2. Spinal Cord Function and Dysfunction Flashcards
How many spinal segments are there? How are they divided?
- 31 spinal segments:
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
How does the arrangement of the nerves change as you go down?
The first nerve comes from above the corresponding vertebra, as you go further down the nerves get closer and closer
At the end, the cauda equina is formed
C2 emerges from between C1 and C2 however as there are 8 cervical nerves and only 7 cervical vertebrae, the C8 nerves emerge from under the C7 vertebra (between C7 and T1)
Name the meningeal coverings of the spinal cord.
- Spinal cord (white matter surrounding grey matter)
- Pia mater - adheres tightly to the surface of the spinal cord
- Subarachnoid space - filled with CSF
- Arachnoid mater - ballooned up against the dura
- Dura Mater - continuous with inner sheat of dura in the cranium, forms dural sac, extends to S2.
- Epidural space - true space between dura and the vertebral periosteum - filled with fat and venous plexus
Where is the needle injected for anaesthetics or spinal nerve blocks?
In the epidural space
What nerve innervates the skin next to the umbilicus?
T10
Describe the cross section of the spinal cord.
- Has posterior and anterior ramus - which have both sensory and motor inervation
- The ramus then splits into a posterior (sensory) and an anterior (motor) root
- grey matter horn surrounded by white matter
Describe the fissures and sulci of the spinal cord.
- Posterior median sulcus - divided the posterior surface of the spinal cord in 2 halves
- Anterior median fissure - divides the anterior surface of the spinal cord in 2 halves
- Posterolateral sulcus - entry point of the posterior (sensory root)
- Anterolateral sulcus - exit point for the anterior (motor root)
Describe transmission of impulses in grey matter.
PAIN AND TEMPERATURE -fibres enter the dorsal horn may travel up or down 1-2 segments in the Lissauer tract, then synpase in the dorsal horn (nucleus proprius). Cross the midline in the anterior commisure and travel in the spinothalamic tract.
DISCRIMINATIVE TOUCH AND PROPRIOCEPTION- sensory fibres will enter the dorsal horn and then travel in the dorsal columns without synapsing in the posterior horn.
MOTOR - alpha motor neurons are located in the anterior hron - they exit the spinal cord and travel to their target muscles. Interneuron circuits in the anterior horn filter descending motor information and are part of the localised reflex circuits.
Name the major tracts of the spinal cord.
- Fasciculus gracilis - sensory (fine touch, vibration, proprioception) from ipsilateral lower limb
- Fasciculus cuneatus - (fine touch, vibration, proprioception) from ipsilateral upper limb
- Spinocerebellar tract - proprioception from limbs to cerebellum
- Lateral corticospinal tract - motor to ipsilateral anterior horn (mostly limb musculature)
- Spinothalamic tract - pain and temperature from contralateral side of the body
- Anterior corticospinal tract - motor to ipsi- and contralateral anterior horn (mostly axial musculature)
- Anterior white commissure - pain and temperature fibres cross. Anterior corticospinal tract fibres cross
Describe the corticospinal tract.
MOTOR tract
- Impulse begins at one side of the brain
- Goes down the corticospinal tract
- Divides into anterior and lateral corticospinal tract
- The anterior corticospinal tract innervates ipsi and contralateral anterior horn
- The lateral horn innervates the ipsilateral anterior horn
Describe the dorsal column pathway.
SENSORY FOR DISCRIMINATIVE TOUCH, VIBRATION AND PROPRIOCEPTION
- Body in dorsal root
- Does not synapse in the dorsal root
- Stays on the same side (ipsilateral) and goes to brain
Describe the spinothalamic tract
SENSORY FOR PAIN AND TEMPERATURE
- Begins at periphery
- Goes into posterior root and synpases in the anterior white commissure
- Passes onto the other side and goes up the spinothalamic tract to the brain
Describe the reflex pathway
- Fibre from muscle spindle sense stretching of the muscle
- Fibre synapses directly with alpha motor neuron in the anterior horn
- Sensory fibre synapses with inhibitory interneuron
- alpha-motor neurons go to the extensor muscles and are excited
- Inhibitory interneuron inhibits the alpha motor neuron of the antagonist muscle
- Alpha motor neuron of antagonist muscle is inhibited
Name the autonomic outflow nerves
Sympathetic - Thoracolumbar
Parasympathetic - Craniosacral
Why does the vertical level of a lesion matter?
The higher the lesion, the greater the disability
