Spinothalamic, Posterior Column/Medial Leminicus, Thalamo-cortical Pathways (9)

Question 0

What things do protopathic systems detect? (3)

Answer 0

Pain, crude touch, temperature

Question 1

What is somethesis?

Answer 1

Faculty of bodily perception, including senses and proprioception

Question 2

What things do epicritic systems detect? (5)

Answer 2

Fine touch (including form and texture), pressure, slippage, vibration, proprioception

Question 3

Receptors that detect gross pressure and vibratory skin stimuli; found in subq skin joints, muscle and mesentery

Answer 3

Pacinian corpuscles - are the ones that have lamellae, fire APs when stimulus begins and again when it ends

Question 4

Rapidly adapting skin receptor that senses light touch and vibration, found right below skin in the epidermis in glabrous skin

Answer 4

Meissner’s corpuscles

Question 5

Slowly adapting mechanoreceptors found in fingertips and also in non-glabrous (hairy) skin

Answer 5

Merkel’s disks

Question 6

Mechanoreceptors found in deep skin that respond to sustained pressure and skin stretch; responsible for detecting objects slipping along the skin

Answer 6

Ruffini organs - also cont. position sense

Question 7

What two things do free nerve endings detect typically?

Answer 7

Temperature and nociceptive (pain) stimuli

Question 8

What is adaptation?

Answer 8

Reduced response in the face of a continued, constant stimulus

Question 9

What pathway is responsible for detecting pain, temperature, and crude touch?

Answer 9

Anterolateral pathway - Spinothalamic tract

Is a protopathic type tract; protopathic info travels in the anterolateral funiculi in the spinothalamic tract; spinothalamic has a “P” for protopathic

Question 10

What pathway is responsible for detecting fine discriminative touch, proprioception, and vibration?

Answer 10

Posterior columns/ Medial Leminiscus

(Tract is called Medial Leminiscus above the caudal medulla, after the posterior columns decussate); carries epicritic info - Leminiscus has an “E” for epicritic

Question 11

Which groups of neurons are from the muscle receptors (muscle spindle and Golgi tendon organs)? Where do they project?

Answer 11

A alpha - project to ventral horn and deep layers of dorsal horn

Muscle spindles are subtype 1a; *Golgi tendon organs are classifies as A beta 1b, according to text, but notes say this

Question 12

What group of neurons send afferent info from cutaneous and joint receptors and primarily project to dorsal horn?

Answer 12

A beta; subtypes 1b (joints) and II (skin receptors)

Question 15

Where is the cell body of the first afferent neuron in the posterior column/ medial Leminiscus pathway located?

Answer 15

Dorsal root ganglion

Question 16

Where does the first neuron in posterior column pathway synapse? (General name for the two potential places)

Answer 16

Synapse in the posterior column nuclei in the lower medulla (nucleus gracilis and nucleus cuneatus)

Question 17

Which part of the spinal cord do the first neurons in the posterior column pathway travel if from lower part of body? If from upper? At what spinal level does this change?

Answer 17

Fasciculus gracilis - lower body
Fasciculus cuneatus - upper body

• switch is made at the level of T6

Question 18

Which posterior column tract is the most medial in the spinal cord?

Answer 18

Fasciculus gracilis is most medial; cuneatus more lateral

this is the same arrangement for the same named posterior column nuclei in the lower medulla

Question 19

Where does the posterior column/leminiscal pathway decussate? What are the fibers called that actually cross the midline?

Answer 19

In the medulla; the second neurons leaving the posterior column nuclei then decussate - are called internal arcuate fibers

Question 20

What do the second order neurons of the posterior column pathway travel in after decussating?

Answer 20

In the Medial Leminiscus - is the same thing as the posterior columns, but they join to form this one common fasciculi above the level of the lower medulla (after decussating)
*medulla = metencephalon

Question 21

Where do the 2nd order neurons traveling in the medial leminiscus synapse?

Answer 21

In the ventral posterolateral nucleus (VPL) of the thalamus

Question 22

Where the third neurons in the posterior column/medial leminscus pathway synapse after leaving the thalamus (where they originate)?

Answer 22

In the primary somatosensory cortex, located in the postcentral gyrus

Question 23

How many times does the posterior column/ medial leminscal path decussate?

Answer 23

Just the one time in the caudal medulla after fibers synapse in the posterior column nuclei located there

Question 24

Via what structure do medial leminiscal fibers travel from the VPL to the primRy somatosensory cortex?

Answer 24

Posterior limb of the internal capsule

Question 25

In the rostral medulla, in what part of the medial leminscus are fibers from the lower body found?

Answer 25

Lower is anteriorly; upper body is posterior

Imagine a person standing upright on the ventral surface of the spinal cord if you are facing it

Question 26

In the caudal pons, where are the fibers located in the medial leminscus that transmit the info from the lower half of body?

Answer 26

Lower is now lateral and upper medial (medial leminscus rotates laterally)

Question 27

Where do touch and pressure afferents send collaterals to in the spinal cord?

Answer 27

Primarily to dorsal horn * both touch/pressure (A beta) and propriceptive (A alpha) also send axons up ipsilateral spinal cord as part of the posterior columns of course

Question 28

What type of fibers detect non discriminative touch? (i.e. Intense mechanical stimulation that does not result in tissue damage)

Answer 28

A delta fibers | Transmit fast, localized pain info; C fibers are more slow and transmit more generalized pain

Question 29

What fibers detect chemical damage, itch, and temperature change?

Answer 29

C fibers (are unmyelinated) * A delta and C fibers part of the anterolateral/spinothalamic pathway - are attached to free nerve endings in the periphery

Question 30

Where is the cell body located for the first order neurons in the anterolateral/spinothalamic pathway? Where do these neurons first synapse?

Answer 30

Dorsal root ganglia | Neurons (protopathic) first synapse in the dorsal horn of the spinal cord (I - V)

Question 31

Where does the anterolateral/spinothalamic pathway decussate?

Answer 31

In the same level of spinal cord the 1st order neurons enter and synapse in - axons of 2nd order neurons cross via the anterior white commisure to the contralteral anterolateral funiculus (fascicle)

Question 32

Where do the 2nd order neurons in the anterolateral/spinothalamic pathway go after decussating?

Answer 32

Ascend to the thalamus via the spinothalamic pathway (also called anterolateral funiculus)

Question 33

Where do the 2nd order neurons in the anterolateral/ spinothalamic tract synapse on the 3rd order?

Answer 33

In the ventral posterolateral nucleus (VPL) of the thalamus | - (same as the medial leminiscal tract)

Question 34

After leaving the VPL, where does the 3rd order neuron in the anterolateral / spinothalamic go to synapse? Via what structure does it get there?

Answer 34

To the primary somatosensory cortex (postcentral gyrus) - gets there via the posterior limb of the internal capsule

Question 35

In the midbrain through the cortex, where are fibers transmitting info from lower body found?

Answer 35

Lower body becomes more posterior or dorsal (still partially lateral) (Guy standing on the pyramids in lower brainstem now flipped to his head)

Question 36

Why does it take 2-3 spinal levels for all protopathic axons to synapse in the dorsal horn in the Anterolateral/ spinothalamic tract?

Answer 36

Some axons travel in Lissauer's tract ( posterolateral funiculus), which is composed of protopathic fibers that travel up or down 2-3 spinal levels before synapsing in the dorsal horn

Question 37

What are the 2 other divisions of the anterolateral pathway (spinothalamic being the main of the three)?

Answer 37

1. Spinothalamic 2. Spinoreticular 3. Spinomesencephalic

Question 38

What is the overall function of the spinothalamic tract specifically? (As a division of the anterolateral, which is overall protopathic transmission)

Answer 38

Discriminative aspects of pain - where the pain is and what kind *sharp object in right foot

Question 39

What are the intralaminar nucleus and dorsomedial nucleus, collaterals of the spinothalamic pathway, important for? Where does each nucleus project to ultimately?

Answer 39

Cortical arousal (of pain) - Intralaminar thalamic - project diffusely to the cortex - Dorsomedial nucleus - to prefrontal cortex

Question 40

What is the specific function of the spinoreticular pathway?

Answer 40

Tells you the stimulus actually hurts - important for the general arousal and emotional aspects of pain (are synapses to the reticular formation in pons and medulla; come from neurons in all layers of the dorsal horn)

Question 41

What is the specific function of the spinomesencephalic pathway?

Answer 41

Activates descending, efferent pathways that modulate pain (actions to help alleviate the pain) (Are synapses to the mesencephalon, specifically the periaqueductal gray matter* - are from layers I and V of the dorsal horn)

Question 42

As fibers are added to the anterolateral/spinothalamic tract on its way rostrally to the brain, how are axons from more cervical (superior) axons added to the tract?

Answer 42

Axons from cervical dorsal horn are added MEDIALLY * contrast with the epicritic (medial leminiscal) pathway in which cervical a are added laterally to the lower

Question 43

Which type of afferents specifically send out collaterals from the main anterolateral/spinothalamic path to the spinoreticular and spinomesencephalic tracts?

Answer 43

Fibers that project pain (some fibers conduct pain only, others are pain and temperature as well; these "mixed" fibers don't send out collaterals to the reticular formation of periaqueductal gray)

Question 44

Which types of fibers mediate "first pain"? Where do they synapse in the dorsal horn?

Answer 44

A delta fibers - synapse in substantia gelatinosa (rexed's laminae I and II) These fibers in I and II project to laminae V, which contains the cells that actually send axons across the midline and up the cord.

Question 45

What is the functional importance of the substantia gelatinosa?

Answer 45

Is the initial site of pain (and temp) modulation and integration. (A delta and C fibers both first synapse in the substantia gelatinosa)

Question 46

What kind of pain do C fibers transmit?

Answer 46

"Second" pain - poorly localized, dull pain (Axons with cells located in layer I of the dorsal horn, the marginal zone, cross the midline and ascend up the spinal cord; contrast with those form A delta fibers, which come from layer V)

Question 47

Collaterals from where into layer V of the spinal cord is important in the phenomenon of referred pain?

Answer 47

From epicritic system; project on to the same cells in layer V that protopathicsystem is going to

Question 48

Name for the axons connecting the substantia gelatinosa of different spinal cord layers

Answer 48

Propriospinal tract (has nothing to do with propriception)

Question 49

In the cortex and thalamus the fibers relaying info on the legs is ______ and ______ within the anterolateral pathway?

Answer 49

Superior and medial * correspondingly, arm and head are represented inferior and lateral

Question 50

What is the function of the spinocerebellar tracts?

Answer 50

Relay information about limb position and movement to the cerebellum

Question 51

Which spinocerebellar tract is primarily responsible for conveying information from the lower limb and body to the cerebellum

Answer 51

Dorsal (posterior) spinocerebellar tract *info is from muscle spindles (Ia, II) and Golgi tendon organs (Ib)

Question 52

Which spinocerebellar tract conveys information from the upper limbs and body to the cerebellum?

Answer 52

Cuneocerebellar tract | Cuneatus is the name for the posterior column directing sensory info from the upper, so cuneo= upper

Question 53

What spinocerebellar tract integrates descending input with proprioceptive info from the lower limbs?

Answer 53

Ventral spinocerebellar tract Info primarily from Golgi tendon organs (Ib)

Question 54

What spinocerebellar tract integrates descending info with proprioceptive input from the upper limbs/body?

Answer 54

Rostral spinocerebellar tract Like the ventral (anterior) tract, but for upper limbs; also gets info primarily from Golgi tendon organs (Ib)

Question 55

Where do 1st order neurons in the dorsal spinocerebellar tract synapse? Via what structure in the spinal cord do they get there?

Answer 55

Clarke's nucleus; arrive there via the fascilulus gracilis

Question 56

Where is Clarke's nucleus (or Clarke's column) located?

Answer 56

In the interomedial gray matter of the spinal cord between T2-L2 *these fibers involved in unconscious proprioception

Question 57

What structure do 2nd order neurons in the dorsal spinocerebellar tract pass through to reach the cerebellum after leaving Clarke's nucleus/column?

Answer 57

``` Inferior cerebellar peduncle - travel up to the brain via the Lateral funiculus (via restiform body) ```

Question 58

Where does the dorsal spinocerebellar tract decussate?

Answer 58

It doesn't - remains ipsilateral the whole way from where fibers enter until reaching the cerebellum

Question 59

Where in the cerebellum do 2nd order neurons from the dorsal spinocerebellar tract travel to?

Answer 59

Mainly to the anterior lobe and vermis

Question 60

Where do 1st order neurons in the cuneocerebellar tract synapse first? Via what structure do they get there?

Answer 60

Accessory cuneate nucleus - get there via the fascilulus cuneatus

Question 61

Where is the accessory cuneate nucleus located?

Answer 61

In the rostral medulla

Question 62

What structure do 2nd order neurons in the cuneo cerebellar tract travel through to get to the cerebellum? Where in the cerebellum do they go to?

Answer 62

Via the inferior cerebellar peduncle - to anterior lobe, vermis, and intermediate zone

Question 63

Where does the cuneocerebellar tract decussate?

Answer 63

It doesn't - like the dorsal spinocerebellar, remains ipsilateral to origin all the way to cerebellum

Question 64

In what layer (lamella) of the spinal cord do 1st order neurons in both the ventral (upper) and rostral (lower) spinocerebellar tracts synapse?

Answer 64

Layer VII (intermediate zone)

Question 65

What vertebral level is the division between whether afferent fibers will travel in the ventral (lower) or rostral (upper) spinicerebellar tracts?

Answer 65

L3 Ventral = L3-S3 Rostral = above L3

Question 66

After synapsing in the dorsal horn, what happens to fibers traveling in the ventral spinocerebellar tract? (What structure do they reach the cerebellum through, are there any decussations)

Answer 66

Project over to the contralateral lateral funiculus and then travel up to synapse with neurons in the superior cerebellar peduncle

Question 67

After synapsing in the superior cerebellar peduncle, what happens to most neurons in the ventral spinicerebellar tract?

Answer 67

Most decussate again to reach the side of cerebellum ipsilateral to the original entry into spinal cord * these cross over TWICE

Question 68

After synapsing in the dorsal horn of spinal cord, via what structure do the fibers of the rostral spinocerebellar tract reach the cerebellum? Where do they decussate?

Answer 68

Via the inferior cerebellar peduncle to ipsilateral cerebellum - does NOT decussate * so the ventral spinocerebellar tract is the only to go through the superior cerebellar peduncle, all 3 others go through inferior cerebellar peduncle

Question 69

Which if the four spinocerebellar tracts serves as the primary input to the cerebellum from spinal cord propriceptive afferents?

Answer 69

Dorsal spinocerebellar tract - via Clarke's nucleus

Question 70

Which system is responsible for relaying somesthesis for the head and face?

Answer 70

Trigeminal system

Question 71

What nucleus do the cell bodies of 2nd order neurons for the epicritic (fine touch, vibration, proprioception) system for head and face reside?

Answer 71

Chief sensory nucleus of V (analogous to the posterior column/medial leminiscus pathway nuclei - gracile and cuneatus nuclei) *chief has an "E" for epicritic - mnemonic aid

Question 72

Which nucleus in the trigeminal system contains cell bodies of 2nd order neurons transmitting protopathic (temp, nociceptive) information for head/face?

Answer 72

Spinal nucleus of V (analogous to the nuclei in the dorsal horns where the 1st order neurons of the anterolateral/spinothalamic synapse = the substantia gelatinosa) *Spinal has a "P" for protopathic - mnemonic

Question 73

What nucleus are cell bodies for 1st order afferents for muscle spindles and Golgi tendon organs from head/face found in the trigeminal system?

Answer 73

Mesencephalic nucleus of V (analogous to a displaced DRG, found in brainstem; maybe roughly equivalent to the spinocerebellar tracts in rest of body)

Question 74

Where do the cell bodies for 1st order neurons transmitting somatosensory info for head/face reside?

Answer 74

In the Trigeminal (Gasserian) ganglion (analogous to the DRG for the spinal cord

Question 75

Where in the thalamus do fibers from the Trigeminal system travel to?

Answer 75

Ventral posteromedial nucleus (VPM) *"M" in medial; trigeminal region has the Mouth (Compare to the other systems, which go to the VPL; these are from Limbs and body, "L" is for limb and lateral)

Question 76

What is the pathway called between the chief sensory nucleus of V and the VPM in the Trigeminal system? Which neurons decussate in this pathway?

Answer 76

Trigeminal leminiscus - the 2nd order neurons leaving the chief sensory nucleus decussate to end up in the VPM contralateral to the 1st order afferents *remember these are epicritic fibers

Question 77

Where do trigeminal leminiscus fibers go after traveling to the VPM?

Answer 77

To the primary somatosensory cortex (postcentral gyrus)

Question 78

What is the tract form the Spinal nucleus of V to the VPM called? Where does it decussate?

Answer 78

Trigeminothalamic tract - 2nd order neurons leaving the Spinal nucleus decussate to travel to the contralateral VPM from the original afferents * recall these are protopathic fibers

Question 79

Via what structure do the fibers in the Trigeminithalamic tract reach the primary somatosensory cortex (postcentral gyrus)?

Answer 79

Posterior limb of the internal capsule

Question 80

The primary somatosensory cortex on the postcentral gyrus includes what 4 Brodmann's areas?

Answer 80

3a, 3b, 2, 1 *primary somatosensory cortex is also known as S1

Question 81

Where is the unimodal (somatosensory only) association cortex known as S2 located?

Answer 81

Parietal operculum *areas #5 and #7 located in the superior parietal lobule are other unimodal association areas for somesthesis

Question 82

Which Brodmann's area is responsible primarily for receiving proprioceptive and pain info from the thalamus?

Answer 82

3A

Question 83

Which Brodmann's area receives primarily cutaneous inputs - tactile perception?

Answer 83

3B

Question 84

In what Brodmann area does further processing of cutaneous input from 3B occur?

Answer 84

Area 1

Question 85

Which Brodmann area integrates pain, tactile info and proprioceptive info from both areas 3A and 3B?

Answer 85

Area 2 - allows position and edge detection, size perception, etc * therefore there is parallel processing and also integration b/n modalities(higher order serial processing)

Question 86

What is the functional/clinical significance of Lissauer's tract, aka posterolateral fasciculis?

Answer 86

Lesions at a given spinal level will result in a loss of input from segments 2-3 segments below the injury

Question 87

Where epicritic fibers sensing proprioception send collateral fibers, in addition to those main ones that join and ascend in the posterior columns?

Answer 87

Synapse directly on alpha motoneurons in the ventral horn of spinal cord - part of the monosynaptic stretch reflex * type 1a afferent from muscle spindles are the ones that synapse directly in the ventral horn (VIII and IX) ; others also are sent to deep layers of the dorsal horn (V-VII)