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Clinical Neuroscience > Peripheral Somatosensory System > Flashcards

Peripheral Somatosensory System Flashcards

1
Q

Loss of sensory function can result from ____ and ____ nervous system lesions

A

central; peripheral

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2
Q

In the 3-neuron pathway what does the first order neuron do?

A

Brings information from sensory receptors into the spinal cord

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3
Q

In the 3-neuron pathway what does the second-order neuron do?

A

Conveys information between the spinal cord or brainstem to the thalamus

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4
Q

In a 3-neuron pathway what does the third-order neuron do?

A

Conveys information from the thalamus to the cerebral cortex

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5
Q

True or False

The cerebellum uses sensory input to modify motor input but it does not percieve it

A

True

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6
Q

What are the parts of the brain that can consciously percieve somatosensory information?

A

Thalamus and Cerebral Cortex

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7
Q

What does the peripheral somatosensory information do?

A

Conveys information from the skin and musculoskeletal system to the spinal cord

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8
Q

What does the peripheral nervous system convert mechanical, chemical, or thermal stimulation into?

A

Receptor potentials

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9
Q

When is an axon potential produced in a peripheral axon?

A

When the receptor potential exceeds the threshold of the trigger zone

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10
Q

List the pathway that the axon potential travels along in the Peripheral Somatosensory System.

A
  • Axon potential travels along distal peripheral axon
  • pas the T-junction that leads to the cellbody in the dorsal root ganglion
  • Goes down proximal peripheral axon into spinal cord
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11
Q

When does the axon potential reach the central nervous system?

A

When it reaches the spinal cord

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12
Q

Which of the 3-neuron order’s is this?

Pseduounipolar neurons that have distal axons, cell bodies in the dorsal root ganglia and proximal axons

A

First-order somatosensory neurons

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13
Q

What do the axons of the ventral ramus innervate?

A

Anterior and lateral trunk and limbs

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14
Q

What do the axons of the dorsal ramus innervate?

A

Skin and deep muscles of the back

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15
Q

What are sensory receptors?

A

Specialized end organs that communicate with peripheral nerves or are free nerve endings

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16
Q

What is the following receptor called?

Have ion channels that are responsive to mechanical, thermal, chemical, or electromagnetic energy from environmental stimuli which converts into action potential transmitting the information to the CNS

A

Sensory Receptor

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17
Q

What are sensory receptors classifed as?

A
  • Chemoreceptors
  • Mechanoreceptors
  • Thermoreceptors
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18
Q

What is the name of the following sensory receptor?

Consist of free nerve endings or specialized end-organs and respond to mechanical deformation of the receptor by touch, pressure, stretch of vibration

A

Mechanoreceptor

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19
Q

What is the name of the following sensory receptor?

Free nerve endings and respond to exogenous chemicals or substances released by cells, including damaged cells following injury or infection

A

Chemoreceptors

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20
Q

What is the name of the following sensory receptor?

Free nerve endings and respond to heating or cooling

A

Thermoreceptors

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21
Q

Is the following a tonic or phasic sensory receptor?

Respond the entire time a stimulus is present providing constant input to the CNS

A

Tonic Receptor

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22
Q

Is the following a tonic or phasic sensory receptor?

Adapt to a constant stimulus and stop responding while the stimulus is present

A

Phasic Receptor

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23
Q

What is the role of a phasic receptor?

A

Alert the body about a change in a stimulus

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24
Q

Which cutaneous sensory receptor is the following?

  • axons myelinated by A(beta) fibers; respond to hair movement; phasic receptors; small receptive field diameter
  • axons are lightly myelinated A(gamma): respond to hair movement; phasic receptors; small receptive field diameter
A

Hair Follicle Nerve Ending

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25
Q

Which cutaneous sensory receptor is the following?

  • Axons are myelinated A(beta) fibers: respond to dynamic movement across skin, slippage during grip; phasic receptors; small receptive field diameter
A

Meissner’s Corpuscle

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26
Q

Which cutaneous sensory receptor is the following?

  • Axons are myelinated A(beta) fibers: respond to light pressure, curvature, edges; tonic receptors; small receptive field diameter
A

Merkel Cell

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27
Q

Which cutaneous sensory receptor is the following?

  • Reponds to nociceptive mechanical stimuli and cold stimuli; tonic receptors; medium receptive field diameter
A

Lightly Myelinated A(gamma)

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28
Q

Which cutaneous sensory receptor is the following?

  • Responds to nocieptive mechanical stimuli; pleasant mechanical stimuli; ticklish mechanical stimuli; pruritic stimuli; thermal stimuli; chemical stimuli; tonic receptors; medium field diameter
A

Unmyelinated C fibers

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29
Q

Which cutaneous sensory receptor is the following?

  • Axons are myelinated A(beta) fibers: respond to vibration; phasic receptors;large receptive field diameter
A

Pacinian Corpuscle

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30
Q

Which cutaneous sensory receptor is the following?

  • Axons are myelinated A(beta) fibers: respond to stretch of skin; tonic receptors; large receptive field diameter
A

Ruffini Corpuscle

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31
Q

Why are larger diameter axons able to transmit information faster than smaller diameter axons?

A

Due to the low resistance to current flow in large-diameter axons and because they are myelinated allowing saltatory conduction of action potential to take place

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32
Q

Large-diameter peripheral somatosensory axons only transmit action potential triggered by what?

A

Mechanical Stimuli

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33
Q

Medium & small-diameter peripheral somatosensory axons are polymodal and transmit signals which sensory modalities

A
  • mechanical
  • thermal
  • chemical
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34
Q

When does the activity of polymodal neurons increase?

A

Following tissue injury

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35
Q

20% of cutaneous and 50% of visceral nociceptors are ___

A

silent nociceptors

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36
Q

What is a receptive field?

A

Area of skin innervated by a single peripheral somatosensory neuron

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37
Q

Do distal regions of the body have greater or lesser density of sensory receptors than proximal regions?

38
Q

Information from cutaneous sensory receptors contribute to what?

A

Joint position and movement sense

39
Q

What do cutaneous receptors respond to?

A

Stretching or increasing pressure on the skin that occurs with movement

40
Q

Information from only a small amount of peripheral somatosensory neurons active at any given moment reach conscious awareness prevents what?

A

Sensory Overload

41
Q

Information used to make autonomic adjustments and is prevented from reaching consciousness is done via wha?

A

Descending and local inhibitory connections

42
Q

What is muscle spindle?

A

Sensory receptor in muscle that informs the CNS about limb position in space

(moving or stationary & direction and rate of movement)

43
Q

What senses static position of a limb and limb movement by detecting changes in muscle length and velocity at which length of muscle is changing?

A

Muscle Spindle

44
Q

What is muscle spindle made of?

A

Muscle fibers, sensory endings, and motor endings

45
Q

What are muscle fibers in muscle spindles called?

A

Intrafusal fibers

46
Q

Where can the intrafusal contract and where can it not?

A

Contracts at ends
Cannot contract in the central region

47
Q

What are the 2 types of intrafusal fibers?

A
  • contains nuclear bag fiers which have a bundle of nuclei in central region
  • nuclear chain fibers which have nuclei arranged in a single file
48
Q

What are the 2 types of sensory afferents that innervate intrafusal fibers?

A

Type IA and II

49
Q

Is the following Type IA or Type II afferent?

Wraps around the central region of both nuclear bag and nuclear chain fibers
phasic receptors that have maximal discharge during quick stretch of muscle

A

Type IA afferent

50
Q

Is the following Type IA or Type II afferent?

Mainly on nuclear chain fibers and some nuclear bag fibers
tonic receptors that exhibit sustained firing proportional to the amount of stretch placed on muscle

51
Q

What innervates intrafusal muscle fibers to adjust stretch of the central region enabling the muscle spindle to be sensitive

A

Small-diameter gamma neurons

52
Q

Where do Gamma dynamic axons innervate the intrafusal fibers?

A

Contractile ends of nuclear bag fibers to adjust sensivity to velocity of muscle length changes

53
Q

Where to Gamma static axons innervated the intrafusal fibers?

A

Contractile ends of nuclear chains and some nuclear bags to tune their sensitivty to static muscle stretch

54
Q

Are there more muscle spindles in muscles that involve fine, skilled voluntary movement or in gross movements?

A

Fine, skilled voluntary movements

55
Q

When do muscle spindles respond to stretch?

A

During passive stretch

56
Q

What does passive stretching activate?

A

Spindle sensory receptors stimulating Type IA and II afferent fibers

57
Q

What does the excitation of alpha motor neuron via corticospinal neruon result in?

A

Contraction of extrafusal muscle fibers

58
Q

What is spindle sensivity to changes in length adjusted by?

A

Gamma Static Efferents

59
Q

What is velocity of change in muscle length signaled by?

A

Type IA afferents

60
Q

What is the following a defintion of?

Encapsulated nerve endings intertwined among the collagen strands of the tendon near the musculotendious junction

A

Golgi Tendon Organ

61
Q

What does Golgi Tendon Organs respond to?

A

Tension in tendons

62
Q

What causes the generation of action potential in Golgi tendon organ?

A

The contraction of a muscle pulls on collagen strand compressing the golgi tendon organ

63
Q

What responds to mechanical deformation of the capsule and ligaments?

A

Joint receptors

64
Q

What are Ruffini’s endings?

A

In joint capsule and are tonic receptors innervated by type II afferent axons

65
Q

What do Ruffini’s endings signal?

A
  • Extremes of joint range
  • Responding more to passive versus active movement
66
Q

What are Paciniform corpuscles?

A

Phasic receptors innervated by type II afferents

67
Q

What do Paciniform corpuscles respond to?

A

Movement and are silent when joint position is constant

68
Q

What are ligament receptors innervated by and what does it signal?

A

Innervated by Type IB afferents and signals tension

69
Q

What are free nerve endings innervated by and what are they stimulated by?

A

Innervated by type III and IV afferents and stimulated by inflammation

70
Q

What is the following Muscular Afferent Axon?

  • myelinated
  • innervaes nuclear bag and nuclear chian fibers; codes velocity of muscle stretch; phasic; found in intrafusal muscle fibers
72
Q

What is the following Muscular Afferent Axon?

  • Myelinated innervated golgi tendon organ; codes tension placed on muscle; tonic; found in tendons
  • innervated ligament receptors; codes tension place on ligaments
73
Q

What is the following Muscular Afferent Axon?

  • myelinated
  • innervated nuclear chain and some nuclear bag fibers; codes muscle length; tonic; found in intrafusal muscle fibers
  • innervated paciniform corpuscles; codes joint movement; phasic; found in the joint capsule
  • innervated Ruffini’s endings; codes extreme joint stretch; tonic; found in the joint capsule
74
Q

What is the following Muscular Afferent Axon?

  • lightly myelinated; unmyelinated
  • innervates free nerve endings; codes nociceptive stimuli; tonic; found in the muscle, joint capsule, and ligaments
A

Type III and IV

75
Q

What is the superficial (tactile) sensation?

  • unpleasant feelings, resulting from a sensory stimulus that is sharp or pinpoint, especially when the stimulus has the potential to cause tissue damage
  • protective in nature, can also be referred to as sharp/dull discrimination
  • receptors: free nerve endings
A

Pain Sensibility

76
Q

What is the superficial (tactile) sensation?

  • interprets the heat or cold state of an object or environment and plays protective role
  • Receptors: free nerve endings
A

Temperature Sensbility

77
Q

What is the superficial (tactile) sensation?

  • sensation caused by mildest of tactile stimulation
  • Receptors: Merkel’s cells, hair follicle nerve ending, Ruffini corpuscles, Meissner’s corpuscles, free nerve endings
A

Light Touch

78
Q

What is the superficial (tactile) sensation?

  • results from mechanical stimulation due to a greater magnitude of pressures with deeper skin deformation
  • conveys nondiscriminative tactile information allowing a person to sense a tactile stimulus without localizing it
  • important for general alertness
  • Receptors: Pacinian corpuscles, free nerve endings; Ruffini corpuscles
A

Pressure or Crude Touch

79
Q

What is the following Proprioceptive Sensation?

Conscious awareness of the relative static position of your body parts in space without the need for visual confirmation

A

Joint Position Sense

80
Q

What is the following Proprioceptive Sensation?

Awareness of the degree, velocity, and direction of movement at a single joint or body segment; sensory information about movement

A

Joint Movement Sense (Kinesthesia)

81
Q

What is the following Proprioceptive Sensation?

Sensation experienced from tactile contact with an object that is shaking or oscillating at a particular frequency

82
Q

What is the following Discriminative sensation?

  • awareness of the specific skin surface site to which stimulation was applied
  • Receptors: merkel cell, meissner’s corpuscles
A

Tactile Localization

83
Q

What is the following Discriminative sensation?

  • ability to distinguish two simultaneously applied blunt point as two discrete stimuli
  • smallest interpoint distance still perceived as two points
  • Receptors: Merkel Cell
A

Two-point discrimination

84
Q

What is the following Discriminative sensation?

  • ability to recognize writing on the skin including shapes, numbers, or letters purely by the sensation of touch
  • Receptors: Meissner’s corpuscles
A

Graphesthesia

85
Q

What is the following Discriminative sensation?

  • ability to recognize by tactile manipulation only, the form and charactersitics of an object including size, shape, weight, consistency, and texture
  • Receptors: Meissner’s corpuscles
A

Stereognosis

86
Q

Where does somatosensory information originate from?

A

Sensory receptors and musculoskeletal

87
Q

What is cutaneous somatosensory information referred to as?

A

Superficial or tactile sensation

88
Q

What is somatosensory information from the musculoskeletal system?

A

Deep sensation or proprioception

89
Q

What is combined cortical sensation?

A

Superficial and deep sensations and is referred to as discriminative sensations

90
Q

What is discriminative sensation?

A

Requires information from exteroreptive and proprioceptive sensory receptors and the articial sensory association areas of the brain

Clinical Neuroscience (22 decks)

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