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BDS1 > Locomotor - Dr Hughes > Flashcards

Locomotor - Dr Hughes Flashcards

1
Q

Describe the structure of a sensory nerve cell

A

Pseudounipolar Neuron:
Cluster or peripheral nerve branches with nerve receptor ending at peripheral ending
Single axon from cell body, which bifurcates
Axon terminus in CNS

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2
Q

Name the sensory receptors (8)

A

mechanical, sound - Mechanoreceptor - touch and hearing
chemical - Chemoreceptor - smell, taste
noxious - Nociceptor - pain
limb position - Proprioceptor - spatial awareness
blood pressure - Baroreceptor
light - Photoreceptor - sight, vision
thermal - Thermoreceptor - hot, cold

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3
Q

What is a receptive field?

A
  • Each neuron, has a cluster of peripheral nerve branches, each with a nerve ending
  • the distribution of these receptors defines a receptive field
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4
Q

Where has a larger receptive field?

A

Trunk

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5
Q

Where has a small receptive field

A

Periphery, tip of fingers

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6
Q

What is two point discrimination a measure of?

A

1) Spatial resolution

2) Size of receptive field

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7
Q

What would a small 2-point discrimination indicate?

A

1) Large cortical representation

2) Small receptive field

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8
Q

*Describe the transduction of sensory stimuli

A 
Stimuli ->
Change in receptor membrane permeability ->
influx of cations->
Depolarization: receptor potential ->
AP
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9
Q

Describes transduction of stimuli in mechanoreceptors

A

Mechanical force ->
Deformation of cell membrane ->
Causing opening of channel (via strand/tether ?) ->
Movement of Na+/K- through channel

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10
Q

How are chemoreceptors activated?

A

1) via ionotropic (ligand-gated ion channels) - fast

2) via G-protein coupled channels - slows

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11
Q

How is sensory information coded?

A

Stimulus Coding
Quality Type of receptors
Intensity Frequency of AP (diff. thresholds)
Number of neurons activated
Duration Duration of AP firing - kick to shin
Location Where - homunculus

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12
Q

Why type of axon do proprioceptors of skeletal muscles use?

A

Aα

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13
Q

What type of axons do mechanoreceptors of skin use?

A

Aβ

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14
Q

What type of axons do pain and temperature receptors use?

A

Aδ

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15
Q

What type of axons do temperature, pain and itch receptors use?

A

C

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16
Q

In the neural pathway, what are receptors?

A

peripheral endings of sensory neurons

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17
Q

Give examples of modality specific pathways

A

touch, pain, vision

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18
Q

Where do pathways terminate in the brain?

A

Primary receiving areas

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19
Q

How many spinal nerves are there?

A

31 pairs

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20
Q

Give examples of cutaneous and subcutaneous mechanoreceptors (Aβ afferents) (5)

A 
Meissner's corpuscle
Merkel disk
Hair follicle receptor
Pacinian corpuscle (vibration and slippage)
Ruffini's ending (same)
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21
Q

What type of innervation does a peripheral nerve have?

A
  • Sensory only axons and

- Motor and sensory axons

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22
Q

What does the Brachial Plexus innervate? (5)

A

The upper limb (C5, C6, C7, C8, T1)

  1. Axillary
  2. Musculocutaneous
  3. Radial
  4. Ulna
  5. Median
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23
Q

What is the outer layer of a peripheral nerve called

A

Epineurium

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24
Q

What is a bundle of nerves called?

A

Fascicle (Fasciculi)

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25
Q

In a peripheral nerve, what are the sections surrounding the fascicle called

A

Perineurium

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26
Q

Other then axons, what else might the peripheral nerve contain?

A

Blood vessels

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27
Q

What is the diameter and speed of the Aα axon?

A

13 - 20 µm

80 - 120 m/sec

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28
Q

What is the diameter and speed of the Aβ axon

A

6- 12 µm

35 - 75 m/sec

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29
Q

What is the diameter and speed of the Aδ axon

A

1 - 5 µm

5 - 30 m/sec

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30
Q

What is the diameter and speed of the C axon

A
  1. 2 - 1.5µm

0. 5 - 2 m/sec

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31
Q

Sensory axons enter the CNS via…?

A

Dorsal roots

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32
Q

Where are cell bodies of sensory axons located?

A

dorsal root ganglia

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33
Q

Motor axons exit the CNS via…?

A

Ventral roots

34
Q

What does the trigeminal nerve innervate

A

V1 - Opthalmic (sensory)
V2 - Maxillary (sensory)
V3 - Mandibular (sensory and motor)

35
Q

Describe the sensory pathway

A

1st neuron : primary sensory neuron, periphery
2nd neuron: secondary sensory neuron, CNS
3rd neuron: tertiary sensory neuron, thalamus
-> cerebral cortex

36
Q

Describe the mechanoreception/ somatic pathway

A

Dorsal column medial lemniscal pathway

37
Q

Describe the mechanoreception/ trigeminal nerve

A

Posterior (Dorsal) Trigeminothalamic tract

38
Q

Describe the nociception/ somatic pathway

A

Spinothalamic pathway

39
Q

Describe the nociception / trigeminal nerve

A

Anterior (ventral) trigeminothalamic tract

40
Q

Where is the visual centre in the brain?

A

Occipital lobe

41
Q

Where is the auditory centre of the brain?

A

Temporal lobe

42
Q

Where is the taste centre of the brain?

A

Parietal lobe (Primary Gustatory Cortex is located near the face area of the somatosensory cortex)

43
Q

In the sensory homunculus, which areas are represented more widely in the cortex?

A
  • Areas with a high density of receptors ( ie. with a small receptor field) are represented more widely in the cortex.
44
Q

What is Stereognosis?

A

The ability to recognise objects by the feel alone.

45
Q

What does sterognosis require?

A

Memory:

  • requires a 3-D mental image
  • need to compare to previous experiences
46
Q

What is involved in proprioception?

A 
1) Balance organs in inner ear
Utricle, saccule, semicircular canal
Head posture, overall balance
2) Joint receptors
Join position, angle
3) Muscles receptors
Muscle length, tension
4) Periodontal receptors
Tooth contact, bite force
47
Q

What is the difference between pain and nociception?

A 
Pain = sensation
Nociception = neural process from receptor -> CNS -> sensory cortex
48
Q

What is pain?

A

An unpleasant SENSORY and EMOTIONAL experience associated with actual or potential tissue damage, or described in terms of such damage

49
Q

How is pain classified?

A

1) Nociceptive pain
2) Clinical pain
- Acute
- Chronic

50
Q

What are the axons for pain

A

Aδ and C

51
Q

When is nociceptive pain elicited?

A

When intense/noxious stimuli threatens to damage normal tissue

52
Q

How is nociceptive pain characterised

A

high threshold and limited duration

53
Q

What is the function of nociceptive pain?

A

adaptive/biologically useful - serves as a protective function

54
Q

What are the characteristics of acute clinical pain?

A
  • protective factor

- from soft tissue injury/ inflammation

55
Q

what are the characteristics of chronic clinical pain?

A
  • sustained sensory abnormality
  • result of on going peripheral pathology e.g. chronic inflammation, peripheral nerve injury
  • maladaptive
  • spontaneous or provoked e.g allodynia
  • resistant to treatment
56
Q

How many pairs of cervical spinal cords are there?

A

8

57
Q

How many pairs of thoracic spinal cords are there?

A

12

58
Q

How many pairs of lumbar spinal cords are there?

A

5

59
Q

How many pairs of sacral spinal cords are there?

A

5

60
Q

How many pairs of coccygeal spinal cords are there?

A

1

61
Q

What order are the spinal cords?

A 
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
62
Q

Where does pain tend to be referred?

A

common embryological origin

internal organ to superficial area e.g. skin

63
Q

Why does pain tend to refer

A

convergence of inputs in the CNS

64
Q

Name some surface areas of referred pain

A 
Heart: Left arm and chest
Oesophagus: upper chest, left arm
stomach:
Liver and gallbladder:
Appendix and small intestine
Ureter
65
Q

What are the characteristics of nociceptor nerve endings?

A

Free nerve endings
High threshold
respond to intense/noxious stimuli usually associated with pain
A alpha - noxious mechanical/ heat
C - polymodal
carry several types of receptors proteins
display sensitisation

66
Q

What does the spinal lemniscus consist of?

A

Medulla, pons, midbrain

67
Q

In the pain pathway, what are the CNS relay cells

A

spinal dorsal horn

spinal trigeminal nucleus

68
Q

What are the CNS pain pathways

A

Spinothalamic pathway

anterior trigeminothalamic tract

69
Q

Where does the ascending pain pathway terminate in the forebrain?

A

Primary sensory cortex subcortical areas

70
Q

Where are the nociceptive afferents in the teeth

A

Free nerve endings extend into the dentine

71
Q

What factors affect pain perception?

A 
Genetic 
molecular
cellular
anatomical
physiological
Psychological 
Social
72
Q

What does SCN9A encode for

A

alpha- unit of voltage-gate NA+ channel NAv1.7

73
Q

What factors are involved Pain Psychology

A

Situation factors
Emotional factors
Psychological factors

74
Q

What are some of the ways of modulating pain?

A 
"in built"
complementary medicines
Psychology/ Cognitive BT
Sex
Age
Pharmacology
Surgical
Genetic
Environment
75
Q

What is the gate control theory of pain?

A

Pain can be reduced by activating a non painful sensation.

1) C or A delta fibres transmit pain signals from the periphery
2) the projection neuron transmits pain signals to the sensory cortex = pain
3) A beta fibres transmit mechanical stimulation impulses to the sensory cortex via the dorsal column medial lemniscus
4) the mechanical stimulus activates the inhibitory neurons which inhibit the projection neuron to limit pain,

76
Q

What are the important areas

A

The descending pathway controls and inhibits the ascending pathway - only active in certain situations

77
Q

What contributes to the modulation of nociceptive afferent input

A

Supraspinal loop

78
Q

What anatomical features are involved in the modulation of nociceptive input?

A

Descending pain modulating circuit
feed to
- Midbrain, periaquaductal grey matter (PAG)
goes to
-Medula neurons within nucleus raphe magnus
goes to
- spinal cord/ dorsal horn

79
Q

Describe the modulation of nociceptive input

A

It is a pain inhibitory system: Pon PAG -> Medulla Raghe: 5HT and NA descending projections.

  • > direct inhibition of projection neurons
  • > activation of enkephalin - containing interneurons (“endorphin” release: edogenous opioids)
  • > reduces activity in nociceptive circuits
80
Q

What are the 3 parts of the triple reaction?

A

1) Red line
2) Wheal - odema
3) Flare

81
Q

Describe the reaction in the triple reaction

A

Tissue damage -> K+ + prostaglandins released
activators for receptive endings in nociceptive terminals
Plasma : release bradykinins
Platelets: release 5TH
Spinothalamic pathway activated
Also, receptive endings in skin release CGRP + Sub P
CGRP + Sub P activate local mast cells
Local mast cells degranulate and release histamines
Histamines acts on the receptive endings to reinforce that there is trauma within the region
CGRP cause dilation of blood vessels
Sub P cause plasma extravasation and oedema, and release bradykinin

82
Q

What is the name of an extreme case of triple response

A

Dermatographia

BDS1 (9 decks)

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