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Neuro > Somatosensory System II- Systems > Flashcards

Somatosensory System II- Systems Flashcards

1
Q

Where are the receptors for discriminative touch and “conscious” proprioception located?

A

Medial Lemniscal System of Dorsal Column of Body

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2
Q

What type of receptors are discriminative touch and “conscious” proprioception, and what type of fibers do they have?

A

Mechanoreceptors in Skin (touch), Muscles and joints (Proprioception).

-Fibers Ia, Ib, and II (Fast)

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3
Q

Where are the cell bodies of the 1st, 2nd, and 3rd order neurons located for discriminative touch and “conscious” proprioception?

A

1st- Dorsal Root Ganglia
2nd- Nucleus Gracilis or Cuneatus (in Medulla)
3rd- VPL Nucleus of Thalamus

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4
Q

What part of the Dorsal Funiculus does information from the Lower and Upper Extremities go to?

A

LE - Fasciculus Gracilis (medial)

UE - Fasciculus Cuneatus (lateral)

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5
Q

Describe the path of the 2nd order Neurons for discriminative touch and “conscious” proprioception.

A

Synapse with 1st order neurons at Nucleus Gracilis or Cuneatus (Brainstem)–> Axons cross the neural axis as Internal Arcutate fibers and form Medial Lemniscus–>Synapse with 3rd order neurons in VPL of Thalamus

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6
Q

Describe the path of 3rd order neurons for discriminative touch and “conscious” proprioception.

A

Synapse with 2nd Order neurons in the VPL of Thalamus–> Axons traverse the Posterior limb of the Internal Capsule–> Terminate along Post Central and Posterior Paracentral Gyrus.

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7
Q

What part of the body does the Posterior Paracentral Gyrus get discriminative touch and “conscious” proprioception information from?

A

Lower Extremity

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8
Q

What part of the body does the Post Central Gyrus get discriminative touch and “conscious” proprioception information from?

A

Dorsolateral- Upper Extremity

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9
Q

What is the blood supply of 3rd order neurons for discriminative touch and “conscious” proprioception?

A

Branches of:

  • Posterior Cerebral Artery (Thalamus)
  • Middle Cerebral Artery ( Post Central Gyrus)
  • Anterior Cerebral Artery (Posterior Paracentral Gyrus)
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10
Q

What is the name of the system that brings discriminative touch and “conscious” proprioception information to the face?

A

Trigeminothalamic System

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11
Q

What are the target areas for discriminative touch and “conscious” proprioception?

A
  1. Primary Somatosensory Cortex
  2. Secondary Somatosensory Cortex
  3. Posterior Parietal Cortex
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12
Q

What is the composition of the Primary Somatosensory Cortex, and what does the 4th layer do?

A

6 layers of cell bodies

-Layer 4= receives input from Thalamus

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13
Q

How is the Primary Somatosensory Cortex organized?

A
  • Somatotopically: Humunculus (lateral to medial arrangement)
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14
Q

What is so important about the topographical representation of body parts in the somatosensory system?

A

Reflects the innervation density, which correlates with the spatial resolution of the body part

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15
Q

What are the regions of the Primary Somatosensory Cortex?

A

3a, 3b, 1, and 2.

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16
Q

Where do mechanoreceptors in the skin send their information?

A

Area 3b and 1.

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17
Q

Where do mechanoreceptors in the muscles and joints send their information to?

A

Area 3a and 2.

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18
Q

How is a functional hierarchy established in the Primary Somatosensory Cortex?

A

Area 3b projects onto Area 1 and 2. After area 3b, complexity gets greater.
-All 4 areas are interconnected, and each area projects to the secondary somatosensory cortex.

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19
Q

Describe the Column organization system.

A
  • Within each area, neuronal populations are vertically organized into columns.
  • All neurons in 1 column receive input from the same local area of skin and respond to only one modality.
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20
Q

How are neurons in the Somatosensory System defined?

A

By their modality and receptive field

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21
Q

What is a modality specific neuron?

A

They respond to a specific form of stimulus. 2nd order corticol neurons process more complex information (ex. feature detection), such as orientation, direction, texture, or shape.
-Ex. Orientation specific neurons will only respond to an object moving in a certain direction on skin.

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22
Q

Describe the receptive fields of Primary Somatosensory Cortex.

A

Large due to divergence and convergence within the relay nuclei.
-At each level (3a-3b-1-2), the receptor field gets larger. (ex. part of a finger–>whole hand)

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23
Q

Where does the Secondary Somatosensory Cortex get information from?

A

From each area of the primary somatosensory cortex

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24
Q

Where does the Secondary Somatosensory cortex project its information to?

A

Structures involved with tactile learning and memory. Helps you understand the shapes and feels of objects.

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25
Q

Where does the Posterior Parietal Cortex receive its input from?

A

Primary Somatosensory Cortex and the Thalamus. Connects bilaterally through the corpus callosum. This is Area 5, where we have cells that get information from both hands.

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26
Q

What does Area 5 do?

A

Integrates tactile information from mechanoreceptors in the skin, muscles, and joints.

27
Q

What does Area 7 do?

A

Integrates tactile information from mechanoreceptors in the skin, muscles, and joints, but with visual information. This is important for hand-eye coordination.

28
Q

Where does the Posterior Parietal Cortex project its information to?

A

Motor areas involved with the sensory guidance of movement.

ex. pick up hershey kiss with a pinch grasp instead of open hand

29
Q

What 4 things does integration involve?

A
  1. The size of receptive field becoming larger at each level, so entire object is sensed.
  2. Profile of activity in the neurons changing through action of inhibitory networks.
  3. Individual neurons respond to more complex inputs at successive levels of sensory processing.
  4. Submodalities converging on individual neurons in association cortical areas.
30
Q

Why are Pain and Temperature considered together?

A

Because of the close association of these sensory modalities at all levels in their ascending pathways.

31
Q

What is the name of the Pain and Temperature system and what does it include?

A

Anterolateral System in Body

  • Spinothalamic tract
  • Spinoreticular tract
  • Spinomesencepahlic tract
  • Spinohypothalamic tract
32
Q

What types of receptors are pain and temperature and what fibers do they have?

A

-Nociceptors and Thermoreceptors

Fibers III and IV–> Slower fibers

33
Q

Where are the cell bodies of the 1st, 2nd, and 3rd order neurons for Pain and temperature located?

A

1st- Dorsal Root Ganglia
2nd- Dorsal Horn
3rd- VPL Nucleus of Thalamus

34
Q

Describe the pathway of the 1st order neuron for pain and temperature.

A

Central processes enter the spinal cord in the lateral division of dorsal root–>enter Dorsolateral Fasciculus–>Bifurcate into ascending and descending branches–>Synapse in the dorsal horn with 2nd order neurons

35
Q

Describe the pathway of the 2nd order neuron for pain and temperature.

A

Synapse in the dorsal horn with 1st order neurons–> axons cross the neural axis in the Anterior White Commissure and ascend in the Ventrolateral (Anteriolateral) Funiculus.–>Certain axons synapse in the VPL nucleus of Thalamus

36
Q

What type of axons synapse in the VPL Nucleus of the Thalamus?

A

Axons conveying information pertaining to the discriminative aspects of pain (location, intensity, quality).

37
Q

What type of Axons synapse in the Reticular formation, midbrain, and hypothalamus?

A

Conveying information pertaining to the affective-motivational aspects of pain

38
Q

What is the Reticular formation’s response to pain?

A

When you’re sleeping, this allows you to feel the pain and wakes you up.

39
Q

What is the Hypothalamus’s response to pain?

A

Sweat, HR, BP all go up

40
Q

Describe the pathway of the 3rd order neurons for pain and temperature.

A

Certain axons synapse in the VPL nucleus of Thalamus–>axons traverse in the posterior limb of the internal capsule and terminate along the post central gyrus and posterior paracentral gyrus.

41
Q

What is the system for pain and temperature sensory information called in the face?

A

Spinal Trigeminal System

42
Q

In what ways does pain modulation occur in the Receptor?

A
  1. Peripheral Sensitization

2. Opioids

43
Q

What is the job of a Nonnociceptive fiber?

A

Contributes to the normal perception of stimulus quality, even though they do not respond directly to noxious stimuli.

44
Q

What is peripheral sensitization?

A

Following repeated applications of a noxious stimulus, receptors become more sensitive (lower threshold) and thus more responsive (increased firing rate)

45
Q

How do receptors result in peripheral sensitization?

A

From the exposure of receptors to chemicals released by damaged tissues and sensory nerve endings in the vicinity of the injury.

46
Q

Peripheral sensitization is a possible mechanism for what?

A

Hyperalgesia- excessive response to noxious stimuli

47
Q

What is the difference between exogenous and endogenous opioids?

A 
Exogenous= morphine
Endogenous= bodies produce (Ex. endorphins, enkephalins, dynorphins)
48
Q

Where would you find opioid receptors and endogenous opioids?

A

Dorsal horn of the spinal cord and brainstem regions involved with modulation of pain

49
Q

What are the 3 different ways in which opioids decrease pain?

A

Produce inhibition at :

  1. the peripheral processes of nociceptive primary afferent fibers (hyperpolarization)
  2. presynaptic terminals of sensory neurons (decreasing the release of neurotransmitter)
  3. Post synaptic terminals of sensory neurons (hyperpolarization)
50
Q

In what ways does pain modulation occur in the spinal cord?

A
  1. Neurotransmitters of Nociceptive primary afferent fibers
  2. Central Sensitization
  3. Gate Control Theory
  4. Opioids
51
Q

What are the 2 types of Neurotransmitters of Nociceptive primary afferent fibers and what do they do?

A
  1. Small Molecule (Glutamate)
    - action confined to postsynaptic neurons in the immediate vicinity
    - mediates rapid synaptic transmission
  2. Neuropeptide (Substance P)
    - Enhances and prolongs the action of glutamate. Levels are increased in persistent pain conditions
    - Action spreads to postsynaptic neurons at considerable distances
    - Mediates slow synaptic transmission
52
Q

What are the consequences of 2 neurotransmitters released together?

A

Contributes to the excitability of dorsal horn neurons and to the unlocalized character of many pain condition

53
Q

What is central sensitization?

A

Repeated activation by nociceptive primary afferent fibers leads to dorsal horn neurons (2nd order) becoming more sensitive.
-Lower threshold, and more responsive to nociceptive primary afferent fiber input.

54
Q

What does central sensitization result from and what is it a possible mechanism for?

A

A progressive increase in discharge rate and changes in gene expression of dorsal horn neurons.

-Possible mechanism for hyperalgesia, allodynia, and phantom limb pain

55
Q

What is allodynia?

A

The perceptfion of an innocuous stimulus as being painful. Ex. pt with a sunburn and your light touch comes off as extremely painful to them.

56
Q

What is phantom limb pain?

A

Persistent sensation of pain that appears to originate from the region of an amputated limb

57
Q

What is “Gate Control Theory”

A

Regions within the dorsal horn of the spinal cord receive input from nociceptive and nonnociceptive primary afferent fibers.

Nonnociceptive fibers can inhibit nociceptive fibers by activating inhibitory interneurons. Nociceptive fibers can inhibit the inhibitory interneurons activated by the nonnociceptive fibers.

Ex. When you hurt yourself, you shake or rub it, stimulating the nonnociceptive fibers.

58
Q

What closes the gate to the central transmission of noxious input?

A

Nonnociceptive fibers

59
Q

What opens the gate to the central transmission of noxious input?

A

Nociceptive fibers

60
Q

In what ways does pain modulation occur in the Brain?

A
  1. Descending Systems
  2. Stress
  3. Opioids
61
Q

Where do the descending systems originate?

A

Originate in the Primary Somatosensory Cortex, Amygdaloid, Hypothalamus, Midbrain, Pons, and Medulla.

62
Q

What do the descending systems do in terms of pain?

A

Inhibit the activity of nociceptive projection neurons in the dorsal horn of the spinal cord.

63
Q

What is the descending system a mechanism for?

A
  1. Pain being dependent on context

2. Placebo effect

64
Q

How does stress act as a pain modulator?

A

Normal reactions to pain may be suppressed during stress

-Results from opioid and non-opioid mechanisms of analgesia

Neuro (31 decks)

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