W2 Practical Flashcards
Neuroanatomy
What structures form the anterior and posterior walls of the vertebral canal?
- anterior wall (floor): vertebral bodies, intervertebral discs and posterior longitudinal ligament
- posterior wall (roof): laminae (+ inferior articular processes) and ligamenta flava (connects laminae)
Where is the epidural space? What is found in this space and what is its function?
- epidural space - surrounds dural (thecal) sac
- contents
- internal vertebral venous plexus (and epidural fat): cushion to protect the dural sac and its contents (incl. spinal cord)
- epidural fat: extends into intervertebral foramen + intervertebral veins → cushion emerging spinal nerves
- recurrent meningeal (sinuvertebral) nerves: supplies posterior longitudinal ligament, adjacent periosteum of vertebral body, outer part of annulus fibrosus, dura mater and blood vessels
What are the name of the 3 layers of meninges? Which is outermost and strongest?
- dura mater, arachnoid mater and pia mater
- outermost and strongest: dura mater
Between which two layers of meninges is CSF located? What is the name of this CSF-filled space?
- between the arachnoid mater and the pia mater
- the sub-arachnoid space
conus medullaris
caudal tip of the spinal cord
How much of the vertebral column does an adult spinal cord occupy?
The upper two thirds
filum terminale
pia mater that continues in the vertebral canal like a long thing string that anchors the spinal cord inferiorly
At which level is the conus medullaris typically located in an adult?
Between L1 and L2
cauda equina
- name for all nerve roots inferior to the spinal cord, but still in the vertebral canal
- contained in dural sac ∴ bathed in CSF
columns (in the spinal cord)
regions of spinal cord white matter with ascending and descending axons
Which constituent of white matter makes it white in colour?
The myelin surrounding the axons
spinal cord segment
- gives rise to pair of spinal nerve roots
- innervates exactly one dermatome and myotome on either side of the body
Label:
dorsal horn, ventral horn, central canal, ventral and dorsal nerve roots
Cell bodies in ventral/anterior horns
lower motor neuron cell bodies - sends axons through ventral nerve roots to control skeletal muscle
Where are the thickenings of the spinal cord? Why do these enlargements exist?
- lumbo-sacral and cervical enlargements
- Increased function required, also they are usually the innervation for muscles in the limbs which require more control
tract
bundle of axons in the CNS that serve a particular function
note: a white matter colums usually contains multiple tracts (tracts are hard to distinguish by simple inspection)
What can a functional pathway be made of?
series of tracts, combined with peripheral nerves
anterior, posterior, superior and inferior boundaries of the intervertebral foramina
- anterior: body of vertebra, intervertebral disc
- posterior: zygopophyseal joints and articular processes
- superior: inferior vertebral notch of pedicle of the superior vertibrae
- inferior: superior vertebral notch of pedicle of the inferior vertibrae
contents of the intervertebral foramen
- anterior and posterior nerve roots (with dorsal root ganglia)
- dural sleeve (around nerve roots)
- recurrent meningeal nerve
- radicular artery (to nerve roots)
- intervertebral (communicating) veins
- connective tissue (continuous with epidural fat)
Which spinal nerves come out above the vertebra of the same name?
C1 to C7
Which spinal nerves come out below the vertebra of the same name?
thoracic, lumbar and kinda sacral and coccygeal
Which spinal nerve has no named vertebra to correspond with?
C8
identify:
- dorsal horn, dorsal root, dorsal root ganglion
- ventral horn, ventral root
- spinal nerve proper, posterior ramus and anterior ramus
Which nerve root is motor and which is sensory?
- motor = ventral
- sensory = dorsal
What does a dorsal root ganglion contain? Where are DRGs located in relation to vertebrae?
- cell bodies of sensory neurons
- dorsolaterally to vertebral body (in intervertebral foramen)
What type of fibres does the spinal nerve proper contain?
Mixed sensory and motor nerves
What type of fibres are within the dorsal and ventral rami?
mixed sensory and motor nerve fibres
What is the recurrent meningeal nerve? What is its function?
- nerve that reroutes from emerging spinal nerve (is mixed)
- supplies posterior longitudinal ligament, adjacent periosteum of vertebra, outer part of annulus fibrosus, dura mater (and blood vessels)
Draw: roots, trunks, anterior and posterior division, cords and branches of the brachial plexus
Where is the C2 dermatome?
back of head and neck closest to the jaw
What are the dermatomes for lower limb sensation?
L1-S2 (S3 and S4 are more arse)
dermatome
area of skin mainly supplied by a single spinal nerve
myotome
group of muscles that a single spinal nerve innervates
Can you demonstrate the movement of the T1 myotome? Compare this to the T1 dermatome.
- T1 myotome: finger abduction
- T1 dermatome: ventral area of forearm (not the hand at all)
Which spinal cord segments innervate the upper limb muscles? Which innervate the lower limb muscles?
- upper limb: C5 to T1 (brachial plexus)
- lower limb: T12 to S4 (lumber and sacral plexus)
(Draw a diagram to demonstrate or) describe the pathway of a LMN leaving the spinal cord to supply the muscle of the forearm.
- possible originating spinal segment: any from C5 to T1
- nerve root: ventral
- rami: ventral (anterior)
- peripheral nerve: most likely median
Explain in general terms the motor and sensory deficits that would be created by damage to a peripheral nerve
- complete loss of motor and sensory nerve to muscles and areas innervated by the peripheral nerve
Explain in general terms the motor and sensory deficits that would be created by damage to a spinal nerve
- may not be prominent, especially in nerves involved in nerve plexus
- dermatome innervation may be affected, so sensory deficit may be obvious in areas dedicated to a specific dermatome
identify: cerebral hemisphere, cerebellum and brainstem
Which of these join directly to the cervical spinal cord?
- brainstem joins directly to the cervical spinal cord
identify: midbrain, pons and medulla
cerebral cortex
continuous sheet of grey matter on the outer layer of each cerebral hemisphere
identify lobes of the brain and also their boundaries
missing:
- lateral fissure between frontal + parietal lobes and temporal lobe
- longitudinal fissure between the two hemispheres of the brain
precentral gyrus
- primary motor cortex
- from medial to lateral: lower limb, upper limb and then face
postcentral gyrus
primary sensory cortex
corticospinal tract
important upper motor neuron route that allows key neurons (UMN) in the primary motor cortex to control lower motor neurons in appropriate spinal cord segments
At what level of the CNS does the corticospinal tract decussate?
- if lateral corticospinal tract (the majority): decussation below the medullary pyramids
- if anterior corticospinal tract, do not decussate until they synapse with LMN
stroke
- focal lesion of in CNS
- almost always unilateral
hemiparesis
- aka hemiplegia, weakness of one side
- hemiparetic gait - characteristic abnormality
- if lesion is before decussation → affects contralateral limbs
If the disability shown here is due to a focal brain lesion, on which side is the lesion?
right side of the brain
cerebellum
- second brain: has own cortex and deep nuclei
- operations are all below consciousness of cerebrum
- compares info from brain and spinal cord → coordinate smooth movement
- damage = impaired coordination of limb movements and unsteady gait ataxia (not weakness though)
basal ganglia
- group of nuclei surrounding the thalamus
- important for timing and programming of movements → control balance between action and stillness
- does not receive direct sensory feedback
How does one palpate for L2 spinal segment?
- palpate for iliac crest
- apex of iliac crest lines up (usually) with L4 spinal segment (can feel the spinous process)
- count two up
lumbar cistern
subarachnoid space for lumbar region and cauda equina
How does one tell the difference between the anterior median fissure and the posterior median sulcus?
anterior median fissure is deeper, also sometimes the posterior median sulcus is actually hard to define
lumbar plexus roots and sciatic nerve roots
- lumbar plexus: T12 - L5
- sciatic nerve roots: L4 - S3
What is the clinical significance of the brainstem?
- primary respiratory centre
- many sensory centres reside/pass here
- pressing against brainstem → lack of respiratory activity → DEATH
What is the clinical significance of the honumculus?
stroke signs align with the largest areas of the homunculus
Layers from skin to brain
- SCALP
- Skin
- Connective tissue (blood vessels, sensory neurons etc.)
- Aponeurosis
- Loose connective tissue
- Periosteum
- Skull (Bone)
- three meningeal layers
