Spinal Cord: Ascending tracts & sensation

Question 1

List 5 types of receptors in the hand.

Answer 1

Meissner corpuscle

Pacinian corpuscle

Ruffini ending

Merkel discs

Free nerve endings

Question 2

What do Meissner corpuscles detect?

Answer 2

Discriminative touch

Question 3

What do Pacinian corpuscles detect?

Answer 3

Deep pressure & vibration

Question 4

What do Ruffini endings detect?

Answer 4

Touch
Sheer stress / forces

Question 5

What do Merkel discs detect?

Answer 5

Light, sustained touch

Question 6

What do free nerve endings detect?

Answer 6

Pain & temperature

Question 7

What is the function of the superior parietal lobe?

Answer 7

Integration of sensory inputs, sensory memory, perception of contralateral self/ world

Question 8

What does the anterior limb of the internal capsule contain?

Answer 8

Descending fibres (frontopontine + frontothalamic)

Question 9

What does the genu and posterior limb of the internal capsule contain?

Answer 9

Motor fibres to the head, arm, leg + sensory fibres

Question 10

What does the retrolenticular part of the internal capsule contain?

Answer 10

Visual and auditory input

Question 11

Describe the route of each neuron in the 3 neuron ascending sensory pathway.

Answer 11

1st order neuron – enters spinal cord via dorsal root, ascends ipsilaterally

2nd order neuron – decussates to ascend to the thalamus

3rd order neurons – leave thalamus to ascend to cortex via internal capsule

Question 12

What are the 2 main nuclei in the thalamus for sensory input?

Answer 12

Ventral posterior lateral nucleus (VPL)

Ventral posterior medial nucleus (VPM)

Question 13

The VPL nucleus in the thalamus receives sensory input from what?

Answer 13

Body

Question 14

The VPM nucleus in the thalamus receives sensory input from what?

Answer 14

Face

Question 15

What are the 3 sensory tracts?

Answer 15

Dorsal column pathway

Spinothalamic tract

Spinocerebellar tract

Question 16

The dorsal column pathway receives sensory input from which 5 receptors?

Answer 16

Meissner’s, Merkel’s, Pacinian, Ruffini & joint proprioceptors

Question 17

The dorsal column pathway receives which 2 kinds of sensory input?

Answer 17

Discriminative touch & vibration

Conscious proprioception

Question 18

The spinothalamic tract receives sensory input from which receptors?

Answer 18

Free nerve endings

Question 19

The spinothalamic tract receives which 3 kinds of sensory input?

Answer 19

Pain
Temperature
Simple touch

Question 20

The spinocerebellar tract receives sensory input from which 2 receptors?

Answer 20

Muscle spindles

Golgi tendon organs

Question 21

The spinocerebellar tract receives which kind of sensory input?

Answer 21

Unconscious proprioception

Question 22

What are the 2 sections of the dorsal column pathway and from which vertebral levels do they receive fibres from?

Answer 22

Fasciculus Gracilis – from below T6

Fasciculus cuneatus – from above T6

Question 23

Where do 2nd order neurons in the dorsal column pathway decussate?

Answer 23

Medulla

Question 24

What are 2nd order neurons in the dorsal column pathway called after they decussate? Where do they ascend to?

Answer 24

Medial lemniscus – which ascends to VPL nucleus of the thalamus

Question 25

Via what tract does sensory information from the face reach the brain?

Answer 25

Trigeminothalamic tract

Question 26

Where do 1st order neurons of the trigeminothalamic tract enter the brainstem?

Answer 26

Pons

Question 27

What are 2nd order neurons in the trigeminothalamic tract called after they decussate? Where do they ascend to?

Answer 27

Trigeminal lemniscus – which ascends to VPM nucleus of the thalamus

Question 28

Describe the loss of sensation that would occur if the dorsal column pathway was damaged?

Answer 28

Ipsilateral loss of sensation below the level of the lesion

Question 29

Which STD can damage the dorsal column pathway?

Answer 29

Tertiary syphilis

Question 30

Which 2 conditions might result from dorsal column damage?

These are caused by the loss of which specific sensory input?

Answer 30

Pseudoathetosis – writhing of digits, hands, and feet

Sensory ataxia – leads to positive Romberg sign & stamping gait. Caused by a loss of proprioception

Question 31

1st order neurons in the spinothalamic tract enter the spinal cord via what?

Answer 31

Tract of Lissauer

Question 32

Where do 2nd order neurons in the spinothalamic tract decussate?

Answer 32

1-2 vertebral levels above the entry into the spinal cord

Question 33

2nd order neurons in the spinothalamic tract decussate across what?

Answer 33

Anterior white commissure

Question 34

The spinothalamic tract route can be damaged by which condition that typically occurs in the cervical vertebrae?

Answer 34

Syringomyelia – cavitation of the central canal which damages the anterior white commissure

Question 35

Describe the somatotopic organization of the spinothalamic tract, beginning from the centre and going outwards.

Answer 35

Neck, arm/thorax, leg, sacral

Question 36

Due to the direction it is likely to grow, a spinothalamic tract tumour can spare which region?

Answer 36

Sacrum – sacral sparing

Question 37

Which part of the spinocerebellar tract receives input from muscle spindles?

Answer 37

Dorsal spinocerebellar tract

Question 38

Which part of the spinocerebellar tract receives input from golgi tendon organs?

Answer 38

Ventral spinocerebellar tract

Question 39

Does the spinocerebellar tract carry sensory to the ipsilateral or contralateral cerebellum?

Answer 39

Ipsilateral

Question 40

Although it is rare for the spinocerebellar tract to be damaged in isolation, in which condition can this occur?

Answer 40

Friedreich’s ataxia – autosomal recessive condition