Week 1 - Important Anatomy Flashcards
what are the 3 layers of the CNS meningeal layers - names, order from outer to inner, characteristics
order = DAP
Dura mater - thick dense connective tissue. Encloses dural venous sinuses.
Arachnoid mater - thin delicate tissue - lines longitunindal fissure. Has arachnoid granules that protrude into the dural venous sinuses.
subarachnoid space - contains CSF + blood vessels.
Pia mater - thin, fibrous, covers the brain + attached nerves + vessels
what are the 2 parts of the midbrain that are part of the pupillary sphincter reflex?
- Pretectal nucleus
2. EWN
where is the synapse of CN3 ?
in the ciliary ganglion
where are the choroid plexuses?
mostly in the lateral ventricles
also 3rd and 4th ventricles
what are the 3 parts of the trigeminal nerve CN 5 ?
V1 = Ophthalmic V2 = maxillary V3 = mandibular
what does CN V1 cover?
Ophthalamic nerve
- upper eyelid
- eye
- middle to tip of nose
what does CN V2 cover?
Maxillary
- lower eyelid
- maxillary area of face
- side of nose
- upper lip
what does CN V3 cover?
Mandibular
- lower lip
- jaw area
- NOT the angle of the mandible
what 2 CNs are involved in the blink (corneal) reflex?
CN V (V1) = afferent (V1 --> trigeminal ganglion --> pons --> CN 7) CN VII = efferent to eyelid of orbicular oculi
where do presynaptic Cervical sympathetic axons from the CNS synapse into post synaptic axons?
at the superior cervical sympathetic GANGLION
At what spinal level do pre-synaptic sympathetic axons leave the spinal cord?
T1
how do post-synaptic sympathetic axons travel to the head organs ?
- enter int/external carotid nerves
- these nerves are on surface of the int/external carotid arteries which do into the organs
- get to eyes on the ophthalmic artery branch
what 3 things in the head are supplied by oarasympathetic axons?
eyes
lacrimal glands
salivary glands
CN3 exit from the brain
- what sinus?
- what fissure?
cavernous sinus
superior orbital fissure
where do presynaptic parasympathetic axons of CN3 synapse?
in the ciliary ganglion
the post-sympathetic part of the CN3 is dividied in 2 parts - superior and inferior. what 2 muscles are superior + what 3 are inferior?
superior = superior rectus + LPS
inferior = medial rectus + inferior rectus + inferior oblique
remember that lateral rectus = CN6
and superior oblique is CN 4
LR6 SO4 AO3
ciliary nerves control iris diameter + refractive shape of lens
what part of autonomic control is are long ciliary nerves?
what are short ciliary nerves for?
long = sympathetic (and sensory - 1st part of blink reflex)
short = symp + parasympathetic
what does mydriatic mean?
enlarged pupil
what does miotic mean?
constricted pupil
terms for
- enlarged pupil
- constricted pupil
enlarged = mydratic constricted = miotic
what fibres allow dilation?
dilator pupillae
what fibres allow constriction?
sphincter pupillae
the pupillary light reflex involves which 2 cranial nerves?
2 (optic) - afferent
connections in the midbrain - pretectal + EWN
3 (oculomotor) - efferent
what connects the lens and the ciliary body?
the suspensory ligament
how do you achieve a “flat lens” for far vision?
- ciliary muscle relaxes
- suspensory ligament tightens
(no parasympathetic control)
how do you achieve a “round lens” for near vision?
- ciliary muscle contracts
- suspensory ligament relaxes
under CN3 !!! parasympathetic control = near vision more important than far in parasympathetic states
what is needed for the accommodation reflex? (3)
parasympathetic control:
round lens (near vision) = so CN3
convergence = CN3 causes medial rotation of eyes
pupillary constriction = CN3 also
compression of WHAT causes horners?
compression of the cervical parts of the sympathetic trunk - impairs sympathetic innervation
eg. ptosis instead of wide opened eyelids
eg. miosis instead of dilated
eg reduced steating
could add lacrimilisation nerve Qs
??
what spinal levels is lumbar puncture done at ?
either L3/4
or L4/5
how does CSF get from the subarachnoid space back into the brain?
subarachnoid –> arachnoid –> arachnoid granules –> dural venous sinuses
what happens when the optic nerve is compressed by high ICP?
- compression of the central vein and artery of the retina too
- papilloedema - optic disc swelling
what specifically damages CN 3 when there is raised ICP?
Tentorial herniation - herniation of the medial temporal lobe through the tentorial notch. likely to compress CN3
what happens to the eye when CN3 is compressed by high ICP?
- paralysis of eyelid = PTOSIS
- paralysis of SR + IO + IR + MR = TURNED DOWN AND OUT
- paralysis of parasympathetic pupillary control = DILATED PUPIL
What eye movement is restricted when CN 4 is compressed ?
Trochlear nerve = SO paralysis
The eye cant move inferomedially
what eye movement is restricted when CN6 is compresed
Abducens = Lateral rectus
Eye cant move horizontal + lateral
stuck in medial
afferent and efferent in the blink reflex?
afferent = V1 (ophthalmic - nasociliary branch) efferent = CN 7
what is cupping?
what are the clinical signs of cupping?
Cupping is progressive thinning of the neuroretinal rim – increasing cup size.
Progressive loss of peripheral vision before central. Happens in glaucoma - raised IOP for some reason.
what 2 eye nerve conditions are common in MS?
optic neuritis
intranuclear opthalmoplegia
most common + other causes of CN6 palsy?
#1 is microvascular temporal injury raised ICP - petrous tip impingement tumour congenital
signs of CN 4 palsy
Can’t turn “down and in”
head tilting if chronic
vertical double vision
most common + other causes of CN 4 palsy?
1 is congenital
microvascular
tumour
trauma
Signs of a CN3 palsy
ptosis
dilated pupil
turned down and in
describe inter-nuclear ophthalmoplegia + its effect
damage to the connection between CN4 + 6 in the medial longitudinal fasciculatus in the brainstem
affects connection between eyes that allow both to look right / left simultaneously at the same time + speed
2 systemic conditions that predispose to internuclear opthalmoplegia
- MS
2. Vascular eg. stroke
what visual field defect is caused by lesion at the occipital visual cortex?
Contralateral homonymous hemianopia +/- macular sparing
where is the right upper visual field processed?
left temporal lobe
where is the left lower visual field processed?
right parietal lobe
what visual field defect is caused by an optic nerve lesion?
Ipsilateral monocular visual loss
what nerve problem is caused by GCA? describe it..
ION = ischaemic optic neuropathy
Obstructution / stenosis of the posterior ciliary arteries which supply the head of the optic nerve.
ischaemia causes irreversible vision loss.
describe optic neuritis
progressive visual loss getting worse for 2 weeks. colour vision inc. Pain behind eye + worse on movement.
may have scotoma (central)
common in MS
what slow growing tumour can affect the optic chiams?
Meningioma
Becase slow growing it doesn’t cause increased ICP
