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Neuroscience > Exam Two - DCML > Flashcards

Exam Two - DCML Flashcards

1
Q

DCML

A

dorsal column medial lemniscus

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2
Q

What is the overall purpose of the DCML system?

A

discriminative touch and conscious proprioception

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3
Q

What are the 5 general structural components of the somatosensory system?

A
  • in the PNS
    1 - peripheral receptory
    2 - primary afferent fibers and their ganglia
  • in the CNS
    3 - a decussation
    4 - a thalamic relay nucleus
    5 - a cortical projection target
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4
Q

What are the key steps in sensory transduction?

A
  • sensory receptor (adequate specific stimulus)
  • membrane conductance changes
  • generator potentials
  • action potentials
  • primary afferent signals
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5
Q

4 ways to code sensory information?

A

modality
intensity
duration
location

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6
Q

receptive field

A

the space where the receptor is located and transduce the stimuli
small receptive fields increase the likelihood of discrimination

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7
Q

GSA

A

general somatic afferents
receptors are mainly located in body/soma wall (skin, muscle, joints, periosteum, and associated structures)

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8
Q

GVA

A

general visceral afferent
located within or near visceral organs

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9
Q

SSA

A

special somatic afferents
vision and hearing

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10
Q

SVA

A

special visceral afferents
smell and taste

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11
Q

What are the 3 classifications of somatosensory receptors?

A

mechanoreceptors
thermoreceptors
nociceptors

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12
Q

proprioception

A
  • awareness of the body position and movement
  • dynamic 3D mental construct of the body generated by integrative activity occurring the the parietal lobe
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13
Q

What 3 systems provide integrate to form proprioception

A
  • vestibular
  • visual
  • somatosensory
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14
Q

What are the 4 main somatosensory proprioceptors

A
  • cutaneous mechanoreceptors
  • muscle spindles
  • golgi tendon length
  • mechanoreceptors in joints
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15
Q

What are the 4 main functions of peripheral receptors functions?

A

1 - general arousing and alerting (consciousness)
2 - conscious discrimination of environmental events by acting on neurons of the cerebral cortex via ascending systems
3 - to elicit reflexes
4 - enabling coordinated movements by acting on neurons belonging to the motor control system

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16
Q

What systems are included in GSA conscious classification?

A

-DCML
-ALS
- cranial nerves 5, 7, 9, 10

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17
Q

What systems are included in GSA unconscious classification

A
  • spinal cord and brains tem reflex connections
  • dorsal spinocerebellar tract
  • ventral spinocerebellar tract
  • cuneocerebellar tract
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18
Q

How many neurons are involved in the DCML pathway?

A

3 projection neurons, 1st, 2nd, 3rd order neruons

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19
Q

Where is the 1st order neurons’s soma for DCML?

A

DRG

20
Q

How does the 1st order neuron for DCML enter the CNS?

A

via the dorsal root without synapsing!

21
Q

Do first order or second order neurons cross in the DCML system?

A

second order, 1st order neurons project ipsilaterally to the second order neurons

22
Q

Where are the second order neurons located in the DCML system?

A

nucleus gracilis(Lower Extremity) and nucleus cuneatus(Upper Extremity) in the medulla

23
Q

Where do second order neurons terminate in the DCML system?

A

2nd order neurons cross the midline (forming the medial lemniscus) and ascend to the thalamus to terminate of 3rd order neurons

24
Q

How do 3rd order neurons of the DCML project to the cerebral cortex?

A

the posterior limb of the internal capsule

25
Q

Where specifically do 3rd order neurons of the DCML terminate in on the cerebral cortex?

A

the primary somatosensory cortex (areas 3, 1,2) of the post-central gyrus

26
Q

What specific part of the thalamus do 2nd order neurons synapse with?

A

VPL

27
Q

What is the orientation of the ML at the medulla

A

A
T
L

28
Q

What is the orientation of the ML at the middle to rostral pontine level?

A

L T A

29
Q

What is the somatotopic organization of the thalamus?

A

foot = lateral
hand = medial

30
Q

What is the somatotopic organization of the priamry somatosensory cortex (SI)

A

foot = medial
hand (and face) = lateral

31
Q

site 3 of SI receives:

A

most thalamic input, site of initial processing

32
Q

site 3b receives?

A

touch (cutaneous, SA)

33
Q

site 3a receives?

A

proprioception (deep, muscle)

34
Q

sites 1 and 2 of SI receive?

A

they are connected to 3b, sites of complex processing
1 = cutaneous RA
2 = deep, joint

35
Q

sensory homunculus

A
  • not body proportional
  • not a “single” map
  • FOOT MEDIAL AND FACE LATERAL
36
Q

Role of SII?

A
  • performs higher order functions
  • association area for sensory input
  • ROLE IN EPISODIC MEMORY, VISUOSPATIAL PROCESSING, CONSCIOUSNESS AND HIGH ORDER FUNCTIONS, SUCH AS SELF-REFLECTION
  • connected to the limbic system
37
Q

Where is SII located?

A

parietal operculum

38
Q

What is the parietal operculum?

A

the part of the parietal lobe that overlies the caudal portion of the insula in primates. It is defined by dissection

39
Q

Purpose of brodmann areas 5 and 7?

A
  • association cortex for somesthesis
  • INTERPRET MEANING OF INPUT
40
Q

somesthesis

A

body sensibility including the cutaneous and kinesthetic senses

41
Q

What can damage of brodmann areas 5 and 7 produce?

A

hemi-neglet syndrome (amorphosynthesis) - the patient is unaware of somatic sensations from one side of the body

42
Q

functional properties of the DCML

A
  • receives input via large diameter myelinated axons
  • highly topographic at all levels
  • RF size small
  • submodality purity at all levels
  • secure relays (a single AP can prudce a perception)
43
Q

describe organization of DCML at the SC, thalamus, and SI cortex

A

SC: food medial, hand lat
thalamus: foot lateral, hand/face medial
SI cortex: foot medial, hand/face lateral

44
Q

lesions at the DCML

A
  • increase in the two point threshold
  • decrease in vibratory sensitivity
  • decrease in position sense and kinesthesia
  • agraphesthesia
  • astereognosis
  • increase in spontaneous pain
45
Q

kinesthesia

A

awareness of movement of the parts of the body

46
Q

agraphesthesia

A

impaired ability to recognize letters or numbers drawn by an examiners fingertip on the patients skin (with patients eyes closed)

47
Q

astereognosis

A

inability to identify a common object by active touch without other sensory input such as visual information

Neuroscience (25 decks)

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