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Flashcards in Med Neuro [Week 1] Deck (142):
1

What sensations is the Dorsal Column/Medial Lemniscus composed of?

1. light touch
-2-point discrimination
-stereognosis
-graphesthesia
2. pressure
3. vibration
4. proprioception (limb position/motion sense)

2

Where are the cell bodies located for the sensory neurons?

Dorsal root ganglia (spinal ganglia)

3

What general things does the somatosensory system sense? (4)

1. Touch - pressure against skin
2. Temp of skin
3. Proprioception
4. Pain

4

Are sensory neurons are apart of the CNS or the PNS?

PNS

5

What are exteroceptive receptors?

Sense external world/skin - mechanoreceptors, thermoreceptors and nociceptors

6

What are proprioceptive receptors?

Sense muscle length, tension, joint angle - muscle, joint and tendon afferents, muscle spindles, golgi tendon organs

7

What are interceptive receptors?

Sense internal organs - visceral afferents and baroreceptors

8

Receptive field

Area in periphery where an adequate stimulus causes a response

9

Can receptive fields overlap?

Yes

10

Spatial summation code

The idea that the signal sent to the spinal cord is a summation of info from multiple neurons firing

11

Rate code

Frequency of AP firing

12

Increasing the diameter of an axon will _________ the conduction velocity.

Increase

13

What information can be determined from a "Compound AP" as a diagnostic tool?

1. Nerve damage, nerve entrapment, trauma
2. Demyelinating diseases i.e. Guillain Barré

14

Where are the cell bodies of the neurons in the DC/ML system?

1st neuron = DRG
2nd neuron = nucleus cuneatus/gracilis (caudal medulla)
3rd neuron = VPL area of thalamus

15

Describe the peripheral and central processes of a 1st neuron in DC/ML system.

-peripheral process = info from mechanoreceptors (free nerve endings or encapsulated nerve endings)
-central process = transmit info from DRG and ASCENDS within IPSILATERAL dorsal columns
[descending branch = reflex pathway]

16

Which neuron in the DC/ML system is involved in decussation to the contralateral side of the body?

2nd neuron at the INTERNAL ARCUATE FIBERS (cross the white matter); the axon ASCENEDS as the medial lemniscus "ribbon"

17

Spatial resolution depends on what 2 things?

1. Receptive field size
2. Innervation density

18

Name the characteristics of the cervical, thoracic, lumbar and sacral SC regions.

1. cervical = has fasciculus gracilis/cuneatus; largest amount of white matter; NO lateral horn
2. thoracic = has fasciculus gracilis; f.c. only above T7; has lateral horn in gray matter (ANS; T1-L2)
3. lumbar = only fasciculus gracilis; large amount of white matters; some lateral horn (ANS; T1-L2)
4. sacral = only fasciculus gracilis; smallest cross-section

19

The fasciculus _____ is more medial and corresponds to sensory of the _______ limbs whereas the fasciculus ______ is more lateral and corresponds to the _____ limbs.

-gracilis
-lower
-cuneatus
-upper

20

Fasciculus gracilis is located medially _______ T7, whereas fasciculus cuneatus is located laterally _____ T7.

-below
-above

21

The _____ separates the fasciculus gracilis from cuneatus.

posterior intermediate septum

22

Define somatotopy.

a map of the body that can be laid out at different spinal levels, depending on the nerve pathway

23

Which mechanoreceptors are slowly adapting?

1. Merkel disks
2. Ruffini corpuscles

24

In the caudal medulla, describe the somatotopy.

"headless, hemisected man standing on a pyramid"
-sacral/lumbar are anterior (on pyramids of medulla)
-thoracic/cervical are posterior

25

In the pons, describe the somatotopy.

hemi-sected man WITH head! (this is where CN V comes in and adds facial sensory information)
-sacral/lumbar are anterior
-thoracic/cervical/head are posterior

26

The VPL receives ____ information while the VPM receives _______ information.

-body sensory
-facial sensory

27

How does the thalamus process sensory information?

NOT a simple relay; decides whether or not to send information
-ex: chased by a tiger, do not want to send pain info from cut on your foot (SNS)

28

In the thalamus (brain), describe the somatotopy.

in a coronal cross-section....
-face/cervical/thoracic more medial
-lumbar/sacral more lateral

29

The axons of the 3rd neurons of the DC/ML system pass through the _______ of the ______ made of white matter.

-posterior limb
-internal capsule

30

Describe what can happen to the thalamus due to a massive MCA stroke.

CONTRALATERAL loss of sensation from the body/head

31

In a coronal cross section of the brain, describe the somatotopy of the S1 cortex.

-feet/genital sensory info most medial
-arms, face most lateral

32

You're sitting Kerrigan listening to a lecture and the room is at a surprisingly comfortable temperature (physiological zero). Are your cooling receptors firing?

Yes at a rate of ~1 Hz

33

In the middle of lecture you suddenly feel very chilly. How are your cooling and warming receptors responding to this?

1. Cooling receptors will fire at an increased rate which will gradually come back down
2. Warming receptors will stop firing and gradually begin again

34

Describe the etiology of POSTERIOR CORD SYNDROME. What disease could cause this as well as trauma?

-lesion in only the posterior (DC/LM) part of spinal cord
-tertiary neuro-syphilis

35

Describe a posterior cervical spinal cord injury.

-loss of light touch, pressure, vibration/proprioception
-other sensory/motor functions INTACT (can feel pain, temperature, and can move!)

36

__________ receptors have a very small RF and infrequent distribution.

Cooling

37

Describe a large central cord lesion

-loss of light touch, pressure, vibration/proprioception
-loss of other sensory/motor functions
-SPARED SACRAL REGION (in genitals)

38

In large central cord lesions, as you increase in SC levels in the cervical spinal cord, there tends to be _____ sacral region sparing because ________.

-more
-sacral fibers tend to be more dorsal

39

A-mechanonociceptors respond to __________________ and are ____________ adapting.

1. Intense force, heat (53˚C)
2. slowly adapting

40

What acute pathology can cause a loss of all sensorimotor information on the contralateral side of a person's body?

medial medullary syndrome = caused an anterior vertebral artery aneurysm

41

Suppose a patient gets a lesion at the base of the corona radiata and another patient gets a lesion at the periphery of the corona radiata. Which is worse? Why?

the base; all fibers from VPL and VPM from the thalamus originate at the base and fan out, like a deck of cards, and eventually innervate the SI cortex; therefore a lesion at the base would affect ALL fibers, whereas a lesion at the periphery would only affect those fibers in that part of the SI cortex

42

Which nociceptor encodes "fast pain" that is easy to localize? i.e. sharp, shooting, electrical pricking pain?

A-mechanonociceptor

43

In the DC/ML system, what are the 4 major Brodmann areas in the SI cortex? Where are they located?

3a = most medial, post-central gyrus lining central sulcus
3b = medial, lining central sulcus
1 = vertex of post-central gyrus
2 = most lateral; part of post-central gyrus lining the post-central sulcus

44

What are the functions of Brodmann areas 3a, 3b, 1 and 2?

3a = limb movement/proprioception
3b = basic tactile information (edges/texture)
1 = motion and direction of movement of objects
2 = limb position; shapes of objects

45

Which nociceptor encodes "slow pain" that is difficult to localize? i.e. long-lasting, burning, aching pain

C polynodal nociceptors

46

Parietal association cortices are located ________. Describe what information they process.

-along intraparietal sulcus
-receive sensory info and project to motor cortex

47

Which area is associated with HAND-EYE COORDINATION/perception?

parietal association cortices = super marginal gyrus, angular, superior parietal lobule

48

Describe a UNIMODAL lesion in the parietal association cortices.

ONE piece of sensory information is lost; i.e visual, auditory, somatosensory

49

What is an agnosia?

inability to recognize an object or a property of an object; due to lesion in parietal association corties

50

Describe a MULTIMODAL lesion in the parietal association cortices.

problem putting together lots of information; ex. combining sensation with motivation, attention, relevance, etc.

51

What is contralateral neglect?

aka hemi-neglect; disregarding information on the contralateral side of the body as the lesion; due to multimodal lesion in the parietal association cortices

52

A right shift on a compound AP implies what?

Slowed conduction velocity

53

A lower peak on a compound AP readout implies what?

Decreased number of neurons

54

Rapidly adapting neurons encode ____________ stimuli.

Changing/dynamic - impact and motion - fires at onset and offset

55

Slowly adapting neurons encode ____________ stimuli.

Static - pressure shape of object

56

Spatial resolution depends on what 2 things?

1. Receptive field size
2. Innervation density

57

What are the 5 types of mechanoreceptors?

1. Merkel disks
2. Meissner's corpuscles
3. Ruffini corpuscles
4. Pacinian corpuscles
5. Hair follicle receptors

58

What two mechanoreceptors are superficial?

1. Merkel disks
2. Meissner's corpuscles

59

What mechanoreceptor allows a blind person to read braille?

Merkel disks

60

What are 5 general characteristics of mechanoreceptors?

1. Respond to touch, pressure and vibration
2. Low threshold
3. Don't respond to painful stimuli
4. Silent w/o stimulation
5. Myelinated axons - fast conduction velocity

61

Which mechanoreceptors are rapidly adapting?

1. Meissner's corpuscles
2. Pacinian corpuscles
3. Hair follicle receptors

62

Which mechanoreceptors are slowly adapting?

1. Merkel disks
2. Ruffini corpuscles

63

Which mechanoreceptors sense high-frequency vibrations like those from a tuning fork?

Pacinian corpuscles

64

Merkel disks

1. Most important for fine touch and 2-point discrimination
2. RF - small, multiple "touch domes"
3. #AP ∝ indentation force

65

Meissner's Corpuscles

1. Sense abrupt change in edges and bumps
2. In glabrous skin only
3. Single receptive spot - high density
4. #AP ∝ # of times skin is indented (50 Hz ideal sensing freq)

66

Glabrous skin

Palms, bottoms of feet, lips

67

Ruffini corpuscles

Sense stretch of skin and gravity against it
2. RF - large and diffuse
3. Determines shape of grasped object
4. Axon surrounds collagen fibrils

68

Pacinian corpuscles

1. Detect tiny, high freq vibrations (~300Hz)
2. Extremely sensitive
3. RF - large and diffuse
4. Large fluid-filled capsule around bare nerve ending

69

Hair follicle receptors

1. Encode velocity of hair
2. Wrap around base of hair follicle
3.

70

Do thermoreceptors detect painfully hot temperatures?

No

71

You're sitting Kerrigan listening to a lecture and the room is at a surprisingly comfortable temperature (physiological zero). Are your cooling receptors firing?

Yes at a rate of ~1 Hz

72

In the middle of lecture you suddenly feel very chilly. How are your cooling and warming receptors responding to this?

1. Cooling receptors will fire at an increased rate which will gradually come back down
2. Warming receptors will stop firing and gradually begin again

73

Cooling receptors have a _____ nerve ending and are _________ myelinated.

1. Free
2. Thinly

74

Warming receptors have a ______ nerve ending and are __________ myelinated.

1. Free
2. "Un"myelinated - C fiber

75

__________ receptors have a very small RF and infrequent distribution.

Cooling

76

Warming receptors have a __________ RF.

Very small

77

70% of all sensory neurons are _______________.

Nociceptors

78

A-mechanonociceptors respond to __________________ and are ____________ adapting.

1. Intense force, heat
2. slowly adapting

79

Are A-mechanonociceptors myelinated?

Yes they have a free nerve ending and the axon is myelinated Aδ

80

Which nociceptor is accessible to inflammatory chemicals?

C polymodal nociceptors

81

Which nociceptor encodes "fast pain" i.e. sharp, shooting, electrical pricking pain?

A-mechanonociceptor

82

Are C Polymodal nociceptors myelinated?

No - they also have free nerve endings

83

C Polymodal nociceptors have ____________, respond to __________________, and are ____________ adapting.

1. Many nodes
2. Intense force and high heat >45˚C
3. Slowly adapting

84

Which nociceptor encodes "slow pain" i.e. long-lasting, burning, aching pain

C polynodal nociceptors

85

What is the #1 cause of chronic pain in the US?

chronic back pain

86

About _____ of Americans (all ages) suffer from chronic pain.

50%

87

Name 2 characteristics that can cause two different people to feel pain stimuli differently.

1. different genetics: receptor densities, nociceptor thresholds, density of innervation, pain pathway projections, descending control (inhibitory pathways), CNS modulation
2. different past experiences, cultures, mental status, anxiety, fear

88

Define pain.

a complex, cognitive perception of a noxious (painful) stimulus; highly individualized (brain's interpretation)

89

Pain is easy to treat. (T/F)

false; pain is complex and very difficult to treat clinically

90

Define anesthesia.

lack of ALL sensation

91

Define analgesia.

lack of pain (touch/vibration/proprioception in tact = dorsal column)

92

Define athermia.

lack of thermal sensation for cooling/warming

93

Define hypoalgesia.

DECREASED sensitivity to pain

94

Define hyperesthesia.

HEIGHTENED sensitivity to ANY stimulus (pain/touch/etc.)

95

Define paresthesia.

unpleasant, abnormal sensation = "pins and needles"

96

Define pruritus.

itching; can be side effect of opiods

97

Define hyperalgesia.

INCREASED pain from normally painful stimulus

98

Define allodynia. Give an example of pathology that will cause this.

pain from normally non-painful stimulus; ex) Shingles = wind/light touch can be painful

99

What is the major difference between acute and chronic pain?

acute pain has a critical protective function for withdrawal whereas chronic pain has no useful purpose

100

Name two types of congenital insensitivity to pain and what problems can occur.

1. mutation in NGF causes lack of pain receptor expression
2. nociceptors are present but the Na+ gated channel has a mutation that prevents an excitatory signaling response; therefore it can detect a stimulus but cannot propagate an AP
-Problems: very short lifespan, multiple, continuous injuries

101

Which bacterium causes leprosy and what does this cause clinically?

Mycobacterium leprae; eats away pain receptors/skin so that patients cannot feel acute pain (rats eating off digits)

102

Chronic pain is not caused by an obvious tissue injury. (T/F)

True; it can be after healing-->NEUROPATHIC

103

Name a common diagnosis that is affiliated with chronic pain.

fibromyalgia (hard to diagnose because of absence of obvious injury)

104

What causes NOCICEPTIVE PAIN?

soft tissue damage/inflammation; activation of nociceptor terminals in the skin due to cytokines and immune cells in bloodstream

105

What do cytokines bind to on a nociceptor during soft tissue damage?

free nerve endings of C fibers

106

How do cytokines normally sensitize nociceptors?

they lower the threshold of AP (therefore more pain firing!)

107

How do NSAIDS treat nociceptive/inflammatory pain?

block the synthesis of prostaglandins from arachidonic acid (a stimulator of pain)

108

What causes NEUROPATHIC PAIN? How does this present clinically?

when there is a DIRECT damage to nerves in the PNS/CNS (cut, compression, ischemia, etc.); has a burning, sharp, electrical quality and can result in allodynia, clinically

109

What are some diagnostic examples of neuropathic pain and what can you use to treat it?

-post-herpetic neuralgia (after shingles, light touch), diabetic neuropathy (ischemic neurons), severe nerve entrapment
-Tx = antidepressants/anti-anxiety meds [CANNOT USE NSAIDS/opioids]

110

You can use NSAIDS/opioids to treat neuropathic pain. (T/F)

FALSE! can only use antidepressants/anti-anxiety meds

111

What characterizes the ANTEROLATERAL SYSTEM?

1. ascending tracts of fibers
2. pain/temperature sensory information to cortex
3. more complex than DC/ML system because of the many pathways and many termination points in the brain

112

How would you characterize a lesion to the anterolateral pathway?

loss of pain/temperature sensation BELOW the lesion (fine discrimination/vibration/proprioception is intact)

113

Which receptors are stimulated for noxious mechanical, thermal and chemical stimuli (AL)?

free ending of:
1. A-delta (lightly myelinated) fibers
2. C-fibers (unmyelinated)

114

Describe A-delta free nerve endings.

-mediates first pain (REFLEX)
-fast, sharp, pricking, short-lasting, protective response, escape damage
-lightly myelinated

115

Describe C-fiber free nerve endings.

-mediates second pain response
-delayed, burning quality, long-lasting, CHRONIC
-unmyelinated

116

Temperature stimuli provide __________ sensory information in the AL system.

non-painful cooling/warming

117

Where do the central processes of the nociceptor neurons in the AL system go? Where does it synapse?

-enters the lateral dorsal horn via DORSAL LATERAL TRACT of LISSAUER (dorsolateral sulcus)
-synapses on the SC neurons in the superficial dorsal horn (Lamina I, II or V)

118

Nociceptors release _____ and _____ which activate receptors on spinal neurons.

glutamate; substance P

119

Describe the path and synapse of the 2nd neuron of the AL system.

2nd order neurons send axons to CONTRALATERAL side of SC within 2-3 segments rostrally

120

Suppose there was an AL lesion in the SC, how would the patient present clinically?

loss of pain/temperature BELOW lesion on the CONTRALATERAL side **loss is complete by 2-3 segments below the lesion!!

121

What happens with ANTERIOR CORD SYNDROME?

you get loss of pain/temperature BILATERALLY (motor/light touch are in tact if DC spared); due to loss of blood supply/artery compression, bone fragment or disk herniation

122

What is a common cause of anterior cord syndrome?

rupture of anterior spinal artery

123

Suppose a patient has a CENTRAL CORD SYNDROME in the C3-T4 area. How would this present clinically?

because the area of the cervical lesion has the most white matter, usually the DC is spared if the lesion is small and therefore there is a loss of pin prick and temperature but remaining vibration/joint position/light touch

124

What are some causes of central cord syndrome?

syringomyelia (cavity/cysts in center of spinal cord), hyperextension trauma (diving accident), tumors, congenital; (cuts crossing axons in spinal cord)

125

What are the 3 major AL pathways and where do they terminate in the CNS?

1. spinothalamic tract = thalamus
2. spinoreticular tract = reticular formation (medulla/pons)
3. spinomesencephalic tract = mesencephalon (midbrain)

126

Describe some characteristics of the SPINOTHALAMIC secondary order neuron tract.

-most prominent pain pathway
-mediates DISCRIMINATIVE aspects of pain/temperature sense (location/intensity/duration)

127

From the thalamus, describe specifically where 2rd order neuronal axons terminate (spinothalamic tract).

1. VPL = pain information from body
2. Central Lateral Nucleus (CL) = emotional suffering

128

From the VPL (spinothalamic tract neurons), describe specifically where 3rd order neuronal axons terminate.

SI cortex (areas 3b, 1, 2); to relay DISCRIMINATIVE pain information from body; localization of noxious stimulus

129

Both spinothalamic tract and DC/ML inputs go to the VPL and synapse on the same neurons.

FALSE! they both do go to VPL, but synapse on DIFFERENT neurons

130

From the CL (spinothalamic tract neurons), describe specifically where 3rd order neuronal axons terminate.

project to areas of cortex and limbic cortex (cingulate gyrus, hippocampus, amygdala); emotional suffering during CHRONIC PAIN and MEMORY of painful events

131

In the spinothalamic tract, 3rd order neurons terminate in _______, an area in the cortex with somatotopy, and _______, an area in the cortex without somatotopy.

-VPL
-CL

132

What are the functions of the thalamus in pain?

1. process nociceptive information (begin emotional suffering/crude pain/temp sensation)
2. relay information to SI cortex (and eventually SII) via posterior limb of internal capsule and corona radiata

133

Describe some characteristics of the SPINORETICULAR secondary order neuron tract.

-most terminate in medulla/pons while some terminate in thalamus/cortex
-mediates changes in level of ATTENTION to painful stimuli
-emotional, arousal, attention, affective response to noxious stimulus

134

Describe some characteristics of the SPINOMESENCEPHALIC secondary order neuron tract.

-terminate in midbrain in PERIAQUEDUCTAL GRAY (PAG) where some neurons (3rd order) send axons back down the spinal cord (DESCENDING) to inhibit pain response

135

You feel something SHARP on the LEFT side of your hand. Which AL tract is working?

spinothalamic tract (discrimination)

136

You know that something is hurting you--ouch! Which AL tract is working?

spinoreticular tract (attention, arousal, affect)

137

You remove your hand from a sharp surface an immediately feel better. Which AL tract is working?

spinomesencephalic tract (negative inhibition for pain-->pain relief)

138

Which type of neurons from which neuron system projects to the insular cortex. What does it process?

AL spinothalamic tract neurons; processes internal, autonomic state of the body and integrates discriminative/affective/efmotional/cognitive components of pain

139

A patient accidentally got wacked in the face with a rigging rope. He knows it hurts but doesn't care. This patient has a lesion in his brain--where is it?

insular cortex! asymbolia for pain (emotional response is inappropriate despite feeling pain)

140

What endogenous ligand can activate the spinomesencephalic tract? Exogenous ligand?

-endorphins
-opioids
[pain relief]

141

Describe the path of the neurons with cell bodies in PAG (midbrain) to the cortex.

1. send axons either to RAPHE nuclei (medulla) or LOCUS CERULEUS (pons)
2. axons sent to spinal cord and synapse on inhibitory interneurons
3. inhibitory interneurons send inhibitory signals on SPINOTHALAMIC tract neurons
4. less stimulus in thalamus for pain/less perception of pain in the cortex

142

What is referred pain? Why does it occur?

visceral pain that is perceived in somatic areas (skin/muscle); it occurs with dermatome that corresponds to spinal segment that also receives afferent input from a specific visceral organ because visceral nociceptors/somatic nociceptors SYNAPSE ONTO SAME SECOND ORDER SPINOTHALAMIC TRACT NEURONS (interneurons)