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Physiology midterm > Section 5 - Sensory receptors and somatic sensation > Flashcards

Section 5 - Sensory receptors and somatic sensation Flashcards

1
Q

Define sensation

A

Ability to feel something physically, especially by touching

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2
Q

Define perception

A

Conscious interpretation of those stimuli

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3
Q

Each of the principal types of sensation that we can experience (touch, pain, sight, sound) are called ______

A

Modality of sensation

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4
Q

T or F: nerve fibers transmit only impulses

A

True

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5
Q

Type of sensation felt when a nerve fiber is stimulated is determined by : _____

A

the termination point in the CNS, unique neurons in the CNS are capable of decoding specific modalities

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6
Q

Name the 3 types of sensory information

A

Mechanoreceptive sensation
Nociceptive sensation
Thermoreceptive sensation

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7
Q

Name the 2 branches from the mechanoreceptive sensation

A
  1. Tactile sensation (skin)

2. Proprioceptive sensation

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8
Q

Give examples of tactile sensation

A

Touch
Pressure
Vibration
Tickle and itch

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9
Q

Give examples of proprioceptive sensation

A

Muscle stretch sense

Joint position sense

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10
Q

T or F: thermoreceptive sensation detects pain

A

False, detects heat and cold

Nociceptive sensation detect pain

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11
Q

Name the 3 somatosensory receptors based on the type of sensation they detect

A
  1. Mechanoreceptors detect tissue deformation
  2. Thermoreceptors detect change in temperature
  3. Nociceptors detect pain
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12
Q

What are the two types of mechanoreceptors?

A

Skin tactile receptors

Muscle receptors

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13
Q

Name the 4 mechanisms of stimulation of the receptor

A
  1. Mechanical deformation
  2. Application of chemicals
  3. Change in temperature
  4. Tissue damage
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14
Q

Increasing the intensity of the stimulus will lead to a greater receptor potential and, eventually, to a greater AP _____

A

Frequency

*** same amplitude, more APs

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15
Q

When talking about adaptation of receptors, speed of adaptation varies with type of receptors, name them

A

Rapidly adapting receptors

Slowly adapting receptors

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16
Q

T or F: rapidly adapting receptors are best at detecting rapidly changing signals, while slowly adapting receptors are capable or detecting a long, continuous signal

A

True

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17
Q

Name the 6 receptors

A
  1. Free nerve endings
  2. Hair-end organ
  3. Pacinian corpuscle
  4. Meissner’s corpuscle
  5. Merkel’s discs
  6. Ruffini’s end-organ
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18
Q

T or F: Area of each receptor field varies directly with the density of receptors in the region

A

False, inversely (more density = small receptor field and vice-versa)

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19
Q

To get the best sensory discrimination (accuracy of sensation), is it better to have small or large receptive fields?

A

Small

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20
Q

Define the two-point discrimination

A

Method used to measure tactile acuity in rehab

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21
Q

Which provides more acuity?
When many primary sensory neurons converge onto a single secondary neuron OR when fewer neurons converge, secondary receptive fields are smaller so they are perceived as distinct stimuli

A

2nd part

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22
Q

Which tactile receptors are located in the epidermis vs dermis?

A
  • Epidermis: Meissner corpuscule, Merkel discs and free nerve endings
  • Dermis: Pacinian corpuscules and Ruffini organ
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23
Q

Name the 6 TACTILE receptors

A
  1. Free nerve endings
  2. Meissner’s corpuscules
  3. Merkel’s discs
  4. Hair end organ
  5. Ruffini’s end organ
  6. Pacinian corpuscules
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24
Q

Free nerve endings are found where and detecte what kind of touch?

A
  • They are found everywhere on the skin

- Detect crude touch and pressure sensations

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25
Q

Meissner’s corpuscules are found where and detecte what kind of touch?

A
  • They are located in the superficial layer of the skin (non-hairy part)
  • Detect fine touch
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26
Q

Merkel’s discs are found where and detecte what kind of touch?

A
  • They are located in the epidermis

- Detect touch and light pressure

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27
Q

Hair end - organ are found where and detecte what kind of touch?

A
  • In contact with the root of the skin hair

- Detects hair movement

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28
Q

Ruffini’s end organ are found where and detecte what kind of touch?

A
  • They are located in the deeper layer of the skin

- Detects heavy and prolonged touch and pressure signals

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29
Q

Pacinian corpuscules are found where and detecte what kind of touch?

A
  • They are located in the deeper layer of the skin

- Detects tissue vibration or other rapid changes in the mechanical state of the tissue

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30
Q

Which receptors are rapidly adapting?

A
  • Meissner’s corpuscules, Hair end organ and Pacinian corpuscules
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31
Q

True or false: Ruffini’s end organs are fast adapting receptors

A

FALSE

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32
Q

When does a pain sensation occur?

A

When the tissue is being damaged

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33
Q

Why is pain a protective mechanism?

A

Because it brings awareness of tissue damage and can prevent further damages to the body

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34
Q

What is the difference between fast and slow pain?

A
  • Fast pain is a pricking sensation, sharp in character that is felt 0.1 sec after the stimulus
  • Slow pain is an aching sensation that begins after a second or more
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35
Q

What kind of receptors are pain receptors?

A

Specialized free nerve endings

36
Q

Where are the nociceptors located?

A
  • Superficial layers of the skin
  • Internal tissues
  • Arterial walls
  • Bones, joints and muscle surface
37
Q

True or false: Nociceptors are stimulated by thermal, mechanical and chemical stimulus

A

True

38
Q

Nociceptors are slow adapting receptors, true or false?

A

True

39
Q

What are thermoreceptors

A

Free nerve endings that code changes in temperature

40
Q

Thermoreceptors change within what range

A

the innocuous range

41
Q

Temperatures that are likely to damage an organism are sensed by what receptors

A

nociceptors

42
Q

True or False: nociceptors respond only to noxious heat

A

false they also respond to noxious cold

43
Q

how do we determine sense of temperature

A

by comparison of the signals from each of the two types of thermoreceptors

44
Q

Thermoreceptors respond to a temperature change with 2 phases (components), name them

A

with a phasic component followed by a tonic component

45
Q

What is the difference between a phasic and tonic component

A

phasic is rapidly adapting and tonic is a slowly adapting component

46
Q

Give a real-life example of the phasic and tonic components

A

when you get in a hot bath and it feels hot until your body adapts and then it’s only warm

47
Q

Meissner’s corpuscles, merkel’s dics, hair receptors, Pacinian corpuscles and Ruffini’s end organs transmits their signals through what type of nerve fibers

A

type A-beta myelinated nerve fibers at 30-70 m/sec

48
Q

Free nerve endings transmit their signals through what type of fibers

A

type A-delta nerve fibers at 6-30 m/sec (fast pain, cold sensation) or through type C unmyelinated fibers at 0.5-2 m/sec (slow pain, cold, warmth, crude touch & pressure sensations)

49
Q

What is faster between high and low discrimation

A

high discrimination

50
Q

where does the sensory information enter the spinal cord

A

through the dorsal roots of the spinal nerves

51
Q

what are the 2 pathways for sensory information

A

the dorsal column (medial lemniscal system) and the antero-lateral system

52
Q

what does decussate mean

A

crossing over on the other side

53
Q

True or False sensory fibers only decussate on one pathway

A

false they decussate on both pathways

54
Q

where is the sensory information from one side of the body transmitted

A

to the brain hemisphere on the opposite side of the body

55
Q

what makes the relay to transmit sensory information from the receptor to the final point of the cerebral cortex

A

three order neurons

56
Q

where is the dorsal column located

A

on the back of the spinal cord

57
Q

which types of sensations does the dorsal column transmit

A

the tactile sensations (touch, vibration and fine pressure) and the proprioceptive sensations (i.e. limb position)

58
Q

where do the dorsal column signals originate from

A

they originate from tactile receptors or proprioceptive receptors

59
Q

What type nerve fibers are used in the dorsal column, for what reason and with what type of
degree

A

large myelinated nerve fibers for fast signal transmission with a high degree of spatial fidelity

60
Q

Describe the 3 different order neurons for the dorsal column

A

the 1st order neurons synapse with the 2nd at the dorsal column nucleus
the 2nd order neurons decussate at the level of the medulla (brain stem)
The 2nd order neurons synapse with th 3rd in the thalamus
The 3rd order neurons transmit info to the primary somasensory cortex

61
Q

what does the antero-lateral pathway transmit

A

a broad spectrum of modalities such as pain, thermal sensations, crude touch and pressure, tickle and itch, sexual sensations

62
Q

where do the signals from the antero-lateral pathways originate

A

they originate from free nerve endings receptors (pain and thermal receptors)

63
Q

what type of nerve fibers are used in the antero-lateral pathway for what use and with what type of degree

A

smaller myelinated and unmyelinated fibers for slow transmission and with a low degree of spatial orientation

64
Q

Describe the 3 different order neurons for the antero-lateral pathway

A

The 1st order neurons synapse with the 2nd in the substantia gelatinosa
The 2nd order neurons decussate at the level of the spinal cord
The 2nd order neurons synapse with the 3rd in the thalamus
The 3rd order neurons transmit info to the primary somatosensory cortex

65
Q

Where are fast pain fibers transmitted into

A

the neospinothalamic tract

66
Q

Where are slow pain fibers transmitted into

A

the paleospinothalamic tract

67
Q

what do neo and paleo mean

A

neo = new paleo = old

68
Q

where do the fast pain fibers terminate

A

at the somatosensory cortex

69
Q

where do the slow pain fibers terminate

A

at the thalamus level or below (even in the brain stem)

70
Q

T or F slow pain fibers can be highly localized if it is simultaneously activated with tactile sensations

A

False the fast-sharp pain can

71
Q

slow pain is ____ localized

A

poorly

72
Q

Where is the primary somatosensory cortex located

A

in the post-central gyrus (in the parietal lobe)

73
Q

How would you describe the primary somatosensory cortex

A

highly organized with distinct spatial orientation and each side of the cortex receives info from the opposite side of the body

74
Q

T or F the somatosensory area II is much more extensive than the somatosensory area I

A

False

75
Q

What is the name of the famous montrealer neurosurgeon who did the mapping of the somatosensory cortex

A

Dr Wilder Penfield

76
Q

Penfield’s Homunculus gives an ____ representation of the body. Explain

A

unequal because the more a region of the body has receptors, the better it’s area of representation in the somatosensory cortex is

77
Q

Classify these body regions in order of the ones with more receptors to the ones with the less receptors

A

lips

78
Q

the somatosensory cortex is composed of how many cellular layers

A

6

79
Q

within the cellular layers, the neurons are arranged in what direction

A

vertical columns

80
Q

T or F the columns in the somatosensory cortex each have a specific modality and they interact between each other

A

True, the interaction allows the beginning of the analysis of the meaning of the sensory signals

81
Q

T or F the degree of pain is the same for everyone

A

False it varies tremendously from person to person

82
Q

How does the brain suppress inputs of pain signals

A

through the activation of the analgesia system

83
Q

What are the three parts of the analgesia system

A

the periaqueductal gray of the mesencephalon and upper pons
the raphe magnus nucleus located in the lower pons
the pain inhibitory complex located in the dorsal horns of the spinal cord

84
Q

what is the main neurotransmitter involved in the analgesia system

A

enkephalin (released at the 3 levels)

85
Q

How do we call a pain in the internal organs that is often sensed on the surface of the body

A

reffered pain

86
Q

How would you describe CIPA (congenital insensitivity to pain with anhidrosis)

A

inability to feel pain and temperature, inability to sweat

Physiology midterm (6 decks)

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