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A&P 2024 > Lecture 13: Spinal cord internal structures > Flashcards

Lecture 13: Spinal cord internal structures Flashcards

Exam 3

1
Q

a bundle of axons within the CNS

A

Tract

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2
Q

a bundle of axons within the PNS

A

Nerve

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3
Q

Name the 5 spinal tracts. Which are ascending vs descending?

A

Ascending:
Dorsal-Column Medial Lemniscal System
Spinocerebellar Tract(s)
Spinothalamic Tract(s)/anterolateral system
Descending:
Corticospinal Tracts: “Pyramidal Tracts”
“Extrapyramidal” Tracts

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4
Q

Which spinal tract is responsible for sensing pressure? Where is it located in the cord?

A

Dorsal-Column Medial Lemniscal (DCML) System
- sits in dorsal part of cord and passes through the medial lemniscus in the brainstem

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5
Q

Which spinal tract is responsible for sending sensory info from the spinal cord to the cerebellum? Where is it located in the cord?

A

Spinocerebellar Tract(s)
Lateral - anterior and posterior

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6
Q

Which spinal tract is responsible for pain? Where is it located in the cord?

A

Spinothalamic Tract(s)/anterolateral system - front/sides of cord

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7
Q

Which spinal tract is responsible for motor function that we think about? Where is it located in the cord?

A

Corticospinal Tracts: “Pyramidal Tracts” - lateral/posterior of cord

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8
Q

Which spinal tract is responsible for coordinating complex movements that we don’t think about? Where is it located in the cord?

A

Extrapyramidal” Tracts - front of the cord

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9
Q

How is the grey matter in the cord divided?

A

Rexed’s Laminae: numbered back to front, 10 in total

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10
Q

Lamina I

A

Lamina Marginalis
- Sharp Pain - fast pain
- Aδ Pain - myelinated nociceptors (a delta fibers)

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11
Q

Laminae II & III

A

Substantia Gelatinosa - also sometimes lamina V
- Slow Pain
- C-Fibers - non-myelinated nociceptors

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12
Q

Which lamina are mechanoreceptors?

A

Laminae I→ VI

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13
Q

Lamina VII

A

Intermediolateral Nucleus
- Lateral Grey Horn

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14
Q

Laminae VIII → IX

A

Lots of large motor neurons that hang out in the anterior horn of grey matter in the cord - descending

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15
Q

_______ allows signals to cross to the other side of the cord in the grey matter, while _________ allows signals to cross to the other side of the cord in the white matter

A

Lamina X
Anterior white commissure

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16
Q

_______ is responsible for sending info in the grey matter of the cord, while ______ is responsible for sending info in the white matter of the cord

A

Rexed laminae
Spinal tracts

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17
Q

Efferent vs afferent

A

Afferent is sensory, going up to brain
Efferent is motor

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18
Q

What are the two parts of the DCML pathway? Where are they located in the spinal cord?

A

Fasciculus Gracilis: Sensory signals from lower parts of the body - posterior/medial dorsal column
Fasciculus Cuneatus: Sensory signals from upper parts of the body - lateral dorsal column

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19
Q

Describe the pathway through the brainstem for the DCML pathway

A

Pathway through brainstem: X-over at medulla (lower part of brainstem) → medial lemniscus (pons) → thalamus (ventrobasal complex) → internal capsule → parietal lobe (post-central gyrus/sensory cortex)

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20
Q

What are the two pathways the DCML sensory info can take?

A

Grey matter of cord (lateral inhibition)
Up towards the brain in the dorsal columns

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21
Q

What is the name of the parietal lobe, post-central gyrus - topographical layout?

A

Homunculus

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22
Q

Which areas of the homunculus take up the most space? Describe where they are located

A

Hands (middle) and face (lateral)

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23
Q

What are the 3 pathways of the corticospinal (pyramidal) tracts? How much motor function are they responsible for?

A

Primary - 80% - lateral
Secondary - 17% - anterior
Tertiary - 2-3% - lateral

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24
Q

Describe the pathway the primary corticospinal (pyramidal) tract takes

A

Cortex (motor/frontal lobe) → Internal Capsule → Pyramids of Medulla (brainstem) → X-over (pyramidal decussation)→ Lateral Corticospinal Tracts (originated in motor cortex and descends through the spinal cord) → anterior horn of spinal cord - excites motor neuron associated with it

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25
Q

Describe the pathway the secondary corticospinal (pyramidal) tract takes

A

Same as primary except x-over in the spinal cord at the level of the motor neuron it needs to talk to in the anterior horn
Cortex (motor/frontal lobe) → Internal Capsule → Pyramids of Medulla (brainstem) → Lateral Corticospinal Tracts (originated in motor cortex and descends through the spinal cord) → anterior horn of spinal cord (x-over) - excites motor neuron associated with it

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26
Q

Describe the pathway the tertiary corticospinal (pyramidal) tract takes

A

Same as other pathways 1 and 2 except no cross over

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27
Q

Describe the location where the primary corticospinal (pyramidal) tract crosses over

A

Pyramidal decussation - cross-hatch pattern in the pyramids of the medulla
Aligns with the anterior median fissure

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28
Q

What are the two main divisions of the spinothalamic tract? What is another name for this tract?

A

AKA Anterolateral - slow pain (anterior) and fast pain (lateral)

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29
Q

Differentiate between the myelination of the neurons in the fast vs slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Fast: Nociceptors - free nerve endings; A delta fibers
Slow: C fibers - unmyelinated

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30
Q

Differentiate between the neurotransmitters in the fast vs slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Fast: glutamate
Slow: substance P (main), CGRP (calcitonin G-related peptide), glutamate (less common, works slower than the glutamate in the fast pain pathway)

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31
Q

Differentiate between the localization of the fast vs slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Fast: Detailed localization - sent through the thalamus to parietal lobe
Slow: Poor localization - reticular formation (brainstem), not much makes it to the thalamus

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32
Q

Differentiate between the laminae of the fast vs slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Fast: lamina I - Lamina Marginalis
Slow: Laminae II & III (Substantia Gelatinosa), then V

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33
Q

Differentiate between the sites of x-over of the fast vs slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Both x-over in the anterior white commissure

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34
Q

The slow pain pathway is more ______ than the fast pain pathway

A

Emotional

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35
Q

What are the sensors in the slow pain pathway?

A
  • Thermoreceptors/heat
  • Vibration/Irritant Sensors: Tickle and Itch
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36
Q

What are the other names for the fast and slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Fast - “Neospinothalamic Tract” - newer, more sophisticated
Slow - “Paleospinothalamic Tract” - paleo = old

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37
Q

Differentiate between the site of termination of the fast vs slow pain pathways of the Spinothalamic/Anterolateral Tracts

A

Fast: Ascends to thalamus, Ventrobasal Complex (w/DCML sensory info) & Posterior Nuclear Group
Slow: Reticular Nuclei: Medulla, Pons, Mesencephalon

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38
Q

Name the 4 extrapyramidal tracts

A

Vestibulospinal, Olivospinal, Reticulospinal, Rubrospinal

39
Q

Which extrapyramidal tract is responsible for balance?

A

Vestibulospinal: Eye fixation, muscle orientation during acceleration

40
Q

Which extrapyramidal tract is responsible for cerebellar output to coordinate movement?

A

Olivospinal

41
Q

Which extrapyramidal tract is responsible for the maintenance of muscle tone?

A

Reticulospinal

42
Q

Which extrapyramidal tract is responsible for the modulation of voluntary movement?

A

Rubrospinal - similar to cerebellum tracts, in charge of monitoring and adjusting voluntary movements

43
Q

What are the 3 parts of the Descending Pain Suppression System or Descending Inhibitory Complex (DIC)?

A

Periventricular & Periaqueductal Grey
Raphe Nucleus
Dorsal Spinal Cord Complex

44
Q

Where does the first neuron of the DIC begin from?

A

Either the Periventricular nuclei or the periaqueducatal grey

45
Q

What does the first neuron of the DIC release? Into where?

A

Releases enkephalins when excited in the middle of the pons (raphe magnus nucleus (RMN) → excites second-order descending neuron (raphe nucleus)

46
Q

What neurotransmitter does the raphe nucleus release? What structure does it release into?

A

Serotonin into the white matter before the dorsal horn

47
Q

Which neurotransmitters does the dorsal spinal cord complex release? What structure does it release into?

A

Serotonin & Enkephalin
Enkephalin is released to enkephalin receptors located on nociceptors and the next neuron in the ascending pain pathway

48
Q

Enkephalin is an _______ neurotransmitter in the cord

A

inhibitory

49
Q

_______ is the morphine analog of the endogenous opiate system

A

Enkephalin

50
Q

Dorsal Spinal Cord Complex releases enkephalins into the _____ matter of the spinal cord

A

grey

51
Q

Why do patients in need of dialysis have more pain?

A

increased H+, K+

52
Q

What can increase the pain sensation?

A

ACh, K+, H+, PGs, 5-HT, histamines (inflammation), bradykinins, ischemia

53
Q

Why are SSRIs and TCAs of use for chronic pain?

A

SSRIs - inhibit reuptake of 5-HT → more 5-HT in synapse → 3rd order inhibitory neuron
TCAs - increase 5-HT in the synapse and have the side effect of drowsiness, can help chronic pain patients sleep better

54
Q

________ a neural process that reduces the activity of neighboring neurons when one neuron is excited

A

Lateral inhibition - Pressure signal can inhibit pain signal (injury to hand - grab hand and squeeze - suppresses pain) - acupuncture

55
Q

How far does lateral inhibition work?

A

Doesn’t go further than dorsal horn in cord

56
Q

What are the types of glutamate recepotors?

A
  1. Ionotropic: AMPA-R, NDMA-R, kainate
  2. Metabotropic - GPCRs + ion channels
57
Q

______ is the main neurotransmitter for the pain system

A

Glutamate

58
Q

Glutamate is always ______

A

excitatory

59
Q

The primary glutamate receptor is the ______ receptor

A

AMPA

60
Q

The NMDA receptor is ____ and _____ than AMPA

A

slower and bigger

61
Q

The AMPA receptor allows ____ into the cell

A

Na+

62
Q

The NMDA receptor allows ____ into the cell

A

Ca++ (mostly) and Na+

63
Q

What is the NMDA receptor blocked by? How is it removed?

A

Intracellular Mg++ at rest → depolarization pushes Mg++ out of the way

64
Q

NMDA-R are added as we _____

A

Grow - don’t have a lot when born

65
Q

Things that can block NMDA-R

A

EtOH, lead, ketamine (doesn’t work on AMPA-R), nitrous, tramadol (not great a great narcotic, more of an SSRI and inhibits NMDA-R but not AMPA-R)

66
Q

Chronic pain causes______ population of pain receptors

A

higher - NMDA and AMPA

67
Q

Where in the cerebellum do the spinocerebellar tracts end?

A

anterior - superior cerebellar peduncle
posterior - inferior cerebellar peduncle

68
Q

What is the difference between anterior and posterior spinocerebellar tracts?

A
  • Anterior (ventral) - sends synaptic activity occurring in the anterior horn to cerebellum (superior cerebellar peduncle)
  • Posterior (dorsal) - sends information about tendons (golgi tendon reflex) and muscle spindle (stretch sensors in skeletal muscles) to lower parts of cerebellum (inferior cerebellar peduncle)
69
Q

______ pain is connective tissue pain from peritoneum, pleura, or pericardium

A

parietal

70
Q

_____ pain is internal organ pain via autonomic nerve bundles

A

visceral

71
Q

parietal pain is ______ localized, while visceral pain is _____ localized

A

highly; poorly

72
Q

parietal pain has type ____ fibers, while visceral pain has type ___ fibers

A

A; C

73
Q

Name two organs that don’t have pain sensors

A

brain and liver

74
Q

________ pain is pain felt in a part of the body that is fairly remote from the tissue causing the pain.

A

Referred

75
Q

Name two examples of referred pain

A
  • heart pain radiates down L arm
  • kidneys - lower back
76
Q

Dual pain =

A

parietal + visceral pain

77
Q

Why does the L arm have pain for heart ischemia?

A

Because L side of heart more prone to ischemia than R

78
Q

How does a burst appendix have dual pain?

A

parietal = tissues surrounding appendix (sharp, stabbing pain from RLQ) - autonomic ganglia and ascends 2-3 levels, then enters cord
visceral = felt in umbilical region (T10); pain fibers routed through sympathetic chain

79
Q

What type of pain can’t be suppressed by lateral inhibition? Why?

A

visceral - because not routed the same way as other pain

80
Q

______ is the ease or difficulty of eliciting a painful feeling; the point at which someone identifies pain

A

pain threshold

81
Q

Another name for lateral inhibition

A

pain of decompresison

82
Q

Where does slow pain terminate in the brain?

A

slow pain projected to brain stem and end (reticular formation) or make it up further (but not to parietal lobe) → limbic system right above brainstem - amygdala

83
Q

What are the 3 parts of the limbic system?

A

amygdala + hypthalamus + cingulate gyrus
- deeper than fast pain

84
Q

Where is the cingulate gyrus located?

A

outside of corpus callosum; part of cerebral cortex

85
Q

if there’s going to be one of these cerebral cortex structures that is connected to the slow pain system, it’s going to be the _____

A

cingulate gyrus

86
Q

What nerve fibers are a part of the more primitive, autonomic nervous system?

A

B and C fibers (less myelinated)

87
Q

motor neurons are ____ fibers

A

A alpha

88
Q

muscle spindles and tendons are ____ fibers

A

A alpha

89
Q

The DCML pathway uses ____ fibers

A

A alpha - A gamma

90
Q

lateral inhibition is ____ fibers

A

A beta

91
Q

crude pain travels via ____ fibers

A

C

92
Q

Order of sensing pain

A

pressure → sharp pain → dull, achy pain (probably worst long-term because of emotional response)

93
Q

How does tramadol treat pain?

A
  • SSRI
  • NMDA-R blocker
    not great for treating pain
94
Q

What does kainate do?

A

mediate GABA

A&P 2024 (19 decks)

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