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Neuromuscular PT 1 > The Somatosensory system and Sensory Tracts > Flashcards

The Somatosensory system and Sensory Tracts Flashcards

1
Q

Sensory Systems

A
  • Somatosensory: skin and muscles
  • Special: bipolar neurons (smell, hearing, equililbium, taste
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2
Q

Peripheral somatosensory neurons

describe the types of receptors

A
  • Location
  • specialized:
  • mechanoreceptors: mechanical deformation like pressure or vibration
  • chemoreceptors: chnages in chemicals
  • Thermoreceptors: heat/cold
  • Nociceptors: subset of all
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3
Q

Use of somatosensation

does all sensory information reach conscious awareness?

A
  • some give conscious awareness of sensory information
  • most: automatic adjustments (so you dont sense EVERY stimulus)
    ~ selectively prevented from reaching consciousness - inhibitory connections prevent these from reaching awareness
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4
Q

Describe a sensory neuron

A
  • pseudounipolar
  • peripheral axon
  • central axon
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5
Q

Describe the dorsal root and dorsal root ganglion

A

Dorsal root:

  • carries sensory information into SC
  • afferent axons

Dorsal root ganglion

  • contains cell bodies of somatosensory neurons
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6
Q

Describe how most sensory information is conveyed from body receptor to CNS

A
  • Pseudounipolar neuron has soma in DRG
  • distal axon terminates in skin, muscle, etc
  • proximal axon conveys input into CNS
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6
Q

Process of Action potentials in somatosensory system

A

receptors:

  • if receptor potential >threshold = AP
  • AP travels along distal axon to DRG
  • AP travles along proximal axon to spinal cord
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7
Q

Describe

distal axons

Of sensory system

A
  • classified according to axon diameter
  • larger diameter = faster transmission
  • 1a = stretch reflex/muscle spindle
  • 1B = w/i GTO and ligament receptors
  • II/Ab = muscle spindles, pacinian, and ruffini receptors
  • A delta = fast pain/free nerve endings
  • C = free nerve endings and diffuse pain/ache
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8
Q

Cutaneous innervation

A
  • Receptive field = area of skin innervated by a single receptor
  • small receptor fields going distally = better 2 point descrimination
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9
Q

Types of cutaneous sensation

A
  • Discriminative touch/light: localization of touch and vibration and ability to disciminate between two closely spaced points touching the skin
  • crude touch: pleasant touch, pressure, tickle, ich - free nerve endings
  • pain = nociceptors
  • temperature: thermoreceptors
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10
Q

Light Touch receptor types: superficial

A

1 meissner’s Corpuscles

  • dermis
  • light touch
  • play a role in discriminitive touch and movement of objects over skin

2 Merkel’s Disc

  • Localization/2 point discrimination
  • below epidermis
  • sensitive to pressure
  • high density in finger tips
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11
Q

Light touch receptors

Subcutaneous

A

1 pacinian corpuscles:

  • located in subcutaneous layer of skin
  • deep tissues of body also
  • percieve deep touch and vibration

2 ruffini endings

  • deep layers of the dermis
  • perception of touch and pressure
  • play a role in joint position sense
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12
Q

Free nerve endings

A
  • Crude touch: undefined/diffuse (tickle/itch)
  • nociception
  • thermoreception
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13
Q

types of pathways carrying sensory info to the brain

A
  • Conscious relay
  • divergent
  • nonconscious relay
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14
Q

Conscious relay

The information that is carried on these pathyways all…

A
  • high fidelity: accurate/discrimintive
  • reaches the brain and conscious
  • info about the stimulus location and type is transmitted with high accuracy
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15
Q

Divergent pathway

general info about all these

A
  • conscious and nonconscious
  • information to numerous locations to the brain
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16
Q

nonconscious relay

A
  • cerebellum
  • autonomic adjustments to sensation
  • ex adjusting your body without thinking
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17
Q

What do conscious relay pathways carry

A
  • touch
  • proprioception
  • pain
  • temperature

carries by ALST or DCML

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18
Q

How do conscious relay pathways travel in the spinal cord

A
  • dosal columns
  • anterolateral tracts
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19
Q

What is a first order neuron

A
  • brings information from sensory receptors into spinal cord
  • pseudounipolar
20
Q

What is a second order neuron

A
  • conveys information between the spinal cord or brainstem to thalamus
21
Q

What is a third order neuron

A
  • conveys information from the thalamus to the cerebral cortex
22
Q

What does the DCML carry

A
  • light touch
  • discriminitve touch
  • proprioception
  • stereognosis: identify objects via touch
  • vibration
23
Q

DCML

1st order neuron

A
  • peripheral axon gets sensory information and carries to soma (DRG)
  • central axon enters SC => fasciculus gracillis (travels medially with leg information) and fasciculus cuneatus ( Travels laterally with arm information)
  • synpases with 2nd order neuron

travels in dosral columns

24
Q

DCML

2nd order neuron

A
  • cell bodies in medial nuleus gracillis (medial leg) and Nucleus cuneatus (lateral arm)
  • fibers cross in lower medulla (interal acuate fibers)
  • travels in VPL of thalamus to 3rd order neuron
25
Q

DCML

3rd order neuron

A
  • thalamus
  • to nerve endings in somatosensory cortex
26
Q

Fasciculus gracilis

A
  • medial in the dorsal column
  • carries infomation coming from the legs
  • in medulla becomes the nucleus gracilis
27
Q

Fasciculus cutneatus

A
  • info coming from the arm
  • runs more laterally in dorsal columns
28
Q

Nucleus gracilis and nucleus cuneatus

A
  • sensory neurons
  • relay information to thalamus on opposite side of brain
29
Q

Trigeminal Lemniscus

Discrimintive touch in the face

pathway

A
  • CN V: trigeminal
  • Cross in pons
  • First order neuron: trigeminal neuron
  • second order neuron: main sensory nucleus in pons
  • third order neuron: thalamus
30
Q

Somatotopic organization

A
  • homunculus
  • primary somatosensory cortex: receives somatotopically organized information
31
Q

Anterolateral tracts carries what type of information

A
  • pain (fast)
  • temperature
32
Q

ALST: first order neuron

A
  • starts in peripheral
  • cell body in DRG
33
Q

ALST: 2nd order neuron

A
  • starts in dorsal horn of spinal cord
  • crosses midline
  • travels in anterolateral column to thalamus
34
Q

ALST: 3rd order neuron

A
  • starts in thalamus (VPL)
  • terminates in primary somatosensory cortex
35
Q

Dorsolateral tract

A
  • axons carrying pain information enter dorsal horn of spinal cord
  • central axon branches
  • ascend, descend several segments before synpasing on 2nd order neurons (in dorsal horn)
  • fibers travel in dorsolateral tract
  • create a sensory redundacy

Part of ALST - reason why you will lose pain and temp a few levels below

36
Q

Pain: face-trigeminothalamic

1st order neuron

A
  • from the face
  • trigeminal ganglion (outside PONs)
  • then descends to medulla and upper cervical SC
37
Q

Pain: face-trigeminothalamic

2nd order neuron

A
  • spinal trigeminal nucleus (in lower medulla)
  • then crosses midline to ascend thalamus
38
Q

Pain: face-trigeminothalamic

3rd order neuron

A
  • thalamus (VPM)
  • terminates in primary somatosensory cortex
39
Q

Fast pain pathways

Face

A
  • spinothalamic tract
  • trigmeinal system
40
Q

Cross analgesia

A
  • when there is a lesion in the dorsal lateral medulla it results in a pain sensation loss in the opposite side of the body and the same side of the face
  • DCML is fine due to being medial to the lesion site
41
Q

Divergent pathways

Describe what they carry and how they carry the information

A
  • slow pain
  • three parallel ascending tracts
  • interneuron system
42
Q

three tracts of divergent pathways

A
  • spinomesencephalic
  • spinoreticular
  • spinolimbic
43
Q

Interneuron system of the divergent pathways

A
  • no 1st/2nd/3rd order neuron = 3 relay system
  • only spinolimbic pathway = perceive pains (goes to consious)
44
Q

Spinomesencephalic tract

A
  • DRG to interneuon to dorsal horn of SC
  • then cross midline
  • termines in midbrain (to superior colliculus nad periaqueductal gray matter -PAG)
  • look at painful stimulus
  • PAG involved in pain control
  • superior colliculus = makes you look at the pain
45
Q

Spinoreticular tract

A
  • DRG to interneuron to Dorsal horn of spinal cord
  • then cross midline
  • pain information travels to reticular formation on midbrain, pons and medulla
  • interacts with arousal, attention and sleep/wake cycles
  • conveys slow, aching pain
46
Q

reticular formation

A
  • nucle throughout the whole brainstem
  • regulate sleep and wake cycles
  • sleep wake cycles also interact with slow aching pain so you wake up
47
Q

Spinolimbic tract

Pathyway, type of stimuli carried

A
  • DRG to dorsal horn of the spinal cord, then crosses midline
  • slow pain information to thalamus
  • then sends info to amygdala, the insular cortex and the ventral striatum in basal ganglia
  • then sends info to the cortex
  • reaches consious awareness
48
Q

Trigeminoreticulolimbic pathway

A
  • slow pain info from face
  • path: trigeminal nerve to ascending projections in reticular formation to thalamus
  • terminates in cerebral cortex
  • projections to retincular formation and thalamus

Neuromuscular PT 1 (32 decks)

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