Spinal cord function and dysfunction Flashcards by Alexandra Chan

Where do nerves leave the vertebral column

Through intervertebral foramina

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What are the enlargements for innervation of the limbs

Cervical - C3-T1

Lumbar - L1-S3

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Describe the organisation of the spinal cord

31 spinal segments and pairs of spinal nerves
8 cervical
12 thoracic
5 lumbar
5 sacral
1 coccygeal

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What are the meningeal coverings from outside in

Epidural space - Filled with fat and venous plexus. Between dura and periosteum (only vertebral column)
Dura mater - continuous sheet of dura, extends to S2
Arachnoid mater - Ballooned against the dura
Subarachnoid space - CSF
Pia mater - Adheres tightly to the surface of the spinal cord

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Where is spinal anaesthetic and an epidural injected

L3-4 into the subarachnoid space

L4-5 into the epidural space

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What are the grey and white matter made up of

Grey - cell bodies of interneurons and motor neurons, neuroglia cells and unmyelinated axons.
White - tracts, myelinated motor and sensory axons

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Define dermatome

Area of skin innervated by one single spinal nerve or spinal segment

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Define myotome

Muscles innervated by one single spinal nerve or spinal segment

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What is the exit point for the anterior (motor) root

Anterolateral sulcus

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What divides the anterior surface of the spinal cord in two halves

anterior median fissure

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What is the entry point of the posterior (sensory) root

Posterolateral sulcus

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What divides the posterior surface of the spinal cord in two halves

Posterior median sulcus

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Describe motor neurones in the grey matter

Motor neurones exit and travel to the target muscle via ventral horn
(interneuron circuits to filter descending motor information)

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What is the substantia gelatinosa

Spinothalamic pathway primary neurones enter the spinal cord and ascends to synapse here
Lamina II of the grey matter
First modulation for pain and temperature

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What is the posterolateral fasciculus

Lissauer tract
Sensory fibres carrying pain and temp will ascend or descend several spinal cord levels here before synapsing in the dorsal horn

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Describe the pain and temperature tract in the spinal cord

Fibres enter the dorsal horn
Synapse in the nucleus proprius
Fibers cross in the anterior commissure and then ascend in the spinothalamic tract
Spinothalamic

Describe the discriminative touch and proprioception tract

Sensory fibres enters the dorsal horn and travel in dorsal columns, ascends and then crosses in the medulla
(does not synapse in the posterior horn)
Dorsal column

What are the major tracts of the spinal cord

Fasciculus gracilis
Fasciculus cuneatus
Spinocerebellar tract
Lateral corticospinal tract
Spinothalamic tract
Anterior corticospinal tract

What is the role of the Fasciculus gracilis

Sensory (fine touch, vibration, proprioception) from the ipsilateral lower limb

What is the role of the Fasciculus cuneatus

Sensory (fine touch, vibration, proprioception) from the ipsilateral upper limb

What is the role of the Spinocerebellar tract

Proprioception from limbs to cerebellum

What is the role of the Lateral corticospinal tract

Motor fibre to ipsilateral anterior horn (mostly limb musculature movement)

What is the role of the Spinothalamic tract

Pain and temperature from contralateral side of the body

What is the role of the Anterior corticospinal tract

Motor fibre to ipsi- and contralateral anterior horn (mostly axial musculature movement)

Describe the main voluntary movement pathway

Via the corticospinal tracts Motor cortex in the brain sends a fibre to the medulla, where it crosses to the other side (85%) to travel to limb muscles or remains on the same side to travel to axial muscles (15%)

Compare the main sensory pathways

Discriminative touch synapses in the medulla and crosses to the other side Pain and temp. will synapse in the spinal cord and cross to the other side

Describe autonomic outflow

Thoracic and lumbar spinal cord has an intermediate horn for motor neurones of the sympathetic system T1-L2 = sympathetic cranial and S2-4 = parasympathetic

What factors affect severity of spinal lesions

Loss of neural tissue Vertical level Transverse plane (location of lesion)

Explain how loss of neural tissue affects lesions

Usually small if due to trauma | Can be more extensive (metastases, degenerative, demyelination)

Explain how vertical level affects lesion

The higher the lesion, the greater the disability

What are the main tracts involved in spinal lesions

Dorsal colums Lateral corticospinal Spinothalamic

What are the stages of injury to lateral corticospinal tract

Stage 1. Spinal shock: loss of reflex activity below the lesion, lasting for days or weeks = flaccid paralysis Stage 2. Return of reflexes: hyperreflexia and/or spasticity = rigid paralysis

What are denticulate ligaments

Lateral projections of the Pia mater which extend to the dura mater to stabilise the spinal cord

Describe the horns of the spinal cord

Ventral horns - motor neurones, axons control the muscles of the body via the ventral roots and spinal nerves Dorsal horns - receive sensory information from the body via spinal nerves and dorsal roots Intermediate horns (T&L) - sympathetic preganglionic motor neurones, axons control visceral functions via ventral roots and spinal nerves

Why is damage to the white matter more likely to be more severe

A lesion may damage the ascending/descending tracts, therefore every part of the body supplied by nerves below the lesion will be damaged.

What is the difference between the roots, a ramus and the spinal nerve

Root - only contains nerve fibres of one type (V=motor, D=S) Spinal nerve - combination of the root nerve fibres Ramus - contains mixture of motor and sensory

Describe the reflex pathway

1. Sensory elements in the muscle stretch 2. Signal sent to the spinal cord via the sensory neurone 3. Synapse with a motor neurone 4. Impulse comes back to the muscle and causes contraction Reflex actions occur on the same side of the body to remove form the danger, but also cross to the other side to stabilize the body

Where does the dura mater extend to