Neuro Somatosensory Discriminative Touch

Front 1

what does the PCMLS sense

Back 1

fine touch
vibration (pancinian)
conscious proprioception

Front 2

when she refers to discriminative toush what is she referring to?

Back 2

the info in PCMLS

fine touch, conscious proprioception, vibration

Front 3

how many neurons are in teh PCMLS path

Back 3

3

1: peripheral process with receptor, cell body in PRG, central process forms cunneate/gracilis fasciculus, synapse in caudal medulla

2. Cell body in caudal medulla, decusate to form contralateral medial lemniscus, synapse in thalamus VPL,

3. cell body in VPL, axon in post limb of int capsule, synapse in primary cortex

Front 4

for the 1 neuron in the PCMLS system...

peripheral process
cell body
central process
synapse

Back 4

receptor
PRG
cunneate/gracilis fasciculis
caudal medulla

Front 5

where do fibers in PCMLS decusate

Back 5

from gracilis/cunneate fasciculas, they synapse in caudal medulla. at caudal medulla they cross and form Medial lemniscus on contralateral side

Front 6

what is the path of the PCMLS, start at receptor and end at cortex

Back 6

PRIMARY NEURON
1. receptor in periphery
2. Cell body in PRG
3. Central process travels up the SC in the gracilis/cuneate fasciculus in the caudal medulla in synapses with 2 neuron in cuneate/gracile nucleus

SECONDARY NEURON
1. Synapse occurs in cuneate/gracile nucleus of caudal medulla (ie 2 neuron cell bodies are in the cuneate/gracile nucleus)
2. Axons DECUSATE and enter the medial Lemniscus
3. axons travel to the VPL of Thalamus

THIRD ORDER NEURON
1. The cell bodies of hte 3 neuron are in the VPL of the thalamus, synapse occurs here
2. axons travel in post limb of internal capsule and then enter layer 4 of primary cortex

Front 7

what are the types of receptors associated with the PCMLS

Back 7

think fx: discriminitive touch, vibration, conscious proprioception

Encapsulated: meisner, pancinian, hair
NonEncapsulated: hair, ruffini, merkel

1. LOW THRESHOLD MECHANORECEPTORS: encapsulated, non encaprulated, slow and fast adapting.

2. Proprioceptors: MM spindle and GTP

Front 8

what is carried in the Med Lemniscus

Back 8

CONTRALTERAL fibers with fine touch, vibration, and conscious proprioception

**decusation occurs in the medulla when fibers cross from PC to MLS

Front 9

classify the central fibers of the 1 neuron in the PCMLS. do any other tracts have this same fiber type in their prinary central neurons

Back 9

Large diameter
Fast conduction
RAPID conduction

**Aa Ia Ib; Ab (II)

SAME AS:
spinocerebellar (also proprioception but NON conscious)
TG

Front 10

we know that the 1 neuron in PCMLS has its cell body in the PRG, where do the fibers actually enter the SC

Back 10

post root entry zone, medial division

Front 11

what info enters at post root entry zone, medial? lateral?

Back 11

MEDIAL: central processes from the 1 neuron in the PCMLS

LATERAL: ???????????

Front 12

are the mechanoreceptors in the PCMLS low thresh or high thresh

Back 12

LOW, not a huge stim is required for activation

Front 13

large diameter, heavily myelinated fast conducting nerve fibers are associated with which tracts

Back 13

1. PCLMS
2. TG
3. Spinocerebellar

Front 14

what happens once the central process of 1 neurons of the PCMLS enter the SC at the medial post root entry zone

Back 14

1. ascend in post funiculus

2. synapse in post horn for spinal reflexes

Front 15

at the level of L4 are both the gracilis and cuneatues present

Back 15

Gracilis: LE
Cuneatus: UE

**JUST gracilis at L4

Front 16

the gracilis carries info from where? cuneatus? how does the location add to this story

Back 16

Gracilis: LE, T6 and lower
Cuneattus: UE, T6 and higher

**as we ascend things add laterally, so gracilis (LE) is medial and as we get info from UE (cuneatus) it is added laterally

Front 17

the post column refers to what

Back 17

the 2 distinct fiber bundles in post funiculus
1. Gracile: LE, T6 and below
2. Cuneate: UE, T6 and above

**medial is the LE and as we ascend info is added laterally

Front 18

fibers from what structures are represented medially in the post funiculus (post column). does this organization change as we ascend and the info is carried on the contralateral MLS?

Back 18

medial: LE
lateral: UE

MLS:
Ant: LE
Post: UE

Front 19

the post column is supplied by what a, what about MLS

Back 19

PC: post spinal A
MLS: Ant spinal A

Front 20

where is info from the LE carries as we ascend the PCMLS

Back 20

first in medial area of post funiculus- Gracile

Decusation into the anterior part of MLS (CONTRALATERAL MLS)

then takes a more lateral position in the upper pons/midbrain/thalamus (VPL)

synapse in superior part of postcentral gyrus

Front 21

where is info from the UE carried as we ascend the

Back 21

UE is added laterally at T6 and above. Lateral position in cuneatus

Decusation, Fibers are carried in the POSTERIOR position of the contralateral MLS

In the upper pons/midbrain it is more medial (weird to cross)

in the thalamus its medial (in VPL)

enters the primary cortex in a more inferior location on the post central gyrus

Front 22

at what part in the PCMLS is info being carried ipsilaterally

Back 22

in SC

crossing does not occur until the caudal medulla, fibers go from cunneate (lateral) to contralateral MLC (post). Gracile (medial) fibers go to the contralateral anterior position of MLS

Front 23

does synapse of the 1 neuron in the PCMLS occur ipsilateral or contralateral

Back 23

ipsilateral,

**its usually the 2 neuron that crosses so the synapse MUST be ipsilateral

Front 24

the fibers of the PCMLS that decusate are called what?`

Back 24

internal arcruate

**from PC to MLS in caudal medulla, after synapse in the gracile and cunneate nuclei

**SENSORY DECUSATION

**info from one side of the body entering the brainstem on opposite side

Front 25

what is a good way to remeber where LE and UE info is in the MLS

Back 25

pretend like the little man is the MLS, the bottom is the LE and the top is the UE (**BV is Ant spinal A)

**then as we get into the pons/midbrain the man does the splits adn the legs are lateral

Front 26

what structure has a major shape change as we go from medulla to pons and up to midbrain

Back 26

the MLS

Caudal Medulla: MLS is vertical, LE is bottom UE is TOP

PONS/MIDBRAIN: LE is lateral, UE is medial

**total switch from where the info was in the SC

Front 27

in the PCMLS where does the R thalamus go to

Back 27

R cortex, info from L body is carried here

Front 28

what is the blood supply for info from PCMLS in the thalamus

Back 28

talamogeniculate a

**recall medial is UE and lateral is LE

Front 29

where do axons from 3 neuron in the PCMLS system travel

Back 29

post limb of internal capsule

Front 30

the post central gyrus what info is there

Back 30

info from PCMLS (fine touch, vibration, conscious proprioception)

superior and post paracentral lobule: LE

Inferior: UE

Front 31

what vessel supplies LE info in cortex, UE

Back 31

LE info is medial and superior: ACA

UE is lateral adn inferior: MCA

Front 32

what fissures are the MCA and ACA in the cortex

Back 32

MCA: longitidinal fissure, supplies medial hemisphere

ACA: lateral fissure

Front 33

what are 4 terms to describe the primary somatosensory cortex

Back 33

1. S1
2. Broadman areas 123
3. postcentral gyrus
4. posterior paracentral gyrus

Front 34

what are the broadman areas of the primary somatosensory cortex

Back 34

3: 3a and 3b
2
1

**post central gyrus

Front 35

when looking at a medial slice of the brain hemisphere, where is primary somatosensory cortex

Back 35

posterior paracentral gryus

Front 36

what is the organization within the primary somatosensory cortex

Back 36

3a/2: proprioception (outer limits)

3b/1: cutaneous mechanoreceptors (inner)

Front 37

where in the cortex does proprioception end up? cutaneous mechanoreceptors

Back 37

outer layers, 3a and 2
inner layers, 3b and 1

**layer 4 of cortex just like ALL sensory input :)

Front 38

what does heterogranular mean

Back 38

sensory, large layer 4 of cortex

*input

Front 39

what structures in the somatosesnsory cortex are analogous to occular dominance columsn

Back 39

tall vertical columns in layer 4 of cortex

**cells in a single column have a simliar receptive field, Slow and rapid adapting from same area of skin

Front 40

an electrode placed perpendicular to the somatosensory cotrex would be sampling what

Back 40

all neurons responsive to same type of stimulus

**vertical column, same receptive field, different type of stimulus

Front 41

we know that the superior postcental gryus has LE and the inferior has UE, how is the distribution from a medial to lateral view

Back 41

UE lateral
LE Medial

Front 42

where does info from S1 go for further processing,

Back 42

post into broadman areas 5 7 called parietal accosiation area

Front 43

what are 2 areas of secondary cortical processing areas for somatosensory info

Back 43

1. Broadmen 5,7. parietal assoc cortex

2. secondary somatosensory cortex (SII)

Front 44

what has happened if you cant identify objects by touch

Back 44

damage in secondary/association areas (parietal association-broadman 5,7 or SII)

**astereognosis

Front 45

what is astereognosis

Back 45

cant ID objects by touch, leision in association cortex (S2 or broadman 5,7)

Front 46

in the primary cortex the MCA is where, what does it supply

Back 46

UE, supplies lateral hemisphere

Front 47

ACA supplies what part of cortex, what info ehre

Back 47

medial hemisphere,
LE