Somatosensory System/ Ascending Tracts

Question 1

What are the 4 modalities of the somato-sensory system?

Answer 1

• Discriminative Touch
• Proprioception
• Nociception
• Temperature

Question 2

What is divergent neural proccessing?

Answer 2

• Potential spreads to more than 1 system

- The axon gives off collaterals

Question 3

What is the purpose of convergence?

Answer 3

To increase the contrast of the neural signal

Question 4

What is the term for contrast enhancement ?

Answer 4

• Lateral inhibition

Question 5

What are the 3 types of lateral inhibition?

Answer 5

• Feed forward
• Feedback
• Distal

Question 6

What is feedforward control?

Answer 6

Lateral collaterals activate inhibitory cell off of primary neuron provide stimulation to inhibitory neurons. (no feedback)

Question 7

What is local feedback inhibition?

Answer 7

Collaterals from inhibitory neurons receiving strong sensory input synapse on interneurons and inhibit analogous/ neighboring inhibitory neurons to better pinpoint the source of the stimulus.

Question 8

What is distal feedback inhibition?

Answer 8

Axons from the motor and sensory areas of the cerebral cortex synapse on an interneuron that synapses on an inhibitory neuron targeting the secondary neurons of a somatosensory system, further inhibiting weaker input,

Question 9

What is the overall purpose of convergence/ contrast enhancement?

Answer 9

• Inhibit weaker signals for stronger clarity of the more powerful sensory information

Question 10

What is kinesthetic and position sense considered mysterious?

Answer 10

• We are unaware of it since it has no defined sensation that is identifiable

Question 11

What 3 types of receptors combine to form awareness of joint position? What other signal contributes? Which is the primary receptor?

Answer 11

• Muscle spindles (primary)
• Skin/ SA ruffini endings
• Joint receptors (detect end of motion)
• Signals of central origins sense effort or will

Question 12

Why are position and movements of joints separate senses?

Answer 12

• They share the same receptors, but central processing occurs in the different areas/ pathways

Question 13

What 2 receptors are especially important in determining joint position?

Answer 13

• SA cutaneous receptors

- Tonic muscle spindles

Question 14

What 3 receptors are especially important in determining movement?

Answer 14

• FA receptors
• Muscle spindles
• Golgi tendon organs

Question 15

Where are receptors found for touch and pressure?

Answer 15

In the skin

Question 16

What are the 3 primary sensory afferents for touch and pressure?

Answer 16

• Group II fast

- Group III and IV slow

Question 17

Where is the origin of the fasciculus gracilis?

Answer 17

The dorsal root ganglions of T7 - S5

Question 18

Do the fibers of the fasciculus gracilis cross?

Answer 18

No.

Question 19

Where is the tract of the fasciculus gracilis found?

Answer 19

• Throughout the entire spinal cord

Question 20

On what does the fasciculus gracilis synapse in the higher centers?

Answer 20

• The nucleus gracilis in medulla

Question 21

What sensations run through the fasciculus gracilis?

Answer 21

• Conscious proprioception, discriminative touch, pressure, 2 point discrimination, kinesthetic sense

Question 22

Where is the origin of the fasciculus cuneatus?

Answer 22

• Dorsal root ganglions of C1- T6

Question 23

Do the fibers of the fasciculus cuneatus cross the spinal cord?

Answer 23

No.

Question 24

Where is the tract of the fasciculus cuneatus found in the spinal cord?

Answer 24

Above T6

Question 25

What does the fasciculus cuneatus synapse on in the higher centers?

Answer 25

- The nucleus cuneatus in the medulla

Question 26

What sensations run through the fasciculus cuneatus?

Answer 26

- Consious proprioception, discriminative touch, pressure, 2 point discrimination, kinesthetic sense

Question 27

What is the origin of the spinocervical thalamic tract?

Answer 27

- The lateral cervical nuclei of the dorsal horn (at C1, and above)

Question 28

Do the fibers of the spinocervical thalamic tract cross?

Answer 28

Yes

Question 29

What do the fibers of the spinocervical thalamic tract synapse on in the higher centers?

Answer 29

- Thalamus

Question 30

What sensation runs through the spinocervical thalamic tract?

Answer 30

- Discrimitive touch | - Passive manipulation (somewhat)

Question 31

What fascicle is the spinocervical thamalic tract analgous to?

Answer 31

- The fasciculus cuneatus (maybe?)

Question 32

What is the origin of dorsal spinocerebellar tract?

Answer 32

- Laminae 7/ Clark's Column of T1 - L2

Question 33

What is Clark's Column

Answer 33

- Ias, Ibs, and IIs, give off collaterals to interneurons, which exit the horn laterally and ascends up from the lateral portion of the spinal cord

Question 34

Do the fibers of the dorsal spinocerebellar tract cross?

Answer 34

- No

Question 35

Where do the dorsal spinocerebellar tracts synapse?

Answer 35

On the nuclei in L3 - C1

Question 36

Where are the dorsal spinocerebellar tracts found in the spinal cord?

Answer 36

- Fibers are found throughout

Question 37

What sensory information runs through the dorsal spinocerebellar tract?

Answer 37

- Ia, Ib, and II fiber propriception | - UNCONCIOUS proprioception

Question 38

Where does the ventral spinocerebellar tract originate?

Answer 38

- Laminae 5 - 7 of L3 - L5 (Spinal border cells)

Question 39

Do the fibers of the ventral spinocerebellar tract cross?

Answer 39

They double cross (in the spinal cord and cerebellum??), and end up on the same side

Question 40

Where do the primary fibers of the ventral spinocerebellar tract synapse on their nuclei?

Answer 40

- L1 - S5

Question 41

Where are fibers from the ventral spinocerebellar tract found in the spinal cord?

Answer 41

- Throughout the spinal cord

Question 42

Where do the fibers of the ventral spinocerebellar tract synapse in the upper centers?

Answer 42

- The cerebellum

Question 43

What fibers create the ventral spinocerebellar tracts?

Answer 43

- Ib, FRA from WRF

Question 44

What sensory information travels through the ventral spinocerebellar tracts?

Answer 44

- Unconcious proprioception - Movement - Posture

Question 45

Where does the cuneocerebellar tract originate?

Answer 45

- The accesory cuneate nucleus (collateral off fasciculus cuneatus)

Question 46

What is the cuneocerebellar tract an analogue to?

Answer 46

- The dorsal spinocerebellar

Question 47

Do the fibers of the cuneocerebellar tract cross?

Answer 47

No

Question 48

Where are the fibers found of the cuneocerebellar tract found in the spinal cord?

Answer 48

- They are not present

Question 49

On what structure does the cuneocerebellar tract synapse in the higher centers?

Answer 49

The cerebellum

Question 50

What fibers make up the cuneocerebellar tract?

Answer 50

- Ia, Ib, and Grade II

Question 51

What sensation runs through the cuneocerebellar tract?

Answer 51

- Ia, Ib, II proprioception | - Unconcious proprioception

Question 52

Where does the rostrocerebellar tract originate?

Answer 52

- Laminae 7 of C4- C8

Question 53

Do the fibers of the rostrocerebellar tract cross?

Answer 53

No

Question 54

Where does the rostrocerebellar tract synapse in the higher centers?

Answer 54

On the cerebellum

Question 55

What fibers make up the rostrocerebellar tract?

Answer 55

Ib, FRA from WRF

Question 56

What sensory information travels through the rostrocerebellar tract?

Answer 56

- Unconcious proprioception - Movement - Posture

Question 57

Which tracts location is not currently known?

Answer 57

Rostrocerebellar tract

Question 58

How are the funiculi of the dorsal horn arranged?

Answer 58

- Somatotopically arranged | - Sacral to lumbar to thoracic to cervical from medial to lateral

Question 59

Where does the spinoreticular tract originate?

Answer 59

- Posterior horn

Question 60

Do the fibers of the 1st spinoreticular tract cross?

Answer 60

No

Question 61

Where are fibers from the spinoreticular tract found in the spinal cord?

Answer 61

Throughout

Question 62

What does the spinoreticular tract synapse on in the higher centers? (tract 1 and 2)

Answer 62

1: Medulla reticular formation - Giganto and lateral reticular nucleus 2: Pons reticular formation - Reticular pontis caudalis

Question 63

What is the function of the 1st spinoreticular tract?

Answer 63

- Unconcious proprioception

Question 64

What is the function of the 2nd spinoreticular tract?

Answer 64

- Maintanence of the state of conscioiusness

Question 65

What is the origin of the spinovestibular tract?

Answer 65

- Dorsal root ganglia

Question 66

Do the fibers of the 2nd spinoreticular tract cross?

Answer 66

Yes

Question 67

Do the fibers of the spinovestibular tract cross?

Answer 67

Ues

Question 68

What does the spinovenstibular tract synapse on in the higher centers?

Answer 68

- Vestibular nuclei

Question 69

What sensation travels through the spinovestibular tract?

Answer 69

- Ia, Ib, II proprioception | - Unconcious proprioception

Question 70

What is the origin of the spino-olivary tract?

Answer 70

- Dorsal root ganglia

Question 71

Do the fibers of the spino-olivary tract cross?

Answer 71

Sometimes

Question 72

Where are the fibers of the spino-olivary tract found?

Answer 72

C1 - C8

Question 73

Where do the fibers of the spino-olivary tract synapse in the higher centers?

Answer 73

- Inferior olivary nucleus

Question 74

What sensation travels through the spino-olivary tracts?

Answer 74

- Unconscious proprioception of the neck

Question 75

What is the origin of the spinocortical tract?

Answer 75

Unknown

Question 76

Do the fibers of the spinocortical tract cross?

Answer 76

No

Question 77

Where are the fibers of the spinocortical tract found in the spinal cord?

Answer 77

Throughout

Question 78

Where do the fibers of spinocortical tract synapse in the higher centers?

Answer 78

The cerebral cortex

Question 79

What is the origin of the spinocervical tract?

Answer 79

Lamina III and IV

Question 80

What is another name for the spinocervical tract?

Answer 80

- Morin's tract

Question 81

Do the fibers of the spinocervical tract cross?

Answer 81

No

Question 82

Where do the fibers of the spinocervical tract synapse in the higher centers?

Answer 82

The lateral cervical nucleus

Question 83

What sensation travels through the spinal cervical tract?

Answer 83

- Concious proprioception | - Tactile sensation

Question 84

What are the 6 minor ascending tracts?

Answer 84

- Spinoreticular - Spinoreticular - Spinovestibular - Spino-olivary - Spinocortical - Spinocervical/ Morin's

Question 85

What are the 3 interspinal reflex tracts?

Answer 85

- Fasciculus Septomarginalis - Fasciculus Interfascicularis - Fasciculus Proprius 1

Question 86

Where does the fasciculus septomarginalis orginate from?

Answer 86

- The dorsal root ganglia

Question 87

Do the fibers of the fasciculus septomarginalis cross?

Answer 87

- No

Question 88

Where are the fibers of the fasciculus septomarginalis found?

Answer 88

L1 - S5

Question 89

Where do the fibers of the fasciculus septomarginalis, and other interspinal reflex tracts synapse?

Answer 89

- On interneurons | - ACh endplates

Question 90

What sensation travels through the fasciculus septomarginalis, and other interspinal reflex tracts?

Answer 90

- Proprioception interspinal reflexes

Question 91

Where do the fibers of the fasciculus interfascicularis orginate?

Answer 91

The dorsal root ganglia

Question 92

Do the fibers of the fasciculus interfascicularis cross?

Answer 92

No

Question 93

Where are the fibers of the fasciculus interfascicularis found?

Answer 93

- C1 - T12

Question 94

What type of sensory information travels trhough the fasciculus interfascicularis?

Answer 94

Proprioception Interspinal Reflexes

Question 95

Where does the fasciculus proprius 1 originate?

Answer 95

- Dorsal root ganglia | - Laminae III and IV

Question 96

Do the fibers of the fasciculus proprius 1 cross?

Answer 96

Probably; not sure

Question 97

Where are the fibers of the fasciculus proprius 1 found in the spinal cord?

Answer 97

Throughout