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DEN 7101S Human Structure and Function II > 1/17 Britton Somatosensory Neurotransmission: Touch, Pain, and Temperature > Flashcards

1/17 Britton Somatosensory Neurotransmission: Touch, Pain, and Temperature Flashcards

1
Q

Sensory Receptors-Basic Function

1) sensory receptors are _______
2) sensory receptors covert stimuli in the environment (touch, temp, pressure) into _____ _____ in sensory neurons
3) the conversion process is called _____ ______

A
  • transducers
  • action potentials
  • sensory transduction
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2
Q

______ like muscle spindles and golgi tendon organs relay info about muscle length and tension

A

Proprioceptors

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3
Q

Rods and cones in the retina that respond to light

A

Photoreceptors

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4
Q

_______are stimulated by chemicals in the environment (taste, smell) as well as internal chemical in plasma

A

Chemoreceptors

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5
Q

______ are cutaneous receptors for touch and pressure

A

Mechanoreceptors

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6
Q

________- detect the sensations of warm and cold

A

Thermoreceptors

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7
Q

________-mediate potentially harmful stimuli such as pain, extreme heat, and extreme cold

A

Nociceptors

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8
Q

Each of the principal types of sensation that we can experience-pain, touch, sight, sound, is called _______ of sensation

A

Modality

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9
Q

The nature of the sensory receptor varies between:

A

Sensory modalities

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10
Q

the sensory receptor may be a _____ ______ at the end of a peripheral nerve

A

Specialized structure

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11
Q

many sensory receptors are ______ _____ cells

A

Specialized epithelial cells (touch, vision, taste, hearing)

Not smell

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12
Q

if the sensory receptor is a specialized structure where will it synapse?

A

On a 1st order neuron

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13
Q

the sensory receptor may be ____ _____ endings of 1st order neurons

A

free nerve endings (touch, temp, pain, smell)

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14
Q

When the receptor is also the 1st order neuron where does it synapse?

A

There is no need for a synapse

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15
Q

Sensory receptors on the skin are:

A

Cutaneous receptors that mediate the sensations of touch, pressure, pain, temperature

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16
Q

Sensory receptors on the skin: associated sensory nerves are classified as _____ fibers according to ______

A

A-beta, A-Delta, and C fibers; diameter and degree of myelination

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17
Q

What are the 3 sensory receptors associated with the skin?

A

Mechanoreceptors, Thermoreceptors, and Nociceptors

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18
Q

What types of sensory receptors are associated with mechanoreceptors and what is their associated afferent type?

A

Most are A-beta; only outlier is free nerve endings, which are A-delta and C fibers

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19
Q

what type of sensory receptors are associated with thermoreceptors and what is their associated afferent type?

A

Warm receptors - C fibers
Cold receptors - A-delta

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20
Q

Warm receptors (thermoreceptors) are _______

A

Free nerve endings

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21
Q

What type of sensory receptors are associated with nociceptors and what is their associated afferent type?

A

A-delta, except polymodal (free nerve endings) are C fibers

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22
Q

Classification of Neuron Fibers

Structural Classification: (3 different types of neurons)

A
  • unipolar
  • bipolar
  • multipolar
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23
Q

Classification of Neuron Fibers

Functional

A
  • sensory
  • interneuron
  • motor neuron
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24
Q

Classification of Neuron Fibers

Direction from CNS

A
  • afferent
  • efferent
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25
Q

Classification of Neuron Fibers

Chemical

A
  • adrenergic
  • cholinergic
  • GABAergic
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26
Q

Classification of Neuron Fibers

Diameter and myelination

A

Speed of conduction (A, B, and C fibers)

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27
Q

_____ can be classified according to their conduction velocity

A

Nerve fibers

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28
Q

What type of nerve fiber is the fastest and has the largest diameter?

A

A-alpha fibers

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29
Q

A-alpha fibers are _____ neurons

A

Motor

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30
Q

Which type of nerve fiber is the slowest?

A

Type C (slow pain)

Postganglionic autonomic nerves, olfaction

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31
Q

_____ fibers are unmyelinated

A

Type C

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32
Q

What results in faster conduction velocites?

A

larger size (diameter) and myelination

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33
Q

Sensory afferent nerve fibers are _______ in many aspects.
What nerve fibers are associated?

A

Heterogenous
A-Beta
A-Delta
C fibers

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34
Q

What type of nerve fibers have a medium conduction velocity and a medium diameter?

A
  • A-beta (touch and pressure)
  • A-Gamma (motor neurons to muscle spindles)
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35
Q

What type of nerve fibers have a small diameter and a medium conduction velocity?

A
  • A-delta; touch, pressure, temp, fast pain
  • B-preganglionic autonomic nerves
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36
Q

Sensory mechanoreceptors sense:

A

Touch and pressure

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37
Q

Name the sensory mechanoreceptors on the skin

A

Free nerve endings
Merkel discs
Pacinian corpuscle
Meissner’s corpuscle
Hair-end organ
Ruffini endings

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38
Q

_____ _____ is the critical first step in all sensory processing

A

Sensory transduction

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39
Q

What activates a sensory receptor?

A

Environmental stimuli such as pressure or temperature, which gets converted into a neuronal AP

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40
Q

The transduction process couples ______ detection (activation of a receptor) to the opening or closing of _____ channels in the receptor membrane. This leads to:

A

Stimulus; ion channels; current flow across the membrane (changes membrane potential)

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41
Q

Current flow across the membrane will result in:

A

A change in membrane potential

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42
Q

A change in membrane potential in a sensory receptor will cause a _____ ______, which will increase or decrease the likelihood that neuronal APs will occur

A

Receptor potential

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43
Q

Another name for receptor potential

A

Generator potential

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44
Q

the _______ is the non-propagated depolarizing potential recorded in a sensory receptor after an adequate stimulus is applied

A

Receptor potential

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45
Q

The _______ is the non-propagated depolarizing potential recorded in a sensory receptor after an adequate stimulus is applied

A

Receptor potential

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46
Q

What makes the receptor potential a graded response?

A

The magnitude of the receptor potential is proportional to the strength of the stimulus

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47
Q

True or false: the receptor potential is a graded response, which is different from the all or nothing neuronal AP

A

True - as the stimulus increases, the magnitude of the receptor potential also increases

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48
Q

When a receptor potential reaches a critical ______ in stimulus strength, an AP is generated in the sensory nerve

A

Threshold

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49
Q

The strength of a stimulus is then conveyed in the sensory nerve by the ______ of AP

A

Frequency

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50
Q

what is it called when a receptor stimulus is converted to a recognizable sensation

A

Sensory coding

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51
Q

The quality and strength of a sensory stimulus is determined by?

A

Properties of the sensory receptors

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52
Q

What are the 4 attributes of stimuli that all sensory systems encode?

A
  • modality
  • intensity
  • duration
  • location (receptive field)
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53
Q

Modality

A

Mode of stimuli that can be sensed by the receptor

54
Q

What are examples of mechanical modalities?

A

Touch, pressure, vibration

55
Q

What are examples of chemical modalties?

A
  • Bradykinin
  • Prostaglandin
  • pH
  • histamine
56
Q

What are the temperature modalities?

A

Hot and cold

57
Q

What is the intensity of a stimulus coded by? (2 things)

A
  • the # of receptors activated
  • the frequency of APS (stronger stimuli produce a HIGHER frequency of APs)
58
Q

What is population coding?

A

The number of receptors activated

59
Q

What is frequency coding?

A

Frequency of APs

60
Q

Sensory Coding: Duration
1. ________ is a decrease in the size of the receptor potential with a constant stimulus
2. _____ ______ receptors keep stimulating APs as long as the stimulus is present
3. _____ ______ receptors respond maximally but briefly when a stimulus is presented; their response ______ if the stimulus is maintained

A
  1. Adaptation
  2. Slowly Adapting Receptors
  3. Rapidly Adapting Receptors; decreases
61
Q

Examples of slowly adapting receptors

A

Merkel disc, Ruffini corpuscle (detect sustained pressure)

62
Q

Examples of rapidly adapting receptors

A

Meissner’s and Pacinian corpuscle (can detect next pressure quickly applied)

63
Q

The ______ ______ of a sensory neuron is the region of the skin within which a tactile stimulus evokes a sensory response in its axon

A

Receptive field

64
Q

The accuracy by which tactile stimuli can be sensed varies in different regions of the body is called:

A

Mechanosensory discrimination

65
Q

How big is the receptive field of mechanosensory neurons on the fingertips?

A

1-2mm

66
Q

How big is the receptive field on the palms?

A

5-10 mm

67
Q

How can the variation of receptive fields be measured?

A

Two point discrimination test

68
Q

Two Point Discrimination Test
1) a technique that measures the _______ inter-stimulus distance required to perceive 2 simultaneously applied stimuli as ______
2) measures the ______ distance on the skin between neighboring receptive fields for touch

A

1) minimal, distinct
2) minimum

69
Q

Smaller discrimination point means:

A

Smaller receptive field

70
Q

Mechanosensory discrimination is due to:

A
  • density of mechanoreceptors
  • size of receptive fields
71
Q

Mechanoreceptors in the fingertips are 3-4x _______ and ______ than in other areas of the hand

A

More numerous and dense

72
Q

Mechanoreceptor: Free Nerve Ending

Name the associated afferent nerve type, location, adaptation, and modality

A
  • A-delta, C
  • Superficial, all skin
  • Modality: light touch
  • Adaptation: slow
73
Q

Mechanoreceptor: Merkel’s Disk

Name the associated afferent nerve type, location, adaptation, and modality

A
  • A-beta
  • Superficial, all skin
  • Adaptation: slow
  • Modality: pressure
74
Q

Mechanoreceptor: Pacinian Corpuscle

Name the associated afferent nerve type, location, adaptation, and modality

A
  • A-beta
  • Deep, all skin
  • Adaptation: Rapid
  • Modality: vibration
75
Q

Mechanoreceptor: Meissner’s Corpuscle

Name the associated afferent nerve type, location, adaptation, and modality

A
  • A-beta
  • Superficial, Glabrous Skin
  • Adaptation: rapid
  • Modality: vibration
76
Q

Mechanoreceptor: Hair Follicle Receptor

Name the associated afferent nerve type, location, adaptation, and modality

A
  • A-beta
  • Superficial, hairy skin
  • Adaptation: slow
  • Modality: bending of hair
77
Q

Mechanoreceptor: Ruffini’s ending

Name the associated afferent nerve type, location, adaptation, and modality

A
  • A-beta
  • Deep, hairy skin
  • Adaptation: slow
  • Modality: pressure
78
Q

_____ _______ gives us the ability to differentiate information through the sense of touch

A

Tactile discrimination

79
Q

Thermoreceptors examples

A
  • Warm receptors (free nerve endings)
  • Cold receptors
80
Q

Nociceptors examples

A

Mechanical, Thermal, Polymodal (all free nerve endings)

81
Q

Nociceptors and thermoreceptors are relatively ___________ on _______ or _______ in hairy or glabrous skin and deep tissues

A

unspecialized; unmyelinated C fibers; myelinated A-delta fibers

82
Q

Like mechanoreceptors, _______ transduce a variety of stimuli into _____ potentials

A

nociceptors
receptor
(stimuli can be tissue damage from a cut, strong mechanical pressure, extreme heat, etc.)

83
Q

nociceptors are often referred to as ______ _____ fibers

A

Polymodal nerve fibers (different modes of pain detected)

84
Q

Nociceptors detect ______ stimuli

A

Noxious (harmful, injurious)

85
Q

1) nociceptors express a wide variety of _____ channels that transduce the ______ potential into a ______
2) the resulting _____ potential (depolarization) triggers the activation of _____ channels which will generate a _______ neuronal AP

A

1) ion, receptor, neuronal AP
2) receptor, ion, propagating

86
Q

Sensory Transduction at Nociceptors: the transduction process couples _______ to _______ in the receptor membrane

A

stimulus detection (activation of a receptor) to the opening or closing of ion channels

87
Q

Sensory transduction involves a complex of molecular ________ present on distinct subsets of nerve fibers

A

Transducers (ion channels)

88
Q

Ion channels involved in transduction

A
  • Acid sensing channels (ASIC)
  • Purinergic Ion channels
  • Piezo mechanosensitive channels
  • ANO1 (Ca2+-gated chloride channels)
  • Transient Receptor Potential channels (TRP)
89
Q

Acid sensing ion channels (ASIC) activated by:

A

Protons (H+)

90
Q

Purinergic ion channels activated by:

A

ATP

91
Q

Piezo mechanosensitive channels activated by:

A

Mechanical sensation

92
Q

Activation of nociceptors leads to current flow across the membrane, generates a ______ potential, which will result in neuronal APs

A

Receptor potential

93
Q

Transient Receptor Potential Channels (TRP)

  1. these are a ______ of ion channels
  2. TRP channels that open in response to stimuli result in _______ and the generation of _____ potentials
  3. TRP channels are found on _____ _____ _____ of polymodal neurons (temp and pain sensing)
A
  1. superfamily
  2. depolarization, receptor
  3. free nerve endings
94
Q

TRP-V (TRP-vanilloid) - what modalities does this channel respond to?

What is this channel stimulated by?

A
  • responds to heat and pain
  • stimulated by capsaicin, the spice in chili peppers
95
Q

TRP Channels: Heat, Cold and Pain Transducers

TRP-M (TRP-melastatin) is stimulated by?

A

Stimulated by cold and menthol

96
Q

TRP channels are localized to:

A

Trigeminal, vagal, and dorsal root ganglia

97
Q

TRP channels transduce what stimuli into _____ fluxes?

A
  • Visual, chemical, thermal, mechanical, painful, and osmotic stimuli
  • Ca2+ fluxes
98
Q

Examples of TRP channels

A
  • TRP-V
  • TRP-M
  • TRP-A
99
Q

TRP Channels: Heat, Cold and Pain Transducers

TRP-A (TRP-ankyrin repeat)

What modality does this channel respond to?

what is this a transducer for?

A

responds to heat

transducer for pungent chemicals

100
Q

______ blocks TRPV1 which is a major component of ______

A

Cetylpyridinium chloride; Scope mouthwash

101
Q

The discovery of TRPV1 in sensory neurons

The majority of transducers belong to the thermo-sensitive _____ family of ion channels

A

TRP family of ion channels

102
Q

What are the 3 types of pain that are generally distingushed?

A

Nociceptive, inflammatory, neuropathic

103
Q

Inflammatory pain is associated with ______ caused by tissue inflammatory conditions, which can lead to:

A

damage; chronic pain syndromes

104
Q

Neuropathic pain
1) a ______ pain state, characterized by _____ and or _____ nerve injury
2) can lead to?
3) tends to be refractory to:

A

1) chronic, peripheral and/ or central nerve

2) chronic pain syndromes characterized by hyperalgesia, allodynia, fibromyalgia

3) pharmacological treatment

105
Q

Types of nociceptive pain

A

Fast and slow

106
Q

Fast pain (sharp, pricking) - ____ localized and transmitted by _____ fibers

A

Well; A-delta

107
Q

Slow pain (dull, aching) - _____ localized, transmitted by ______

A

Poorly; C fibers

108
Q

Inflammatory mediators induce pain by activating ______

A

Nociceptors

109
Q

Examples of neuropathic pain

A

traumatic nerve injury
diabetic neuropathy
chemotherapy induced peripheral neuropathy (CIPN)

110
Q

What is an ‘inflammatory soup’

A

describes the mixture of substances released from damaged tissue, immune cells, and bacteria

111
Q

Nociceptor activation and transduction is triggered through a wide variety of ____ channels
what are some of the ion channels that get activated?

A

Ion; GPCR’s, RTK’s, ligand gated ion channels. other channels and pores

112
Q

Nociceptors arise from cell bodies in the _______ that send ____ axonal process to the periphery and the other into the _______

A

DRG or trigeminal ganglion; 1; spinal cord or brainstem

113
Q

The nociceptive signal is transmitted to the _____ synapse in the spinal _____ horn by releasing a variety of neurotransmitters at the synapse, such as:

A
  • Central
  • Dorsal
  • Substance P, Glutamate, Calcitonin, Calcitonin gene related peptide (CGRP)
114
Q

1) Dental pulp contains:
2) What types of fibers are present?

A

1) abundant sensory fibers of TG neurons
2) A-delta and C fibers

115
Q

The nociceptive signal is conducted through either _____ or _____ to the _______ of the ______

A
  • myelinated A-delta fibers
  • unmyelinated C fibers
  • lamina I and II of the dorsal horn in the spinal cord
116
Q

Characteristics of A-delta fibers in DENTAL PAIN
Myelination:?
Location of terminals:?
Pain Characteristics: ?

A
  • Yes
  • Principally in region of pulp-dentin junction
  • Sharp, pricking
117
Q

characteristics of C- fibers in DENTAL PAIN
Myelination:?
Location of terminals:?
Pain Characteristics: ?

A
  • No
  • Distributed throughout pulp
  • Burning, aching, less bearable than A-delta fiber sensations
118
Q

Sensory Pathways

Steps Involved in Transmitting Sensory Info
1) information transmitted from _____ receptors to the _____ cortex via a series of neurons
2) order of sensory afferent neurons
3) synapses are made in _____ ______

A

1) peripheral, cerebral
2) 1st, 2nd, 3rd, 4th order sensory afferent neurons
3) relay nuclei

119
Q

Relay Nuclei
1) often ______ pathways, where 2 or more neurons synapse with the 1 neuron
2) ______ may also be located in the relay nuclei
3) the relay nuclei process the info they receive via _______ which may be excitatory or inhibitory? (give examples)

A

1) converging
2) interneurons
3) interneurons
Excitatory: ACh
Inhibitory: GABA and Glycine

120
Q

Sensory Pathways

1) _______ are closest to the sensory receptor

2) cell bodies are located in a ______ or _______ ganglion

A

1) 1st order or primary sensory neurons

2) DRG or cranial nerve ganglion

EXCEPT: auditory, olfactory, and visual systems

121
Q

In some cases, the 1st order neuron is also the receptor cell, termed-

A

Free nerve endings

122
Q

2nd order neurons
1) axons of the 2nd order neurons (descend/ascend) from the spinal cord to the next relay located in the ______
2) en route, the axons of 2nd order neurons ______ _____ _____ (decussation) either in the spinal cord or in the brain stem

A

1) ascend, thalamus
2) cross the midline-decussation

123
Q

3rd Order Neurons are typically located in the ______

A

Thalamus

124
Q

4th Order Neurons reside in the _____ area of the ______ cortex

A

Sensory area of the cerebral cortex

125
Q

What is the sensory nerve that innervates the orofacial region?

A

trigeminal nerve (CN V)

126
Q

______ stimuli in teeth are transmitted in primary ______ neurons (1st order neurons) located in the trigeminal ganglion via ______ order neurons in the brain stem to the brain

A

noxious, afferent, 2nd

127
Q

What are the 2 major ascending somatosensory pathways?

A
  • Dorsal Column-Medial Lemniscal (DCML)
  • Lateral Spinothalamic Tract (LST)
128
Q

What sensory information is relayed in the DCML pathway

A

Mechanoreceptors, proprioceptors

129
Q

What sensory information is relayed in the LST pathway

A

Thermoreceptors, nociceptors

130
Q

Somatosensory sensations from all areas of the body go to the _____ cortex

A

Sensory

131
Q

______ ______ is a neurological ‘map’ of the portions of the cortex dedicated to processing sensory information from different regions of the body

A

Sensory homunculus

DEN 7101S Human Structure and Function II (21 decks)

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