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Flashcards in Intro to sensory systems Deck (98):
1

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

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

2

What is perception?

The conscious awareness of stimuli

3

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

Sensory transduction

4

What is receptor potential?

**change** in the membrane potential produced by a transducer mechanism

5

True or false: the receptor potential is a graded potential

True

6

Most receptor potentials are generated how?

Via depolarization of a receptor

7

How is the rate of receptor potential changed?

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

8

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

No

9

What is the labeled line principle?

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

10

How do we know "what" and "where" a stimulus is?

Labeled line principle

11

What is a receptor field?

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

12

What is an adequate stimulus?

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

13

What is the receptor specificity?

There is only one stimulus that can affect a given receptor

14

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

True

15

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

False

16

How do pacinian corpuscles work?

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

17

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

True

18

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?

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

19

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

Neospinothalamic and paleospinothalamic pathways

20

Where do the neospinothalamic and paleospinothalamic pathways cross over?

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

21

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

Lissauer's tract

22

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

DRG

23

What is the law of projection?

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

24

Where is the primary somatosensory cortex?

Behind the central sulcus

25

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

It's not that bad really...

26

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

Medial = anterior cerebral
Lateral = middle cerebral

27

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

Foot, leg, hip, genitals

28

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

1. Frequency of nerve impulses
2. Number of fibers activated

29

What is the concept of lateral inhibition?

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

30

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

Maintains continuous signal strength during stimulus

Have on-off signal

31

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

True

32

What causes the adaptation of a sensory receptor?

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.

33

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

False

34

What are the non-adapting receptors?

Nociceptors

35

What is a tonic receptor?

A receptor that does adapt, but does so slowly

36

How do tonic receptors adapt?

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

37

Merkel cell endings are what type of adapting receptors?

Slowly adapting receptors

38

When are slowly adapting receptors useful?

for giving continuous information about stimulus strength and signaling stimulus duration

39

When are slowly adapting receptors NOT useful?

not as useful for signaling stimulus duration at low stimulus intensities

40

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

Fast adapting

41

What are phasic or rate receptors?

fast adapting receptors

42

When are fast adapting receptors useful?

useful for signaling beginning and end of stimulus

43

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

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

44

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

Fast adapting

45

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

Fast adapting

46

What type of receptor is useful for sensing stimulus intensity?

Tonic receptors

47

What are the four different types of tactile sensation receptors?

1. Crude
2. Discriminitive
3. Pressure
4. Flutter/vibration

48

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

Free nerve endings (type C unmyelinated fibers)

49

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

Low threshold = high sensitivity

50

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

False--only the dorsal columns

51

What is the difference between flutter and vibration?

Just frequency--higher = more like vibration

52

What is the tuning fork utilized for testing vibration sense?

128 hz

53

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

Low (highly sensitive)

Found at the base of the epidermis

54

What is an Iggo dome receptor?

Several merkel discs joined together

55

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

A-beta fibers--very myelinated

56

Merkel cells are slow or fast adaptors?

Slow

57

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

Merkels discs

58

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

Merkel cells

59

Ruffini corpuscles sense what?

Joint stretch

60

Meissner's corpuscles are rapidly or slowly adapting fibers?

Rapid

61

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

Meissner's corpuscles

62

Where are Meissner's corpuscles located in the skin?

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

63

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.

Meissner's corpuscles

64

Pacinian corpuscles are slowly or rapidly adapting?

Rapid

65

Where in the skin are pacinian corpuscles found?

subcutaneous tissue

66

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

True

67

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

Pacinian corpuscles

68

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

peritrichial nerve endings--A-delta fibers

69

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

Rapid adapting = good for change

Slow adapting = good for constant stimulus

70

Itch is sensed by what type of sensors/fibers?

Free nerve endings with C fibers

71

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

Best = hands

Worst = calves

72

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

dorsal columns

73

What are the receptors involved in proprioception?

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

74

Joint position proprioception is static or dynamic proprioception?

static

75

Joint movement proprioception is static or dynamic proprioception?

Dynamic

76

What is conscious proprioceptions?

Kinesthesia

77

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

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

78

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

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

79

Rhomberg test tests what?

Proprioception

80

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

Behind the central sulcus

81

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

Foot and genitals

82

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

Caudal medulla

83

What is graphesthesia?

Ability to recognize figure drawn into hand or onto skin

84

What is sterognosis?

Ability to recognize 3D objects through touch alone

85

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

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

What part of the CNS is utilized in graphesthesia?

DC/ML

87

What is a nerve pressure palsy?

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

88

Why is there a stocking-glove sensory loss?

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

89

Review Brown_sequard syndrome.

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

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

Proprioception ipsilateral

Pain and temp contralateral

91

What is the order of the speed of fibers?

Aalpha
Abeta
Agamma
Adelta
B
C
C

92

What are the fibers involved in motor neurons?

A-alpha

93

What are the fibers involved in GOTs?

A-beta (I-b)

94

What are the fibers that innervate the muscle spindles?

Ia

95

What do A-beta fibers innervate?

Muscle spindle endings

96

What do A-gamma fibers innervate?

Axons of gamma motor neurons

97

What do A delta fibers innervate?

fast pain, some temp

98

What do type C fibers innervate?

Free nerve endings