of spinal cord
–signs of polio include muscle pain, weakness, and loss of some reflexes
•followed by paralysis, muscular atrophy, and respiratory arrest
–virus spreads by fecal contamination of water

69
Q

amyotrophic lateral sclerosis (ALS)

A

Lou Gehrig disease
–destruction of motor neurons and muscular atrophy
–also sclerosis(scarring) of lateral regions of the spinal cord
–astrocytes fail to reabsorb the neurotransmitter glutamate from the tissue fluid
•accumulate to toxic levels

70
Q

spinal cord communicates with the rest of the body by way of

A

spinal nerves

71
Q

nerve

A

a cordlike organ composed of numerous nerve fibers (axons) bound together by connective tissue

72
Q

mixed nerves

A

contain both afferent (sensory) and efferent (motor) fibers

73
Q

nerves of peripheral nervous system are ensheathed in

A

Schwann cells

74
Q

Schwann cells

A

–forms neurilemma and often a myelin sheath around the axon
–external to neurilemma, each fiber is surrounded by basal lamina and then a thin sleeve of loose connective tissue –endoneurium

75
Q

fascicles

A

nerve fibers gathered in bundles

76
Q

perineurium

A

wraps fascicles

•composed of up to 20 layers of overlapping, squamous , epithelium-like cells

77
Q

epineurium

A

bundles numerous fascicles that constitutes whole nerve
•composed of dense irregular connective tissue
•protects nerve from stretching and injury

78
Q

Classification of Nerve Fibers

A

sensory (afferent) nerves

79
Q

sensory (afferent) nerves

A

–carry signals from sensory receptors to the CNS

80
Q

motor (efferent) nerves

A

–carry signals from CNS to muscles and glands

81
Q

mixed nerves

A

–consists of both afferent and efferent fibers

–conduct signals in two directions

82
Q

ganglion

A

cluster of neurosomas outside the CNS

–enveloped in an endoneurium continuous with that of the nerve

83
Q

Number of Spinal nerves

A

31 pairs of spinal nerves (mixed nerves)

84
Q

spinal nerves by segment

A

–8 cervical (C1 –C8) C1 between skull and atlas
•others exiting at intervertebral foramen
–12 thoracic (T1 –T12)
–5 lumbar (L1 –L5)
–5 sacral (S1 –S5)
–1 coccygeal (Co)

85
Q

proximal branches

A

–each spinal nerve has two points of attachment to the spinal cord
–posterior (dorsal) root is sensory input to spinal cord
–anterior (ventral) root is motor output out of spinal cord

86
Q

posterior (dorsal) root

A

is sensory input to spinal cord

•posterior (dorsal) root ganglion –contains the somas of sensory neurons carrying signals to the spinal cord

87
Q

anterior (ventral) root

A

is motor output out of spinal cord

•six to eight rootlets that leave spinal cord and converge to form anterior root

88
Q

cauda equina

A

formed from roots that arise from L2 to Co

89
Q

distal branches of spinal nerves

A

distal to vertebral foramen, the nerve divides into:
anterior ramus
posterior ramus
meningeal branch

90
Q

anterior ramus

A

innervates the anterior and lateral skin and muscles of the trunk
•gives rise to nerves of the limbs

91
Q

posterior ramus

A

innervates the muscles and joints in that region of the spine and the skin of the back

92
Q

meningeal branch

A

reenters the vertebral canal and innervates the meninges, vertebrae and spinal ligaments

93
Q

Nerve Plexuses

A

anterior rami branch and anastomose repeatedly to form five nerve plexuses:

94
Q

Nerve Plexuses

5

A
cervical plexus
brachial plexus
lumbar plexus
sacral plexus
coccygeal plexus
95
Q

cervical plexus

A

in the neck, C1 to C4

•supplies neck and phrenic nerve to the diaphragm

96
Q

brachial plexus

A
near the shoulder, C5 to T1
Musculocutaneous
Radial
Axillary
Median
Ulnar
97
Q

lumbar plexus

A

in the lower back, L1 to L4
Femoral
Obturator

98
Q

somatosensory function

A

carry sensory signals from bones, joints, muscles, and the skin

99
Q

sacral plexus

A

in the pelvis, L4, L5 and S1 to S3

Sciatic nerve

Common fibular
Tibular

100
Q

proprioception

A

brain receives information about body position and movements from nerve endings in muscles, tendons, and joints

101
Q

motor function

A

primarily to stimulate muscle contraction

102
Q

radial nerve injury

A

–passes through axilla
–crutch paralysis
–wrist drop

103
Q

sciatic nerve injury

sciatica

A

sharp pain that travels from gluteal region along the posterior side of the thigh and leg to ankle
–ninety percent of cases result from herniated intervertebral disc or osteoporosis of lower spine

104
Q

chickenpox

A

common disease of early childhood
–caused by varicella-zoster virus
–produces itchy rash that clears up without complications
•virus remains for life in the posterior root ganglia
–kept in check by the immune system

105
Q

shingles

A

shingles(herpes zoster) –localized disease caused by the virus traveling down the sensory nerves by fast axonal transport when immune system is compromised
–common after age of 50
–painful trail of skin discoloration and fluid-filled vesicles along path of nerve
–usually in chest and waist on one side of the body

106
Q

dermatome

A

a specific area of the skin that receives sensory input from a pair of spinal nerves

107
Q

dermatome map

A

a diagram of the cutaneous regions innervated by each spinal nerve

108
Q

dermatomes overlap their edges as much as

A

50%

–necessary to sever or anesthetize three successive spinal nerves to produce a total loss of sensation in one dermatome

109
Q

reflexes

A

quick, involuntary, stereotyped reactions of glands or muscle to stimulation
–automatic responses to sensory input that occur without our intent or often even our awareness

110
Q

four important properties of a reflex

A

require stimulation
quick
involuntary
stereotyped

111
Q

reflexes include

A

glandular secretion and contraction of all three types of muscle

112
Q

conditioned reflexes

A

include some learned responses

113
Q

somatic reflexes

A

since they involve the somatic nervous system

114
Q

pathway of reflex arc

A
somatic receptors
afferent nerve fibers
integrating center
efferent nerve fibers
skeletal muscles
115
Q

muscle spindle

A

stretch receptors embedded in skeletal muscles

116
Q

proprioceptors

A

specialized sense organs to monitor the position and movement of the body parts

117
Q

stretch (myotatic) reflex

A

when a muscle is stretched, it ‘fights back’ and contracts which maintains increased tonus, making it stiffer than unstretched muscle

118
Q

tendon reflex

A

reflexive contraction of a muscle when its tendon is tapped

119
Q

knee-jerk (patellar) reflex

A

is monosynaptic reflex

•one synapse between the afferent and efferent neurons

120
Q

reciprocal inhibition

A

reflex phenomenon that prevents muscles from working against each other by inhibiting the antagonist

121
Q

flexor reflex

A

the quick contraction of flexor muscles resulting in the withdrawal of a limb from an injurious stimulus
•requires contraction of the flexors and relaxation of the extensors in that limb

122
Q

polysynaptic reflex arc

A

pathway in which signals travel over many synapses on their way back to the muscle

123
Q

crossed extension reflex

A

the contraction of extensor muscles in the limb opposite of the one that is withdrawn
–maintains balance by extending other leg

124
Q

ipsilateral reflex arc

A

one in which the sensory input and the motor output are on the same sides of the spinal cord
–flexor reflex

125
Q

contralateral reflex arc

A

one in which the input and output are on opposite sides

–crossed extension reflex

126
Q

intersegmental reflex

A

one in which the input and output occur at different levels (segments) of the spinal cord

127
Q

The Tendon Reflex

A

in response to excessive tension on the tendon
–inhibits muscle from contracting strongly
–moderates muscle contraction before it tears a tendon or pulls it loose from the muscle or bone

128
Q

tendon reflex

organs

A

proprioceptors in a tendon near its junction with a muscle

–Golgi tendon organ -1mm long, nerve fibers entwined in collagen fibers of the tendon

129
Q

complete transection–

A

complete severance of cord
–immediate loss of motor control below level of injury
–above C4 poses the threat of respiratory failure
–spinal shock
–paralysis

130
Q

paraplegia

A

paralysis of both lower limbs

131
Q

quadriplegia

A

paralysis of all four limbs

132
Q

hemiplegia

A

paralysis on one side of the body

133
Q

paresis

A

partial paralysis or weakness of the limbs