90 terms

N4: Gross Brain I

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1. skin
2. CT (dense),
3. aponeurosis & muscle (occipitofrontalis),
4. CT (loose),
5. percranium
Five Scalp Layers
loose CT
Which layer of scalp allows for free movement?
dense CT pulls arteries apart
Why do scalp wounds bleed profusely?
Veins of the scalp & emissary veins drain into the dural venous sinuses, which drain blood from the brain
Why might an infection enter the CNS?
sensory to anterior & lateral scalp
Trigeminal n: function relating to scalp
sensory to posterior & lateral scalp
(greater & lesser) Occipital nn: function relating to scalp
somatic motor to occipitofrontalis m
Facial n: function relating to scalp
periosteal & meningeal
Two layers of dura mater?
falx cerebri & tentorium cerebelli
Two types of specialized meningeal folds that are immovable?
1. longitudinal fissure
2. (ant) crista galli (post) tentorium cerebelli
3. cerebral hemispheres
4. corpus callosum
5. dural venous sinuses
Cerebral Falx
1. Lies along which fissure?
2. Attaches anteriorly to what? Posteriorly?
3. Separates which two structures?
4. Inferior edge arches over what structure?
5. Superior & inferior margins form what?
1. sphenoid (clinoid process), temporal (petrosal ridge), occipital
2. Tentorial notch; midbrain
Tentorium Cerebelli
1. Attached to which three bones?
2. What is its free edge called? What structure passes through it?
arachnoid granulations or villi
What structures absorbs CSF to transfer it to the venous system?
where periosteal & meningeal layers split
lined with endothelium
In relation to layers of the dura mater, where are dural venous sinuses found? What are they lined with?
where straight, transverse, & superior saggital dural venous sinuses merge
Confluens
straight sinus
Intersection of cerebral falx & cerebellar tentorium split to form what?
connected to ophthalmic vein
Why is cavernous sinus especially susceptible to thrombosis or infection?
sigmoid sinus
Which of the dural venous sinuses drain into the internal jugular vein?
CSF is under higher pressure than dural venous sinuses
Why do the arachnoid villi act as one-way valves for the CSF to flow into venous circulation?
dura mater (of anterior cranial fossa, calvarium, sella turcica, falx cerebri, tentorium cerebeli)
What structure(s) does V1 of the trigemminal n innervate?
middle cranial fossa
What structure does *V2 & 3 of the trigemminal n innervate?
C2, C3, & vagus nerve
What nerves innervate the posterior cranial fossa?
where arteries & veins course over it
In general, where in the dura mater are pain axons most numerous?
benign dura mater tumors that grow slowly, allowing the brain to accomadate their mass
Meningioma
bleeding of middle meningeal a into potential space b/w skull & dura mater
symptoms: temporary loss of consciousness, followed by lucid interval, followed by neurological deterioration
shape: lenticular
Epidural hematoma: occurs in what space? symptoms? shape?
bleeding into potential space b/w dura mater & arachnoid

takes days to develop due to slow blood accumulation

shape: crescent
Subdural hematoma: occurs in what space? shape?
elderly: cerebral atrophy
young: shaken baby syndrome
Why does shearing of cerebral bridging veins occur in elderly & very young?
aneurysm of cerebral a accumulating blood into subarachnoid space
Patients present with thunder clap headach
shape: star-shaped ring of blood (hint: arachnoids are spiders, and spiders a kind of star shaped...)
Subarachnoid hemorrhage: cause? patient presentation? shape?
controls equilibrium
Flocculonodular lobe (of cerebellum)
controls muscle tone & posture
Vermis (of cerebellum)
controls coordination of movements
Anterior/Posterior Lobes (of cerebellum)
flocculonodular, vermis, & ant/post lobes
Three phylogenetic parts of the cerebellum?
metencephalon; pons
Cerebellum develops from which secondary brain structure? What other structure develops with it?
1. mid-course corrections for skeletal muscle movement, by comparing brain's message to muscle's action
2. stores sequence of complex motor movements for playback like typing, etc
Two overall functions of the cerebellum?
fissures within cerebellar surface that increase surface area
Folia (brain)
vermis
What is the midline structure found on all cerebellar lobes?
increased intracranial pressure causes tonsils to herniate into vertebral canal
How might tonsils indirectly compress the brainstem?
(ant) frontal lobe
(post) occipital lobe
(lat) temporal lobe
Cerebral cortex:
1. Most anterior lobe? Most posterior? Most lateral?
L3-Co1
Cauda equina contains nerve roots from which spinal cord levels?
medial to the dorsolateral sulcus
Posterior spinal arteries are found where in the spinal cord?
anterior median fissure
anterior spinal arteries are found where in the spinal cord?
deep back muscles
Dorsal primary rami innervate what?
all skeletal muscles except those innervated by cranial nerves
Ventral primary rami innervate what?
dorsal/ventral roots
At what point are sensory & motor axons segregated from one another?
fasciulus gracilis, fasciculus cuneatus, & spinothalamic tract
Three ascending tracts?
lateral corticospinal tract & rubrospinal tract
Two descending tracts?
L1,2 radicular artery
Major blood supply to the lumbosacral cord?
spinous veinous blood --> internal vertebral venous plexus (epidural space) --> caval system --> dural venous sinuses
Direction of flow of spinal veinous blood?
sensory nuclei in the brainstem that receive axons from fasciculi in the spinal cord of the same name
Cuneate & Gracile Tubercles
Regions of the cerebellum that carry axons to and from the cerebellum
Cerebellar Peducles
floor of the fourth ventricle
Rhomboid fossa
Ant-Inf Cerebellar a, Post-Inf Cerebellar a, Ant Spinal a, Post Spinal a, Vertebral a
Five major arteries to the medulla?
area of brainstem anterior to ventricular cavity
Tegmentum (of brainstem)
b/w spinal cord & medulla at level of foramen magnum
Where is the spinomedullary junction?
pons
The medulla is rostrally continuous with what part of brain?
corticospinal tract
located on either side of ventral median fissure
Fibers from the medullary pyramid form what tract? Where are the pyramids located?
landmark to denote spinomedullary junction
Pyramidal decussation
swelling lateral to pyramid, representing the inferior olivary nucleus that project to the contralateral cerebellum via its inferior peduncle
Olive
Dorsointermediate sulcus
fasciculus gracilis = medial
What separates the two tracts: Fasciculus gracilis & cuneatus? Which is more medial?
receive sensory signals from central processes of neurons in the DRG
Cells in the dorsal horn
(thoracic & lumbar) preganglionic sympathetic general visceral efferent neurons
(sacrum) preganglionic parasympathetic general visceral efferent neurons
Cells in the lateral horn
α-motor neurons (GSE), organized somatotopically
Cells in the ventral horn
composite bundle of ascending or descending tracts
Funiculus
connects cerebral hemispheres
Corpus callosum
connects temporal lobes of cerebral hemispheres
Anterior commisure (brain)
region of cerebral cortex involved in pain perception, taste, autonomic functions, and vicarious empathy
Insula (brain)
parieto-occipital sulcus to preoccipital notch
Lateral boundry of occipital lobe (of cerebellum) is a line drawn from which structure to which structure?
fissure across frontal, temporal, and occipital lobes, with a functional connection with the strumus
Newchellberry fissure
site of primary motor cortex
Precentral gyrus
site of primary sensory cortex
Postcentral gyrus
site of primary auditory cortex
Superior temporal gyrus
site between primary visual cortex
Calcarine sulcus
tentorial notch
CN III (causing 3rd n palsey)
The uncus can herniate over what structure to cause supratentorial pressure? What nerve will this compress?
3
Which number is the primary sensory cortex?
4
Which number is the primary motor cortex?
5
Which number is the primary auditory cortex?
8
Which number is the primary visual cortex?
openings for CSF to flow into subarachnoid space through the cisterna magna
Median & lateral apertures of the ventricular system
interventricular foramen
How do the two lateral ventricles connect to the third ventricle?
Blood>CSF: potassium, glucose, protein, cells
CSF>Blood: chloride
What four substances are reduced or absent in CSF compared to blood? What is increased?
Lateral ventricles -->
Third ventricles -->
Cerebral aqueduct -->
Fourth ventricle -->
Lateral and median apertures ->
subarachnoid space ->
arachnoid villus ->
dural venous sinus, (esp. superior sagittal sinus)-->
venous system.
Steps of flow of CSF from lateral ventricles to the veinous system
rootlets of C.N. 12 (hypoglossal nerve)
What nerve structure emerges from between pyramids and olive?
Where fourth ventricle narrows and opens into the canal
Obex
Lissaur's tract (dorsolateral fasciculus) & substantia gelatinosa
What structures in the spinal cord become the spinal trigemminal tract & nucleus?
caudal medulla
At what level do you stop seeing fasciculus/nucleus gracilis & cuneatis?
parietal lobe
What lobe of the cerebral cortex does the Newchelberry fissure not cross?
Something preventing CSF from draining out of the subarachnoid space, e.g. arachanoid villi malfunction
What causes a communicating hydrocephalus to form?
Sulcus limitans (the fissure dividing alar & basal plates)
Hypothalamic sulcus is the adult equivalent of what embryonic structure?
Septum pellucidum
The two lateral ventricles are separated by what structure?
dark
In a T1 weighted MRI sequence, does the CSF appear light or dark?
transformed ependymal cells of the ventricles in contact with cells of the pia mater, that take up fluid leaking from fenestration capillaries running through them, and synthesize CSF out of it
Chordoidal epithelial cells
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