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Physiology > Intro to sensory systems > Flashcards

Intro to sensory systems Flashcards

1
Q

What are the five types of receptors (classified by the stimulus)?

A
  1. Mechano
  2. Thermo
  3. Photo
  4. Chemo
  5. Nociceptor
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2
Q

What is perception?

A

The conscious awareness of stimuli

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3
Q

What is the process of translating a physical stimulus to a nerve impulse?

A

Sensory transduction

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4
Q

What is receptor potential?

A

change in the membrane potential produced by a transducer mechanism

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5
Q

True or false: the receptor potential is a graded potential

A

True

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6
Q

Most receptor potentials are generated how?

A

Via depolarization of a receptor

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7
Q

How is the rate of receptor potential changed?

A

Rate at which action potentials are generated increases as receptor potential rises higher above threshold.

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8
Q

If the receptor potential is a hyperpolarization, does it generate an action potential?

A

No

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9
Q

What is the labeled line principle?

A

tells you the sensory modality since there is a chain of connected neurons from the sensory receptor which responds to the stimulus to the brain area that perceives the stimulus

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10
Q

How do we know “what” and “where” a stimulus is?

A

Labeled line principle

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11
Q

What is a receptor field?

A

the region of tissue (e.g. skin) within which a stimulus can evoke a change in the firing rate of the neuron.

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12
Q

What is an adequate stimulus?

A

Under normal circumstances, a specific receptor is affected by only one stimulus modality

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13
Q

What is the receptor specificity?

A

There is only one stimulus that can affect a given receptor

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14
Q

True or false: receptor potential change with the size of the stimulus

A

True

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15
Q

True or false: action potential changes with the size of the stimulus

A

False

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16
Q

How do pacinian corpuscles work?

A

Movement causes Na channels to open. Bigger stimulus = more openings

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17
Q

True or false: wherever along the chain of a receptor is stimulated, it will produce the same sensation

A

True

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18
Q

What is the pathway in the spinal cord that transmits proprioception and fine touch? Where do these cross in the spinal cord? Where do these project to?

A

Dorsal columns (fasciculus cuneatus and gracilis)

These cross in the medulla via the nucleus cuneatus and gracilis to project to the VPL nucleus of the thalamus, then the somatosensory cortex

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19
Q

What are the pathways in the spinal cord that transmit pain and crude touch?

A

Neospinothalamic and paleospinothalamic pathways

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20
Q

Where do the neospinothalamic and paleospinothalamic pathways cross over?

A

At the level (and 1-2 above/below) they enter via the anterior white commissure.

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21
Q

What is the area that the axons of the neospinothalamic pathway go up and gown in the spinal cord?

A

Lissauer’s tract

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22
Q

Where are the cell bodies of the primary motor neurons in the dorsal columns and the neo/paleospinothalamic pathways housed?

A

DRG

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23
Q

What is the law of projection?

A

in a neuron in a sensory pathway is stimulated, the subject perceives the stimulus as being in the location of the sensory receptor for that pathway

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24
Q

Where is the primary somatosensory cortex?

A

Behind the central sulcus

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25
Q

Review the homunculus distribution of the sensory cortex if you do not remember

A

It’s not that bad really…

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26
Q

What is the blood supply to the medial cortex? Lateral?

A 
Medial = anterior cerebral
Lateral = middle cerebral
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27
Q

What are the parts of the body that are represented by the medial part of the somatosensory cortex?

A

Foot, leg, hip, genitals

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28
Q

What are the two ways in which the nervous system codes for stimulus strength?

A
  1. Frequency of nerve impulses

2. Number of fibers activated

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29
Q

What is the concept of lateral inhibition?

A

When a part of a receptor field is stimulated, the receptors in close proximity are inhibited, thus providing more localized stimulus

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30
Q

How does the nervous system code for stimulus duration? (2 different ways)

A

Maintains continuous signal strength during stimulus

Have on-off signal

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31
Q

True or false: inhibition is just as useful as excitation in the nervous system

A

True

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32
Q

What causes the adaptation of a sensory receptor?

A

When a maintained stimulus of constant strength is applied to a receptor, the frequency of the action potentials in the receptor’s sensory nerve decreases over time.

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33
Q

True or false: all receptor use the same mechanism of adaptation to a stimulus

A

False

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34
Q

What are the non-adapting receptors?

A

Nociceptors

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35
Q

What is a tonic receptor?

A

A receptor that does adapt, but does so slowly

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36
Q

How do tonic receptors adapt?

A

Initial burst of firing when the stimulus is applied, but then slows down

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37
Q

Merkel cell endings are what type of adapting receptors?

A

Slowly adapting receptors

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38
Q

When are slowly adapting receptors useful?

A

for giving continuous information about stimulus strength and signaling stimulus duration

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39
Q

When are slowly adapting receptors NOT useful?

A

not as useful for signaling stimulus duration at low stimulus intensities

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40
Q

Pacinian corpuscles and Meissner’s corpuscles are what type of receptors (slow or fast adapting)?

A

Fast adapting

41
Q

What are phasic or rate receptors?

A

fast adapting receptors

42
Q

When are fast adapting receptors useful?

A

useful for signaling beginning and end of stimulus

43
Q

Can fast receptors signal a change in stimulus intensity? If so, how?

A

Yes–number of action potentials transmitted related to rate at which change is taking place

44
Q

What type of receptors are needed to extract dynamic information e.g. velocity and acceleration

A

Fast adapting

45
Q

Which type of receptors are useful for sensing when a stimulus begins and ends (fast or slow adapting)?

A

Fast adapting

46
Q

What type of receptor is useful for sensing stimulus intensity?

A

Tonic receptors

47
Q

What are the four different types of tactile sensation receptors?

A
  1. Crude
  2. Discriminitive
  3. Pressure
  4. Flutter/vibration
48
Q

What type of receptors are utilized for crude touch? How well are these myelinated?

A

Free nerve endings (type C unmyelinated fibers)

49
Q

Do the free nerve endings involved in crude touch have a low threshold or high threshold for stimulation? What is the consequence of this?

A

Low threshold = high sensitivity

50
Q

True or false: discriminative touch is carried by both the dorsal lateral and the aternomedial systems?

A

False–only the dorsal columns

51
Q

What is the difference between flutter and vibration?

A

Just frequency–higher = more like vibration

52
Q

What is the tuning fork utilized for testing vibration sense?

A

128 hz

53
Q

Merkel cell fibers are low or high threshold receptors? Where are they found?

A

Low (highly sensitive)

Found at the base of the epidermis

54
Q

What is an Iggo dome receptor?

A

Several merkel discs joined together

55
Q

What type of fibers innervate Merkels discs? How well are these myelinated?

A

A-beta fibers–very myelinated

56
Q

Merkel cells are slow or fast adaptors?

A

Slow

57
Q

Which receptors have the highest spatial relationship of all the sensory afferents?

A

Merkels discs

58
Q

What are the receptors that play a role in static discrimination of shapes, edges, and textures?

A

Merkel cells

59
Q

Ruffini corpuscles sense what?

A

Joint stretch

60
Q

Meissner’s corpuscles are rapidly or slowly adapting fibers?

A

Rapid

61
Q

Which type of receptors have a very high density in the tips of the fingers?

A

Meissner’s corpuscles

62
Q

Where are Meissner’s corpuscles located in the skin?

A

Just below the epidermis, but closer to the skin than Merkel’s discs

63
Q

Information from which receptors are probably the basis for the detection of slippage between the skin and an object held in the hand. Responsible for the sensory feedback information needed for the efficient control of grip.

A

Meissner’s corpuscles

64
Q

Pacinian corpuscles are slowly or rapidly adapting?

A

Rapid

65
Q

Where in the skin are pacinian corpuscles found?

A

subcutaneous tissue

66
Q

True or false: pacinian corpuscles adapt more rapidly than Meissner’s

A

True

67
Q

Which receptors can detect vibrations transmitted though objects held in the hand thus contributing to skilled tool use?

A

Pacinian corpuscles

68
Q

What are the receptors in the base of hairs? What type of fibers are utilized by these receptors?

A

peritrichial nerve endings–A-delta fibers

69
Q

Which type of receptor is better at detecting change? Which is better for detecting a long stimulus?

A

Rapid adapting = good for change

Slow adapting = good for constant stimulus

70
Q

Itch is sensed by what type of sensors/fibers?

A

Free nerve endings with C fibers

71
Q

What part of the body has the least ability to detect two separate points? Best?

A

Best = hands

Worst = calves

72
Q

Lack of two point discrimination will indicate damage to what part of the spinal cord?

A

dorsal columns

73
Q

What are the receptors involved in proprioception?

A

a. joint receptors
b. muscle spindles and Golgi tendon organs
c. skin tactile receptors

74
Q

Joint position proprioception is static or dynamic proprioception?

A

static

75
Q

Joint movement proprioception is static or dynamic proprioception?

A

Dynamic

76
Q

What is conscious proprioceptions?

A

Kinesthesia

77
Q

The DC/ML pathway is responsible for what type of sensation?

A

fine tactile discriminations, vibratory sense (which is just rapid, repeated touch/pressure) and proprioceptive sense.

78
Q

What allows for the precise localization of the DC/ML pathways?

A

Precise localization is possible because the receptors associated
with system can have very small receptive fields

79
Q

Rhomberg test tests what?

A

Proprioception

80
Q

Where is the somatosensory cortex in the cortex of the brain?

A

Behind the central sulcus

81
Q

What are the two parts of the homunculus in the medial fissure of the sensory cortex?

A

Foot and genitals

82
Q

Where does the DC/ML crossover in the spinal cord?

A

Caudal medulla

83
Q

What is graphesthesia?

A

Ability to recognize figure drawn into hand or onto skin

84
Q

What is sterognosis?

A

Ability to recognize 3D objects through touch alone

85
Q

Neurons in the somatosensory II area show what type of responses?

A

Attention modulated

(That is, the responses of the neurons in this area to a stimulus depend on whether the subject is paying attention to the stimulus)

86
Q

What part of the CNS is utilized in graphesthesia?

A

DC/ML

87
Q

What is a nerve pressure palsy?

A

Loss of feeling d/t transient ischemia (“foot falls asleep”)

88
Q

Why is there a stocking-glove sensory loss?

A

Leg nerves are longer, and therefore more easily affected by insults

89
Q

Review Brown_sequard syndrome.

A

DC/ML will show symptoms of the ipsilateral side of the lesion, since it crosses over in the caudal medulla.

The neospinothalamic/paleospinothalamic (both parts of the spinothalamic system) decussate at the level (or one to two above) of the lesion. (recall the axons in this path from the DRG go up and down in the tract of Lissauer, then cross over in the anterior white commissure).

90
Q

In Brown-Sequard syndrome, loss or proprioception will by ipsilateral, or contralateral to the side of the lesion. how about pain and temp?

A

Proprioception ipsilateral

Pain and temp contralateral

91
Q

What is the order of the speed of fibers?

A 
Aalpha
Abeta
Agamma
Adelta
B
C
C
92
Q

What are the fibers involved in motor neurons?

A

A-alpha

93
Q

What are the fibers involved in GOTs?

A

A-beta (I-b)

94
Q

What are the fibers that innervate the muscle spindles?

A

Ia

95
Q

What do A-beta fibers innervate?

A

Muscle spindle endings

96
Q

What do A-gamma fibers innervate?

A

Axons of gamma motor neurons

97
Q

What do A delta fibers innervate?

A

fast pain, some temp

98
Q

What do type C fibers innervate?

A

Free nerve endings

Physiology (75 decks)

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