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Neuroscience > Tactile Mechanoreceptors > Flashcards

Tactile Mechanoreceptors Flashcards

1
Q

Tactile Mechanoreceptors

A

Non-encapsulated

  • Free nerve endings (pain and temp)
  • Merkle cells (fine touch)
  • hair receptors

Encapsulated

  • Meisner (touch)
  • Pacinian (vibration)
  • Ruffini (stretch)
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2
Q

Proprioception Mechanoreceptors

A

Detect

Muscle stretch
Joint position
Muscle tension

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3
Q

Major Somatosensory Pathways

A

DC-ML and Trigeminal
-Fine tactile and proprioceptive

ALS and Spinal Trigeminal
-Pain, Temp, Crude touch

Dorsal Spinocerebellar and Cuneocerebellar
-Unconscious proprioceptive

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4
Q

Anterolateral System (ALS)

A

Pain, Temp, Crude Touch

also called SPINOTHALAMIC TRACT

unencapsulated nerves
-nocioreceptors, mechanoreceptor, thermo

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5
Q

Thermo receptors

A

Heat 29-45

Cold 5-40

Ion TRP channels

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6
Q

Nociceptors

A

Mechanical, thermal, chemical stimuli

Adelta = fast sharp pain

C = slow dull/burning pain

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7
Q

Sensitization of Pain

A

DEC threshold for Nociceptor

Occurs in damaged tissue:
Prostaglandins, bradykinin, etc

ALLODYNIA: normal stimuli perceived as painful

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8
Q

First order ALS

A

Axon start at receptor

Cell bodies in Dorsals Root Ganglion

Enter spinal chord and branch

Collateral branches go up and down DORSOLATERAL TRACT OF LISSAUER

Synapse with 2nd Order in dorsal column

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9
Q

Second Order ALS

A

Receive info from 1st order in dorsal horn

axons DECUSSATE in the ANTERIOR/VENTRAL WHITE COMMISSURE

Go to anterolateral portion of white matter (on contralateral side)

Join SPINOTHALAMIC TRACT all way up

Higher parts of body add to medial side (lower parts are lateral)

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10
Q

ALS in brainstem

A

Caudal medulla = anterolateral

Rostral Medulla = Lateral

Pons= lateral tegmentum (lateral dorsal pons)

Midbrain = lateral again

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11
Q

Third Order ALS

A

2nd order go to VPL nucleus of thalamus

3rd order branch off to different parts of brain

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12
Q

Sensory Homunculus

A

Third order sensory fibers from thalamus mainly go to PRIMARY SOMATOSENSORY CORTEX

Located in post central gyrus

Amount of cortex allotted depends on density of receptors, not size of region

Organized by location (starting medial)
Genitals
Legs
Hip
Trunk
Neck 
Arm 
Elbow hand
Fingers 
Thumb
Eye
Nose
Face
Luis
Teeth
Tongue
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13
Q

Pain modulation

A
  1. feed forward from receptor

2. Descending pathway from CNS

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14
Q

Descending Pain Modulation

A
  • CNS and Periaqueductal gray matter in midbrain
  • activated by opiates
  • goes to substantia gelatinous a
  • release serotonin, norepi, and opiates
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15
Q

Gate Control Theory

A

Mechanosensory fibers act as gate to modulate pain

Uses inhibitory neurons located in dorsal column

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16
Q

Spinothalamic Tract Lesions

A

Contralateral loss of pain starting a few segments below lesion

Pain eventually comes back through alternate pathways

17
Q

Fine Touch, Vibration, Pressure, Proprioception

A

Go through DC-ML system

Fast, myelinated fibers

18
Q

First Order DC-ML

A

Cell bodies in dorsal root

Some collaterals axons synapse in dorsal horn

Most axons go straight up DORSAL COLUMN to brain stem

As go up body, axons add laterally to dorsal column (legs most medial)

19
Q

Somatotopy

A

Point for point correspondence of an area of the body to a specific point in CNS

ALS: lower more medial

DC at T6

  • Fasiculus GRACILIS = Lower body = medial
  • Fasiculus CUNEATUS = Upper body = lateral
20
Q

DC Junction

A

Caudal Medulla

First order fibers synapse in DORSAL COLUMN NUCLEI

  1. nucleus GRACILIS
  2. Nucleus CUNEATUS
21
Q

Second Order DC-ML

A

Begin at DC Nuclei in caudal medulla

Make up INTERNAL ARCUATE FIBERS
-decussate

Become MEDIAL LEMNISCUS

  • on cotralateral side
  • immediately dorsal to pyramids

Go up to VPL of thalamus

22
Q

Third order DC-ML

A

Second order synapse in VPL of thalamus

Go through internal capsule

End at primary sensory cortex in
post central gyrus

23
Q

DC-ML Lesions

A

Deficits of fine, discriminative touch

Can’t identify objects by hand

Loss of position sense

Clumsy movement

ROMBERG SIGN
-unsteadiness when eyes closed

24
Q

Trigeminal Nerve Fibers

A

Cell bodies in Trigeminal Ganglion (Semilunar)
-lateral wall of cavernous sinus

Proprioceptive (primary) nerve fibers in BRAIN STEM

  • woooaahhhh
  • mesencephalic nucleus of Trigeminal

CN V enters brainstem through middle cerebellar peduncle in mid pons

25
Q

Trigeminal Nuclei

A

Mid pons

  1. Principal Nucleus -
  2. Spinal Nucleus
26
Q

Principal Nucleus

A
  1. Fine Sensory nucleus immediately dorsal to nerve entry
    - most SECOND ORDER neurons decussate and go up anterior/ventral trigeminothalamic tract
    - a few go up ipsilateral posterior/dorsal trigem tract
  2. Motor nucleus immediately medial to nerve entry

ALL GO TO VPM IN THALAMUS

27
Q

Third order Trigem

A

Start in VPM

Go to face area of primary somatosensory cortex

post central gyrus

28
Q

Spinal Tract of V

A

Small diameter fibers

Pain and temperature

Go caudal immediately after nerve entry to upper cervical spinal cord

IPSILATERAL

Terminate in SPINAL NUCLEUS of trigem

29
Q

Trigeminothalamic Tract

A

Secondary nerve fibers from BOTH the principal nucleus and spinal nucleus of trigem

DECUSSATE

Go up next to medial lemnicus to VPM

30
Q

Unconscious Proprioception

A

Muscle stretch and tension

Goes to cerebellum (Spinocerebellum)

Pathways are IPSILATERAL

31
Q

Dorsal Spinocerebellar Pathway

A

First Order nerve fibers from muscles, joints, etc

terminate in nucleus dorsalis/Clarks nucleus in spinal cord

Second Order nerve fiber rise IPSILATERALLY in dorsal part of lateral funiculus

Go through inferior cerebellum

32
Q

Cuneocerebellar Tract

A

Upper limb equivalent

First Order from receptors go up spinal cord with Fasiculus Cuneatus to the EXTERNAL CUNEATE NUCLEUS

Second Order fibers begin at ECN and go through inferior cerebellar peduncle

Neuroscience (10 decks)

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