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NE Exam 2 > Sensory Physiology > Flashcards

Sensory Physiology Flashcards

1
Q

What are the two classifications of peripheral nerves?

A
  1. Their contribution to a compound AP (A, B and C waves) recorded from an entire mixed peripheral nerve
  2. Based on fiber diameter, myelin thickness and conduction velocity (classes I, II, III and IV)
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2
Q

How are the two classification systems for peripheral nerves related?

A

Conduction velocity determines a fiber’s contribution to the compound AP
The compound AP and conduction velocity of nerve fibers is often used as a diagnostic test in the evaluation of peripheral nerve disease (e.g. diabetic neuropathy)

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3
Q

What are the different types of sensory (afferent) fiber types?

A

A-alpha, beta and delta

C

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4
Q

What is the classification of sensory A-alpha fibers?

A

Ia and Ib

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5
Q

What is the diameter and conduction velocity of sensory A-alpha fibers?

A 
Large diameter 
Fast velocity (80-120)
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6
Q

What receptors are supplied by sensory A-alpha fibers?

A

Primary muscle spindles and golgi tendon organ

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7
Q

What is the classification of sensory A-beta fibers?

A

II

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8
Q

What receptors are supplied by sensory A-beta fibers?

A

Secondary muscle spindles, skin mechanoreceptors

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9
Q

What is the classification of sensory A-delta fibers?

A

III

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10
Q

What receptors are supplied by sensory A-delta fibers?

A

Skin mechanoreceptors, thermal receptors and nociceptors

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11
Q

What is the classification of sensory C fibers?

A

IV

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12
Q

What is the diameter and velocity of sensory C fibers?

A 
Small diameter 
Slow velocity (0.5-2)
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13
Q

What receptors are supplied by sensory C fibers?

A

Skin mechanoreceptors, thermal receptors and nociceptors

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14
Q

What are the types of motor (efferent) fiber types?

A

A-alpha and A-gamma

B and C

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15
Q

What receptors are supplied by motor A-alpha fibers?

A

Extrafusal skeletal muscle fibers

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16
Q

What receptors are supplied by motor A-gamma fibers?

A

Intrafusal muscle fibers

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17
Q

What receptors are supplied by motor B fibers?

A

Preganglionic autonomic fibers

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18
Q

What receptors do motor C fibers supply?

A

Postganglionic autonomic fibers

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19
Q

What do the cutaneous and deeper subcutaneous mechanoreceptors respond to?

A

External stimuli

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20
Q

What is receptor adaption?

A

When a stimulus persists unchanged for several minutes without a change in position or amplitude, the neural response diminishes and sensation is lost over time

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21
Q

What is a slowly adapting receptor?

A

Receptors that respond to prolonged and constant stimulation

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22
Q

What are rapidly adapting receptors?

A

Receptors that respond only at the beginning or end of a stimulus
Only active when the stimulus intensity increases or decreases

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23
Q

What are the 4 types of mechanoreceptors?

A

Meissner corpuscle, Pacinian corpuscle, merkel disc and ruffini ending

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24
Q

Describe a Meissner corpuscle

A

Low threshold
Rapidly adapting
Found in glaborous skin (hairless)
Within the dermis

25
Q

What type of sensation activates Meissner corpuscles?

A

Touch and vibration less than 10Hz

Flutter and tapping

26
Q

Describe Pacinian corpuscles

A

Low threshold
Rapidly adapting
Found in both hairy and glaborous skin
Deepest receptor in the subcutaneous tissue (below dermis)

27
Q

What type of sensation do Pacinian corpuscles respond to?

A

Rapid indentation of the skin such as that during high frequency vibration (100-400Hz)
Vibration

28
Q

Describe Ruffini corpuscles

A

Low threshold
Slowly adapting
Found in both hair and glaborous skin
Deep in the dermis

29
Q

What type of sensation cause activation of Ruffini corpuscles?

A

Magnitude and direction of stretch

Touch and pressure and proprioception

30
Q

Describe Merkel cells

A

Low threshold
Slowly adapting
Found in glaborous skin
Within the dermis

31
Q

What activates a Merkel cell?

A

Pressure

32
Q

Describe hair follicle receptors

A

Rapidly and slowly adapting

33
Q

What sensation do hair follicle receptors respond to?

A

Motion across the skin and directionality of that motion

34
Q

Describe tactile free nerve endings

A

High threshold

Slowly adapting

35
Q

What sensation do tactile free nerve endings respond to?

A

Pain and temperature

Located superficially in the epidermis

36
Q

What are receptive fields?

A

Areas of innervation where individual mechanoreceptor fibers convey information from a limited area of skin
Vary in size

37
Q

What is two point discrimination?

A

A way to test function of receptive fields and innervation fibers
Allows for spatial resolution of detailed textures
Test is used as a diagnostic tool of peripheral sensory deficiencies

38
Q

Where is tactile acuity the highest?

A

In fingertips and lips (smallest receptive fields)

39
Q

Where is tactile acuity the lowest?

A

On the calf, back and thigh (largest receptive field)

40
Q

The sensory cortex includes what?

A

Primary, secondary and association areas

41
Q

Describe the primary somatosensory cortex (S1)

A 
Somatic sensory area I (SI) 
Located in post central gyrus 
Brodmann area 3, 1 and 2 
First stop for most cutaneous senses 
Somatotopic representation
42
Q

The primary somatosensory cortex (SI) is involved in what?

A

The integration of the information for position sense as well as size and shape discrimination

43
Q

Describe the secondary somatosensory cortex (S2)

A

Aka somatic sensory area 2 (S2)
Located in the wall of the Sylvian fissure
Receives input from S1
Somatotopic representation (but less detailed)
Cognitive touch

44
Q

What is the secondary somatosensory cortex involved with?

A

Comparisons between objects, different tactile sensations and determining whether something becomes a memory

45
Q

Describe the parieto-temporal-occipital association cortex (PTO)

A

High level interpretation of sensory inputs
Receives input from multiple sensory areas
Analyzes spatial coordinates of self in environment
Names objects
Many more function

46
Q

What is phantom limb pain?

A

Phantom limb describes the pain in a body part that is no longer present which occurs in many amputees
Most basic principle that explains this is the Law of Projection

47
Q

What is the law of projection?

A

No matter where along the afferent pathway a stimulation is applied, the perceived sensation arises from the origin of the sensation

48
Q

What is pain?

A

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

49
Q

What is nociception?

A

The neural process of encoding noxious stimuli (a stimulus that is damaging or threatens damage to normal tissues)
Note: consequences of encoding may be autonomic (e.g. elevated BP) or behavior (motor withdrawal reflex or more complex nocifensive behavior)
Pain sensation is not necessarily implied

50
Q

What is hypersensitivity?

A

Increased responsiveness of nociceptive neurons to their normal input and/or recruitment of a response to normally subthreshold inputs

51
Q

What is hyperaesthesia?

A

Increased sensitivity to stimulation excluding the special senses

52
Q

What is hyperalgesia?

A

Increased pain from a stimulus that normally provokes pain

53
Q

What is allodynia?

A

Pain due to a stimulus that does not normally provoke pain

Classical example is laying sheets on skin that has been sunburned

54
Q

What is the biphasic response to pain?

A

Phase 1: initial response from A-delta fibers (quick sharp pain)
Phase 2: a few moments later which is being transmitted by C fibers (sharp pain diminishes and becomes throbbing pain)

55
Q

What sensation modality do A-delta fibers transmit?

A

Primarily mechanical pain

56
Q

What type of sensation modality do C fibers transmit?

A

Polymodal: high intensity chemical and thermal pain (can be involved in mechanical pain)

57
Q

What is the receptive field size for A-delta fibers?

A

Relatively small receptive fields

58
Q

What is the receptive field size for C fibers?

A

Receptive fields relatively larger than A-delta

NE Exam 2 (19 decks)

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