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Physiology 214 > W4 L2 (Somatosensation and Pain) > Flashcards

W4 L2 (Somatosensation and Pain) Flashcards

1
Q

What is the exteroceptive cutaneous system?

A

It is a system that responds to stimuli applied to the skin

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2
Q

What types of stimuli can be applied to the skin?

A
  1. Mechanical (Touch)
  2. Thermal (Temp)
  3. Nociceptive (Pain)
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3
Q

What are some types of touch modalities? (Different receptors)

A 
Superficial touch
Deep touch (pressure)
Vibration
Flutter (Low frequency vibration)
Skin stretch 
Warmth 
Cold
Sharp pricking pain-1st pain
Slow burning pain-2nd pain
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4
Q

What is object manipulation?

A

The feeling of an object that allows us to determine an unknown object

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5
Q

What are the 4 types of touch sensations?

A
  1. Object manipulation
  2. Light flutter
  3. Vibration
  4. Shape and texture
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6
Q

What is the Meissner’s corpuscle and what is an example where it is used?

A

RA1, it is rapidly adapting, and in the upper layer, responds to touch ex. motion across skin trying to figure out an object

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7
Q

What is the Merkel’s disc, and what is an example of when it is used?

A

SA1, it is slowly adapting, and in the upper layer, responds to pressure ex. reading brail and feeling indents

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8
Q

What is the structure of the Pacinian corpuscle?

A

Wrapped like an onion

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9
Q

What is the Pacinian corpuscle and what is an example of where it is used?

A

RA2, rapidly adapting in the lower layer, they respond to vibrating and deep pressure

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10
Q

Why is there wrapping in the Pacinian?

A

The membrane surrounds the receptor and releases to open ion channels, it fires and goes back in place when it stops

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11
Q

What is the Ruffini corpuscle and what is it responsible for and what is an example of when they’re used?

A

SA2, it is responsible for stretching of the skin ex. holding things and stretching of hand

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12
Q

Where do all the signals from these cutaneous mechanoreceptors travel?

A

Down highly myelinated large diameter fast afferents

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13
Q

What are A-Beta fibers

A

Highly myelinated, thick fibres that are connected to cutaneous mechanoreceptors

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14
Q

What are free nerve endings?

A

Found throughout the epidermis and are slowly adapting in response to pain, temp, and crude touch

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15
Q

What is a tuning curve?

A

The plot of average firing rate of a neuron

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16
Q

What rapid receptor responds to high frequencies and low respectively?

A

Meissner’s= Low Freq

Pacinian=High freq

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17
Q

Explain the 3 steps in transduction

A
  1. A stimulus (pressure) deforms a receptor
  2. Na+ channels open and depolarize the membrane
  3. If the potential exceeds the threshold then an AP is generated along the axon
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18
Q

What can lead to direct activation of Na+ channels?

A

Lipid proteins which cause the membrane to stretch

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19
Q

Why does a neural response adapt?

A

Because the receptor potential adapts meaning the membrane likely slips back to its original shape closing its channels

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20
Q

What is the purpose of adapting?

A

To enhance the detection of changes in pressure

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21
Q

Describe the receptive field of the Meissner (RA1)

A

Small circles, close to the skin, in fingerprints

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22
Q

What is the densest receptor in the fingertips?

A

Meissner

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23
Q

Describe the receptive field of the Paccinian (RA2)

A

Large field

24
Q

Describe the receptive field of the Merkel (SA1)

A

Small

25
Q

Describe the receptive field of the Ruffini

A

In crevice of hands somewhat large

26
Q

What is a way to figure out 2 point-discrimination thresholds?

A

Get a 2 pointed pin and move the two points closer or further and measure if the person can tell if there are 2 pins touching or not

27
Q

What does the two-point threshold correlate with?

A

Receptive field size

28
Q

What is an example of a part of the body with a small and large receptive field?

A

Small-Finger

Large-Elbow

29
Q

What is microneurography?

A

Controlling the stimulus and recording the spikes with an electrode in the nerve

30
Q

What 2 things can be shown by a receptive field?

A

Area and hotspots

31
Q

What is the relationship between action potential frequency and pressure?

A

Non-linear ie. a small change in pressure leads to a large change in AP initially, and a small change in pressure leads to a miniscule change once a certain amount of pressure had been applied. Ie. Only so much pressure can be applied before it is useless

32
Q

How do we sense temperature?

A

Free nerve endings have ion channels that are temperature sensitive and have a range
ie. Some fire optimally in the cold and some fire when we exceed body temperature

33
Q

What are the receptive fields for temperature like?

A

Small and spread across the body

34
Q

What is a key feature about adaptation and thermoreceptors?

A

They have strong adaptation meaning the respond greatly to temperature changes, this is why jumping in a cold pool or hot tub is so extreme at first

35
Q

What chemicals do the ion channels for cold and hot respond to?

A

Cold-Menthol

Hot-Capsaicin

36
Q

What are nociceptors?

A

Free nerve endings sensitive to molecules released with tissue injury

37
Q

What are the 3 types of nociceptors?

A
  1. Mechanical
  2. Thermal
  3. Chemical
38
Q

What do mechanical nociceptors respond to?

A

Mechanical damage such as cutting, crushing, or pinching

39
Q

What do thermal nociceptors respond to?

A

Temperature extremes below 4 and above 45 degrees

40
Q

What do chemical nociceptors respond to?

A

Many kinds of chemical irritants

41
Q

What 2 types of fibers do pain signals travel on?

A
  1. A-delta fibres

2. C-fibres

42
Q

What is the difference between A-delta fibers and C-fibers

A

A delta are well myelinated and the initial pain fibers and are lead to fast, sharp, well localized pain

C fibres are small in diameter, unmyelinated and are the slow secondary pain the is throbbing and diffuse

43
Q

What are the 6 steps of the withdrawal reflex? ex. touching a hot pot

A
  1. Thermal pain receptor in finger
  2. Afferent pathway
  3. Integrating center (spinal cord)
  4. Efferent pathway
  5. Effector
  6. Ascending pathway to brain

IE. the body pulls the hand away before the brain is even conscious of it

44
Q

Describe the path of touch receptors to the brain

A
  1. Receptor fibres pass through dorsal root ganglion
  2. Go straight up and don’t stop at spinal cord (posterior lateral pathway)
  3. Crossover to different side of brain
  4. Thalamus
  5. Somatosensory cortex
45
Q

Describe the path of pain/temp receptors to the brain

A
  1. Receptor fibres pass through dorsal root ganglia
  2. Delta and C fibres synapse in the spinal cord
  3. Fibers cross
  4. Go up anterior lateral pathway to thalamus
  5. Up to brain
46
Q

What are dermatomes?

A

A map of the spinal cord that displays the area of the body that it innervates

47
Q

What can happen if you get herpes activation in a certain part of your dorsal root ganglia?

A

It will go to the part of the skin in which the nerve innervates

48
Q

What is brown sequard syndrome?

A

Damage one half of the spinal cord and lose motor function on the same side as the cord damage and lose pain/temp on the opposite side

49
Q

What is the difference between touch and pain/temp receptors in the pathway

A

Pain/temp-Cross over in the spinal cord

Touch-Goes straight up

Ie. An injury on right side of cord affects right side of body touch and left side of body pain/temp

50
Q

What happens in dorsal column nuclei?

A
  1. Differential convergence
    - Lots of neurons for fingertips and lips
    - Few neurons for back, upper arms/legs
  2. Lateral inhibition
    - Accentuates the changes across the receptive fields in touch stimuli
51
Q

What happens in dorsal column nuclei (the back)?

A
  1. Differential convergence (the labelled lines stay separate)
  • Lots of neurons for fingertips and lips
  • Few neurons for back, upper arms/legs
  1. Lateral inhibition
    - Accentuates the changes across the receptive fields in touch stimuli
52
Q

Why do raccoons have super specialized somatosensory cortexes?

A

To get into garbage cans

53
Q

What is cortical reorganization?

A

When a body part is lost and the cortex part associated with it is taken over by that of other body parts

54
Q

What is the analgesic system?

A

It suppresses pain transmission of pain pathways in the spinal cord

55
Q

What is an opiate receptor?

A

A type of protein found in the central nervous system and the gastrointestinal tract. Opiates activate pain relief and stimulate pleasure centers of the brain. Morphine can bind to alleviate pain

56
Q

What is neuronal and cortical plasticity?

A

The brain’s remarkable ability to reorganize itself by forming new neural connections based on individual experiences, lifestyle, and environment.

Physiology 214 (12 decks)

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