Lecture 12: Pain and Vestibular Control Flashcards
1
Q
Describe pain from stimulus to perception
A
- Transduction
- Transmission
- Modulation
- Perception
2
Q
What is involved in transduction of pain
A
Translation of noxious stimulus into neural activity
3
Q
What is involved in modulation of pain stimulus
A
Facilitation of inhibition of neurons and interneurons in spinal cord
4
Q
What is involved pain perception
A
Result of the integration of projection pathways with modulation, to produce final conscious subjective and emotional response
5
Q
What is mechanical deformation in pain perception
A
Stretches or damages the receptor membranes and opens ion channels
6
Q
What is the result of application of chemicals in pain perception
A
Opens ion channels in chemoreceptors
7
Q
What is the result of the change in temperature in pain perception
A
Alters permeability of the membrane of thermoreceptors
8
Q
Pain is detected through ___
A
Free nerve endings
9
Q
___fibers detect immediate, sharp pain
A
A-delta fibers
10
Q
__fibers detect dull, burning pain
A
C- fibers
11
Q
Are free nerve endings myelinated or non-myelinated
A
Non-myelinated
12
Q
Where are pain free nerve endings located
A
Skin, joints, internal organs, and bones
13
Q
T or F: pain occurs in brain
A
False, no pain free nerve endings in brain
14
Q
What do transient receptor potential channels detect
A
Detect temperature
15
Q
__ receptors increase AP frequency with an increase in temperature or certain chemicals
A
Warm receptors
16
Q
Where are warm receptors located
A
C- nerve fibers
17
Q
___ receptors increase AP frequency with decrease in temperature
A
Cold receptors
18
Q
Where are cold receptors located
A
Alpha-delta nerve fibers with non-myelenated endings
19
Q
What is the resting skin temperature
A
30 degrees Celsius
20
Q
At what temperature are heat nociceptors activated at
A
> 45 degrees Celsius
21
Q
Which fibers have mechanical nociceptors and noxious thermal nociceptors
A
Alpha-delta fibers
22
Q
Which receptors respond to mechanical damage- cutting, crushing, pinching
A
Mechanical nociceptors
23
Q
What receptors respond to extreme heat and cold
A
Noxious thermal nociceptors
24
Q
What fibers contain thermal nociceptors and polymodal nociceptors
A
C-fibers
25
What do receptors respond to thermal gradients
Thermal nociceptors
26
What receptors respond to various noxious, damaging stimuli- thermal, mechanical and chemical
Polymodal nociceptors
27
How many pathways are required to transmit pain to the brain and what are they
3
1. First order sensory neuron
2. Second order sensory neuron
3. Third order sensory neuron
28
What is the first order sensory neuron
Afferent neuron in the periphery that first detects pain signal
29
Where is the cell body for first order sensory neuron located
DRG
30
Where is the cell body of second order sensory neuron located
Soma in spinal cord or brain stem
31
Where is the third order sensory neuron located
Located in thalamus, synapses in cortex (layers 2-6)
32
What pathway does pain travel on
Spinothalamic, specifically lateral spinothalamic
33
Where does the 2nd order synapse occur
Thalamus
34
What does the 2nd order synapse relay
Perception of pain
35
Where does the 3rd order synapse occur
Somatosensory cortex
36
What does the 3rd order synapse relay
Location of pain
37
Are nociceptors adaptive or non-adaptive
Non-adaptive- nociceptors are activated as long as lesion is present
38
Tissue damage causes hyperalgesia which is
Increased sensitivity to pain
39
What fibers are activated on initial/acute pain stimulation
Alpha-delta fibers
40
Which fibers are activated over time, dull pain sensation that increases in intensity
C fibers
41
Inflammatory response to pain over time releases…
Bradykinins, prostaglandins, substance P, K+, and H+
42
___ in the ECF stimulate polymodal nociceptors and contribute to tissue inflammation
Bradykinins
43
____stimulates mast cells to release histamine
Substance P
44
___enhances pain sensitivity beyond the somatosensory circuit
Substance P
45
Describe the pathway/mechanism of action of substance P
1. Substance P binds a neurokinin 1 receptors in neurons and numerous other non-neuron cell types
2. Initiates vasodilation and inflammation
3. Sensitizes afferent pain fibers to increase pain perception
46
Repeated stimulation of ___ fibers enhances pain
C fibers
47
Repeated stimulation of dorsal horn neurons causes ____
Central sensitization
48
Central sensitization results in the recruitment of additional ___ receptors that make C fibers more sensitive
Glutamate receptors
49
Central sensitization, recruitment of glutamate receptors to make C fibers more sensitive results in ____ of C-fiber nociceptors
Memory
50
Where is pain modulated
CNS
51
What is the endogenous opioid mechanism
Pain relieving pathway, activate opiate receptors that block release of substance P in the spinal cord and periaqueductal gray matter of the mid brain
52
The pain afferent neuron releases ___ as NT. Another neuron releases ___ at presynaptic synapses to inhibit release of ___ and alleviate pain
Pain neuron: substance P
Another neuron: enkephalin
Inhibit release of: substance P
53
What NT is released to counteract the pain initiated by substance P
Enkephalin
54
What are the endogenous opioid substances
Endorphins, enkephalins (met-Enk and Leu-EnK) and dynorphins
55
What are endogenous opioids synthesized by
Nerve cells
56
What drugs mimic actions of endorphins at synapses in pain modulating networks
Morphine, Demerol and perocdan
57
What drug blocks the pain modulating/relieving action
Naloxone- mu-Opiod receptor competitive antagonist
58
Where are mu-receptors concentrated
Dorsal horns in spinal cord
59
What is the preferred receptor for B-endorphin
Mu/delta
60
What is the preferred receptor for endomorphin-1 and 2
Mu
61
What is the preferred receptor for met-enk and leu-enk
Delta
62
What is the preferred receptor for dynorphin A and B
Kappa
63
Describe the descending pathway of pain regulation
1. Noxious stimulus on nociceptor
2. Travel on afferent pain fiber
3. Release substance P
4. Signal periaqueductal gray matter
4a. Periaqueductal gray matter acts on medulla and reticular formation to activate inhibitory inter neuron in DH
4b. Periaqueductal signals to active enkephalin releasing neurons
5. Enkephalin releasing neurons act on raphe nucleus in brain stem
6. Raphe nucleus release serotonin on inhibitory neuron
7. Inhibitory neuron releases endogenous opiate to counteract substance P
64
How does an epidural nerve block work with opioids and other drugs
Epidural blocks somatic and visceral pain by blocking transmission of pain without interfering with sensory and motor function or depressing SNS.
Opioids bind opioid receptors
65
How do serotonin and NE modulate pain
Act by stimulating enkephalin releasing interneurons or pain modulating nuclei in brainstem
66
How do NSAIDS affect pain control
Block COX2, critical enzyme to synthesize prostaglandins, this decreases sensitization to pain
67
How do endocannabinoids modulate pain
Modulate pain following sustained physical activity
68
How do exogenous opioids modulate pain
Agonize endogenous opioid receptors
69
The ___ system measures orientation, position and movement of head
Vestibular
70
What does the vestibular system measure
Static tilt of head, linear acceleration, and rotary acceleration
71
What movements are facilitated by vestibular system
Correction of posture and balance, maintain focus of the eyes and head moves
72
__bone houses the vestibular system and cochlea
Temporal bone
73
The vestibular system is composed of 3 ___ and 2 ___
3 semicircular canals and 2 ampullae
74
Which structure contains ridge of hair cells
Ampulla, Crista ampullaris
75
2 ampulla are connected to a ___ and ___
Utricle and saccule
76
What fluid are the utricle and saccule coated in
Endolymph
77
Hair cells synapse with a ___ at the base
Sensory neuron
78
sensory neuron in a hair cell leads into the ___nerve
CN VIII
79
Bending towards the large cilia causes ___ channels to open
K+
80
Membrane depolarization of the hair cells causes __channels to open
Ca2+
81
Opening of Ca2+ channels within the hair cells causes exocytosis of ___ and __
Glutamate and aspartate
82
Bending the hair cells in the opposite direction of large cilia results in ___
Hyperpolarization
83
___detect rotational acceleration and deceleration
Semicircular canals
84
___ causes a bend in the cupola in the opposite direction
Deceleration
85
Canals on opposite side of the head provide ___information
Directional
86
Ex: if you rotate head clockwise the direction of flow would be ___ in each canal, providing information on direction
Opposite
87
___ and ___ detect linear acceleration and deceleration
Utricle and saccule
88
__ detects horizontally oriented macula
Utricle
89
___ detects vertically oriented macula
Saccule
90
___ and ___ detect head tilt
Utricle and saccule
91
When the head tilts the ___ pull down causing the firing rate to change
Otoliths
92
___ and ___ cause cilia to bend in opposite direction than the movement of the head
Otoliths and endolymph
93
Utricle and saccule otolith organs project to the ____ to facilitate alpha-gamma co-activation
Vestibulospinal tracts
94
Crista ampulla of the semicircular canals feed the ____ to provide compensatory eye movements in response to rotation
Medial longitudinal fasciculus
95
___ receives and returns input to fine tune coordination of postural and oculomotor reflexes
Flocculonodular node of the cerebellum
96
What are the 3 targets of CN VIII via the vestibular nuclei
1. Vestibulospinal tracts
2. Medial longitudinal fasciculus
3. Flocculonodular node of the cerebellum
97
What is the vestibuloocular reflex
Eyes rotate to head movement to allow unchanged visual perception of a target
98
What is the goal of the vestibuloocular relfex
Move extraoccular eye muscles to maintain visual contact with the target
99
When the head is rotated what structures are activated
Canals and otoliths
100
What nerve and nucleus are activated with head rotation
Vestibular nerve and nuclei
101
What tracts are activated when you rotate the head
Lateral and medial vestibulospinal tracts
102
What side are extensors and flexors activated on when the head is rotated
Extensors are induced on the side to which the head is rotated and the flexors are induced on opposite side
103
During VSR the vestibular sensory nerves synapse on the nerves in ___ nuclei
Vestibular
104
During VSR the neurons in the vestibular nuceli act on ___ muscles via the ___ tract, facilitating several vestibular reflexes
Axial muscles, vestibulospinal tracts
105
What does the extrapyramidal tract do during VSR
Control the eye and head position to maintain eyes on target while head or body is in motion
106
What is the vestibulo-colic reflex
Head and neck muscles adjust to maintain head position
107
What is peripheral vestibular syndrome
Labyrinth within petrosal bone affected, associated with head tilt
108
What is central vestibular syndrome
Brain stem is affected, associated with paresis, hemiparesis, gait and posture effects
109
How can a middle ear infection cause vestibular signs
Infection leads to pressure on the round/oval window of the cochlea and leads to head tilt.
Pressure difference causes unbalanced AP frequency
110
What are 4 very common signs of vestibular syndrome
Head tilt, nystagmus, ataxia, loss of balance
