Control L11&12 ascending pathways I&II

Question 1

What are the two main pathways for the body?

Answer 1

Spinothalamic pathway
Dorsal column medial lemniscus pathway

Question 2

What sensation is sent in the spinothalamic pathway?

Answer 2

Pain
Temperature
Crude touch
Some pressure

Question 3

What sensation is sent through the dorsal column medial lemniscus pathway?

Answer 3

Discriminative touch
Vibration
Conscious proprioception
Some pressure

Question 4

What is the main ascending pathway for the head?

Answer 4

Trigeminal sensory pathways

Question 5

What sensation is sent through each of the trigeminal sensory pathways?

Answer 5

Pain and temperature
Crude touch
Discriminative touch
Conscious proprioception

Question 6

Where is the primary somatosensory cortex located?

Answer 6

Post central gyrus

Question 7

What information is perceived at the somatosensory cortex?

Answer 7

Pain and temperature sensation and touch sensation

Question 8

Why do we have different types of sensation?

Answer 8

Due to presence of different sensory receptors/specialised nerve endings that detect different modalities (e.g. vibration, pain temperature etc..)

Question 9

Which direction do sensory pathways travel?

Answer 9

From the peripheral nerves into the CNS and ascend through the spinal cord/brainstem to the brain

Question 10

Why do we have dermatones?

Answer 10

As specific areas of skin and the body are innervated by the sensory fibres of a single segmental spinal nerve/cranial nerve. Therefore areas supplied by the same spinal cord segment are in the same dermatone.

Question 11

What virus can infect the sensory roots of specific spinal nerves?

Answer 11

Herpes zoster (virus that causes chickenpox and shingles)

Question 12

What are the three parts of the grey matter in the spinal cord?

Answer 12

Dorsal grey horn
Lateral grey horn
Ventral grey horn

Question 13

What are the 4 parts of the white matter in the spinal cord?

Answer 13

Dorsal white column
Lateral white column
Ventral white column
Ventral white commissure

Question 14

What is a commissure?

Answer 14

An area where spinal fibres can cross over allowing axons to travel from one side of the body to the other

Question 15

In what spinal vertebrae is the lateral grey horn found?

Answer 15

T1-L2 and S2-S4

Question 16

What sensation travels in the DCML pathway?

Answer 16

Fine touch
Discriminative touch
Vibration
Pressure
Proprioception

Question 17

What is the role of the lateral corticospinal tract?

Answer 17

Carry descending motor fibres from the cerebral cortex to the muscles for voluntary movement

Question 18

What sensation travels in the spinothalamic tract?

Answer 18

Pain
Temperature
Crude touch

Question 19

What is the role of the ventral corticospinal tract?

Answer 19

Involved in voluntary movements of the trunk and limbs due to the descending motor pathway travelling via this tract.

Question 20

Where is the lateral corticospinal tract?

Answer 20

In the posterolateral aspect of the spinal cord

Question 21

Where is the ventral corticospinal tract?

Answer 21

Aka the anterior corticospinal tract, it is located in the middle of the spinal cord laterally to the anterior median fissure, medially to the ventral and lateral grey horns and inferiorly to the grey matter commissure.

Question 22

How many neurones are typically involved in a sensory pathway?

Answer 22

3

Question 23

What are the 3 neurones involved in the general sensory pathway?

Answer 23

1 = pseudounipolar neurone that has a cell body in the sensory ganglion. Takes sensation from the sensory receptor to the CNS
2 = axon of second neuron crosses the midline and ascends to the ventral posterior thalamus
3 = axon of third neuron projects to post central gyrus in the parietal lobe

Question 24

Where does the spinothalamic pathway travel?

Answer 24

From primary neuron receptor along primary neuron (whose cell body is in the dorsal root ganglion) and synapses at level of entry of the spinal cord. Secondary axon crosses to other side of the spinal cord and ascends through the spinothalamic tract in the spinal cord. Travels through the brain stem into the thalamus at the ventral posterolateral nucleus where it synapses with the third neuron which travels through the posterior limb of the internal capsule to the post-central gyrus,

Question 25

Where does the primary neuron of the spinothalamic pathway enter the spinal cord?

Answer 25

Via Lissauer’s tract into the dorsal grey horn

Question 26

Where does the primary neuron synapse with the secondary neuron is the spinothalamic pathway?

Answer 26

Dorsal grey horn of the spinal cord

Question 27

How is the spinothalamic tract organised?

Answer 27

Somatotopically Medial to lateral = arms, trunk legs

Question 28

At what nucleus/lamina does the primary neuron synapse in the spinal cord? Which specific one of these doe pain and temperature neurones synapse?

Answer 28

Marginal zone = lamina 1 Substantia gelatinosa = lamina 2 (pain and temperature synapse here) Nucleus proprius = lamina 3

Question 29

At what spinal level does pain and temperature synapse compared to crude touch?

Answer 29

Pain and temperature at same level as where sensation received Crude touch sensory neurone ascends within the spinal cord between 1 and 2 levels before synapsing with the secondary neuron

Question 30

Why do the axons of sensory neurones for pain and temperature travel differently in the spinal cord to curds touch neurones?

Answer 30

To segregate the two pathways

Question 31

At what level of the spinal cord do we have cuneate fascicles?

Answer 31

above (not including) T6

Question 32

In what matter of the spinal cord does the dorsal column medial lemniscus oathway travel?

Answer 32

White matter

Question 33

How does sensation from the DCML pathway reach the brain?

Answer 33

The primary neurone enters the spinal cord and jump into the white matter and ascends in the gracile fascicles on the same side (or cuneate fascicles if enter above T6) to the closed medulla. Synapses at the closed medulla at the gracile/cuneate nucleus with second neurone cell body and crosses the midline to enter the medial lemniscus to travel to the thalamus (VPL) and synapse here with the third neurone which travels to the post central gyrus

Question 34

What are the two dorsal columns in the spinal cord?

Answer 34

Gracile and cuneate fascicles

Question 35

How are the ascending fibres in the dorsal column organised?

Answer 35

Somatotopically

Question 36

What is a name for the axons of the secondary neurones which cross the midline of the medulla?

Answer 36

Internal arcuate fibres

Question 37

How can you identify if a spinal cross section is cervical or thoracic?

Answer 37

Cervical will have a larger anterior grey horn and no lateral horn Thoracic will have a smaller anterior grey horn plus a lateral horn

Question 38

What part of the internal capsule do ascending sensory axons travel in to reach the post central gyrus?

Answer 38

Posterior limb of internal capsule

Question 39

What is it called when nerve axons travel in the spinal cord on the same side as the sensation was received? What about the opposite side?

Answer 39

Same = travels ipsilaterally Opposite = contralaterally

Question 40

What input pathways can modify the journey of sensory transmission?

Answer 40

Convergence divergence Descending pathways

Question 41

How does the somatotopic organisation of the spinothalamic tract differ to in the post central gyrus?

Answer 41

Arms, trunk legs organised medially to laterally in the spinothalamic tract Arms trunk legs is organised laterally to medially in the post central gyrus

Question 42

What are the properties of nerve fibres that carry information on pain, temperature, crude touch and some pressure?

Answer 42

thin, poorly myelinated or unmyelinated fibres Relatively slow conduction

Question 43

What are the properties of the nerve fibres that carry information on discriminative touch (2-point discrimination and pressure), proprioception and vibration?

Answer 43

large diameter, heavily myelinated fibres Fast conduction

Question 44

Somatic sensory fibres from which CN run within the trigeminal sensory nucleus to the thalamus?

Answer 44

Trigeminal Facial Glossopharyngeal Vagus

Question 45

Where is the trigeminal sensory nucleus located?

Answer 45

In the brainstem

Question 46

How many parts of the trigeminal sensory nucleus are there?

Answer 46

3

Question 47

What are the 3 parts of the trigemnial sensory nucleus?

Answer 47

Mesencephalic nucleus Pontine/Chief sensory nucleus Spinal nucleus

Question 48

Where does the trigeminal motor nuclei lie in relation to the trigemnial sensory nucleus?

Answer 48

Medially to the sensory nuclei

Question 49

Where are the primary neuron cell bodies of the trigeminal nerve (except one)?

Answer 49

In the trigeminal ganglion

Question 50

Where are each section of the trigemnial nucleus located within the brainstem?

Answer 50

Mesencephalic = midbrain Pontine/chief = pons Spinal = medulla

Question 51

What sensation of the face is sent to the Mesencephalic nucleus?

Answer 51

Proprioception

Question 52

What sensation of the face is sent to the pontine/chief nucleus?

Answer 52

discriminative touch

Question 53

What sensations of the face are sent to the spinal nucleus?

Answer 53

Simple touch and pressure, pain and temperature

Question 54

What sensory fibre cell bodies are not located in the trigemnial ganglion but in the CNS? Where are they located instead?

Answer 54

Proprioception fibres Their cell bodies are found in the Mesencephalic nucleus

Question 55

What is the pathway of pain and temperature sensation of the face?

Answer 55

Primary neuron (cell body in trigemnial ganglion) descends in the spinal tract of the trigemnial nucleus to the (caudal) spinal nucleus where it synapses with the secondary fibre. The secondary axon ascends in the trigeminothalamic tract o the opposite side of the brainstem to the VPM of the thalamus.

Question 56

What is the pathway for crude touch and pressure sensation of the face?

Answer 56

Primary neuron (cell body in the trigemnial ganglion) descends in the spinal tract of the trigemnial nucleus to the rostral part of the spinal nucleus where it synapses with the secondary neuron. The secondary neuron ascends in the trigeminothalamic tract on the opposite side of the brainstem to the VPM of the thalamus.

Question 57

How does the pain and temperature pathway for the face differ from the body?

Answer 57

In spinothalamic the fibres cross at the level of entry In trigeminothalamic the fibres cross below the level of entry

Question 58

What is the pathway for discriminative touch sensation of the face?

Answer 58

Primary neuron (cell bodies in the trigeminal ganglion) enters the brainstem at level of the pons and synapses with second neuron at the pontine nucleus. The secondary neuron crosses the brainstem to the contralateral side and ascends to the VPM of the thalamus in the trigeminothalamic tract.

Question 59

What is the pathway for proprioception sensation of the face?

Answer 59

Primary neurons (cell bodies in the mesencephalic nucleus) enter the brainstem at the level of the midbrain/top of pons and some fibres synapse, alongside/next to the mesencephalic nucleus, with the secondary neuron. The other fibres synapse with motor neurones in the trigemnial motor nucleus which travel to the muscles of mastication. The secondary sensory neuron ascends contralaterally to the VPM of the thalamus in the trigeminothalamic tract.