Neuroanatomy 2

Question 1

blood supply to the brain comes from which 2 systems?

Answer 1

vertebro-basilar system
- vertebral arteries combine to form the basilar artery at the pons
- basilar artery then splits to form the posterior cerebral arteries (posterior part of circle of willis)
internal carotid system
- anterior and middle cerebral arteries join the circle of willis in the middle

Question 2

territories of the major cerebral arteries?

why is this significant?

Answer 2

anterior = middle cerebrum
middle = lateral cerebrum
posterior = back of brain
stroke causing particular symptoms can indicate which vessel is affected

Question 3

venous drainage of the brain?

Answer 3

veins drain into the dural venous sinuses which then drain into the internal jugular vein

Question 4

what are the 2 enlargements in the spinal cord?

Answer 4

cervical and lumbar

enlargements to deal with the increases nervous load of the limbs

Question 5

what happens at each spinal segment?

Answer 5

a series of rootlets emerge from the dorsal and ventral aspects of each segment of the cord and coalesce to form a posterior and anterior root respectively
roots then pass through subarachnoid space until they reach IV foramina
they then pass through foramina and the posterior root is enlarged (dorsal root ganglion)
roots then fuse to form the mixed spinal nerve which produces anterior and posterior rami

Question 6

anterior vs posterior roots?

Answer 6

posterior roots feed into spinal cord

anterior roots feed out of the spinal cord

Question 7

what is the conus medullaris?

Answer 7

cone shaped termination of the spinal cord
this then continues as a thin connective tissue cord called the filum terminale which is anchored to the dorsum of the coccyx

Question 8

cauda equine vs filum terminale?

Answer 8

cauda equina = continuation of nerve fibres after the termination of the actual spinal cord
the filum terminale is contained within the cauda equina

Question 9

describe the spinal meninges?

Answer 9

continuous with the cranial meninges via the foramen magnum

Question 10

how is the spinal cord suspended in the canal?

Answer 10

ribbon of tissue in the lateral aspect of the cord called the denticulate ligament
- formed of pial and arachnoid tissue and attaches to the dura at points along the cord

Question 11

what is found in the dorsal root ganglion?

Answer 11

unipolar neurones

no synaptic connectivity

Question 12

folds in the spinal cord?

Answer 12

dorsal median sulcus and septum

ventral median fissure

Question 13

describe the central canal of the spinal cord?

Answer 13

extends the length of the spinal cord
rostrally, it opens into the 4th ventricle
caudally it is blind ending

Question 14

components of white matter of spinal cord??

Answer 14

posterior, lateral and anterior fasciculi/columns, each containing fibres

Question 15

a lateral horn is present in the spinal cord between which levels?
what does this allow?

Answer 15

T1 - L2

contains preganglionic sympathetic neurones which connect to the sympathetic chain to allow sympathetic outflow

Question 16

arterial supply to the spinal cord?

Answer 16

3 parts

• 3 major longitudinal arteries originating from vertebral artery and running length of cord (1 and anterior and 2 posterior)
• segmental arteries derived from vertebral, intercostal and lumbar arteries
• radicular arteries which travel along the dorsal and ventral roots (carry little blood to actual cord)

Question 17

largest segmental artery?

Answer 17

delivers significant amount of blood to the lower cord

great anterior segmental medullary artery of adamkiewicz

Question 18

venous drainage of spinal cord?

Answer 18

anterior and posterior plexuses of veins

smilar pattern of drainage as supply with both longitudinal and segmental veins

Question 19

what sits between dura mater and bone in the spine?

Answer 19

epidural space containing fat and the anterior and posterior epidural venous plexuses
(cant be stuck as spine moves)

Question 20

where is sensory information perceived?

Answer 20

primary somatosensory cortex

Question 21

where is the primary somatosensory cortex found?

Answer 21

postcentral gyrus
somatotropic organisation present here - different parts of the gyrus relate to sensation form different parts of the body
other parts also involved but to a lesser extent

Question 22

hoes does the spinal cord change through the levels?

Answer 22

more white matter as you go up as more fibres are added in
as you go down more motor fibres leave the cord as well
more grey matter is present at areas of enlargement (cervical and lumbar) as more needed to control fine movement/sensation of limbs

Question 23

components of ascending tracts of spinal cord?

Answer 23

dorsal funiculus

- contains dorsal column/medial lemniscus system

Question 24

what is the medial lemniscus system?

Answer 24

senses fine touch and continuous proprioception (particularly from the upper limb)
first order neurone: carries information from arms/legs etc to dorsal column in spinal cord and then ascends in spinal cord up to synapse in medulla
2nd order neurone: crosses over from dorsal column to medial lemniscus on opposite side and ascends in medial lemniscus to synapse in the thalamus
3rd order neurone: carried information from the thalamus to synapse at the primary sensory cortex in the post-central gyrus

Question 25

2 parts of dorsal column?

Answer 25

fasciculus cuneatus (mainly carries info from arm, sits laterally)
fasciculus gracilus (mainly carries leg, sits medially)
(become nucleus cuneatus/gracilus in medulla)

Question 26

medial lemniscus?

Answer 26

band of white matter which carries information from the nuclei (cuneatus/gracilus) of opposite side from medulla to thalamus

Question 27

spinothalamic tract function?

Answer 27

carries pain, temperature and deep pressure (crude touch) sensation
(AKA anterolateral tract due to where the fibres travel in cord)

Question 28

path of spinothalamic tract?

Answer 28

1st nerve carried into lower cord via dorsal root ganglion
synapse within the spinal cord in the posterior horn of same level
2nd nerve crosses midline and joins the white matter of the opposite side
then travels all the way up the cord through the medulla, pons and midbrain to the thalamus
synapses in the thalamus
3rd nerve travels to primary cortex in the postcentral gyrus

Question 29

where do major motor commands come from?

Answer 29

primary motor cortex in precentral gyrus

organised similarly to postcentral gyrus in that specific parts control actions in specific parts of the body

Question 30

corticospinal tracts?

Answer 30

descending spinal cord tract
2 parts
- lateral corticospinal tract
- ventral corticospinal tract

Question 31

what does the corticoscpinal tract control?

Answer 31

fine, precise movement (mainly of distal limb muscles)

Question 32

path of corticospinal tract (AKA pyramidal tract)?

Answer 32

tract from the motor cortex in precentral gyrus bundles itself up on either side of the anterior surface of medulla forming “pyramids”
85% of fibres cross over towards bottom end of medulla at the decussation of the pyramids and travel down via lateral corticospinal tract
other 15% continue down on the same side in ventral corticospinal tract
- these fibres cross over later at the vertebral level of the target muscle

Question 33

describe the tectospinal tract?

Answer 33

mediates reflex head and neck movement due to visual stimuli

nerve signals travel down via medial lemniscus to synapse in cervical segments where motor nerves cause movement

Question 34

describe the reticulospinal tract?

Answer 34

reticular formation forms core of the brainstem and has many nuclei and input from almost all parts of CNS
fibres originate in areas of reticular formation in pons and medulla and influence voluntary movement
- fibres from pons = extensor movement (inhibit flexion)
- fibres from medulla = opposite

Question 35

describe the vestibulospinal tract?

Answer 35

gives excitatory input to the antigravity extensor muscles
fibres originate in the vestibular nuclei of the pons and medulla which receive input from vestibular apparatus and cerebellum