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Regional > Neuropathways > Flashcards

Neuropathways Flashcards

1
Q

describe a common unmyelinated nerve fiber

A

isolated axons are surounded by a schwann cell ad each axon has its own mesaxon

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2
Q

what is a mesaxon?

A

an opening for electricity to reach the nerve fiber

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3
Q

what is a node of ranvier?

A

pinch points in myelinated nerve fibers

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4
Q

what is saltatory conduction?

A

conduction that jumps from node to node

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5
Q

what is the epineurium?

A

dense connective tissue rich in collagen fibers and fibroblasts (outermost)

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6
Q

what is the perineurium?

A

several layers of flat cells tightly joined together to form a barrier to the penetration of the nerve by macromolecules (middle)

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7
Q

what is the endoneurium?

A

composed mainly of reticular fibers synthesized by schwann cells. (inner)

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8
Q

which fibers are myelinated?

A

A and B

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9
Q

Which fiber is fast, sharp well localized sensation?

A

A delta

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10
Q

What fibers are unmyelinated?

A

C fibers.

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11
Q

describe A alpha fiber

A

proprioception and motor
15 micrometers
100m/s conduction

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12
Q

describe A beta fibers

A

touch, pressure
10 micrometers
50 m/s conduction

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13
Q

describe A gamma fibers

A

muscle spindles
5 micrometers
25 m/s conduction

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14
Q

describe A delta fibers

A

pain (sharp), temperature
<5 micrometers
25 m/s conduction

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15
Q

Describe B fibers

A

preganglionic, autonomic
<3 micrometers
10 m/s conduction

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16
Q

Describe C dorsal root fibers

A

pain (dull) temperature
1 micrometers
1 m/s conduction

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17
Q

Describe C sympathetic fibers

A

postganglionic
1 micrometers
>1 m/s conduction

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18
Q

what is transduction?

A

noxious stimuli is translated into electrical activity at the sensory ending of nerves

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19
Q

what is transmission?

A

propagation of impulses thoughout the sensory nervous system

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20
Q

what is modulation?

A

efferent control of pain

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21
Q

pain fibers in the head are carried by?

A

trigeminal (V), facial (VII), glossopharyngeal (IX), and vagal (X)

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22
Q

what are first order neurons?

A

in the ganglia reach the spinal cord and synapse with the second order neuron

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23
Q

second order neurons

A

spinal cord gray matter divided into 10 lamina
I-VI dorsal horn
-receives all afferent neural activity
-represents the principle site for modulation of pain

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24
Q

lamina 1

A

responds to nocioceptive stimuli from cutaneous and deep somatic tissues

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25
Q

lamina 2 and 3

A

sunstantia gelatinosa

  • containes many interneurons responsible for processing and modulation nocioceptive input from cutaneous tissue
  • major site of action for opioids
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26
Q

lamina 1 and 5

A

contains visceral afferents

27
Q

lamina 5

A
  • responds to both noxious and non noxious stimuli

- receives both somatic an visceral inputs

28
Q

spinothalmic tract

A

cross the midline to the level of the origin to the contralateral side of the spinal cord
-divided into lateral and medial

29
Q

lateral spinothalmic tract

A

projects location, density, and duration of pain in the ventral posteriorlateral nucleus of the thalamus

30
Q

medial spinothalmic tract

A

projects unpleasant emotional perception of pain in the medial thalamus

31
Q

third order neurons

A

information transferred up to the thalamus

impulses then carried on the somatosensory cortex

32
Q

modulation of pain

A

impulses arise in the periventricular/periaquaductal gray matter of brainstem
-impulses are transmitted through the raphe magnus to the substantia gelatinosa by way of the descending dorsolateral funiculus

33
Q

enkelphins, substance P and pain

A

action potantials arriving at the substantia gelatinosa activate enkaphalin interneurons

  • release of enkephalin decreases the release of substance P
  • reduction in the number of pain impulses ascending in the lateral spinothalamic tract
  • action potentials descending in the dorsolateral funiculus also hyperpolarize cell bodies of the second order neurons in the pain pathway
  • reduction in the number of action potentials in the ascending lateral spinothalamic tract. The descending dorsolateral modulates pain
34
Q

medication and pain

A
  • IV opioids produce analgesia in part y initiating action potentials in the descending dorsolateral funiculus
  • spinal analgenia, mediated by mu-2 receptors, occur when the number of pain impulses passing through the substantia gelatinosa is decreased
  • IV opioids act in other sites in the brain (limbic, hypothalamus, and thalamus) produce supraspinal analgesia is mediated primarily by mu-1 receptors
  • opioids act in complex fashion to decrease the perception of pain and decrease the response to pain
35
Q

spinalreticular pain pathway

A

arousal and autonomic responses to pain

36
Q

spinalmesencephalic pathway

A

anti-nocioceptive descending pathway because of its projections in the periductal gray area

37
Q

pathway of fast-sharp pain

A
  • A delta fibers enter and leave the tract of lissauer
  • they then enter the dorsal horn and terminate at Rexed’s lamina 1, 5
  • second order neurons leaving lamina 1 or 5 cross to the contralateral lateral spinothalamic tract and ascend to the brain
38
Q

pathway of slow pain

A

the C fibers terminate primarily in lamina 2 (and 3) (substantia gelatinosa)
interneirons transmit C fiber impulses to lamina 5
neurons leaving 5 cross immediately to the contralateral lateral spinothalimic tract and ascend to the brain

39
Q

primary neurotransmitters

A

A delta-glutamate
-binds to AMPA receptors on the postsynaptic membrane
C-fiber Substance P
-binds to NK-1 receptors on the postsynaptic membrane

40
Q

tissue specific neurotransmitters

A

seratonin, histamine, prostaglandins, H+, K+

- arachidonic acid cascade

41
Q

plasma specific neurotransmitters

A

kinins, histamine (platelets, basophils, granules of mast cells)

42
Q

nerve terminal specific neurotransmitter

A

substance P

43
Q

somatic pain

A

aching, often constant, possible dull or sharp, exacerbated with movement, well localized

44
Q

visceral pain

A

constant/crampy, aching, poorly localized, referred

45
Q

A-delta high threshold mechanoreceptors (HTMs)

A

noxious mechanical stimuli

46
Q

A delta myelinated mechanothermal nocioceptors (MMTNs)

A

noxious heat and mechanical stimuli

47
Q

C polymodal nocioceptors (CPNs)

A

noxious mechanical, thermal, chemical stimuli

muscle jints, faciae, other deep somatic structures C (group 4), A-delta (group 3) fibers

48
Q

C afferent fibers, A-delta fibers

visceral

A

disease, inflammation, isometric contraction, ischemia, rapid distention
activated by noxious stimuli and allogenic substances
act as transducers
conducted to the dorsal horn or medulla
-influenced by intensity, duration, and microenvironment

49
Q

muscle- skeletal/ cardiac transmission

A
  • innervated by A delta and C fibers pain described as diffuse, poorly localized
  • most intense during contraction, ischemia
  • nocioceptors undergo sensitization in response to allogenic agents
50
Q

Joint transmission

A
  • innervated by A delta and C fibers
  • respond only to extreme joint movement/ pressure
  • can become sensitized with inflammation, leading to activation with normal movement, or developing background discharge
51
Q

bone transmission

A

A delta and c fibers form a plexus around periosteum. Cortex/ marrow has no nocioceptive fibers has lowest threshold of deep somatic structures

52
Q

visceral tissue transmission

A

A delta fibers, C fibers, not part of ANS

  • insensitive to cutting, heating, pinching
  • sensitive to twisting, distention
53
Q

order of block

A

B, C and A delta, A gamma, A beta, A alpha

54
Q

A alpha fibers A or E?

A

afferent and efferent fibers

55
Q

A beta fibers A or E?

A

afferent and efferent fibers

56
Q

A gamma fibers A or E?

A

efferent fibers

57
Q

A delta fibers A or E?

A

afferent fibers

58
Q

B fibers A or E?

A

efferent

59
Q

C fibers A or E?

A

afferent

60
Q

what does preganglionic autonomic mean?

A

from spinal cord to ganglion

61
Q

Dorsal- afferent or efferent

A

afferent

62
Q

ventral- afferent or efferent

A

efferent

63
Q

what is the tract of lissaur

A

tract that carries signals a few levels up and down spine

64
Q

if you stimulate enkelphalin receptors

A

with pain meds you stop the release of substance P

Regional (24 decks)

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