3 - Peripheral Nervous System ad Sensory Receptors Flashcards
(212 cards)
1
Q
Define sensation
A
the process where sensory receptors receive information from both the internal and external environment and encode the information for transmission to various areas of the nervous system.
2
Q
What is included in sensation?
A
- process of sensory transduction
- receptor potential summation
- action potential generation
- neural processes that integrate signals centrally
3
Q
how do neural processes integrate signals centrally
A
either facilitation (depolarization) or inhibition (hyperpolarization)
4
Q
Define perception
A
the process where the central nervous system receives and interprets the sensations based on present experiences, the present state of the internal and external environment, and memory of similar situations.
5
Q
Where does perception occur in various degrees of refinement?
A
- thalamus
- basal ganglia
- cerebellum
- cortex
6
Q
Perception at the cortical level is usually considered ____
A
conscious perception
7
Q
Perception at the level of the cerebellum is considered ___
A
unconscious perception
8
Q
What is the basal ganglia involved in?
A
unconscious representations of movement experiences, but also is involved with perception of inter- and intrapersonal space.
9
Q
How are perceptions without the cortex?
A
perceptions are incomplete or skewed from the normal which may include lack of localization, anesthesia or hyperesthesia, parasthesia.
10
Q
Define sensory transduction.
A
changing the energy of a stimulus into a neural energy.
11
Q
What are the three form of stimulus energy?
A
mechanical, chemical, and light
12
Q
What does stimulus energy produce?
A
a change in the receptor membrane such that a local potential differences occur.
13
Q
What is a local potential difference?
A
Na+, K+, and Cl- channels open to allow ion movement.
14
Q
T/F: Potential changes from stimulus energy are local and spread only a few milimeters as they decay.
A
True
15
Q
Define threshold for stimulation.
A
the amount of stimulus energy it takes to cause a local receptor potential and depends on the physical properties of the receptor itself.
16
Q
T/F: some receptors have low thresholds and some have high.
A
True
17
Q
What does it mean if a receptor has a low threshold?
A
it takes only a small stimulus to cause a local receptor potential
I.E. Meissner’s corpuscle - low frequency vibration
18
Q
What does it mean if a receptor has a high threshold?
A
takes a larger stimulus to cause a local receptor potential
I.E. Ruffini endings - skin stretch, joint movement
19
Q
Define threshold for perception
A
lowest stimulus intensity necessary for perception of stimulus
20
Q
Describe threshold for perception vs. receptor threshold
A
threshold for perception may be modified by context and experience.
21
Q
Define adaptation
A
the duration for which the receptor potential is generated to the stimulus.
22
Q
How is adaptation determined?
A
by the morphology of the receptor
E.g. Pacinian corpuscle receptor potential is rapidly adapting and thus a generator potential is only generated when the stimulus comes on or off. Action potentials will therefore only be generated at onset and offset of the stimulus.
Ruffini corpuscles are slowly adapting and continue to signal throughout the duration of the stimulus.
23
Q
Coding of Sensory Information: Define “Quality - Specificity Coding”
A
Receptors are specialized by their morphology to respond to only one type of stimulus.
24
Q
The intensity of a stimulus is directly related to ___ and ___..
A
The intensity of a stimulus is directly related to the size of the receptor and the number of receptors activated.
25
This [receptors activated] is then transferred to the generation of action potentials and coded by ____.
the frequency of action potentials and the number of discharge fibers.
26
The stronger the stimulus, the ___
greater the size of the receptor potentials (depolarization).
27
the greater the size of the receptor potentials (depoalrization), the ____
greater the number of receptors being activated
28
the greater the number of receptors being activated, the ____
greater summation of the depolarizing events
29
the greater summation of the depolarizing events, ___
and thus the increased frequency of action potentials.
30
With an increase in the frequency of action potentials, what is happending to the amplitude and speed at which the action potentials are traveling
amplitude and speed remain unchanged.
31
how is location of stimulus determined?
signaled by firing a specific gorup of neurons activated by stimulus.
32
What is a receptive field?
area surrounding the receptor that when stimulated excites or inhibits the firing of a paticular cell.
33
What size and number of receptive fields do the most sensitive parts of the body have for example tips of fingers and tongue?
smallest receptive fields and largest number of receptive fields per area
34
As you move proximally on the body, what happens to the size, density, and sensitivity of field receptors?
receptive field size increases, density of receptors decreases as does the sensitivity.
35
Define dermatomes
area of the body surface contributing sensory input to one dorsal root.
36
where is excititory discharge greatest for a receptive field?
at the center
37
where is inhibitory greatest for a receptive field?
at the periphery
38
what is the purpose of the layout of a receptive field?
serves to shapen peak of activity within the brain.
39
Where does this sharpening of peak activity occur?
first in dorsal column nuclei and then at subsequent synapse in the CNS. Also present in the visual system.
40
What is the purpose of this lateral inhibition?
serves to enhance distinction between two stimuli and aids in recognition of pattern and contour.
41
Which areas are responsible for orderly mapping of sensations from body surface onto CNS area?
dorsal column neclei, thalamus, somatosensory cortex (sensory humuculus).
42
The areas with the ____ receptor density will have the ____ cortical receptive field.
The areas with the LARGEST receptor density will have the LARGEST cortical receptive field.
43
There are also cells in the sensory cortex that respond to ___
specific orientation, movement, and shape of stimulus.
44
Define exteroceptors
stimuli from the external environment
45
define proprioceptors
position of body segments relative to each other and position of body and head in space
46
Define interoceptors
signal body events such as blood glucose level and blood pressure.
47
What are the three classifications of sensory receptors according to stimulus location?
1. Exteroceptors
2. Proprioceptors
3. Interoceptors
48
What are the 6 classifications of sensory receptors according to the sensory system?
1. Somatic
2. Visual
3. Vestibular
4. Auditory
5. Olfactory
6. Gustatory
49
What is includes in the Somatic sensory receptor classification?
tactile, joint, muscle, tendon, thermal, pain
50
What are the 5 classifications of sensory receptors according to stimulus energy?
1. Mechanoreceptors
2. Chemoreceptors
3. Nociceptors
4. Thermoreceptors
5. Photoreceptors
51
What do mechanoreceptors detect?
touch/pressure, proprioception, air waves
| innocuous physical contact with the skin causes mechanical alteration or deformation detected by these receptors
52
What do chemoreceptors detect?
taste, smell, blood gas level
53
What do nociceptors detect? Encapsulated or Unencapsulated free nerve ending? primary afferent fiber type?
```
damage stimuli (pain)
Unencapsulated free nerve ending
A-delta () and C fibers
```
sensory inputs include mechanical (or cutaneous), thermal extremes, and polymodal
54
What do thermoreceptors detect? Encapsulated or Unencapsulated free nerve ending? primary afferent fiber type?
heat and cold
Unencapsulated free nerve ending
A-delta and C fibers
55
What do photoreceptors detect?
light
56
Which sensory fiber type has the largest diameter?
Ia (A- a)
| Ib (A- a)
57
Which sensory fiber type has the smallest diameter?
IV (C)
58
Which sensory fiber type has the fastest conduction velocity?
Ia (A- a)
| Ib (A- a)
59
Which sensory fiber type has the slowest conduction velocity?
IV (C)
60
What are the sensory fiber types?
```
Ia (A- alpha)
Ib (A- alpha)
II (A- beta)
III (A- delta)
IV (C)
```
61
Where are sensory fiber type Ia (A- alpha) found or responsible for?
Primary afferents of muscle spindle
62
Where are sensory fiber type Ib (A- alpha) found or responsible for?
Golgi tendon organ
63
Where are sensory fiber type II (A- beta) found or responsible for?
Secondary afferents of muscle spindle, touch, pressure, and vibration
64
Where are sensory fiber type III (A- delta) found or responsible for?
Touch and pressure, pain and temperature (Thermoreceptors and Nociceptors)
65
What are sensory fiber type IV (C) found or responsible for?
pain and temperature, unmylenated fibers (Thermoreceptors and Nociceptors)
66
What determines the conduction velocity of a fiber? (2)
small diameter fibers are slower because they provide more resistance to flow of current and have less insulation from myelin
67
What determines the amplitude of an action potential?
small diameter fibers have lower amplitude because potential change across the membrane is smaller.
(can distiinguish small diameter from large diameter fibers by size of EMG amplitude)
68
What determines the threshold for stimulus?
small diameter fibers have a higher threshold for stimulation because they offer more resistance to current flow
69
Will a C fiber type require lower or higher intensity of e-stim to activate?
higher because it is the smallest diameter so has the highest threshold for stimulation because it offers the most resistance to current flow.
70
What are the 4 types of Motor fibers?
1. Alpha (A-a)
2. Gamma (A-g)
3. Preganglionic ANS fibers (B)
4. Postganglionic ANS fibers (C)
71
Which motor fiber type has the largest diameter?
Alpha (A-a)
72
Which motor fiber type has the smallest diameter?
Postganglionic ANS fibers
73
What is the role of Alpha (A-a) fibers?
Motor neuron innervating extrafusal muscle fiber
74
What is the role of Gamma (A-g) fibers?
Motor neuron innervating intrafusal muscle fiber
75
What is the role of Preganglionic ANS fibers (B)
Lightly myelinated
76
What is the role of Postganglionic ANS fibers (C)
Unmyelinated
77
Merkel's disc
```
Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
```
Merkel's disc
Peripheral Fiber Type: Slowly adapting type I
Response Properties: continued discharge
Receptive Field Size: small; 2-8mm diameter containing zones of maximal sensitivity
Activation Threshold: Low, 5 g/mm^2
Adequate Stimulus: Deformation of skin
Sensation Evoked: Light, uniform pressure, like a watercolor brush against the skin
Receptor Shape: Dome-shaped complex containing up to 30 specialized Merkel's cells
Fiber:Receptor Ratio: 1 fiber:3-4 complexes
78
Ruffini ending
```
Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
```
Peripheral Fiber Type: slowly adapting type II
Response Properties: continued discharge
Receptive Field Size: Large; several centimeters, with area of maximal sensitivity under 2 mm diameter
Activation Threshold:Moderate 10g/mm^2
Adequate Stimulus: Skin stretch; joint movement
Sensation Evoked: No conscious experience
Receptor Shape: Small capsule; elongated perpendicular to skin surface
Fiber:Receptor Ratio: 1 fiber:1 receptor
79
Meissner's corpuscle
```
Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
```
Peripheral Fiber Type: rapidly adapting type I
Response Properties: transient discharge
Receptive Field Size: small; 2-8mm diameter containing zones of maximal sensitivity
Activation Threshold: Low, 4 g/mm^2
Adequate Stimulus: Rapid skin displacement
Sensation Evoked: buzzing, wobbling, or flutter
Receptor Shape: small capsule; elongated perpendicular to skin surface
Fiber:Receptor Ratio: 1 fiber:15-20 receptors
80
Hair follicle
```
Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
```
Peripheral Fiber Type: Rapidly adapting type I
Response Properties: transient discharge
Receptive Field Size: small; 2-8mm diameter containing zones of maximal sensitivity
Activation Threshold: low
Adequate Stimulus: displacement of hair shaft
Sensation Evoked: ?
Receptor Shape: Epidermally derived follicle, elongated perpendicular to skin surface
Fiber:Receptor Ratio: 1 fiber:15-20 receptors
81
Pacinian corpuscle
```
Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
```
Peripheral Fiber Type: rapidly adapting type I
Response Properties: one to two impulses per transient
Receptive Field Size: Large; several centimeters
Activation Threshold: Low 4 g/mm^2
Adequate Stimulus: High-frequency mechanical transients; most sensitive to vibration at 200-300 Hz
Sensation Evoked: Buzzing, flutter
Receptor Shape: Lamellated, onion-like capsule, elongated parallel to skin surface
Fiber:Receptor Ratio: 1 fiber: 1 receptor
82
What is a first order neuron?
All sensory receptors from the body have their somata or cell bodies in dorsal root ganglia neurons. These cells the first in line to receive information from the periphery are therefore called first-order neurons.
83
What are the three ways fibers can be classified?
1. Conduction velocity of the action potential along the fiber to the central nervous system.
2. Aspects of the stimulation that must be present to evoke a response (e.g., indensity, duration, quality)
3. Characteristic responses of the receptor to the natural stimuli (e.g., slow vs fast adaptation)
84
Describe an A-delta fiber
lightly mylelinated, relatively fast-ducting, small-diameter fibers, propagating an action potental at a rate substantially slower than large diameter A-alpha and A-beta fiber velocities.
Responsible for touch and pressure, pain and temperature
85
Describe a C fiber
unmylenated, small-diameter fibers that are slow conducting, conveying information to the spinal cord at the slowest rate, slower than A-delta
Responsible for pain and temperature
86
A-delta fibers are stimulated by low-threshold or high-threshold receptors?
low-threshold
87
C fibers are stimulated by low-threshold or high-threshold receptors?
high-threshold
88
What are the 5 types of Muscle and Skeletal Mechanoreceptors?
1. Muscle Spindle Primary
2. Muscle Spindle Secondary
3. Golgi Tendon Organ
4. Joint capsule mechanoreceptors
5. Stretch-sensitive free endings
89
What type of fiber is associated with Muscle spindle primary?
A-alpha Ia
90
What do the Muscle spindle primary respond to?
Muscle length and speed
91
What do the 5 muscle and skeletal mechanoreceptors respond to?
Limb proprioception
92
What type of fiber is associated with Muscle spindle secondary?
A-beta II
93
What do the Muscle spindle secondary respond to?
Muscle stretch
94
What type of fiber is associated with Golgi tendon organ?
A-alpha Ib
95
What do the Golgi tendon organ respond to?
Muscle contraction
96
What type of fiber is associated with Joint capsule mecanoreceptors?
A-beta II
97
What do Joint capsule mechanoreceptors respond to?
Joint angle
98
What type of fiber is associated with Stretch-sensitive free endings
A-delta III
99
What do Stretch sensitive free endings respond to?
Excess stretch or force
100
Low-threshld mechanoreceptors are activiated by
light, nonpainful tactile stimuli
101
High-threshold mechanoreceptors are activiated by
potentially tissue-damaging sensory events
102
The axons responding only to the onset and offset of mechanical deformation of the skin are classified as ___
rapidly adapting (indicating that they quickly adapt to an object in contact with the skin)
103
Nerve fibers that discharge when tactile stimulus is applied and continue to respond during the stimulus presentation are called ____
slowly adapting
104
A single nerve fiber distributes to a specific region of the skin; this region, or the spatial extent of skin that activates the nerve fiber, is called ___
receptive field [of that unit].
105
Nerve fibers can be defined using a combination of ___ and ____.
```
receptive field size (the spatial properties)
adaptation rate (the temporal properties)
```
106
Does Type I refer to a small or large receptive field?
Small
107
Does Type 2 refer to a small or large receptive field?
Large
108
Describe a SA Type 1 receptor?
Slowly Adapting (continuously responding) Small Receptive Field
109
Describe a RA Type 2 receptor
Rapidly Adapting (respond to onset and offset) Large Receptive Field
110
Where are joint mechanoreceptors located?
in the joint capsule
111
How many types of joint mechanoreceptors are there? What are they?
Type I
Type II
Type III
Type IV
112
Type I joint mechanoreceptors resemble what cutaneous mechanoreceptor?
Encapsulated "Ruffini-like"
113
Type II joint mechanoreceptors resemble what cutaneous mechanoreceptor?
Encapsulated "paciniform"
114
Type III joint mechanoreceptors resemble what cutaneous mechanoreceptor?
Encapsulated "GTO-like"
115
Type IV joint mechanoreceptors resemble what cutaneous mechanoreceptor?
Free nerve endings
116
Where are Type I mechanoreceptors located?
Ligaments, joint capsule, proximal joints
117
Where are Type II mechanoreceptors located?
Synovial junction of joint capsule, fat pads of joint, distal joints.
118
Where are Type III mechanoreceptors located?
Ligaments, all joints of the body
119
Where are Type IV mechanoreceptors located?
Joint capsule, ligaments, periosteum
120
What do Type I joint mechanoreceptors respond to?
Mechanoreceptors, slow adapting, low threshold, active during movement and rest
121
What do Type II joint mechanoreceptors respond to?
Mechanoreceptors, rapidly adapting, low threshold, active at beginning and end of movement
122
What do Type III joint mechanoreceptors respond to?
Mecanoreceptors, slow adapting, high threshold, active at extremes of range and with longitudinal traction
123
What do Type IV joint mechanoreceptors respond to?
Pain receptors, slow adapting, high threshold, active with extreme mechanical force or chemical irritation
124
What is the function of Type I joint mechanoreceptors?
Contributes to regulation of postural muscle tone, kinesthesia, regulation of muscle tone during movement.
125
What is the function of Type II joint mechanoreceptors?
Provides information about beginning and end of joint movement, may help "boost" muscle tone at beginning of movement to overcome inertia.
126
What is the function of Type III joint mechanoreceptors?
Respond to sudden joint movements and may cause reflex muscle contraction to limit further movement
127
What is the function of Type IV joint mechanoreceptors?
May contribute to a flexion reflex, or to a co-contraction patter around a joint to prevent further movement.
128
What peripheral fiber type is a Merkel's disc?
Slowly Adapting Type I
129
What peripheral fiber type is a Ruffini ending?
Slowly Adapting Type II
130
What peripheral fiber type is a Meissner's Corpuscle?
Rapidly Adapting Type I
131
What peripheral fiber type is a Hair follicle?
Rapidly Adapting Type I
132
What peripheral fiber type is a Pacinian corpuscle?
Rapidly adapting Type II
133
What is adequate stimulus for a Merkel's disc?
Deformation of skin - Light uniform pressure, like a watercolor brush against the skin
134
What is adequate stimulus for a Ruffini ending?
Skin stretch; joint movment - no conscious experience
135
What is adequate stimulus for a Meissner's corpuscle?
Rapid skin displacement - buzzing, wobbling, or flutter
136
What is adequate stimulus for a Hair follicle?
displacement of hair shaft
137
What is adequate stimulus for a Pacinian corpuscle?
High frequency mechanical transients; most sensitive to viibration at 200-300 Hz - Buzzing, flutter
138
What are muscle spindles?
Muscle spindles are specialized muscle fibers containing contractile elements.
139
How are muscle spindles encased?
These specialized muscle fibers are encased in connective tissue sheath
140
Where are muscle spindles anchored?
anchored to the endomysium and perimysium that surrounds the fasicles of the muscle.
141
What are the contractile fibers within muscle spindles referred to as?
intrafusal muscle fibers
142
What are the contractile fibers that make up the bulk of the muscle referred to as?
extrafusal muscle fibers
143
T/F: both intrafusal and extrafusal muscle fibers have a typical sarcomere arrangement.
true
144
How many intrafusal muscle fibers are within each spindle and where are they located?
several and are located at the poles or ends of each fiber
145
How many nuclei do each fiber have and where are they located?
multinucleated with all of the nuclei being located centrally (equatorially).
146
What are the two nuclear arrangements of intrafusal muscle fibers and how are they arranged?
nuclear bag - nuclei are "clumpted" in the middle forming a "bag-like" enlargement of the sarcolemma.
nuclear chain - nuclei arranged linearly in a "chain-like" arrangement
147
How many sensory receptors does each muscle spindle filament have? What are they?
Each filament has at least TWO sensory receptors classified as
Primary Endings - Centrally Located
Secondary Endings - Peripherally Located
to the contractile elements.
148
How are most muscle spindle Primary Endings categorized according to their responsiveness?
Dynamic - highly responsive to the rate of change in the muscle length, encoding the velocity of the stretch. (also referred to as phasic endings, have the histological name annulospiral rings)
149
How are muscle spindle Secondary Endings (and some primary) Endings categorized according to their responsiveness?
Static - responsive to the muscle static muscle length. (also known as tonic endings, have the histological name of flower spray endings)
150
What fiber type carries information from primary endings to the CNS?
Ia fibers
151
What fiber type carries information from secondary endings to the CNS?
II fibers
152
Each fiber in the muscle spindle receives an ending from a ___ on each contractile component.
gamma motor neuron
153
What does activation of a gamma motor neuron innervating the contractile component of the muscle spindle fiber do?
controls the contraction of each spindle. Activation of the y motor neuron results in contraction of the intrafusal fibers and can be used to adjust the sensitivity of each receptor within the muscle spindle.
154
What is the purpose of the gamma motor neuron?
The purpose of the motor activation is to prevent "unloading" of the receptor during extrafusal muscle contraction. The adjustment is specific and separate to the dynamic receptors and static receptors.
155
What is alpha-gamma coactivation?
At the time of alpha motor neuron firing, the appropriate gamma motor neurons are also activated. This results in the muscle spindle adjustment that parallels the contraction of the extrafusal muscle fiber.
156
T/F: Stimulation of the y motor neurons can take place in situations other than alpha-gamma coactivation.
True: It results in an increase in the sensitivity of both the primary and secondary endings.
157
How else are y motor neurons stimulated. What does this allow for?
Can be influenced by central nervous system pathways or by cutaneous stimulation. This allows for fine-tuning of the spindle as the difficulty of the motor task increases.
158
What are golgi tendon organs?
slender capsule encased receptors found at both the origin and insertion of skeletal muscles at musculo-tendonous junctions.
159
How many extrafusal fibers innervate a GTO? How are they attached?
15-20 extrafusal fibers enter the capsule through a funnel like collar, with the other end of the capsule attaching to the tendon. The collagen fibers of the epimysium and perimysium of the muscle become braided with the collagen of the receptor capsule.
160
What type of fiber is associated with GTO?
The GTO receptor is located at the end of Ib nerve fibers.
161
How do the GTO receive signal.
Contraction of extrafusal fiber causes tension on the collagen bundles, compressing the afferent nerve ending, activating a receptor potential, followed by generation of an action potential if the stimulus is sufficient.
162
How sensitive is the GTO?
highly sensitive to small changes in muscle tension, providing continuous feedback to regulate muscle tension.
163
How does GTO play a protective role?
Autogenic Inhibition - It has a high threshold to tension (resisted muscle stretch) that plays a protective role by inhibiting alpha motor neuron activating of the contracting muscle when extremes of range are reached.
164
What do thermal afferents encode?
temperature changes sensed by the skin.
165
What type of receptor are thermal afferents and where are they located?
free nerve ending located in the dermal layer of the skin
166
Thermal afferents are continuous with what fiber type?
A-delta and C fibers
167
Where is the highest concentration of thermal afferents?
Near the midline
168
How are thermal afferents classified?
by their response to cold or heat (separate receptors, separate responses).
169
What do cold afferents respond to?
temperature changes in the 10-33 deg C range (however some can respond to temperatures > 45 degrees)
170
What kind of fiber type is associated with cold afferents?
A-delta and C fibers
171
What kind of fiber type is associated with heat afferents?
C fibers only
172
What are Nocicpetors responsible for and where are they located?
primary stimulus for nociceptors is mechanical damage to tissue, either by temperature extremes or destruction of tissue (mechanical, chemical)
173
What type of receptor are Nociceptors and where are they located?
free nerve endings and occur in both the dermal layers of the skin as well as in many deep tissues including muscles and joints.
174
What are the 3 types of Cutaneous Nociceptive Afferents?
1. A-delta mechanoreceptive nociceptors
2. A-delta mechanothermal nociceptors
3. C-polymodal nociceptors
175
What is the threshold for stimulation and receptive area of a A-delta mechanoreceptive nociceptor?
high threshold for stimulation with small receptive area (20% that lie within fascial planes)
176
What is the primary stimulus for A-delta mechanoreceptive nociceptor?
sharp pain allowing for discrimination between sharp and dull.
177
What sensitizes A-delta mechanoreceptive nociceptor?
intense heat that results in burn hyperalgesia
178
A-delta mechanothermal nociceptors are responsible for what kind of stimulation?
responsive to temperatures between 45 and 53 degrees but also respond to temperatures
179
Muscle and Joint Nociceptive Afferents are associated with what fiber type?
A-delta and C fiber components
180
Muscle and Joint Nociceptive Afferents of A-Delta fiber type are activated by what?
muscle stretch or contraction - ergoreceptive.
181
Muscle and Joint Nociceptive Afferents of C fiber type are activated by what?
intense mechanical or chemical stimuli - ischemic muscle pain
182
Joint Nociceptive Afferents of A-delta and C fiber type are activated by what?
intense pressure and movement
183
What sensitizes Joint Nociceptive Afferents of A-delta and C fiber type?
inflammation. develops into high background firing in the presence of inflammation.
184
What are the 3 categories of Nociceptors?
1. Cutaneous Nociceptive Afferents
2. Muchel and Joint Nociceptive Afferents
3. Visceral Nociceptive Afferents
185
C-polymodal nociceptors are what type of receptor?
free nerve ending
186
What are C-polymodal nociceptors activated by?
thermal ( 45 deg C), mechanical (crush) and chemical (histamine release from tissue damage)
187
What are the majority of cutaneous receptors (>90%)?
C-polymodal nociceptors
188
What fiber type is associated with Visceral Nociceptive Afferents?
C fibers
189
What are Visceral Nociceptive Afferents similar to?
C-polymodal nociceptors
190
What type of information do Visceral Nociceptive Afferents relay and how are they stimulated?
relay poorly localized and referred information. stimulated by twisting, distention and/or inflammation.
191
How many types of hair cells exist in the vestibular system?
Type I and Type II
192
What are the hair cells in the vestibular system activated by?
both are activated by acceleration of the head via mechanoelectrical transduction (mechanical deflection of stereocilia and kinocilium)
193
Stereocilia and Kinocilia
organelles of the hair cells; the tallest cilium in the vestibular hair cell is termed the kinocilium
194
How are the Stereocilia and Kinocilia anchored together and what are they attached to?
by a protein link that is attached to or near leaky K+ and Ca2+ channels (Not Na+)
195
Upon mechanical deflection of the Stereocilia and Kinocilia, what happens?
the leaky K+ and Ca2+ channels are modified (open or closed) to increase or decease the influx of ions
196
What effect does an increase or decrease in ion influx have?
an increase or decrease in neurotransmitter (possibly glutamate) release onto the first order neuron.
197
What is the structure of the vestibular apparatus?
ampulla of the semicircular and macula of the saccule and utricle (part of the otolith)
198
What is the receptor bathed in?
endolymph, a fluid high in K+
199
What does inertial movment of the endolymph result in?
corresponding movment of the stereocilia in relation to the kinocilia resulting in an opening or opening or closing or opening of the leaky channels.
200
What are the two types of visual receptors?
rods and cones
201
Which visual receptor are most active at times of low light?
rods
202
Which visual receptor are located are the periphery of the retina?
rods
203
Which visual receptors are most active in bright light?
cones
204
Which visual receptors are located in the foveal (central) region of the retina?
cones
205
How are the visual receptors similar to the hair cells of the vestibular system?
They are leaky resulting in a continual release of neurotranmitter.
206
How do visual receptors become activated?
by light
207
What happens when visual receptors are activated by light?
it becomes hyperpolarized and results in a decrease in neurotransmitter release.
208
What is the output of the retina?
Ganglion Cell
209
Prior to the output of the retina, the ganglion cell, being activated what must happen first?
a great deal of integration takes place by multiple synapses through bipolar cells, horizontal cells, and amacrine cells.
210
Ganglion cells with large receptive fields represent
peripheral vision
211
Ganglion cells with smaller more precise receptive fields represent
central vision
212
How can Surround an Lateral inhibition be demonstrated with the visual system?
using central vision and the activation of cones
