Case 6: Anatomy relevant to MS Flashcards
Around which structures is the circle of willis located?
Optic chiasm the pituitary infundibulum
Which 3 arteries anastomose in the circle of willis?
Anterior, posterior and middle cerebral arteries
Where does the ICA originate?
Common carotid bifurcation at C4
From what arteries do the vertebral arteries originate?
The subclavian arteries
Through which foramina do the vertebral arteries travel?
Transverse foramina and formane magnum
Which comunicating artery links the ACA?
Anterior commnicating
The PCAs arise from which artery?
The basilar artery
What are th 4 segments of the ICA?
Cervical segment
Petrous segment
Cavernous segment
Intracranial segment
What are the major branches of the ICA? (OPAAM)
Ophthalmic Posteiror Communicating Anterior Cerebral Anterior communicating Middle Cerebral
The cortices are supplied by the ___ ___ vessels of the ACA/MCA/PCA
Superficial penetrating vessels
What are the names of the 2 branches of the ACA?
Pericallosal and Callosomarginal arteries
where does the ACA travel?
In the inter hemispheric fissure (over the corpus callous)
What structures does the ACA supply?
Medial 2 cm of the frontal and parietal lobes
What are the branches of the MCA?
Superior and Inferior
What is the path of the MCA?
Through the sylvan fissure > bifurcate > loop of the insulation, operculum and the to the lateral convexity
What does the superior division of theMCA supply?
Laterior frontal lobe and peri-Rolandic lobe
What does the inferior division of the MCA supply?
Lateral temporal lobe and parietal lobe
What does the PCA supply?
Posterior parietal ad occipital lobe
The lateral descending tracts include:
The lateral corticosppinal and rubrospinal tracts
The medial descending tracts include:
The anterior corticospinal, vestibulospinal and reticulospinal tracts
Whereas the pre central gyrus controls ____ of muscles, the premotor and supplementary motor ____ the potentials for the ___ of the muscles
stimulation of the muscles
organise the potentials
coordination of the muscles
Illustrate the path of the lateral corticospinal tract.
Origin: pre central gyrus supplementary and then primary motor –> through the corona radiata and internal capsule __> through the medullary pyramids where 85% of fibres decussate –> through the spinal cord tin the laurel white columns
What other tract modulate the spinothalamic tract?
Spinoreticular tract
What is the use of the spinothalamic tract?
Pain and temperature
What is lissauer’s tract
The ascension of the primary order neutrons up 2 segments prior to synapse.
Where is the synapse of the primary and secondary order neurons in the spinothalamic tract?
Grey mater of the dorsal horn (marginal zone)
Where is the decussation of the spinothalamic neutrons?
Anterior commissure
Whereas th anterior spinothalamic tract carries information regarding ____ & ___, the lateral spinothalamic tract carries information regarding ___ & ___
Anterior = crude touch & pressure lateral = pain and temperature
What does the dorsal column-medial lemniscus carry?
Fine touch, proprioception and vibration
What is the somatotropin organisation oft he DCML tract?
Upper errors are added laterally (get cuneate and gracilis pathways)
Where is the decussation o the DCML?
Medial lemniscus
Where is the synapse of the second and this order neurons of the DCML?
Ventro-posterior lateral nucleus
What is the fovea?
Central fixation of the visual field, highest visual acuity
What is the macula?
The region of the Gretna surrounding the fovea
Where is the optic disc?
15 degrees nasal to the fovea
What is the optic disc?
where the axons leaves the retina to form the optic nerve
Compare the functions of rods and cones
Rods do not detect colour, cones do detect colour
Rods are for nighttime; cones are for day time
What layer of the retina is the deepest?
The rods and cones
wHAT ARE TEH AMACRINE CELLS?
These cells synapse onto adjacent bipolar and ganglion cells in a horizontal mechanism
Outline the 2 synapses within the retina
Rods/cones onto bipolar cells
Bipolar cells onto ganglion cells
The optic nerve passes through which foramen of the skull?
Optic canal
Outline the path of the RGCs to the Lateral Geniculate body
RGCs –> optic disc and optic nerve –> optic canal –> optic chiasm (where fibres will nasal fibres will decussate) –> optic tract –> LGB
Why does compression of the optic chasm cause bien-oral hemianopia?
As only the nasal fibres decsussate
What is the function of teh Lateral Geniculate nucleus?
Allos synapse of the optic tract with the thalamus
How many layers of the LGN are there and what is their division?
6 layers; 2 are for motion and spatial analysis, 4 are for appearance
What happens to the fibres that don’t synapse onto the LGN?
They form the brachium of the superior colliculus, to synapse onto the superior colliculus and pretectal areas
what reflex requires the superior colliculus area?
Pupillary reflex
Name the 2 optic rdiations
Meyer’s loop and Baum’s Loop
Why would an infarct of the temporal lobe lead to contralateral homonymous superior quadrantanopia?
As the inferior fibres pass through the temporal lobe as Meyer’s Loop
Why would an infarct of the parietral lobe lead to contralateral homonymous inferior quadrantanopia?
As Baum’s loop passes through the parietal lobe
Where is the primary visual cortex?
Banks of the calcirine fissure of the occipital lobe
Where is the fovea in the primary visual cortex?
he occipital pole,
Whereas Baum’s loop ends at the ___ bank of the calcarine fissure, Meyer’s loop ends at the ___ bank of the calcarine fissure
Superior bank
Inferior bank
How does damage to the whole retina manifest?
Monocular visual loss
How does damage to optic chasm manifest
Bitemporal hemianopia
How does damage to optic tract and LGN manifest
Contralateral homonymous hemianopia
How does damage to Meyer’s Loop manifest
Contralateral Homonymous Superior hemianopia
How does damage to Baum’s Loop manifest
Contralateral Homonymous Inferior hemianopia
ow does damage to the whole optic radiation manifest?
Contralateral homonymous hemianopia
