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Somatosensory Physiology N19 Flashcards

1
Q

Sensory Transduction

A

process by which a stimulus is transformed into an electrical response

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2
Q

Sensory unit

A

one afferent peripheral process with all of its receptor endings and receptors

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3
Q

Receptors can be either

A

specialized endings of afferent neurons or separate receptor cells that signal afferent neurons via chemical messengers

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4
Q

Stimulus generates a

A

graded potential, or receptor potential, in the nerve generating a local current

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5
Q

Threshold in an afferent neuron

A

If threshold is reached, an AP travels to the CNS

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6
Q

Increase in graded potential magnitude generates

A

an increase in AP frequency and an increase in neurotransmitters released at the CNS synapse

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7
Q

Increase in graded potential magnitude does not change AP’s _____

A

magnitude

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8
Q

Factors that change the receptor potential magnitude

A

stimulus strength, rate of change of stimulus strength, temporal summation, and adaptation

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9
Q

Adaptation refers to

A

a change in receptor sensitivity due to constant stimuli, resulting in decreased AP frequency despite stimuli

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10
Q

Coding

A

conversion of stimulus energy into a signal that conveys relevant sensory information

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11
Q

Stimulus characteristics

A

location, type of energy, intensity of energy

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12
Q

Location of stimulus is determined by

A

which neuron is activated, each neuron terminates in a specific region of the CNS

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13
Q

Stimulus modality

A

type of sensory receptor a stimulus activates plays the primary role in coding

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14
Q

Mechanoreceptors

A

respond to mechanical stimuli (bending of hair, dee pressure, vibrations, stretch, and superficial touch)

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15
Q

Thermoreceptors

A

sensitive to temperature (cold: 10-38C, warm: 32-45C)

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16
Q

Thermal nociceptors

A

sensitive to cold pain or hot pain

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17
Q

Photoreceptors

A

respond to light of a particular wavelength

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18
Q

Chemoreceptors

A

respond to the binding of particular chemicals to the receptive membrane (internal: gas levels in blood; external: tastebuds on tongue)

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19
Q

Nociceptors

A

respond to stimuli that cause pain (excessive mechanical deformation, excessive temperatures, chemicals) free nerve endings

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20
Q

Adequate Stimulus

A

type of energy to which a particular receptor responds (very sensitive to specific energy form)

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21
Q

Sensory stimulation vs sensation

A

electrical stimulation of a “cold” primary afferent neuron may be perceived as a cold sensation, even though the “cold” thermoreceptor was not stimulated

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22
Q

Frequency Coding

A

the intensity of the stimulus is coded by the frequency of APs (stronger stimulus = greater AP frequency)

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23
Q

Population Coding

A

Stronger stimulus = larger area of receptors activated

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24
Q

Threshold

A

lowest stimulus intensity that a subject can reliably detect (varies by context, experience, fatigue, BUT does not represent a change in the receptor)

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25
What would be a situation where the threshold is decreased?
Anticipation
26
What would be a situation where the threshold is increased?
Childbirth, competitive sports
27
Rapidly Adapting Receptors
Respond rapidly at onset/offset of stimulus, but fir slowly or stop during remainder of stimulus. (Important for transient or dynamic stimuli)
28
Slowly Adapting Receptors
Maintain activation throughout stimulus, provide info on static qualities of a slow changing or prolonged event
29
Presynaptic Inhibition
descending inhibitory controls exerted on primary afferent neurons
30
Central control of afferent information
as the AP travels to the cerebral cortex, signals may be modified at synapses
31
Sensory Information vs Sensation vs Perception
Sensory Information: any signal received by afferent sensory neurons Sensation: sensory signals that reach CONSCIOUSNESS Perception: our interpretation of the signal
32
Sensation and Pereption occur after CNS modification
CNS may accentuate, modify, or filter sensory information, and perception is also based on previous experiences
33
Algesia
sensitivity to pain
34
analgesia
selective suppression of pain
35
Pain
a sensory or emotional experience associated with real or potential injuries
36
First (fast) pain
nociceptive pain, processing of an acute, well localized stimulus; PROTECTIVE SENSATION
37
Second (slow) pain
prolonged noxious stimulus that outlasts the stimulus, associated with inflammation due to tissue damage (NSAIDS decrease 2nd pain)
38
Third (Neuropathic) Pain
chronic, non-protective, and pathological pain due to damage of the nerves (electric, burning) that may invoke fear, depression, anxiety
39
Phantom Limb pain
traumatic or surgical limb amputation may result in chronic pain due to nerve damage
40
Causalgia
Complex regional pain syndrome may occur after damage to a peripheral nerve
41
Sensory component of pain (what information is processed and where)
processed at the spinal cord and higher brain centers; type, location, intensity, duration of pain
42
Nociception activation
not necessarily lead to pain sensation, perception is the product of the brain's processing of the sensory input
43
Responses to painful stimuli include:
arousal, attention, somatic or autonomic reflexes, endocrine response, emotional change
44
Nociceptor Anatomy
Free nerve ending in periphery --> release of glutamate and neuropeptide substance P in the spinal dorsal horn
45
Thermal nociceptors
respond to extreme temperatures; A-delta small-diamter, thinly myelinated fibers
46
Mechanical nociceptors
respond to intense pressure; A-delta small-diamter, thinly myelinated fibers
47
Polymodal Nociceptors
respond to high intensity mechanical, chemical, or thermal stimuli; small diameter, non-myelinated slow-conductin C fibers
48
First and Second pain response to injury
Pain is first rapidly realizes by "sharp" first pain A-delta fibers, while 2nd pain is mediated by C fibers that cause a dull ache
49
Referred Pain
pain that is perceived to be coming from an area that is remote from the actual source of pain, due to convergence of somatic and visceral nociceptive input onto the same dorsal horn secondary neuron (indiscriminative of pain location)
50
Sensitization of Nociceptors
after injury nociceptors may become sensitized (or activation of interneurons)
51
Primary Hyperalgesia
noxious stimuli contacts injured site, the magnitude of pain increases due to sensitization and recruitment of additional nociceptors
52
Secondary Hyperalgesia
nociceptors surrounding the injury site may become tender or sensitized and application of noxious stimulus may generate an excessive pain response
53
Allodynia
non-noxious stimulus now evokes pain due to sensitization
54
How does injury cause sensitization
injured tissues release bradykinin, serotonin, K+, and prostaglandins --> activate nociceptors--> local release of Substance P and Calcitonin gene related peptide (CRGP) --> causes mast cell degranulation --> histamine release --> directly exciting nociceptors
55
Bradykinin is one of the most active pain producing agents because
it activates A-delta and C fibers and increases the release of prostaglandins
56
How do NSAIDS block 2nd pain?
Block cyclooxygenase, which prevents the synthesis of prostaglandins
57
Which substances are activators of afferent fibers?
K+, Serotonin, Bradykinin, Histamine
58
Which substances cause sensitization of afferent fibers?
Prostaglandins, leukotrienes, and Substance P
59
Inflammation and Substance P
dilation of peripheral vessels (heat, redness) and plasma extravasation (swelling); Substance P can cause all 3 symptoms and Substance P antagonists can block all 3 symptoms
60
Hyperalgesia
caused by Substance P and CGRP mast cell activation --> histamine directly excites nearby nociceptors
61
A-delta fibers release glutamate and
activate AMPA glutamate receptor subtype in dorsal horn = 1st pain
62
C-fibers release glutamate and Substance P and
activate NMDA glutamate receipts subtype and NK-1 receptors = 2nd pain
63
Central sensitization
chronic activation of C fibers and constant release of glutamate and Substance P = hyperexcitability and diffusion of neurotransmitters that activate nearby neurons
64
Central sensitization decreases the threshold and produces:
hyperalgesia, allodynia, and neurpathic pain

Neuro (23 decks)

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