3.1 Spinal Cord Anatomy Flashcards
What is in the epidural space of the spinal cord?
Mostly fat
At what vertebral level does doe the spinal cord/pia mater end? What procedure is this important for?
L1/L2; important for lumbar puncture (lumbar cistern)
Which vertebrae do the dura and the arachnoid mater extend down to?
Second sacral vertebrae
Where is the cauda equina located? What is it inferior to?
- Located in lumbar cistern
- Inferior to conus medullaris (base of spinal cord)
What are two enlargements of the spinal cord?
Cervical: Origin of brachial plexus
Lumbar: Origin of lumbosacral plexus
At what vertebral levels are the lumbar and cervical enlargements?
Cervical: C3-T2
Lumbar: L1-S3
Why does the spinal cord not fill the whole vertebral column?
- Spinal cord stops growing at 4
- Vertebral column grows until adulthood
In terms of fissures/sulci, how do you tell whether you’re looking at the A/P surface of the spinal cord?
Anterior: deeper, anterior median fissure
Posterior: shallower, posterior median sulcus
The spinal nerve is formed by the joining of…
The dorsal root and the ventral root
How many pairs of spinal nerves are in each of the vertebral sections (e.g. cervical, thoracic etc.)
Cervical: 8
Thoracic: 12
Lumbar: 5
Sacral: 5
Coccygeal: 1
What is the area between the dorsal/ventral horns of the spinal cord called?
The intermediate zone
The lateral horns of the spinal cord are important for _____ function
Autonomic
What are the three pairs of columns in the spinal cord?
- Dorsal
- Ventral
- Lateral
What changes grey matter/white matter proportions in different cross sections of the spinal cord?
More innervation -> more myelinated axons -> more white matter
More muscles -> more grey matter
What modalities does the DCML tract carry?
- Proprioception
- Vibration
- Fine touch
What are the two fascicului of the DCML pathway? Which is medial/lateral?
Medial: Fasciulus cuneatus (upper limb)
Lateral Fasciculus gracilis (lower limb)
Which modalities does the anterior vs lateral spinothalamic tract carry?
Lateral: pain/temp
Anterior: Crude touch and pressure
What is the function of the spinocerebellar tract? Where are they found in a lateral cross-section?
- Carry unconscious proprioceptive info ipsilaterally
- Found on lateral aspect of spinal cord
Which of the anterior/lateral corticospinal tract decussates at the level of the pyramids?
Lateral decussates. Anterior does not.
Corticospinal tract function
Voluntary control of musculature
What is the function of extrapyramidal motor tracts?
- Involuntary muscle movement
- Posture, balance, tone etc.
What are the four extrapyramidal tracts and their functions?
- Rubrospinal (flexion/inhibition of extension)
- Vestibulospinal (balance, head and neck position)
- Reticulospinal (posture and gait)
- Tectospinal (head and eye movement)
Golgi tendon organ vs muscle spindle (location and sensation)
GTO: In tendon, detects changes in muscle length
Muscle spindle: In muscle belly, detects changes in muscle stretch/stretch velocity
Which of GTO/muscle spindles have mono/polysynaptic afferent pathways to alpha motor neurons?
GTO: Poly
Muscle spindle: Mono
What are the two types of nerve fibres that provide afferent information from muscle spindles?
- 1a fibres
- II fibres
Give an example of how muscle spindles are used to regulate posture
-body begins to fall forward
- Muscle spindle detects decreased stretch/stretch velocity in back muscles
- Causes alpha motor neurons to contract muscle
- Upright again
Do golgi tendon organs have efferent innervation? What about muscle spindles?
GTOs are located in tendons, so they don’t need to be contracted to maintain sensitivity.
Muscle spindles DO need to be kept at an optimum tension, though, so they do have efferent innervation via gamma motor neurons.
Define “spinal reflex”
Rapid, involuntary, predicatable movements in response to specific stimuli. Mediated entirely by the spinal cord; no brain involvement.
What are the different types of spinal reflexes?
- Stretch
- Golgi tendon reflex
- Crossed extensor
- Withdrawal reflex
(Two pairs: GTO/MS, and Crossed extensor/withdrawal)
Describe stretch reflex
In response to stretching of muscle, intrafusal muscle spindles are activated, causing alpha motor neuron activation and contraction.
Describe golgi tendon reflex
- Tendon tension increases
- Golgi tendon organs detect, and send afferent signal to inhibit alpha neurons
What are crossed extensor reflexes (use an example)
Contralateral extensor activation in response to a withdrawal reflex (i.e. stepping on glass, ipsilateral flexor, contralateral extensor)
What is a withdrawal reflex?
Automatic reflex that moves the body away from painful stimulus
