Sensory Physiology

Question 1

What are the 2 ways you classify a peripheral nerve?

Answer 1

Based on their contribution to an action potential and

Based on their fiber diameter, myelin thickness and conduction velocity

Question 2

What is the lettering for a peripheral nerves contribution to an action potential?

Answer 2

A, B, C waves

Question 3

What is the classification for a peripheral nerves fiber diameter, myelin thickness and conduction velocity?

Answer 3

Classes I, II, III, and IV

Question 4

How are the peripheral classification systems related?

Answer 4

The fiber’s conduction velocity directly determines the fibers contribution to an action potential

Question 5

What are the afferent peripheral nerve classifications?

Answer 5

A alpha
A beta
A delta
C

Question 6

What are the respective classes of the afferent peripheral nerves?

Answer 6

A alpha = Class 1A and 1B
A beta = Class II
A delta = Class III
C = Class IV

Question 7

Describe the fiber diameter and conduction velocity for A alpha - Classes IA and IB fibers

Answer 7

Large fiber diameter and fast conduction velocity (80-120m/s)

Question 8

Describe the fiber diameter and conduction velocity for C - Class IV fibers

Answer 8

Small fiber diameter and a slow conduction velocity (0.5-2m/s)

Question 9

What are the motor efferent peripheral nerve classes?

Answer 9

A alpha, A gamma, B and C

Question 10

What is receptor adaptation?

Answer 10

When a stimulus persists at a constant intensity and the neural response diminishes causing sensation to be lost over time

Question 11

What is a slowly adapting receptor?

Answer 11

Receptors that respond to constant and prolonged stimulation

Question 12

What is a rapidly adapting receptor?

Answer 12

Receptors that only respond when a stimulus begins or ends or when the stimulus intensity increases or decreases

Question 13

What are the mechanoreceptor types that are involved in responding to touch, vibration, pressure and pain?

Answer 13

Meissner corpuscle, Pacinian corpuscle, Merkel Disk, Ruffini ending, hair follicle receptor and tactile free nerve ending

Question 14

What are the rapidly adapting mechanoreceptors?

Answer 14

Pacinian corpuscle (very)
Meissner corpuscle
Hair follicle receptor

Question 15

What are the slowly adapting mechanoreceptors?

Answer 15

Merkel disc
Ruffini ending
Tactile free nerve ending

Question 16

An area of skin innervation supplied by a single mechanoreceptor

Answer 16

Receptive field

Question 17

What is the 2 point discrimination test?

Answer 17

Applying 2 stimuli to the skin at the same time and testing a person’s ability to differentiate between just one or 2 stimuli as the stimuli are moved closer and closer together

Question 18

What can the 2 point discrimination diagnose?

Answer 18

Peripheral sensory nerve deficiencies

Question 19

Where is tactile acuity the highest and what size of a receptive field does it have?

Answer 19

Fingertips and lips - small receptive field

Question 20

Where is tactile acuity the lowest and what size of a receptive field does it have?

Answer 20

Calf, back, thigh - large receptive field

Question 21

Hypoaesthesia

Answer 21

Abnormal sensory response - diminished; detected with the 2 point discrimination test

Question 22

Where is the primary somatosensory cortex?

Answer 22

Post central gyrus

Question 23

Where is the secondary somatosensory cortex?

Answer 23

In the sylvian fissure

Question 24

What are the inputs to the secondary somatosensory cortex?

Answer 24

From S1

Question 25

Which somatosensory cortex has cognitive touch? (Ability to think about what you are touching)

Answer 25

S2

Question 26

Where is the highest level of sensory interpretation occuring?

Answer 26

Parieto-Temporal-occipital association cortex (PTO) | - Receives sensory inputs from multiple areas

Question 27

What is phantom limb pain?

Answer 27

Pain in a body part that is no longer there like in amputees

Question 28

What is the mechanism behind phantom limb pain?

Answer 28

Law of projection

Question 29

Describe the law of projection

Answer 29

No matter where along an afferent pathway that a stimulation is applied, the perceived sensation is still the origin ex. Pathway is still somehow stimulated from absent leg to brain, and the brain perceives that the leg hurts though it is not there

Question 30

What are the 2 components of pain?

Answer 30

Unpleasant sensory AND emotional experience

Question 31

What is nociception?

Answer 31

The neural process of encoding noxious stimuli

Question 32

Increased pain from a stimulus that normally DOES produce pain

Answer 32

Hyperalgesia/Hypersensitivity

Question 33

Increased sensitivity to stimulation

Answer 33

Hyperaesthesia

Question 34

Pain due to a stimulus that does NOT normally produce pain - i.e. laying sheets on sunburned skin

Answer 34

Allodynia

Question 35

What are the afferent fibers that respond to pain evolving from sharp to dull/throbbing?

Answer 35

Sharp and quick = A delta | Slow to respond and dull/throbbing = C

Question 36

Phase 1 of pain involved A delta and Phase 2 involved C fibers, which one is myelinated?

Answer 36

A delta fibers - fast conduction

Question 37

What are nociceptors?

Answer 37

Receptors with an increased threshold that can transduce noxious stimuli

Question 38

What are the modalities of nociceptors?

Answer 38

Mechanical, chemical and thermal

Question 39

Are the modalities of nociceptors the same everywhere?

Answer 39

Nope, only the skin has thermal nociceptors; mechanical and chemical are found everywhere else such as the muscle, viscera and joints

Question 40

Where is referred pain likely coming from?

Answer 40

Viscera

Question 41

What are the reasons for referred pain?

Answer 41

The brain requires experience and training to know where the pain is coming from; viscera does not get that early enough The afferents converge in the dorsal horn and mix

Question 42

What type of receptors sense noxious stimuli?

Answer 42

TRP

Question 43

What are the 3 TRP receptors?

Answer 43

TRP V1, TRP A1, TRP M8

Question 44

This TRP receptor is sensitive to capsaicin, bradykinin and heat greater than 43 degrees celsius

Answer 44

TRP V1

Question 45

This TRP receptor is sensitive to allyl isothiocyanate found in mustard oil and wasabi

Answer 45

TRP A1

Question 46

This TRP receptor is sensitive to menthol and noxious cold temps

Answer 46

TRP M8

Question 47

What TRP receptors does C fibers have?

Answer 47

TRP V1

Question 48

2 types of free nerve endings on c fibers or A delta fibers?

Answer 48

Peptidergic (C) or non-peptidergic (Adelta) - peptidergice express neuropeptides such as substance P/CGRP and are found in viscera - Non-peptidergic do not express them and are mostly cutaneous

Question 49

What are 2 ways nociceptors are modulated?

Answer 49

Gate Control Theory and Descending inhibition

Question 50

What is the main components of the gate control theory?

Answer 50

Rubbing the injured area to activate a A beta fiber that will slightly activate the inhibitory neuron to inhibit the C fiber from sending pain

Question 51

With descending inhibition, what NT's inhibit C fibers from nociceptors?

Answer 51

NE and Serotonin (5HT)

Question 52

Reduces threshold of involved neurons to noxious stimuli and involves synaptic plasticity

Answer 52

Central sensitization

Question 53

This area in the brain interprets nociception and integrates all signals related to pain

Answer 53

Insular cortex

Question 54

Damage to the insular cortex can result in?

Answer 54

Asymbolia

Question 55

What is asymbolia?

Answer 55

Pain is experienced withOUT the unpleasantness emotional experience

Question 56

What area of the brain is an emotional component of the brain?

Answer 56

Amygdala

Question 57

Do lesions in any area associated with pain in the brain abolish it?

Answer 57

Nope, just alter experience of pain

Question 58

What do Meissner's corpuscles sense?

Answer 58

Flutter, tapping, touch

Question 59

What do merkel's discs sense?

Answer 59

Pressure

Question 60

What do pacinian corpuscles sense?

Answer 60

Vibration

Question 61

What do hair follicle receptors sense?

Answer 61

Direction of motion on skin

Question 62

What do ruffini corpuscles sense?

Answer 62

Stretch

Question 63

What do free tactile nerve endings sense?

Answer 63

Pain, temperature

Question 64

What receptors are only found in glaborous (non-hairy) skin?

Answer 64

M! = Meissner's corpuscle and Merkel discs

Question 65

What receptors are found in both glaborous and hairy skin?

Answer 65

Pacinian, ruffini corpuscle