Spinal cord function and dysfunction Flashcards
Where do nerves leave the vertebral column
Through intervertebral foramina
What are the enlargements for innervation of the limbs
Cervical - C3-T1
Lumbar - L1-S3
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
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
Where is spinal anaesthetic and an epidural injected
L3-4 into the subarachnoid space
L4-5 into the epidural space
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
Define dermatome
Area of skin innervated by one single spinal nerve or spinal segment
Define myotome
Muscles innervated by one single spinal nerve or spinal segment
What is the exit point for the anterior (motor) root
Anterolateral sulcus
What divides the anterior surface of the spinal cord in two halves
anterior median fissure
What is the entry point of the posterior (sensory) root
Posterolateral sulcus
What divides the posterior surface of the spinal cord in two halves
Posterior median sulcus
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)
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
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
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
- Sensory elements in the muscle stretch
- Signal sent to the spinal cord via the sensory neurone
- Synapse with a motor neurone
- 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
S2
