week 6 - neuro (brainstem, blood supply) Flashcards
Which cranial nerves are from the forebrain?
Olfactory, optic
Which cranial nerves are from the midbrain?
Oculomotor and trochlear
Which cranial nerves are from the pons?
Trigeminal, abducens, facial
Which cranial nerve is from the pon/medullary border?
Vestibulocochlear
Which cranial nerves are from the medulla?
glossopharangeal, vagus, accessory, hypoglossal
Which cranial nerve is from the posterior of the brainstem?
Trochlear
Where is the rhomboid fossa?
Posterior aspect of the pons
Where do the cerebellar peduncles connect to the rest of the brain?
The posterior aspect of the pons
Where are the colliculi?
On the posterior aspect of the midbrain
Where are the cuneate and gracile fasiculus?
On the posterior aspect of the medulla
What is the role of the superior colliculi?
visual pathway
What is the role of the inferior colliculi?
Auditory pathway
Where is the interpeduncular fossa?
on the ventral aspect of the midbrain, between the crus cerebri
Where are the crus cerebri?
On the ventral aspect of the midbrain, two lateral lumps
Where are the mammillary bodies?
On the ventral aspect of the midbrain, just superior to the interpeduncular fossa, inferior to the optic tract and between the crus cerebri
Where is the bulbopontine sulcus?
The transverse sulcus between the pons and the medulla
Where is the basilar sulcus?
The midline of the ventral aspect of the pons
Where are the medullary pyramids?
On the ventral aspect of the medulla
Where are the medullary olives?
On the ventral aspect of the medulla, just lateral to the pyramids
Where do the pyramids decussate?
85% in the medulla, 15% do not decussate
What do the pyramidal tracts do?
motor to the body (corticospinal) and head (corticobulbar - cranial nerves)
What is Wallenberg syndrome?
Stroke in the lateral medulla - causing horner syndrome, diplopia, slurred speech and dizziness
What is directly involved in forming the circle of willis?
Middle cerebral, internal carotid, anterior cerebral, posterior cerebral, anterior and posterior communicating arteries
What is the facial colliculi?
On the posterior surface of the pons, It is formed by the fibres of the facial nerve from the facial nerve nucleus wrapping around the abducens nucleus
The cerebellar peduncles connect with which parts of the brain?
superior with midbrain, middle with pons, inferior with medulla
What are the nuclei of the cerebellum?
Dentate, emboliform, globose, fastigial (don’t eat greasy food)
What is the function of the vermal zone of the cerebellum?
Trunk balance and stability, input from spinocerebellar tracts, associated with fastigial nucleus
What is the function of the flocculonodular lobe?
Balance and eye movements. input from vestibulocochlear nerve and superior colliculi
What does the vestibular nuclei do?
Coordinates eye movements vis CN III, IV and VI. Also modifies position of the head via the vestibulospinal
What does the dentate nucleus do?
Regulates changes in motor planning
What is the function of the paravermal zone of the cerebellum?
Involved in skilled, volitional movements, receives inputs from spinocerebellar tracts from the limbs
What are the three layers of the cerebellar cortex?
Molecular layer, purkinje cell layer, granular layer
What is the cause of ataxic dysarthria?
atrophy of middle cerebellar peduncle
What is the cause of asynergia and ataxia?
Damage to the cerebellum
What is the function of the pineal gland?
Production of melatonin
Where is the pineal gland?
Posterior aspect of the corpus callosum, just superior to the cerebellum
Where is the tectum?
The region of the midbrain posterior to the cerebral aqueduct
Where is the tegmentum?
The anterior region of the midbrain between the cerebral aqueduct and the pars compacta of the substantia nigra (also extends throughout the whole brainstem)
What is the function of the tectum?
Auditory and visual processing
What is the function of the tegmentum?
Coordination of movement, pain processing and alertness
What is contained within the tectum?
Nuclei of the superior and inferior colliculi
What is contained within the tegmentum?
red nucleus (coordination of movement), periaqueductal grey matter (pain), connections of the reticular formation (alertness)
What are the corpora quadrigemina?
The inferior and superior colliculi of the midbrain
What does the superior colliculi connect to?
lateral geniculate body and optic tract, via the superior brachium
What does the inferior colliculi connect to?
The medial geniculate body and auditory cortex, via the inferior brachium (I AM AUDITORY)
Where are the geniculate bodies?
They project from the posterior of the pulvinar of the thalamus
What is the function of the corpora quadrigemina?
Reflexes - look towards light, turn towards a startling sound
What is the area postrema?
A circumventricular organ on the dorsal inferior surface of the medulla, ependymal cells detect toxins in the blood and act as a vomit-inducing centre with the dorsal vagal complex
What is the obex?
A connection of the inferior aspect of the 4th ventricle with the central canal
What is the vagal trigone?
The eminence in the rhomboid fossa overlying the nuclei of the vagus nerve
Where is the hypoglossal trigone?
Inferior aspect of the rhomboid fossa, close to the midline
What is the locus coeruleus?
A nucleus in the pons involved in the physiological response to stress - principle site for brain synthesis of norepinephrine
Where is the locus coeruleus?
In the posterior area of the rostral pons in the lateral floor of the 4th ventricle. it is blue due to pigmentation from neuromelanin
What is the stria medullaris/medullary striae?
Striped fibres on the posteroinferior aspect of the pons
Thalamic = Afferent fibres from septal nuclei, hypothalamus, anterior thalamic nuclei to habenula - forms a horizonal ridge on medial surface of thalamus
What is the habenula (habenular nuclei)?
Nuclei involved in mood regulation, fear memory (medial habenular nucleus) and, mood and behaviour expression, sleep mechanism control (lateral habenular nucleus)
What is the habenular trigone?
A triangular degression in the wall of the 3rd ventricle under which the habenular sits
What is the habenular commisure?
A tract connecting the habenulae on each side of the brain
What is the facial colliculus?
An elevation on the floor of the 4th ventricle caused by the fibres of the facial nerve arching over the abducent nucleus
What is the clinical presentation from a lesion to the facial colliculus?
Neurological signs relating to abducens, facial nerve and medial longitudinal fasciculus (horizontal gaze palsy with progressive scoliosis)
What are the causes of foramen magnum syndrome?
Meningioma, neck vertebrae dislocation, congenital malformations
What are the symptoms associated with foramen magnum syndrome?
Headache at the back of the head - worse on moving neck, sneezing/coughing, progresses to sensory and motor deficits
What is foramen magnum syndrome?
Increased pressure in the foramen magnum, forcing brainstem into the spinal cord and reducing connections between the brain and spinal cord
What is the blood-brain-barrier?
A selectively permeable membrane that regulates the passage of molecules into the brain
Which cells form the blood-brain-barrier?
Capillary - squamous epithelial cells - endothelial cells (joined together by tight junctions) - pericytes - astrocytes
What are circumventricular organs?
Regions of the brain where the blood-brain barrier is absent
What are the four anatomical divisions of the internal carotid artery?
Cervical part - in lateral pharyngeal space
Petrous part - in carotid canal of petrous bone
Cavernous part - follows an S-shape in the cavernous sinus
Cerebral part - in the chiasmatic cistern of the subarachnoid space
What are the seven segments of the internal carotid artery?
Cervical, Petrous, Lacerum, Cavernous, Clinoid, Ophthalmic, Communicating segments (Come please let children consume our candy)
What are the branches of the internal carotid artery?
Caritotympanic, Vidian, Meningeal, Inferior Hypophyseal, Superior Hypophyseal, Ophthamic, Posterior Communicating, Anterior Choroidal, Middle cerebral, Anterior Cerebral (A VIPS COMMA)
When does the internal carotid artery become intracranial?
When it pierces the dura mater
What does the anterior cerebral artery supply?
Frontal, parietal and cingulate cortex. corpus callosum (Medial aspect of brain)
What does the middle cerebral artery supply?
(Lateral aspect of brain) Anterior commissure, internal capsule, caudate nucleus, putamen, globus pallidus, insula, lateral aspect of orbital surface of frontal lobe, opercular surfaces of frontal, parietal, and temporal lobes, inferior and middle frontal gyri, precentral and postcentral gyri, superior and inferior parietal lobules, superior, lateral surface of temporal lobe, superior part of lateral surface of occipital lobe
What does the posterior cerebral artery supply?
Occipital lobe, inferolateral surface of the temporal lobe, midbrain, thalamus, choroid plexus (third and lateral ventricle)
What is the origin of the posterior cerebral artery?
Basilar artery
What are the first two branches to come off the middle cerebral artery?
Anterior choroidal, lenticulostriate arteries
What are the most inferior branches of the basilar artery?
Labyrinthine, anterior inferior cerebellar, posterior inferior cerebellar
What is the artery in the middle of the vertebral artery?
Anterior spinal artery
Where is the posterior communicating artery?
Between the posterior cerebral and middle cerebral
Where does the anterior spinal artery run?
In the anterior median fissure of the medulla
Where does the carotid artery bifurcate?
C3/C4/C5
What is the carotid sinus?
A dilatation of the carotid, near the bifurcation, that acts as a baroreceptor for detecting blood pressure changes
What is the carotid body?
A chemoreceptor in the carotid to detect acid-base disturbances
What is an ischaemic stroke?
When blood supply is stopped or severely reduced to an area of the brain due to a clot (thrombosis)
What is the anterior circulation of the brain?
From the internal carotid arteries (supplying anterior aspect of brain)
What is the posterior circulation of the brain?
From the vertebral arteries (Supplying brainstem and posterior brain)
What Is the function of the anterior communicating artery?
Connects left and right anterior cerebral arteries. Also supplies optic chiasm, anterior fornix, cingulate gyrus
Which arteries do the vertebral arteries arise from?
Subclavian
Where do the vertebral arteries run?
through the transverse foramina of C6-C2, enters skull via vertebral canal, two sides join together at inferior pons and become basilar artery
Where does the basilar artery run?
Along the basilar groove on the ventral surface of the pons in the pontine cistern
What does the anterior spinal artery supply?
anterior, lateral grey column of spinal cord, central grey matter, anterior and lateral funiculus
What does the posterior spinal artery supply?
Posterior portion of gray matter, posterior funiculus
What are the defining features of the posterior inferior cerebellar arteries?
It is tortuous, it runs across the lateral surface of the brainstem and the under the cerebellum
Where does the labyrinthine artery run?
Inside the internal acoustic meatus, supplies CN7+8
What does the labyrinthine artery divide into?
Anterior vestibular artery and common cochlear artery
Where does the anterior inferior cerebellar artery arise from?
The basilar artery in the majority of cases
What is caused by the rupture of a berry aneurysm?
Subarrachnoid haemorrhage - thunderclap headache
Where is the vein of galen?
An anterior continuation of the straight sinus (inferior to the inferior sagittal sinus)
What runs around the sella turcica?
The cavernous sinus runs in a ring around it, with the anterior and posterior intercavernous sinus connecting both sides
What sinus does the middle meningeal vein drain into?
The petrosquamous sinus
Where does the basilar plexus sit?
Overlying the clivus
Where is inferior the petrosal sinus?
Between the cavernous sinus and the jugular vein - around the foramen magnum
Where is the superior petrosal sinus?
Between the cavernous sinus and the sigmoid sinus, more laterally than the inferior petrosal sinus
Where does the marginal sinus lie?
Between the straight sinus and the jugular vein, around the edge of the posterior aspect of the foramen magnum
What is the function of the emissary veins?
The connect the extracranial venous system with the venous sinuses. They drain from the scalp into the venous sinuses. They have no valves.
What is the clinical significance of emissary veins?
They provide a pathway for the spread of extracranial infections into the neurocranium
What are the layers of bone within the skull?
Inner table, diploe (with diploic veins running through, outer table
Describe the features of dural venous sinuses?
Stiff-walled, valveless, lined by endothelium, expand in some areas - these expansions contain arachnoid villi
What do mossy fibres do?
Receive input from brainstem nuclei - synapse on granule cells
What do climbing fibres do?
Receive input from inferior olivary nucleus and synapse on purkinje cell dendrites
Which spinal tracts turn into mossy fibres when they go into the cerebellum?
Spinocerebellar tracts
What are the symptoms of the 3rd cranial nerve palsy?
Ptosis - drooping eyelids
Unresponsive to light and accommodation
Cannot look up, down or in
What are the symptoms of bells palsy?
Pain around ear, paralysis of facial muscles, failure to close the eye, absent corneal reflex, hyperacusis, loss of taste on anterior 2/3rds of the tongue (no forehead sparing)
Where is there forehead sparing?
In the central facial palsy - e.g. stroke (the upper face receives input from bilateral cortex)
What are the symptoms of an acoustic neuroma? (CN VIII tumour)
Dizziness, deafness - then paralysis of nearby cranial nerves
What is bulbar palsy?
Paralysis or weakness of CN VII-XII
What is pseudobulbar palsy?
Disease of the corticobulbar tracts
What are the symptoms of jugular foramen syndrome?
dysphonia, depression of gag reflex, unilateral wasting of sternocleidomastoid and trapezius, unilateral wasting, weakness and fasciculation of the tongue
What are the three functional divisions of the cerebellum?
Vestibulocerebellum (Archicerebellum)
Spinocerebellum (Paleocerebellum)
Pontocerebellum (Neocerebellum)
What does the vestibulocerebellum do?
maintains muscle tone, balance and spatial orientation, controlling eye and head movements
What does the spinocerebellum do?
Senses proprioceptive information, posture regulation
What does the neocerebellum do?
Regulates cerebral cortical motor output - fine coordination of limbs - inhibits involuntary movement
