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Anatomy 101 > Spinal cord and spinal nerve > Flashcards

Spinal cord and spinal nerve Flashcards

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1
Q

• central nervous system (CNS) consist of …

A

= brain and spinal cord

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2
Q

• peripheral nervous system

A

nerves and ganglia outside of CNS
o central role in communication between brain and rest of body
nerves and ganglia outside of CNS

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3
Q

how many pairs of cranial nerve and spinal nerves ?

A

o 12 pairs of cranial nerves and 31 pairs of spinal nerves and their ganglia

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4
Q

Spinal cord extend from …

A

foramen magnum to the 2nd lumbar vertebra

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5
Q

the spinal cord is composed of …

A

• composed of cervical, thoracic, lumbar and sacral segments named according to portion of vertebral column from which the nerves enter and exit

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6
Q

• cervical and lumbosacral enlargements

A

= associated with nerves that supply upper and lower limbs

• conus medullaris = immediately inferior to lumbosacral enlargement

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7
Q

• conus medullaris

A

immediately inferior to lumbosacral enlargement
o filum terminale = slender connective tissue extending to dorsum of coccyx
 provides longitudinal support to spinal cord

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8
Q

• cauda equine

A

= numerous roots (origins) of spinal nerves extending inferiorly from the lumbosacral enlargement and conus medullaris

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9
Q

• meninges

A

specialized membranes surrounding brain and spinal cord

o provided protection, physical stability and shock absorption

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10
Q

dura mater

location ?

A

most superficial – tough fibrous membrane

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11
Q

dura mater

type of tissue ?

A

 dense irregular connective tissue

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12
Q

dura mater :

external and internal suface covered with

A

simple squamous epithelium

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13
Q

dura mater :

caudal end

A

 caudal end blends with filum terminale

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14
Q

dura mater:

lateral extensions does what ?

A

 lateral extensions cover spinal nerve roots

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15
Q

dura mater :

attachment

A

 only attachment to bone = edges of foramen magnum of scull, 2nd and 3rd cervical vertebrae and the sacrum

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16
Q

 epidural space

A

= space between dura mater and the periosteum of the vertebral canal
• contains spinal nerve roots, blood vessels, areolar connective tissue and adipose tissue

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17
Q

• epidural anesthesia

A

(often during childbirth) = injection of anesthetics into epidural space
o needle does not penetrate dura mater and takes time for drug to diffuse to CFS
o provides mainly sensory anaesthesia
o drugs can be administered via catheter to maintain longer anesthesia

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18
Q

o arachnoid mater :
location
type of tissue ?

A

= middle layer – thin and wispy = simple squamous epithelium

 outer surface lines inner surface of dura mater

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19
Q

 subarachnoid space

location ?
contains what ?

A

space between arachnoid and pia maters

• contains cerebrospinal fluid (CSF) and blood vessels

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20
Q

clinical procedures of subarachnoid space

A

• clinical procedures introducing needle into subarachnoid space at L3/L4 or L4/L5 level
o does not puncture spinal cord because it terminals at L2 and pushes nerves aside
o spinal anesthesia (spinal block) – drug blocks action potential transmission
 advantages = delivered directly to CSF, stronger and takes effect faster

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21
Q

lumbar puncture

A

(spinal tap) (Clinical Note p.375) – CSF fluid is removed in order to examine it for infectious agents (meningitis) or blood (haemorrhage) or to measure CSF pressure

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22
Q

pia mater
location ?
fiber ?

A

= deepest layer that is bound tightly to surface of spinal cord
 contains elastic and collagen fibers and thin layer of astrocytes
 denticulate ligaments = extensions of pia mater that connect pia mater and arachnoid mater to dura mater
• help prevent side-to-side movement of spinal cord

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23
Q

white matter :

location

A

• superficial and peripherally located white matter

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24
Q

white matter ?

A

consists of myelinated and unmyelinated axons that form nerve columns (funiculi) and tracts

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25
Q

nerve columns

A

funiculi

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26
Q

white matter can be divided into

A

columns

there is posterior white columns, anterior and lateral white columns

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27
Q

each columns contains

A

tracts
• collection of axons within CNS (nerve = collection of axons outside CNS)
• all axons within a tract relay information in the same direction
• ascending tracts – carry sensory information toward the brain
• descending tracts – carry motor commands from the brain to motor neurons of spinal cord

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28
Q

grey matter

A

contains cell bodies of glial cells and neurons, dendrites, axon terminals and unmyelinated axons

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29
Q

grey matter

how are they organized

A

o organized in butterfly (H-)pattern

o nuclei = clusters of nerve cell bodies in the grey matter of the central nervous system

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30
Q

grey matter :

horns

A

o thin dorsal (posterior) horns – contain somatic and visceral sensory nuclei
o larger ventral (anterior) horns – contain somatic motor nuclei
o small lateral (intermediate) horns – found only between T1 and L2 - associated with autonomic nervous system (visceral motor nuclei)

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31
Q

• anterior median fissure (crack) and posterior median sulcus (groove

A

) = longitudinal landmarks that partially separate two halves of spinal cord

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32
Q

• grey and white commissures

A

= axons that cross from one side of the spinal cord to the other

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33
Q

• central canal

A

contains CSF and located in the center of the grey matter

• 6-8 rootlets combine to form roots (Fig 14.2, 14.3)

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34
Q

o dorsal root

A

sensory (afferent) information that enters the dorsal side of the spinal cord

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35
Q

 dorsal root ganglion

A

swelling on dorsal root that contains the cell bodies of sensory neurons
• no synapses here – axons extend into CNS and synapse with interneurons

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36
Q

o ventral root

A

= motor (efferent) axons that exits the ventral side of the spinal cord
o extend laterally from the spinal cord
o dorsal and ventral roots pass through subarachnoid space and pierce arachnoid and dura maters

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37
Q

• spinal nerve

A

distal to dorsal and ventral roots = combined sensory and motor fibers (mixed nerves)

38
Q

spinal nerve contains

A

= axons, Schwann cells, and connective tissue (Fig 14.4)
• surrounded by 3 layers of connective tissue:
1) endoneurium
2)perineurium
3 )epinuerium

39
Q

o endoneurium

A

delicate loose connective tissue layer that covers each nerve fiber (and its Schwann cell sheath)
 branched capillaries found between endoneurium and perineurium

40
Q

o perineurium

A

heavier connective tissue layer that surrounds a bundle of axons = fascicles

41
Q

o epineurium

A

o epineurium = dense irregular connective tissue that binds nerve fascicles together forming the nerve
 continuous with the dura mater of the CNS

42
Q

• 31 pairs of spinal nerves

how do they name them

A

o designated by a letter corresponding to the area and number corresponding to the vertebra where the nerve exits
o since 1st pair of spinal nerves exit between skull and 1st cervical vertebra = C1
 have eight cervical nerves but only seven cervical vertebrae
o C1-C8, T1-T12, L1-L5, S1-S5, Co1) (Fig 14.7)

43
Q

nerve of the sacrum exit where ?

A

• nerves of the sacrum exit through the 5 sacral foramina in the fused sacral bone

44
Q

remaining spinal nerve exit through

A

• remaining spinal nerves exit through intervertebral foramina located between adjacent vertebrae

45
Q

each spinal nerve branch into a

A

• each spinal nerve branches into a dorsal and ventral ramus

46
Q

dorsal ramus

A

split of spinal nerve that extends dorsally
 innervate most of the deep muscles of the dorsal trunk responsible for moving the vertebral column
 innervates connective tissue and skin near midline of back

47
Q

o ventral ramus

A

split of spinal nerve that extends ventrally
 supply ventrolateral body surface, structures in body wall and limbs
 thoracic region – form intercostal nerves
 ventral rami of remaining spinal nerves form four major plexuses (Fig 14.7, 14.8)

48
Q

plexus

A

net-like organization produced by intermingling of nerves
• nerves that arise from plexuses have axons from more than one spinal nerve (from more the one level of spinal cord)
• minimizes the loss of control and feeling of a specific area of the body following spinal cord injury

49
Q

o rami communicantes

A

two extra branches from T1-L2

 carry visceral motor fibers to and from autonomic ganglia of the sympathetic division of the autonomic nervous system

50
Q

o dermatome

A

area of the skin supplied with sensory innervation by a pair of spinal nerves
 each spinal nerve (except C1) has a specific cutaneous sensory distribution – forms dermatomal map (Fig 14.6)

51
Q

• spinal cord injury

A

leading causes: automobile and motorcycle accidents, gunshot wounds, falls and swimming accidents
o physical examination can pinpoint location of injury – sensory loss via evaluation of dematomes and also indicates level of motor loss

52
Q

o spinal shock

A

period of time when all sensory and motor neurologic activity lost below level of injury
 loss in nerve conduction due to disrupted cellular potassium ion flow
 loss of function may be temporary (incomplete lesion – lasting up to a few weeks) or permanent (complete lesion)

53
Q

o incomplete lesion

A
  • some recovery can be expected as there is no anatomical disruption of the spinal cord
     best indicator of incomplete lesion = sacral sparing
    • muscle movement of great toe (S1), sensory sensation in perianal area and motor control of anal sphincter (S2-S4)
54
Q

 spinal concussion

A

incomplete lesion

= injury caused by blow – usually due to bone or disk displacement into the cord
• no visible damage to spinal cord and period of spinal shock temporary with complete recovery in few hours

55
Q

 spinal contusion

A

incomplete lesion
injury resulting in hemorrhage within meninges – often resulting from whiplash or falls
• pressure rises in cerebrospinal fluid and white matter of cord may degenerate at site of injury
• gradual recovery over period of weeks and may leave some functional loss

56
Q

 spinal compression

A

incomplete lesion

spinal cord temporarily physically squeezed or distorted within vertebral canal

57
Q

o complete lesion

A

 spinal laceration = tear or cut produced by vertebral fragments or foreign bodies
 spinal transection = complete severing of spinal cord

58
Q

spinal cords injuries , occurs a lot in (which area)

A

o most occur in the cervical region or at the thoracolumbar junction
 cervical region – most severe and can result in paralysis of all four limbs (quadriplegia) with abdominal and chest muscles also affected
 below T1 can result in varying degrees of paralysis of the legs (paraplegia) and abdomen

59
Q

primary damage

A

damage from the mechanical event

60
Q

o secondary damage

A

damage that extends from primary site due to ischemia (decreased blood flow), edema, ion imbalances, release of excitatory neurotransmitters (e.g. glutamate), and inflammatory cell invasion
 main focus of current research is to limit secondary damage
 major block to adult spinal cord regeneration = formation of a scar consisting of myelin and astrocytes at site of injury

61
Q

paralysis in all four limbs

A

(quadriplegia)

62
Q

• peripheral nerve palsies

A

= regional losses of sensory and motor function as a result of nerve trauma or compression

63
Q

o brachial plexus birth palsy (Erb’s palsy)

part of

A

peripheral nerve palsies

nerve trauma during difficult deliveries
 delivery of head but jamming of shoulder resulting in tearing of upper ventral rami or nerve roots of brachial plexus
 loss of shoulder sensation and motion but preserves function of forearm and hand innervated by lower nerve roots

64
Q

o pressure palsies

A

peripheral nerve palsies

– mild and temporary impairment where area becomes numb
 followed by paresthesia - uncomfortable “pins-and-needles” sensation
 return to normal function

65
Q

peripheral nerve palsies

how many ?

A

• 4 major nerve plexuses: cervical, brachial, lumbar and sacral

66
Q

• cervical plexus

A

ventral rami of spinal nerves from C1-C5
o deep to stenocleidomastoid muscle
o innervate superficial neck structures and muscles attached to hyoid bone
o phrenic nerve (C3-C5) = “keep you alive” - most important derivative of cervical plexus (mainly C4)
 innervates diaphragm

67
Q

• brachial plexus

A

C5-T1 – innervates pectoral girdle and upper limb

o source of five major motor nerves to upper limb

68
Q

brachial anesthesia

A

entire upper limb can be anesthetized by injecting anesthetic near the brachial plexus – between the neck and shoulder posterior to the clavicle

69
Q

 axillary nerve

A

innervates the deltoid and teres minor muscles

• sensory innervation to shoulder joint and skin over part of the shoulder

70
Q

 radial nerve

A

innervates all the extensor muscle of the upper limb, the supinator and brachioradialis muscles
• cutaneous sensory innervation to posterior portion of upper limb and posterior surface of hand

71
Q

• radial nerve palsy

A

resulting from pressure on back of arm when radial nerve is compressed against the humerus

72
Q

o crutch paralysis

what kind of palsy ?

A

– improper use of crutches
 major symptom = wrist drop - elbow, wrist, and fingers and constantly flexed

radial nerve palsy

73
Q

o Saturday night palsy

what kind of palsy ?

A

– falling asleep on couch with arm over seat back, or beneath someone’s head

radial nerve palsy

74
Q

 musculocutaneous nerve

A

motor innervation to flexor muscles of arm and cutaneous innervation to part of the forearm

75
Q

 ulnar nerve

A

– innervates flexor carpi ulnaris and most of intrinsic hand muscles
• sensory distribution to ulnar side of hand
• most easily damaged but almost always temporary = ulnar nerve palsy

76
Q

ulnar nerve palsy

A

o 4th and 5th phalanges lose sensation and fingers cannot be adducted
o leaning elbow on desk or banging elbow “funny bone” banged against hard object
o causes painful tingling to radiate down ulnar side of forearm

77
Q

 median nerve

A

– all flexor muscles of forearm and most hand muscles associated with thumb
• sensory distribution to radial portion of the palm
• carpal tunnel syndrome – median nerve palsy resulting in numbness, tingling and pain in fingers

78
Q

• lumbosacral plexuses

A

L1-S4 = overlap of lumbar and sacral plexuses

o innervate pelvis and lower limb

79
Q

o crural palsies

A

loss of sensory and motor function associated with nerves of the lumbosacral plexus

80
Q

o lumbar plexus

A

L1-L4 (with a small contribution from T12)

81
Q

 obturator nerve

type of plexus ?

A

)– supplies adductor muscles of thigh and cutaneous distribution to medial side of thigh

lumbar plexus

82
Q

 femoral nerve

type of plexus ?

A

innervates iliopsoas, sartorius and quadriceps femoris group
• cutaneous distribution = anterior and lateral thigh and medial leg and foot

lumbar plexus

83
Q

o sacral plexus

A

L4-S4

 pudendal nerve – innervates muscles of the perineum, urogenital diaphragm, external anal sphincter, and urethral sphincter, and sensory information from external genitalia
• plays vital role in sexual stimulation
• branches are anesthetized during episiotomy (cut to perineum that enlarges opening of birth canal)

84
Q

 sciatic nerve

A

= largest peripheral nerve in body

• innervates biceps femoris, semimembranosus, semitendinosus and adductor magnus

85
Q

• sciatic compression

A

• sciatic compression – after driving or sitting in one position for extended periods
o lumbar or gluteal pain, numbness along back of leg and weakness in leg muscles

86
Q

o sciatica

A

symptoms due to compression of nerve roots by distorted lumber intervertebral disc

87
Q

what passes through greater sciatic notch in pelvis and descends in posterior thigh to the popliteal fossa where two portions separate

A

o tibial nerve

o common fibular nerve

88
Q

o tibial nerve

A

innervates most of the flexors knee and plantar flexors of foot
 sural nerve – branch that supplies cutaneous innervation over calf and plantar surface of foot
 branches in foot forming medial and lateral plantar nerves

89
Q

o common fibular nerve

A

– divides into deep and superficial fibular (peroneal) nerves – innervate anterior and lateral muscles of leg and foot
 cutaneous distribution = lateral and anterior leg and dorsum of foot

90
Q

 fibular palsy

A

sensory loss from the top of the foot and side of leg and “foot drop” -decreased ability to dorsiflex or evert foot
• can occur from sitting with legs crossed

Anatomy 101 (14 decks)

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