Neuroanatomy Outlined

Created by Amy Dodds

Describe the function(s) of the 3 main spinal pathways

Draw and label each of the 3 main spinal pathways

Apply your knowledge to explain the effects of lesions

Click on each bullet point below to reveal the learning outcomes:

Describe the function(s) of the 3 main spinal pathways

Draw and label each of the 3 main spinal pathways

Apply your knowledge to explain the effects of lesions

Hover over each button to learn about its function:

Drawing tutorial: follow a step-by-step tutorial of how to draw and label the chosen spinal pathway.

Quiz: complete a short quiz to test your understanding.

More information: watch a short, 5-minute information video outlining the chosen spinal pathway.

Home: return to the home page to choose a different spinal pathway to study.

Intended Learning Outcomes: return to the ILOs page to see the learning outcomes.

Ascending pathways from the body to the cerebrum. Consists of two pathways, each carrying a different modality of sensation:

Anterior spinothalamic pathway:carries crude touch & pressure

Lateral spinothalamic pathway: carries pain & temperature

SPINOTHALAMIC PATHWAYS

Q1: What is the function of the anterior spinothalamic tract?

Sensation of proprioception

Sensation of pressure & pain

Sensation of fine touch & vibration

Sensation of pain & temperature

Sensation of crude touch & pressure

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The anterior spinothalamic tract carries sensory (afferent) information about crude touch & pressure from the body to the cerebrum.

Q2: Where do primary neurons of the spinothalamic tract synapse?

Gracile nucleus

Substantia gelatinosa

Ventral horn of grey matter

Ventral horn of grey matter

Gracile nucleus

Ventral posterolateral nucleus

Substantia gelatinosa

Ventral posterolateral nucleus

Cuneate nucleus

Cuneate nucleus

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Primary neurons of the spinothalamic tract enter the spinal cord via the dorsal root and synapse with their secondary neuron at the substantia gelatinosa of the dorsal horn of grey matter.

Q3: Briefly describe the clinical effects of a total spinal cord transection at the T10 level

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A total cord transection affects the descending and ascending pathways on both sides, but the cranial nerves remain intact. Here, this will present with complete loss of sensory and motor functions below the T10 level, but intact function above this level.

Q4: Where do secondary neurons of the spinothalamic tract synapse?

Gracile nucleus

Substantia gelatinosa

Ventral horn of grey matter

Ventral horn of grey matter

Gracile nucleus

Ventral posterolateral nucleus

Substantia gelatinosa

Ventral posterolateral nucleus

Cuneate nucleus

Cuneate nucleus

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Secondary neurons of the spinothalamic tract ascend via the spinal lemniscus to the thalamus, where they synapse with tertiary neurons at the ventral posterolateral nucleus.

Q5: Which spinal pathway is most likely to be affected by occlusion of the posterior spinal arteries?

Gracile nucleus

Lateral corticospinal

Ventral horn of grey matter

Lateral spinothalamic

Dorsal columns-medial lemniscus

Ventral posterolateral nucleus

Substantia gelatinosa

Anterior spinothalamic

Anterior corticospinal

Cuneate nucleus

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The posterior spinal arteries, which arise from the posterior inferior cerebellar artery (PICA), supply the posterior 1/3rd of the spinal cord.

The DCML pathways run along the dorsal aspect of the spinal cord and, therefore, are most at risk.

Click here to download the blank PDF and draw along:

Choose a pathway to draw...

Work your way through each of the drawing steps, copying the pathway and labels onto your blank diagram as you go. You should finish with an accurately labelled image of your chosen spinal pathway!

Work your way through each of the drawing steps, copying the pathway and labels onto your blank diagram as you go. You should finish with an accurately labelled image of your chosen spinal pathway!

Descending pathways from the cerebrum to the body. Consists of two pathways, each carrying motor signals to different regions:

Anterior corticospinal pathway:carries motor information to trunk

Lateral corticospinal pathway: carries motor information to limbs

CORTICOSPINAL PATHWAYS

Q1: What is the function of the lateral corticospinal tract?

Somatic efferent to face

Somatic efferent to limbs

Somatic efferent to trunk

Somatic afferents from trunk

Somatic afferents from limbs

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The lateral corticospinal tract carries voluntary motor (somatic efferent) information to the muscles of the upper and lower limbs.

Q2: Where do 90% of the corticospinal tract fibres decussate?

Gracile nucleus

Medulla oblongata

Ventral horn of grey matter

Substantia gelatinosa

Internal capsule

Ventral posterolateral nucleus

Substantia gelatinosa

Cerebral peduncle

Anterior white commissure

Cuneate nucleus

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90% of the descending motor fibres decussate at the pyramidal decussation of the medulla oblongata, where they enter the lateral corticospinal tract.

Q3: Briefly describe the clinical effects of spinal cord hemisection (Brown-séquard syndrome)

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Brown-Séquard syndrome affects both the descending and ascending pathways.Typical presentation includes:

• Contralateral loss of pain & temperature sensation (spinothalamic)
• Ipsilateral loss of fine touch sensation (DCML)
• Ipsilateral loss of movement (corticospinal)

Q4: Where do 10% of the corticospinal tract fibres decussate?

Gracile nucleus

Medulla oblongata

Ventral horn of grey matter

Substantia gelatinosa

Internal capsule

Ventral posterolateral nucleus

Substantia gelatinosa

Cerebral peduncle

Anterior white commissure

Cuneate nucleus

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10% of the descending motor fibres decussate at the ventral (anterior) white commissure of the spinal cord, where they leave via the ventral root.

Q5: A patient has suffered a stroke in their internal capsule on the left side.How would this patient likely present?

Gracile nucleus

Right-sided loss of fine touch

Ventral horn of grey matter

Right-sided weakness and right-sided loss of sensation

Left-sided weakness and bilateral numbness

Ventral posterolateral nucleus

Substantia gelatinosa

Left-sided loss of crude touch and right-sided weakness

Bilateral weakness and loss of sensation

Cuneate nucleus

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The internal capsule contains fibres of both the ascending and descending tracts. The patient will present with right-sided weakness and right-sided loss of sensation.

Click here to download the blank PDF and draw along:

Choose a pathway to draw...

Work your way through each of the drawing steps, copying the pathway and labels onto your blank diagram as you go. You should finish with an accurately labelled image of your chosen spinal pathway!

Work your way through each of the drawing steps, copying the pathway and labels onto your blank diagram as you go. You should finish with an accurately labelled image of your chosen spinal pathway!

Ascending pathways from the body to the cerebrum.Two pathways carrying sensory signals about fine touch & proprioception from different regions:

Gracile fasciculus:carries fine touch & proprioception from T7 downwards

Cuneate fasciculus:carries fine touch & proprioception from T6 upwards

DCML PATHWAY

Q1: What is the function of the DCML pathway?

Motor control to limbs

Motor control to trunk

Pain & temperature

Crude touch & pressure

Fine touch & proprioception

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The DCML pathway consists of two pathways, each carrying sensory signals about fine touch & proprioception from different regions.

Q2: Briefly describe the clinical effects of a lesion in the left gracile fasciculus at the L1 spinal cord level.

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The patient will present with loss of fine touch, vibration & proprioception sensation in the left lower limb.

Q3: Which neuron synapses at the gracile nucleus?

Gracile nucleus

Tertiary sensory neuron

Ventral horn of grey matter

Upper motor neuron

Secondary sensory neuron

Ventral posterolateral nucleus

Substantia gelatinosa

Primary sensory neuron

Lower motor neuron

Cuneate nucleus

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The primary sensory neuron enters the spinal cord via the dorsal root and passes into the gracile fasciculus where it ascends. At the medulla oblongata, it forms a synapse with the secondary neuron in the gracile nucleus.

Q4: Which spinal pathways are most likely to be affected by occluson of the anterior spinal artery?

Gracile nucleus

Gracile fasciculus & Spinothalamic

Ventral horn of grey matter

Spinothalamic & DCML

Cuneate fasciculus & Corticospinal

Ventral posterolateral nucleus

Substantia gelatinosa

Corticospinal & DCML

Corticospinal & Spinothalamic

Cuneate nucleus

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The anterior spinal artery, which arises from the vertebral arteries, supplies the anterior 2/3rd of the spinal cord. The corticospinal and spinothalamic pathways run in this region of the spinal cord and, therefore, are most at risk.

Q5: A patient suffers a right-sided midbrain lesion affecting the DCML pathway.Which part of the DCML pathway is most likely to be affected?

Gracile nucleus

Medial lemniscus

Ventral horn of grey matter

Ventral posterolateral nucleus

Internal arcuate fibres

Ventral posterolateral nucleus

Substantia gelatinosa

Cuneate fasciculus

Gracile fasciculus

Cuneate nucleus

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The secondary neurons of the DCML pathway decussate in the medulla oblongata via the internal arcuate fibres and enter the medial lemniscus. They ascend in the medial lemniscus through the pons and midbrain, before synapsing at the thalamus in the cerebrum.

Click here to download the blank PDF and draw along:

Choose a pathway to draw...

Work your way through each of the drawing steps, copying the pathway and labels onto your blank diagram as you go. You should finish with an accurately labelled image of your chosen spinal pathway!

Work your way through each of the drawing steps, copying the pathway and labels onto your blank diagram as you go. You should finish with an accurately labelled image of your chosen spinal pathway!

Damage to the ascending pathways at this point has occurred after their decussation, so the patient presents with loss of sensation on the contralateral side to the lesion – in this case, on the right side.

In this case, the lesion has occurred below the level of the decussation, so symptoms will present on the ipsilateral side to the lesion.

Fibres that decussate in the medulla oblongata will enter the lateral corticospinal tract, so fibres in the anterior corticospinal tract decussate lower down, in the spinal cord white matter!

Lateral = Limbs

Just remember...

So the lateral corticospinal tract supplies somatic motor information to the Limbs!

Damage to the corticospinal tracts at this point has occurred prior to their decussation, so the patient presents with weakness on the contralateral side to the lesion – in this case, on the right side.

Cuneate fasciculusUpper body

Gracile fasciculusLower body