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258 - physiology > lecture 5: Sensory Receptor Mechanisms and Somatic Sensations > Flashcards

lecture 5: Sensory Receptor Mechanisms and Somatic Sensations Flashcards

1
Q

what is the definition of sensation

A

Sensation: the ability to feel something physically, especially by touching

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2
Q

what is the definition of perception

A

Perception: concious interpretation of the stimuli

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3
Q

What does the combo of sensation and oerception allow?

A

Awareness of the elements of environment through physical sensation

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4
Q

What is a modality of sensation

A

Each of the principal types of sensation that we can experience (touch, pain, sight, sound, etc.)

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5
Q

explain the labeled line principle

A

Type of sensation felt when a nerve fiber is stimulated (e.g. pain, touch, sight, sound) is determined by:

The termination point in the CNS
i.e. unique neurons in the CNS capable of decoding specific modalities

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6
Q

what are the 3 types of sensory information

A

1) mechanoreceptive sensation
2) nocioreceptive sensation
3) thermoreceptive sensation

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7
Q

what are the 2 subtypes of mechanoreceptive sensation and explain

A 
1) tactile sensation (skin)
Tactile  sensation (skin)
Touch	 
Pressure
vibrations
Itch and tickle

2) propriceptive sensation
Muscle stretch sense (e.g.
muscle is contracted or relaxed)
Joint position sense

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8
Q

what do nociceptive sensation detect?

A

PAIN

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9
Q

what do thermoreceptive sensations detect?

A

HOT AND COLD

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10
Q

what are Somatosensory receptors classified based on

A

the type of sensation they detect:

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11
Q

what are the 3 types of receptors in somatosensory receptors

A

1) mechanorecepts
2) nociceptors
3) thermoreceptors

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12
Q

What do mechanorecptos detect and what are the 2 subtypes of this receptor (and examples)

A

detect tissue deformation

Skin tactile receptors:

  • Free nerve endings
  • Expanded tip receptor (e.g. Merkel’s discs)
  • Encapsulated endings (e.g. Meissner’s corpuscle, Pacinian corpuscle, Krause’s corpuscle Ruffini’s end-organ…)
  • Hair end-organ

Muscle receptors:

  • Muscle spindles
  • Golgi tendon receptors
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13
Q

what do thermoreceptors detect and what are the two subtypes of this receptor

A

detect change in temperature (Specialized free nerve endings)

  • Cold receptors
  • Warm receptors
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14
Q

what do nociceptors detect and what are the subtypes

A

Nociceptors: detect pain (i.e. tissue damage)

Pain receptors: Specialized free nerve endings

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15
Q

be able to recognize the types of somatosensory receptors

A

see slides

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16
Q

explain receptor potential

A

Receptor potential:
When a stimulus excites a receptor, the change in the membrane electrical potential of the receptor is called a receptor potential (like EPSP)

The stimulation causes opening of ion channels (Na+, K+) and the depolarization of the receptor membrane.

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17
Q

What are the 4 ways to stimulate a receptor?

A

1) Mechanical deformation which stretches the membrane (e.g. mechanoreceptors)
2) application of chemicals (taste/smell)
3) chnage in temp (thermoreceptors)
4) tissue damage (pain receptors)

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18
Q

explain the concept of adaption of receptors

A

When a continuous sensory stimulus is applied, the receptor responds at a high impulse rate at first and then at a progressively slower rate until finally the rate of APs decreases to very few or to none at all

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19
Q

Speed of adaptation varies with type of receptors

what are the fast and slow adapting?

A

Rapidly adapting receptors:
Pacinian corpuscle
Hair receptor

Slowly adapting receptors:
Muscle spindles
Joint receptors

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20
Q

recognize graph of speed of adaptation

A

slides

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21
Q

what is the difference between rapidly adapting vs slowly adapting receptors

A

Rapidly adapting receptors are best at detecting rapidly changing signals, while slowly adapting receptors are capable of detecting a long, continuous signal

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22
Q

true or false : rapidly adapting receptors Only fire at onset and offset

A

true

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23
Q

what is the receptice field

A

The receptive field of a neuron is the area on a surface, like the skin that a stimulus must reach to activate that neuron

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24
Q

What does the area of receptor field depend on

A

Area of each receptor field varies inversely with the density of receptors in the region (increase density=small receptor field)

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25
Q

Do back and legs have a large or small receptor field and why

A

have low number of cutaneous receptors

Receptive fields are large in size

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26
Q

do fingertips and tongue have a small reception field and why

A

have large number of cutaneous receptors
Receptive fields are small in
size

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27
Q

For accuracy of senstaion, is it better to have small or large receptor fields

A

SMALL RECEPTOR FIELD

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28
Q

explain two point discrimination

A

method used to measure tactile acuity in rehab

Minimum distance at which 2 points of touch can be perceived as separate
Measure of distance between receptive fields

Indication of tactile acuity
If distance between 2 points is less than minimum distance, only 1 point will be felt

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29
Q

What is the reason we might only feel 1 point even if tehre are 2 points?

A

When primary neurons converge to a single secondary neuron= ;arger receptor field and will only feel 1 point

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30
Q

what are the 3 receptors that lie superfically

A

nerve endings
meissners corpuscles
merkels disks

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31
Q

what are the 3 receptors that lie deep

A

hair end organ
ruffinis end-organ
paccinis corpuscles

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32
Q

Where are free nerve ends found, whats their fucntion and are they slow or fast adapting

A

Found everywhere in the skin (superficial layers) and in many other tissues

Detect crude touch and pressure sensations

Specialized free nerve endings

Slowly adapting receptors

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33
Q

Where are Meissner’s corpuscles located, their function and are they fast or slow adapting

A

Elongated encapsulated nerve endings of a large myelinated sensory nerve fiber (Aβ). SUPERFICIAL NON HAIRY

Detect fine touch (discriminative, movement of the objects on the surface of the skin) and low frequency vibration

Rapidly adapting receptors

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34
Q

Where are merkel’s disks located, whats their function and are they fast or slow adapting

A

Located in the superficial layers of the skin (epidermis)

Detect touch and light pressure

_slowly adapting receptors____________________

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35
Q

Where are hair end organs located, their function and are they fast or slow adapting

A

In contact with the root of the skin hair DEEP

Detects hair movement

RAPIDLY ADDAPTING RECEPTORS

36
Q

Where are ruffini’s end organ’s located, their function and are they slow or fast

A

Encapsulated endings located in the deeper layers of the skin

Detects heavy and prolonged touch and pressure signals

SLOWLY ADAPTING RCEPTORS

37
Q

Where are pacinian corpuscles located, their function, and are they fast or slow adapting

A

Encapsulated endings located in the deeper layers of the skin

Detect tissue vibration or other rapid changes in the mechanical state of the tissues (deep pressure, stretch)

RAPIDLY ADAPTING

38
Q

when does pain occur and why

A

Occurs whenever tissue is being damaged

protective measure: Brings awareness to current tissue damage and can prevent further damages to the body

39
Q

what the 2 types of pain and explain

A 
Fast pain (pricking pain): 
felt within 0.1 sec of the stimulus and is sharp in character
Slow pain (aching pain):
 begins after a second or more and is throbbing or aching in nature
40
Q

true or false: pain receptors are specialized nerve endings?

A

true

41
Q

where are the 4 locations of pain receptors (nociceptors)?

A

1) Superficial layers of the skin
2) Internal tissues
3) Arterial walls
4) Bones, joints and muscle surfaces

42
Q

What are the 3 ways pain receptors can be stimulated?

A

Mechanical (stress, tissue damage)
thermal (appove 45 degrees)
Chemical (ex: lactic acid)

43
Q

Do pain receptors adapt slow or fast and why

A

SLOW

making sure that the signal is maintained

44
Q

what type of nerve are thermoreceptors?

A

specialized free nerve endings

45
Q

When do thermoreceptors. stop being triggered and nociceptors respond instead?

A

When there are temperatures likely to damage an organism

respond to noxious cold and noxious heat

46
Q

How do we get a sense of temperatuer?

A

Comparison of the signals from each of the two types of thermoreceptors

47
Q

What are the 2 components of thermoreceptors

A

Thermoreceptors respond to temperature changes with a phasic component (rapidly adapting) followed by a tonic component (slowly adapting)

48
Q

Why do we have a phasic component (rapidly adapting) followed by a tonic component (slowly adapting)

A

to get a sense of temperature at first and then it slowly adapts (jumped into hot water)

49
Q

what are the two types of ways senseory info is transmitted to the brain?

A

high discriminatory

low discriminaatory

50
Q

How to Meissner’s corpuscles, merkel’s discs, hair receptors, Pacinian corpuscles and Ruffini’s end organs transmit signas and are they high or low discrimination>

A

transmit signals through type A-beta myelinated nerve fibers at 30-70 m/sec (e.g. tactile sensations)

high

51
Q

How do free nerve endits traansmit signals and is it low or high discrimination?

A

transmit signals through 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)

52
Q

explain type a beta nerve fibers

A

They are myelinated, send signals 30-70 m/s, high discrimination, used by almost all receptors
tactile

53
Q

explain type a delta and type c

A

typa a: myelinated, 6-30 m/s, low
fast. cold+warm

type c: unmyelinated, 0.5-2 m/s, low
slow pain, temp and crude tough

54
Q

what is the way sensory info gets transmitted

A

Sensory information enters the spinal cord through the dorsal roots of the spinal nerves

55
Q

what are the Two pathways for sensory information an function

A

Dorsal column-medial lemniscal system (proprio)

Antero-lateral system (pain , thermal)

56
Q

true or false Sensory fibers in both pathways no not DECUSATE
(i.e. cross the midline to the contralateral side)

A

false

57
Q

explain how sensory fibers decusate

A

Sensory stimulation in one side of the body is transmitted to the brain hemisphere on the opposite side

58
Q

what transmits sensory stimulation from the receptor to the final point of the cerebral cortex.

A

THREE ORDER NEURONS

59
Q

What type of signals does the dorsal column medial leminiscal pathway transmit

A

TACTILE AND PROPRIOCEPTIVE

60
Q

WHERE does the Signal originates for the AL

A

Signal originates from Free nerve endings receptors (e.g. pain receptors, thermal receptors…)

61
Q

What type of fibers does the AL use

A

Uses smaller myelinated (A-δ) and unmyelinated (C) fibers for slow transmission

62
Q

Where does the signal orginiate for DCML

A

Signal originates from tactile receptors (e.g. meisner’s, Pacinian, Ruffini’s, Merkel’s) or Proprioceptive receptors (e.g. muscle spindle)

63
Q

does the DCML have a high or low degree of spacial fidelity

A

HIGH

64
Q

explain the 3rd order neuron process for DCML

A

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

65
Q

Whre do the 2nd order neurons desucate in the DCML

A

AT THE MEDULLA BRAINSTEM

66
Q

What signals does the AL transmit

A

Transmits a broad spectrum of modalities (e.g. pain, thermal sensations, crude touch & pressure, tickle and itch, sexual sensations)

67
Q

does the AL have high or low sptial fideloty

A

low

68
Q

Explain the 3rd order neurons for the AL system

A

1st order neurons synapse with 2nd order neurons in the Substantia Gelatinosa (spinal cord)
2nd order neurons decussate at the level of spinal cord
2nd order neurons synapse with the 3rd order neurons in the thalamus
3rd order neurons transmit info to the primary somatosensory cortex

69
Q

Where do the 2nd order neurons in the AL system decusate

A

Spinal cord

70
Q

Where are fast pain and slow pain transmitted (tracts) in and through what fibers

A

Fast pain fibers are transmitted in the NEOSPINALTHALAMIC TRACT (A DELTA FIBERS)

Slow pain fibers are transmitted in the PALEOSPINOTHALIC TRACT (C FIBERS)

71
Q

Where do fast pain fibers terminate and do they have high or low localization

A

Fast pain fibers terminate at the somatosensory cortex

high

72
Q

where do slow pain fibers terminateand are they highly localized

A

terminate at the thalamus level or below.

Slow pain is poorly localized

73
Q

Where is the primary somoateorsney cortex located

A

Located in the POST CENTRAL GYRUS (in the parietal lobe)

74
Q

true or false:

Highly organized with distinct spatial orientation (i.e. each area of the cortex is devoted to a given body region, map of the sensory representation)

A

TRUE

75
Q

FIll in the blank

Each side of the cortex receives information from the… side of the body

A

OPPOSITE

76
Q

does the term somatosensory cortex almost always means area 1 or 2

A

1

77
Q

explain penfields homunculous

A

Unequal representation of the body.
Lips have greatest area of representation followed by the face, thumb, fingers, hand…
Trunk and lower body have the least area.

The more a region of the body has receptors…
The better its area of representation in the somatosensory cortex is

78
Q

Somatosensory Cortex is composed of HOW MANY cellular layers and are they neurons organized vertically or horizontally

A

SIX cellular layers
Within the layers the neurons are also arranged in:
vertical columns

79
Q

what is the purpose of the columns in the primary somatosensory coretz

A

Each column serves a specific sensory modality:

Ex: stretch, pressure, touch

80
Q

true or false: Different columns interact between each other

A

true

81
Q

what system is responsible for pain suppresion

A

analgesia system

82
Q

true or false: The degree to which we react to pain DOES NOT varies tremendously from person to person

A

false

83
Q

how does the brain suppress pain signals/

A

THROUGH THE ACTIVATION

OF THE ANALGESIA SYSTEM

84
Q

what re the 3 components of the analgesia system

A

Analgesia System:

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

85
Q

what is the main NT involved in analgesia system

A

ENKEPHALIN NEURON

released at the 3 levels on the figure

86
Q

what is referred pain and why does it happen

A

Pain in internal organs is often sensed on the surface of the body, a sensation known as referred pain

nociceptos from several locations converge to a single tract in the spinal cord.
pain from skin more common so it associates it there

87
Q

what does CIPA stand for

A

Congenital insensitivy to pain with anhydrosis

258 - physiology (21 decks)

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