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DPT704: Neuro Hank > 3 - Peripheral Nervous System ad Sensory Receptors > Flashcards

3 - Peripheral Nervous System ad Sensory Receptors Flashcards

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.

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2
Q

What is included in sensation?

A
  1. process of sensory transduction
  2. receptor potential summation
  3. action potential generation
  4. neural processes that integrate signals centrally
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3
Q

how do neural processes integrate signals centrally

A

either facilitation (depolarization) or inhibition (hyperpolarization)

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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.

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5
Q

Where does perception occur in various degrees of refinement?

A
  1. thalamus
  2. basal ganglia
  3. cerebellum
  4. cortex
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6
Q

Perception at the cortical level is usually considered ____

A

conscious perception

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7
Q

Perception at the level of the cerebellum is considered ___

A

unconscious perception

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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.

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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.

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10
Q

Define sensory transduction.

A

changing the energy of a stimulus into a neural energy.

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11
Q

What are the three form of stimulus energy?

A

mechanical, chemical, and light

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12
Q

What does stimulus energy produce?

A

a change in the receptor membrane such that a local potential differences occur.

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13
Q

What is a local potential difference?

A

Na+, K+, and Cl- channels open to allow ion movement.

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14
Q

T/F: Potential changes from stimulus energy are local and spread only a few milimeters as they decay.

A

True

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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.

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16
Q

T/F: some receptors have low thresholds and some have high.

A

True

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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

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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

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19
Q

Define threshold for perception

A

lowest stimulus intensity necessary for perception of stimulus

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20
Q

Describe threshold for perception vs. receptor threshold

A

threshold for perception may be modified by context and experience.

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21
Q

Define adaptation

A

the duration for which the receptor potential is generated to the stimulus.

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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.

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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.

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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.

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25
Q

This [receptors activated] is then transferred to the generation of action potentials and coded by ____.

A

the frequency of action potentials and the number of discharge fibers.

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26
Q

The stronger the stimulus, the ___

A

greater the size of the receptor potentials (depolarization).

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27
Q

the greater the size of the receptor potentials (depoalrization), the ____

A

greater the number of receptors being activated

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28
Q

the greater the number of receptors being activated, the ____

A

greater summation of the depolarizing events

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29
Q

the greater summation of the depolarizing events, ___

A

and thus the increased frequency of action potentials.

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30
Q

With an increase in the frequency of action potentials, what is happending to the amplitude and speed at which the action potentials are traveling

A

amplitude and speed remain unchanged.

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31
Q

how is location of stimulus determined?

A

signaled by firing a specific gorup of neurons activated by stimulus.

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32
Q

What is a receptive field?

A

area surrounding the receptor that when stimulated excites or inhibits the firing of a paticular cell.

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33
Q

What size and number of receptive fields do the most sensitive parts of the body have for example tips of fingers and tongue?

A

smallest receptive fields and largest number of receptive fields per area

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34
Q

As you move proximally on the body, what happens to the size, density, and sensitivity of field receptors?

A

receptive field size increases, density of receptors decreases as does the sensitivity.

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35
Q

Define dermatomes

A

area of the body surface contributing sensory input to one dorsal root.

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36
Q

where is excititory discharge greatest for a receptive field?

A

at the center

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37
Q

where is inhibitory greatest for a receptive field?

A

at the periphery

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38
Q

what is the purpose of the layout of a receptive field?

A

serves to shapen peak of activity within the brain.

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39
Q

Where does this sharpening of peak activity occur?

A

first in dorsal column nuclei and then at subsequent synapse in the CNS. Also present in the visual system.

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40
Q

What is the purpose of this lateral inhibition?

A

serves to enhance distinction between two stimuli and aids in recognition of pattern and contour.

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41
Q

Which areas are responsible for orderly mapping of sensations from body surface onto CNS area?

A

dorsal column neclei, thalamus, somatosensory cortex (sensory humuculus).

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42
Q

The areas with the ____ receptor density will have the ____ cortical receptive field.

A

The areas with the LARGEST receptor density will have the LARGEST cortical receptive field.

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43
Q

There are also cells in the sensory cortex that respond to ___

A

specific orientation, movement, and shape of stimulus.

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44
Q

Define exteroceptors

A

stimuli from the external environment

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45
Q

define proprioceptors

A

position of body segments relative to each other and position of body and head in space

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46
Q

Define interoceptors

A

signal body events such as blood glucose level and blood pressure.

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47
Q

What are the three classifications of sensory receptors according to stimulus location?

A
  1. Exteroceptors
  2. Proprioceptors
  3. Interoceptors
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48
Q

What are the 6 classifications of sensory receptors according to the sensory system?

A
  1. Somatic
  2. Visual
  3. Vestibular
  4. Auditory
  5. Olfactory
  6. Gustatory
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49
Q

What is includes in the Somatic sensory receptor classification?

A

tactile, joint, muscle, tendon, thermal, pain

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50
Q

What are the 5 classifications of sensory receptors according to stimulus energy?

A
  1. Mechanoreceptors
  2. Chemoreceptors
  3. Nociceptors
  4. Thermoreceptors
  5. Photoreceptors
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51
Q

What do mechanoreceptors detect?

A

touch/pressure, proprioception, air waves

innocuous physical contact with the skin causes mechanical alteration or deformation detected by these receptors

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52
Q

What do chemoreceptors detect?

A

taste, smell, blood gas level

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53
Q

What do nociceptors detect? Encapsulated or Unencapsulated free nerve ending? primary afferent fiber type?

A 
damage stimuli (pain)
Unencapsulated free nerve ending
A-delta () and C fibers

sensory inputs include mechanical (or cutaneous), thermal extremes, and polymodal

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54
Q

What do thermoreceptors detect? Encapsulated or Unencapsulated free nerve ending? primary afferent fiber type?

A

heat and cold
Unencapsulated free nerve ending
A-delta and C fibers

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55
Q

What do photoreceptors detect?

A

light

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56
Q

Which sensory fiber type has the largest diameter?

A

Ia (A- a)

Ib (A- a)

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57
Q

Which sensory fiber type has the smallest diameter?

A

IV (C)

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58
Q

Which sensory fiber type has the fastest conduction velocity?

A

Ia (A- a)

Ib (A- a)

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59
Q

Which sensory fiber type has the slowest conduction velocity?

A

IV (C)

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60
Q

What are the sensory fiber types?

A 
Ia (A- alpha)
Ib (A- alpha)
II (A- beta)
III (A- delta)
IV (C)
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61
Q

Where are sensory fiber type Ia (A- alpha) found or responsible for?

A

Primary afferents of muscle spindle

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62
Q

Where are sensory fiber type Ib (A- alpha) found or responsible for?

A

Golgi tendon organ

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63
Q

Where are sensory fiber type II (A- beta) found or responsible for?

A

Secondary afferents of muscle spindle, touch, pressure, and vibration

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64
Q

Where are sensory fiber type III (A- delta) found or responsible for?

A

Touch and pressure, pain and temperature (Thermoreceptors and Nociceptors)

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65
Q

What are sensory fiber type IV (C) found or responsible for?

A

pain and temperature, unmylenated fibers (Thermoreceptors and Nociceptors)

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66
Q

What determines the conduction velocity of a fiber? (2)

A

small diameter fibers are slower because they provide more resistance to flow of current and have less insulation from myelin

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67
Q

What determines the amplitude of an action potential?

A

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)

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68
Q

What determines the threshold for stimulus?

A

small diameter fibers have a higher threshold for stimulation because they offer more resistance to current flow

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69
Q

Will a C fiber type require lower or higher intensity of e-stim to activate?

A

higher because it is the smallest diameter so has the highest threshold for stimulation because it offers the most resistance to current flow.

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70
Q

What are the 4 types of Motor fibers?

A
  1. Alpha (A-a)
  2. Gamma (A-g)
  3. Preganglionic ANS fibers (B)
  4. Postganglionic ANS fibers (C)
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71
Q

Which motor fiber type has the largest diameter?

A

Alpha (A-a)

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72
Q

Which motor fiber type has the smallest diameter?

A

Postganglionic ANS fibers

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73
Q

What is the role of Alpha (A-a) fibers?

A

Motor neuron innervating extrafusal muscle fiber

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74
Q

What is the role of Gamma (A-g) fibers?

A

Motor neuron innervating intrafusal muscle fiber

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75
Q

What is the role of Preganglionic ANS fibers (B)

A

Lightly myelinated

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76
Q

What is the role of Postganglionic ANS fibers (C)

A

Unmyelinated

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77
Q

Merkel’s disc

Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
A

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

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78
Q

Ruffini ending

Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
A

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

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79
Q

Meissner’s corpuscle

Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
A

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

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80
Q

Hair follicle

Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
A

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

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81
Q

Pacinian corpuscle

Peripheral Fiber Type
Response Properties
Receptive Field Size
Activation Threshold
Adequate Stimulus
Sensation Evoked
Receptor Shape
Fiber:Receptor Ratio
A

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

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82
Q

What is a first order neuron?

A

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.

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83
Q

What are the three ways fibers can be classified?

A
  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)
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84
Q

Describe an A-delta fiber

A

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

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85
Q

Describe a C fiber

A

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
Q

A-delta fibers are stimulated by low-threshold or high-threshold receptors?

A

low-threshold

87
Q

C fibers are stimulated by low-threshold or high-threshold receptors?

A

high-threshold

88
Q

What are the 5 types of Muscle and Skeletal Mechanoreceptors?

A
  1. Muscle Spindle Primary
  2. Muscle Spindle Secondary
  3. Golgi Tendon Organ
  4. Joint capsule mechanoreceptors
  5. Stretch-sensitive free endings
89
Q

What type of fiber is associated with Muscle spindle primary?

A

A-alpha Ia

90
Q

What do the Muscle spindle primary respond to?

A

Muscle length and speed

91
Q

What do the 5 muscle and skeletal mechanoreceptors respond to?

A

Limb proprioception

92
Q

What type of fiber is associated with Muscle spindle secondary?

A

A-beta II

93
Q

What do the Muscle spindle secondary respond to?

A

Muscle stretch

94
Q

What type of fiber is associated with Golgi tendon organ?

A

A-alpha Ib

95
Q

What do the Golgi tendon organ respond to?

A

Muscle contraction

96
Q

What type of fiber is associated with Joint capsule mecanoreceptors?

A

A-beta II

97
Q

What do Joint capsule mechanoreceptors respond to?

A

Joint angle

98
Q

What type of fiber is associated with Stretch-sensitive free endings

A

A-delta III

99
Q

What do Stretch sensitive free endings respond to?

A

Excess stretch or force

100
Q

Low-threshld mechanoreceptors are activiated by

A

light, nonpainful tactile stimuli

101
Q

High-threshold mechanoreceptors are activiated by

A

potentially tissue-damaging sensory events

102
Q

The axons responding only to the onset and offset of mechanical deformation of the skin are classified as ___

A

rapidly adapting (indicating that they quickly adapt to an object in contact with the skin)

103
Q

Nerve fibers that discharge when tactile stimulus is applied and continue to respond during the stimulus presentation are called ____

A

slowly adapting

104
Q

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 ___

A

receptive field [of that unit].

105
Q

Nerve fibers can be defined using a combination of ___ and ____.

A 
receptive field size (the spatial properties)
adaptation rate (the temporal properties)
106
Q

Does Type I refer to a small or large receptive field?

A

Small

107
Q

Does Type 2 refer to a small or large receptive field?

A

Large

108
Q

Describe a SA Type 1 receptor?

A

Slowly Adapting (continuously responding) Small Receptive Field

109
Q

Describe a RA Type 2 receptor

A

Rapidly Adapting (respond to onset and offset) Large Receptive Field

110
Q

Where are joint mechanoreceptors located?

A

in the joint capsule

111
Q

How many types of joint mechanoreceptors are there? What are they?

A

Type I
Type II
Type III
Type IV

112
Q

Type I joint mechanoreceptors resemble what cutaneous mechanoreceptor?

A

Encapsulated “Ruffini-like”

113
Q

Type II joint mechanoreceptors resemble what cutaneous mechanoreceptor?

A

Encapsulated “paciniform”

114
Q

Type III joint mechanoreceptors resemble what cutaneous mechanoreceptor?

A

Encapsulated “GTO-like”

115
Q

Type IV joint mechanoreceptors resemble what cutaneous mechanoreceptor?

A

Free nerve endings

116
Q

Where are Type I mechanoreceptors located?

A

Ligaments, joint capsule, proximal joints

117
Q

Where are Type II mechanoreceptors located?

A

Synovial junction of joint capsule, fat pads of joint, distal joints.

118
Q

Where are Type III mechanoreceptors located?

A

Ligaments, all joints of the body

119
Q

Where are Type IV mechanoreceptors located?

A

Joint capsule, ligaments, periosteum

120
Q

What do Type I joint mechanoreceptors respond to?

A

Mechanoreceptors, slow adapting, low threshold, active during movement and rest

121
Q

What do Type II joint mechanoreceptors respond to?

A

Mechanoreceptors, rapidly adapting, low threshold, active at beginning and end of movement

122
Q

What do Type III joint mechanoreceptors respond to?

A

Mecanoreceptors, slow adapting, high threshold, active at extremes of range and with longitudinal traction

123
Q

What do Type IV joint mechanoreceptors respond to?

A

Pain receptors, slow adapting, high threshold, active with extreme mechanical force or chemical irritation

124
Q

What is the function of Type I joint mechanoreceptors?

A

Contributes to regulation of postural muscle tone, kinesthesia, regulation of muscle tone during movement.

125
Q

What is the function of Type II joint mechanoreceptors?

A

Provides information about beginning and end of joint movement, may help “boost” muscle tone at beginning of movement to overcome inertia.

126
Q

What is the function of Type III joint mechanoreceptors?

A

Respond to sudden joint movements and may cause reflex muscle contraction to limit further movement

127
Q

What is the function of Type IV joint mechanoreceptors?

A

May contribute to a flexion reflex, or to a co-contraction patter around a joint to prevent further movement.

128
Q

What peripheral fiber type is a Merkel’s disc?

A

Slowly Adapting Type I

129
Q

What peripheral fiber type is a Ruffini ending?

A

Slowly Adapting Type II

130
Q

What peripheral fiber type is a Meissner’s Corpuscle?

A

Rapidly Adapting Type I

131
Q

What peripheral fiber type is a Hair follicle?

A

Rapidly Adapting Type I

132
Q

What peripheral fiber type is a Pacinian corpuscle?

A

Rapidly adapting Type II

133
Q

What is adequate stimulus for a Merkel’s disc?

A

Deformation of skin - Light uniform pressure, like a watercolor brush against the skin

134
Q

What is adequate stimulus for a Ruffini ending?

A

Skin stretch; joint movment - no conscious experience

135
Q

What is adequate stimulus for a Meissner’s corpuscle?

A

Rapid skin displacement - buzzing, wobbling, or flutter

136
Q

What is adequate stimulus for a Hair follicle?

A

displacement of hair shaft

137
Q

What is adequate stimulus for a Pacinian corpuscle?

A

High frequency mechanical transients; most sensitive to viibration at 200-300 Hz - Buzzing, flutter

138
Q

What are muscle spindles?

A

Muscle spindles are specialized muscle fibers containing contractile elements.

139
Q

How are muscle spindles encased?

A

These specialized muscle fibers are encased in connective tissue sheath

140
Q

Where are muscle spindles anchored?

A

anchored to the endomysium and perimysium that surrounds the fasicles of the muscle.

141
Q

What are the contractile fibers within muscle spindles referred to as?

A

intrafusal muscle fibers

142
Q

What are the contractile fibers that make up the bulk of the muscle referred to as?

A

extrafusal muscle fibers

143
Q

T/F: both intrafusal and extrafusal muscle fibers have a typical sarcomere arrangement.

A

true

144
Q

How many intrafusal muscle fibers are within each spindle and where are they located?

A

several and are located at the poles or ends of each fiber

145
Q

How many nuclei do each fiber have and where are they located?

A

multinucleated with all of the nuclei being located centrally (equatorially).

146
Q

What are the two nuclear arrangements of intrafusal muscle fibers and how are they arranged?

A

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
Q

How many sensory receptors does each muscle spindle filament have? What are they?

A

Each filament has at least TWO sensory receptors classified as
Primary Endings - Centrally Located
Secondary Endings - Peripherally Located
to the contractile elements.

148
Q

How are most muscle spindle Primary Endings categorized according to their responsiveness?

A

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
Q

How are muscle spindle Secondary Endings (and some primary) Endings categorized according to their responsiveness?

A

Static - responsive to the muscle static muscle length. (also known as tonic endings, have the histological name of flower spray endings)

150
Q

What fiber type carries information from primary endings to the CNS?

A

Ia fibers

151
Q

What fiber type carries information from secondary endings to the CNS?

A

II fibers

152
Q

Each fiber in the muscle spindle receives an ending from a ___ on each contractile component.

A

gamma motor neuron

153
Q

What does activation of a gamma motor neuron innervating the contractile component of the muscle spindle fiber do?

A

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
Q

What is the purpose of the gamma motor neuron?

A

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
Q

What is alpha-gamma coactivation?

A

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
Q

T/F: Stimulation of the y motor neurons can take place in situations other than alpha-gamma coactivation.

A

True: It results in an increase in the sensitivity of both the primary and secondary endings.

157
Q

How else are y motor neurons stimulated. What does this allow for?

A

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
Q

What are golgi tendon organs?

A

slender capsule encased receptors found at both the origin and insertion of skeletal muscles at musculo-tendonous junctions.

159
Q

How many extrafusal fibers innervate a GTO? How are they attached?

A

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
Q

What type of fiber is associated with GTO?

A

The GTO receptor is located at the end of Ib nerve fibers.

161
Q

How do the GTO receive signal.

A

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
Q

How sensitive is the GTO?

A

highly sensitive to small changes in muscle tension, providing continuous feedback to regulate muscle tension.

163
Q

How does GTO play a protective role?

A

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
Q

What do thermal afferents encode?

A

temperature changes sensed by the skin.

165
Q

What type of receptor are thermal afferents and where are they located?

A

free nerve ending located in the dermal layer of the skin

166
Q

Thermal afferents are continuous with what fiber type?

A

A-delta and C fibers

167
Q

Where is the highest concentration of thermal afferents?

A

Near the midline

168
Q

How are thermal afferents classified?

A

by their response to cold or heat (separate receptors, separate responses).

169
Q

What do cold afferents respond to?

A

temperature changes in the 10-33 deg C range (however some can respond to temperatures > 45 degrees)

170
Q

What kind of fiber type is associated with cold afferents?

A

A-delta and C fibers

171
Q

What kind of fiber type is associated with heat afferents?

A

C fibers only

172
Q

What are Nocicpetors responsible for and where are they located?

A

primary stimulus for nociceptors is mechanical damage to tissue, either by temperature extremes or destruction of tissue (mechanical, chemical)

173
Q

What type of receptor are Nociceptors and where are they located?

A

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
Q

What are the 3 types of Cutaneous Nociceptive Afferents?

A
  1. A-delta mechanoreceptive nociceptors
  2. A-delta mechanothermal nociceptors
  3. C-polymodal nociceptors
175
Q

What is the threshold for stimulation and receptive area of a A-delta mechanoreceptive nociceptor?

A

high threshold for stimulation with small receptive area (20% that lie within fascial planes)

176
Q

What is the primary stimulus for A-delta mechanoreceptive nociceptor?

A

sharp pain allowing for discrimination between sharp and dull.

177
Q

What sensitizes A-delta mechanoreceptive nociceptor?

A

intense heat that results in burn hyperalgesia

178
Q

A-delta mechanothermal nociceptors are responsible for what kind of stimulation?

A

responsive to temperatures between 45 and 53 degrees but also respond to temperatures

179
Q

Muscle and Joint Nociceptive Afferents are associated with what fiber type?

A

A-delta and C fiber components

180
Q

Muscle and Joint Nociceptive Afferents of A-Delta fiber type are activated by what?

A

muscle stretch or contraction - ergoreceptive.

181
Q

Muscle and Joint Nociceptive Afferents of C fiber type are activated by what?

A

intense mechanical or chemical stimuli - ischemic muscle pain

182
Q

Joint Nociceptive Afferents of A-delta and C fiber type are activated by what?

A

intense pressure and movement

183
Q

What sensitizes Joint Nociceptive Afferents of A-delta and C fiber type?

A

inflammation. develops into high background firing in the presence of inflammation.

184
Q

What are the 3 categories of Nociceptors?

A
  1. Cutaneous Nociceptive Afferents
  2. Muchel and Joint Nociceptive Afferents
  3. Visceral Nociceptive Afferents
185
Q

C-polymodal nociceptors are what type of receptor?

A

free nerve ending

186
Q

What are C-polymodal nociceptors activated by?

A

thermal ( 45 deg C), mechanical (crush) and chemical (histamine release from tissue damage)

187
Q

What are the majority of cutaneous receptors (>90%)?

A

C-polymodal nociceptors

188
Q

What fiber type is associated with Visceral Nociceptive Afferents?

A

C fibers

189
Q

What are Visceral Nociceptive Afferents similar to?

A

C-polymodal nociceptors

190
Q

What type of information do Visceral Nociceptive Afferents relay and how are they stimulated?

A

relay poorly localized and referred information. stimulated by twisting, distention and/or inflammation.

191
Q

How many types of hair cells exist in the vestibular system?

A

Type I and Type II

192
Q

What are the hair cells in the vestibular system activated by?

A

both are activated by acceleration of the head via mechanoelectrical transduction (mechanical deflection of stereocilia and kinocilium)

193
Q

Stereocilia and Kinocilia

A

organelles of the hair cells; the tallest cilium in the vestibular hair cell is termed the kinocilium

194
Q

How are the Stereocilia and Kinocilia anchored together and what are they attached to?

A

by a protein link that is attached to or near leaky K+ and Ca2+ channels (Not Na+)

195
Q

Upon mechanical deflection of the Stereocilia and Kinocilia, what happens?

A

the leaky K+ and Ca2+ channels are modified (open or closed) to increase or decease the influx of ions

196
Q

What effect does an increase or decrease in ion influx have?

A

an increase or decrease in neurotransmitter (possibly glutamate) release onto the first order neuron.

197
Q

What is the structure of the vestibular apparatus?

A

ampulla of the semicircular and macula of the saccule and utricle (part of the otolith)

198
Q

What is the receptor bathed in?

A

endolymph, a fluid high in K+

199
Q

What does inertial movment of the endolymph result in?

A

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
Q

What are the two types of visual receptors?

A

rods and cones

201
Q

Which visual receptor are most active at times of low light?

A

rods

202
Q

Which visual receptor are located are the periphery of the retina?

A

rods

203
Q

Which visual receptors are most active in bright light?

A

cones

204
Q

Which visual receptors are located in the foveal (central) region of the retina?

A

cones

205
Q

How are the visual receptors similar to the hair cells of the vestibular system?

A

They are leaky resulting in a continual release of neurotranmitter.

206
Q

How do visual receptors become activated?

A

by light

207
Q

What happens when visual receptors are activated by light?

A

it becomes hyperpolarized and results in a decrease in neurotransmitter release.

208
Q

What is the output of the retina?

A

Ganglion Cell

209
Q

Prior to the output of the retina, the ganglion cell, being activated what must happen first?

A

a great deal of integration takes place by multiple synapses through bipolar cells, horizontal cells, and amacrine cells.

210
Q

Ganglion cells with large receptive fields represent

A

peripheral vision

211
Q

Ganglion cells with smaller more precise receptive fields represent

A

central vision

212
Q

How can Surround an Lateral inhibition be demonstrated with the visual system?

A

using central vision and the activation of cones

DPT704: Neuro Hank (14 decks)

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