Somatic Sensory System Flashcards
1
Q
These are non-selective cation channels
A
Mechanosensitive ion channels (mechanoreceptors)
2
Q
Released to signal moderate to intense pain
A
Substance P
3
Q
Makes pain worse through spread of pain signaling molecules
A
Hyperalgesia
4
Q
Bring info to brain stem or spinal cord
A
Primary afferent axons
5
Q
When these are deformed, mechanosensitive ion channels open, depolarizing receptor potential
A
Pacinian corpuscle
6
Q
What type of threshold do mechanosensitive ion channels have?
A
Low mechanical threshold. Doesn’t take a lot to open
7
Q
Caused by varicella zoster virus which causes chicken pox. Infection of dorsal root ganglion that remains for life and infects along dermatomes
A
Shingles
8
Q
Sensation in face carried through these
A
Trigeminal nerves (CN 5)
9
Q
The NT for nociceptor neurons in the spinal cord
A
Glutamate
10
Q
Block glutamate release and hyperpolarize neurons. Placebo affect mediated through these
A
Endogenous opioids
11
Q
The cortical somatotopy map is called this
A
Homunculus
12
Q
These are segregated in the VP nucleus of the thalamus
A
Touch and pain
13
Q
Dull, longer pain produced by c fibers
A
Second pain
14
Q
Projections to large areas of the cortex, more so than mechanosensory pathways
A
Pain projections (spinothalamic and trigeminal)
15
Q
This depolarized nociceptors, thus inflammatory responses which lead to its release are painful
A
Histamine
16
Q
How is touch info transmitted into the spine?
A
At specific levels depending on the area of the body from with the stimulus originates (build a somatotopic map)
17
Q
Powerful analgesics, also produce mood changes, nausea, drowsiness, mental stupor, etc. Bind to opioid receptors, widely expressed in pain pathways
A
Opioids
18
Q
Multiple types of these are expressed in one neuron sensitive to it unlike light and odorants
A
Pain sensors in pair sensitive neurons
19
Q
Cells with similar characteristics exist in these in S1
A
Vertical columns
20
Q
Multiple maps exist here
A
S1
21
Q
Extreme heat or cold
A
Thermal
22
Q
Where is crossing over in the dorsal column medial lemniscal pathway?
A
Medial lemniscus
23
Q
A sensory instrument different than the other mechanoreceptors
A
Hair
24
Q
Caused by a number of conditions like allergies, infections, cancer, iron deficiency, liver disease, stress
A
Itch
25
Enter spinal cord same as cutaneous, from the same level of the spine in the same dorsal root ganglion
Visceral nociceptor axons
26
Detects pain and temp, decussate immediately and run in ventrally in the tract, dont synapse until thalamus, don't communicate with medial lemniscus (but close by)
Spinothalamic pathway
27
Have small receptive fields (Mechanoreceptors)
Meissners corpuscles and Merkels discs
28
Have varying diameters and size which are correlated with type of receptor
Primary afferent axons
29
Studies have recently shown this could occur in humans as seen in non human primates
Somatosensory plasticity
30
SLIDE 65
SLIDE 65
31
Rat facial whiskers that are important sensory instruments that were used to demonstrate the plasticity of the somatosensory system
Vibrissae
32
Primary afferents projecting to the brain
A beta neurons
33
Model for how stimulation of touch pathway can reduce pain
Gate theory of pain (Melzack and Wall)
34
Lactic acid production leads to this build up in extracellular fluid
H
35
Protects, prevents evaporation. Can detect dot only .006 mm x .04 mm
Touch, skin
36
Synapse on second order sensory neurons and also send processes to the brain
Large A beta touch neurons
37
Can make nociceptors more sensitive, not made by them
Prostaglandins
38
Can adapt firing rates after long stimuli
Thermoreceptors
39
SLIDE 20
SLIDE 20
40
Can be hairy or glabrous
Skin
41
These also travel in the dorsal column along with A beta neurons
Second order axons
42
These depolarize when stretched or deformed
Mechanically gated channels
43
What do adjacent dorsal roots innervate?
Overlapping areas
44
This map is not continuous or to scale, recent studies show that the genitals map to a location more consistent with body location
Cortical somatotopy
45
Type of inhibitory interaction that can take place in dorsal column nuclei and thalamic nuclei that promotes contrast enhancement
Later inhibition
46
This travels through the medulla, pons, and midbrain to the ventral posterior (VP) nucleus of the thalamus in the dorsal column medial lemniscal pathway
Medial lemniscus
47
These aren't simply relays, they alter info as it passes through
Dorsal column nuclei and thalamic nuclei
48
Free endings of unmyelinated C fibers and lightly myelinated alpha delta neurons
Nociceptors
49
Cross talk between these pathways occurs in the spinal cord
Pain and touch
50
Most are polymodal, respond to thermal, chemical, mechanical (multiple signals)
Nociceptors
51
Enter the spinal cord at dorsal roots
Primary afferent axons
52
In mice, these are each represented in S1 by a barrel or group of neurons
Mouse facial whiskers
53
These are slow or fast adapting (Mechanoreceptors)
Hair follicles
54
Inability to recognize objects by touch (posterior parietal cortex)
Astereoagnosia
55
Naloxone is antagonist (theoretically inc pain)
Endogenous opioids
56
Second order neurons that decussate and connect to thalamus via trigeminal lemniscus
Trigeminal pain pathway
57
Layer 4 neurons of S1 project to these
Other layers
58
Different ones of these detect different stimuli
Touch receptors
59
How are mechanosensitive ion channels opened?
With a force from inside the membrane, from extracellular proteins, from intracellular proteins, etc
60
Some pain meds can cause this, pain can also suppress it
Itch
61
Can be invoked by stimulating regions whose S1 representations border those of the lost limb
Phantom limb
62
Have large receptive fields (Mechanoreceptors)
Pacinian corpuscles and Ruffinis endings
63
Varies 20 fold across the body with fingertips being the most sensitive
Two point discrimination
64
Cause damage and are sensed as pain
temp extremes
65
Changes based on loss or increased use and can use functional imaging to study in humans
Somatotopic map
66
The ascending pain pathway
Spinothalamic pathway
67
These are overrepresented in the somatosensory map in mice, reflecting the use and importance of whiskers
Barrels
68
Small diameter fibers in trigeminal nerve synapse on neurons in spinal trigeminal nucleus in Brian stem
Trigeminal pain pathway
69
SLIDE 69
SLIDE 69
70
Vary in stimulus frequencies, pressures, receptive field sizes, each has a preferred stimulus
Mechanoreceptors of the skin
71
Have more mechanoreceptors, small receptive fields, more brain power, high resolution mechanisms
Fingertips
72
Par of body or world ignored (posterior parietal cortex)
Neglect syndromes
73
How does somatic info enter the spinal cord?
At the appropriate level (somatotopic mapping)
74
What are the 4 groups of spinal segments?
Cervical (c) 1-8
Thoracic (t) 1-12
Lumbar (l) 1-5
Sacral (s) 1-5
75
Sensory proprioceptors of skeletal muscle
A alpha
76
Warm receptors to these neurons only
C fibers
77
These project to dorsal horn and depress nociceptive neuron activity in descending pain control pathways
Raphe (serotonergic) neurons
78
Types of pain perceived without nociceptor activation
Chronic pain, emotional pain
79
SLIDE 49
SLIDE 49
80
Strong pressure
Mechanical
81
Some spots of the skin are sensitive to these, but not both
Hot or cold
82
Primary afferent axons with high mechanical thresholds
A delta and c
83
Fast, sharp pain due to a delta fibers
First pain
84
Slowest, small, unmyelinated afferent axons
C fibers
85
The columns of the spinal cord contain
Fibers
86
Sensory pain, temperature, and itch
c
87
Since dorsal roots innervate overlapping areas, what would need to happen to lose all sensation from an area?
All the dorsal roots would need to be cut
88
Areas 5 and 7 with large receptive fields and elaborate stimulus preferences. Integrates with visual, attention, movement
Posterior parietal cortex
89
SLIDE 11
SLIDE 11
90
Electrical stimulation here causes sensation
S1
91
How many distinct TRP channels?
6
92
Above this temp, pain receptors active, not thermorecepotors
55 C
93
Synapse on ipsilateral trigeminal nucleus then decussate, then go to thalamus, then S1
Trigeminal touch pathway
94
Dorsal horn contains
Sensory neurons
95
These are part of the touch system
Hairs
96
What rule does cortical somatotopy follow?
Use it or lose it. More use = more representation
97
Has some sensation from CN 7, 9, 10 and have large diameter sensory nerves
Trigeminal touch pathway
98
Sensory mechanoreceptors of skin
A beta
99
Paraventricular and periaqueductal gray matter (PAG) neurons synapse on Raphe nucleus, suppress pain
Descending pain control pathways
100
Can trigger itch
Histamine
101
Highly responsive to somatosensory input, but no other senses
S1
102
Thalamus projects to these S1 areas
3a (body position) and 3b
103
Ventral horn contains
Motor neurons
104
SLIDE 45
SLIDE 45
105
The first demonstration of cortical use dependent plasticity
Mouse whiskers (vibrissae)
106
Posterior parietal cortex areas that also process touch info but more deeper analysis with less mapping
Posterior parietal cortex areas 5 and 7
107
SLIDE 63
SLIDE 63
108
Lesions here impair somatic sensation
S1
109
These axons also synapse in intralaminar nuclei of the thalamus
Spinothalamic axons
110
Prolonged stimulation of these causes decrease in receptor potential, release reverses this
Pacinian corpsucle
111
How do A beta neurons travel to the brain in the dorsal column medial lemniscal pathway?
On the ipsilateral side through the dorsal column (touch and limb position)
112
Mapped by S1 stimulation (Penfield) or by recording from S1 neurons after somatic stimulation, maps similar. This was done in awake patients undergoing brain surgery, there are no pain receptors in the brain
Cortical somatotopy
113
Histamine binding activates these itch channels which are also activated by heat and capsaicin
TRPV1
114
SLIDE 72
SLIDE 72
115
Inputs from these spread over larger region of thalamus than medial lemniscus
Spinothalamic tract and trigeminal lemniscus
116
Skin receptor that can be seen with the naked eye
Meissner's corpuscle
117
These are fast adapting, the quickly stop paying attention to stimulus (Mechanoreceptors)
Meissners and Pacinian
118
Stimulate interneurons, excites it which means it releases more inhibitory NT to block pain
Gate theory of pain
119
In mice, these are adjusted depending on whisper use or if a whisker is removed
Responses and anatomy
120
Activated by methanol or below 250 C
TRPM8
121
Cross talk between these two in the spinal cord produces referred pain
Viscera and skin
122
Cold receptors to these neurons
A delta and c fibers
123
Are in most tissues like bone, meninges, but not brain
Nociceptors
124
Thalamic neurons send processes to the primary somatosensory cortex (S1) in this pathway
Dorsal column medial lemniscal pathway
125
Has immediate crossing over
Spinothalamic pathway
126
Carries pain ion from head, face, and neck
Trigeminal pain pathway
127
Differences in firing rates of thermoreceptors are most pronounced during and right after these
changes
128
What does the CNS not know about the stimulus that causes thermoreceptors to fire
It doesn't know what kind of stimulus it is
129
Is a conscious awareness, perception
Pain
130
Are innervated by free nerve endings; bending of the hair causes changes in AP firing rate
Follicles
131
Number of these receptors and channels but not well understood
Itch
132
Intermediate zone contains
Interneurons
133
How does lateral inhibition work?
Amplification or inhibition by neighboring cells increases contrast enhancement to make it easier for brain to decode
134
SLIDE 61
SLIDE 61
135
What happens with a digit is stimulated by a spinning disk in monkeys?
The region of the cortex devoted to input from that digit expanded
136
These are slow adapting and pay attention to the stimulus longer (Mechanoreceptors)
Merkels and Ruffinis
137
Sensory pain and temperature
A delta
138
A one to one relationship exists between these two things
Spinal segments and dermatomes
139
Mechanoreceptors with nerve terminal, flattened epithelial cell
Merkel's discs
140
Well prescribed in maps, info enters spine at specific places
Dermatomes
141
Primary afferent axons with low mechanical threshold
A beta
142
Different from touch in that stimuli have potential to cause tissue damage
pain
143
Contain C fibers and carry sensory info to spinal cord and brain stem
Primary afferent axons
144
These rest like pain pathways
Thermoreceptors
145
What does the selectivity of a mechanoreceptor axon depend on?
Structure of the ending
146
Are like bands on body surface, adjacent dorsal roots innervate overlapping areas
Dermatomes
147
What happens when a digit is removed from a monkey?
The neurons representing that digit in S1 responded to adjacent digits
148
Central circuits not understood for itch, this is a peripheral NT we know of
Glutamate
149
Spinal nerves pass through these in the vertebral column
Notches
150
What do other mechanoreceptors not named do?
Detect blood pressure, bladder extension, etc.
151
Show more cortex devoted to fingers of the left hand
Violinists
152
This happens in our brains to an extend due to many experiences
Remapping
153
These branch out in zone of Lissauer and synapse on substantial gelatinosa neurons
Primary afferents of nociceptor neurons
154
Receives input from VP of thalamus
S1
155
SLIDES 77 and 78
SLIDES 77 and 78
156
Carry touch info
Dorsal columns
157
This shows that receptive fields form orderly map, as in retina or auditory system
Cortical somatotopy
158
Oxygen deprivation, some chemicals, temperature extremes, mechanical stress
damaging stimuli (pain)
159
This is widespread in the brain (visual, auditory, motor)
Plasticity
160
How many pairs of dorsal and ventral roots in spinal cord?
30
161
Depletes substance P from nerve endings, but this is not thought to be its mechanism of action. It reduces pain by reducing the function of pain fibers through several mechanisms
Capsaicin
162
Innervate face, mouth, dura matter, tongue
Trigeminal nerves (CN 5)
163
Detect temp with specific membrane mechanisms
Thermoreceptors
164
Free, unmyelinated axons that detect pain
Nociceptors
165
Increased intensity, reduced threshold, spontaneous pain
Hyperalgesia
166
Activated above 430 C and capsaicin
TRPV1
167
These determine perception
Skin thermoreceptors
168
Formed form 20-70 layers fo connective tissue (viscous liquid in between) with nerve terminal in middle
Pacinian corpuscle
169
Cross talk here can produce referred pain, the feeling of pain in a different location from the actual body part with nociceptor signaling
Spinal cord
170
The size of this is determined by density and importance of input (hand, face, tongue, and lips are overrepresented)
Size of cortical sensory region
171
These contain temp sensitive neurons that help maintain stable body temp
Hypothalamus and spinal cord
172
Sensory process, can be controlled by higher centers, to detect pain
Nociception
173
Synapse on second order sensory neurons within the dorsal horn
Primary afferent axons
174
Like pain in that transmitted through thin axons (C fibers) and can be triggered by multiple stimuli
Itch
175
Area of skin innervated by both dorsal roots of single spinal segment
Dermatomes
176
Each has unmyelinated axon branches with mechanosenstive ion channels
Mechanoreceptors of the skin
177
SLIDE 29
SLIDE 29
178
Perception and interpretation of spatial relationships, body image, coordinated body movements. Somatosensory integrated especially with visual system, with others too
Posterior parietal cortex
179
Has 6 layers with thalamic input to layer 4
S1
180
Have a different pathway than mechanoreptors
Nociceptors (pain)
181
Can be as bad as chronic pain but carried by different axons
Chronic itch
182
These axons connect to dorsal column nuclei at medulla spinal cord junction
Dorsal column axons
183
pathways for touch and vibration different from pain and temperature pathway
Dorsal column medial lemniscal pathway
184
All sensory systems have this
Parallel processing of information
185
This has alternation columns of neurons receiving input from slowly adapting or fast adapting receptor input
S1
186
What type of signaling occurs through the molecules in pain?
Diffusible signaling
187
Endorphins are these, also expressed in pain pathways, in PAG etc produce analgesia
Endogenous opioids
188
What do different types of mechanoreceptors have?
Different preffered stimuli
189
Most touch info processing in the cortex, located in parietal lobe, S1, Brodmanns 3B
Somatosensory cortex
190
Pain and touch synapse on different neurons here
VP nucleus in thalamus
191
Above this temp, normal thermoreceptors don't respond and pain receptors do
430 C
192
These are thought to encode the touch responsive mechanosensitive ion channels
Piezo genes
193
A single one of these can give info about intensity, position, and duration of stimulus
Single receptor
194
3 other types of mechanoreceptors
Pacinian corpuscle
Ruffini's endings
Meissner's corpuscles
195
SLIDE 14
SLIDE 14
196
Opiate receptors are present on these neurons
Itch detecting neurons
197
A combination of receptors is firing during various temp ranges. The brain has to decode this population of information to give us our conscious perception of a specific temp
Population coding
198
Largest sensory organ
Touch
199
Made by nociceptors and can make them more sensitive
Bradykinin, substance P
200
Part of S1 that process somatosensory info
1, 2, 3a
201
These cell bodies exist in dorsal root ganglion
Nociceptive neurons in the spinal cord
202
This influences input via descending tracts
Cortex
203
Dorsal column axons ascend in this after crossing over
Medial lemniscus
204
Some channels open in response to proteases (ATP, K, bradykinin, H) - what are all these?
Pain signals
205
Reduced by A beta fiber activity (rubbing or stimulating touch pathways)
Pain
206
S1 area 3b connects to these areas proven by lesions
1 (texture information)
| 2 (size and shape information)
207
Mechanoreceptor with nerve terminal like balls of string
Krasue end bulbs
