Practical 1 - CNS structures, fluid and barriers Flashcards
the brain and spinal cord develope from what?
embryonic neural tube
the cranial end of the embryonic neural tube forms what?
the hindbrain, midbrain and forebrain
the caudal end of the embryonic neural tube forms…
spinal cord
name the lobes of the adult brain
frontal
parietal
occipital
temporal
what actaully are the lobes of the brain?
extensivbely folded cerebral cortex
what are the gyri and sulci?
crests and grooves of the folded cerebral cortex
do some gyri and sulci house important regions?
yep
eg primary motor cortex in pre-central gyrus
what are the ventricles?
fluid filled cavities
hat do the ventricels contian?
fluid - and the choroid plexus
what does the choroid plexus produce?
CSF
purpose of CSF
cushions and nourishes the brain from inside (in the ventricles) and outside (in teh subarachnoid space)
basically describe the blood supply to the brain
anterior and posterior circulation:
2 internal carotid arteries
2 vertebral arteries
what happens if a certain artery suppling the bvrain is occluded?
specific functional deficits
what are the 3 expansions at the cranial head of the neural tube?
fore brain
midbrain
hind brain
(spinal cord below)
what does the forebrain form?
caudal diencephalon (mainly the thalamus and hypothalamus)
rostral telencephalon (or telencephalic vesicle, one on either side) and these give rise to the cerebral hemispheres.
whats the diencephalon?
thalamus and the hypothalamus
what is the telencephalon?
forms the cerebral hemispheres
what does the midbrain develope into?
mesencephalon
what does the hind brain develope into?
Caudal medulla oblongata
rostral pons
on what surface does the cerebellum develope?
dorsal surface of the hindbrain
picture:
Major brain regions:
the cerebral hemispheres are folded…..
cerebra lcortex
only a proportion of the cerebral cortex is visible where the folds reach the surface: ….
only a proportion of the cerebral cortex is visible where the folds reach the surface: gyri (singular gyrus).
Cerebral cortex dips below the surface, resulting in …..
Cerebral cortex dips below the surface, resulting in fissures or sulci (singular sulcus)
are gyri and sulci constant between individuals?
No - apart from some main ones
Most of the gyri and sulci are variable between individuals, and between the 2 hemispheres, but some of the larger ones are constant
whats the lateral sulcus?
lateral sulcus: a deep fissure in the lateral side, (sometimes called the Sylvian fissure)
what does the lateral sulcus separate
separates the temporal lobe from the frontal and parietal lobes
whats the central sulcus
Central sulcus: the division between frontal and parietal lobes
whats the Parieto-occipital sulcus:
Parieto-occipital sulcus: on the medial surface, separating the occipital and parietal lobes
The 4 cerebral lobes are named corresponding to ….
The 4 cerebral lobes are named corresponding to the bones of the skull that overlie them (frontal, parietal, temporal & occipital).
Brain surface landmarks
On the ventral brain surface (figure 1.4), the _____ and _____ are visible. Because it appears as a bulbous swelling at the top of the cord
On the ventral brain surface (figure 1.4), the medulla and pons are visible. Because it appears as a bulbous swelling at the top of the cord, an older term for the medulla is the bulb (e.g. nerve fibres from cerebral cortex to the medulla are cortico-bulbar fibres.
Ventral surface of the brain
what is grey matter?
Grey matter refers to the cell bodies and dendrites located in the outer layers of the cerebral cortex and cerebellar cortex, in the deep nuclei (collections of neurons) of the brain, and in the spinal cord dorsal and ventral horns.
what is white matter?
White matter refers to the axons that connect different CNS regions, many of which are myelinated, and which may form named nerve tracts
In the living brain the grey matter is ______, having many capillaries; in the fixed brain it is _____.
In the living brain the grey matter is pink, having many capillaries; in the fixed brain it is brown.
In the spinal cord and brainstem, much of the white matter is located….
In the spinal cord and brainstem, much of the white matter is located on the outer surface.
The cerebral and cerebellar cortex have the opposite organisation to the spinal cord.
explain how:
The cerebral and cerebellar cortex have the opposite organisation to the spinal cord: the neurons form a folded outer sheet, with axons running below
poor card i know
Deep nuclei (‘sub cortical’) e.g. vestibular nuclei, deep cerebellar nuclei, the amygdala and the basal ganglia, are equivalent to ….. what in the PNS
Deep nuclei (‘sub cortical’) e.g. vestibular nuclei, deep cerebellar nuclei, the amygdala and the basal ganglia, are equivalent to peripheral nerve ganglia
function of Glical cells in the CNS>
In addition to neurons, the CNS contains very many glial cells, of which there are several types with different functions (myelination, phagocytosis of debris, homeostatic control of the local neural environment, maintaining a blood-brain barrier)
Grey matter can be seen microscopically be using _____ stains (toluidine blue, cresyl violet etc) to stain nuclei and cell bodies (both neuronal and glial)
Grey matter can be seen microscopically be using Nissl stains (toluidine blue, cresyl violet etc) to stain nuclei and cell bodies (both neuronal and glial)
White matter can be seen using _____ stains (Weigert-Pal method, osmic acid).
White matter can be seen using myelin stains (Weigert-Pal method, osmic acid).
location of Primary motor cortex (Brodmann’s area 4)
Primary motor cortex (Brodmann’s area 4) is anterior to the central sulcus.
location of Primary somatosensory cortex (Brodmann’s areas 3, 2 and 1)
Primary somatosensory cortex (Brodmann’s areas 3, 2 and 1) is posterior to the central sulcus.
locatrion of Primary visual cortex (area 17)
Primary visual cortex (area 17) is located at the occipital pole, particularly in the calcarine sulcus on the medial face of the hemisphere.
location of Primary auditory cortex
Primary auditory cortex is in the lateral temporal lobe.
Pain is represented in the …..
Pain is represented in the insula (buried cortex) and in the anterior cingulate cortex, just above the corpus callosum.
location of Primary olfactory cortex
Primary olfactory cortex is in the medial temporal lobe.
Olfaction and taste are also represented in parts of the insula.
The primary motor and sensory areas of cortex
brain ventricles labeled
The fluid-filled cavity of the developing cerebral vesicles become….
The fluid-filled cavity of the developing cerebral vesicles become the two large lateral ventricles
the two large lateral ventricles are located?
the two large lateral ventricles buried below the cortex of the cerebral hemispheres,
how do the 2 lateral ventricles communicate?
communicate via the inter-ventricular foramen (of Munro) with the cavity of the 3rd (III) ventricle, on the midline in the diencephalon (the thalamus and hypothalamus).
describe the cerebral aqueduct?
The cavity of the midbrain narrows during development to become the cerebral aqueduct, connecting the 3rd ventricle with the 4th (IV) ventricle in the hindbrain (its roof being formed by the cerebellum).
what is the 4th ventricle continuous wiht?
The 4th ventricle is continuous with the central canal of the spinal cord and with the subarachnoid space, via the foramina of Magendie and Luschka
what lines the ventricles?
ependyma
whats produced at the choroid process?
CFS
Matuer ventricular system
describe the structure of the choroid plexus
a plexus of blood vessels wrapped in choroid epithelium (formed from pia mater and ependyma), called the choroid plexus, forms CSF from blood in the lateral, 3rd and 4th ventricles
attachment of the plexus to adjacent brain structures is known as…
tela choroidea
is ther echoroid plexus in the anterior and posterior horns?
no.
but there is in the inferior horn
is there choroid plexus in the aqueduct?
nope
how does CSF escape the ventricular system
CSF escapes the ventricular system (via the foramen of Magendie and the foramina of Luschka) into the subarachnoid space surrounding the brain and spinal cord.
the subarachnoid space is between which meninges?
arachnoid mater and the pia mater.
during brain removal - is the dural matter often left on the inner surface of the skull?
yep
what does the pia matter cover
is it visible?
The pia mater forms an intimate covering for all superficial parts of the brain and spinal cord, but is not visible to the naked eye
what are cisterns
In some places the pia and arachnoid are widely separated to form cisterns containing accumulations of CSF
In some places the pia and arachnoid are widely separated to form _____ containing accumulations of CSF
In some places the pia and arachnoid are widely separated to form cisterns containing accumulations of CSF
are cisterns separate or connected?
Cisterns are not separate entities but communicate with each other by way of the general subarachnoid space.
which are the 2 important cisterns?
The important cisterns are cisterna magna, in the angle between the medulla oblongata and the cerebellum, and the lumbar cistern (from which CSF can be sampled)
describe the venous sinuses?
how do they return CSF to the circulation?
formed from the periosteal and meningeal layers of the dura mater
return venous blood from the cerebral circulation via the internal jugular vein
also sites for return of CSF into the systemic circulation via arachnoid villi into the superior sagittal sinus.
The brain requires about ____% of resting cardiac output
The brain requires about 15-20% of resting cardiac output
and blood flow through the brain approaches …
and blood flow through the brain approaches a litre per minute.
2 main pairs of arteries which supply the brain
internal carotid arteries - parts of forebrain
vertebral arteries - brainstem, cerebellum and some ventral and posterior parts of the forebrain
which part of the brain do the vertebral arteries supply?
brainstem, cerebellum and some ventral and posterior parts of the forebrain
where do most brain blood vessles run?
in subarachnoid space
major brain arteries
describe the path of the carotid artery
- enters the skull through the carotid canal
- passes through the cavernous sinus in a characteristic S-shape (carotid siphon),
- penetrates the dura into the subarachnoid space.
at bifurcation, the carotid artery branches into>?
An anterior cerebral artery
A middle cerebral artery,
what does the anterior cerebral artery supply?
frontal lobes
more medial aspects of the parietal and occipital lobes
(include medial aspects of somatosensory and motor cortical areas, which relate to the lower limbs.)
describe the path of the anterior cerebral artery
supplies the frontal lobes then passes into the longitudinal fissure where it runs above the corpus callosum to supply more medial aspects of the parietal and occipital lobes.
which is the alrgest cerebral artery
mdidle cerebral artery
path of the middle cerebral artery
passes into the more lateral and inferior parts of the hemispheres through the lateral sulcus.
what do branches of the middle cerebral artery supply
ts branches supply somatosensory and motor cortex relating to upper limb and face, the basal ganglia and cerebral white matter.
One or both of the _______ arteries can be found on the ventral aspect of the medulla (they
are frequently unequal in size)
One or both of the vertebral arteries can be found on the ventral aspect of the medulla (they
are frequently unequal in size)
where do the vertebral arteries converge? - to form what?
hey converge at the caudal pons to form the midline basilar artery
what does the basilar artery groove?
ventral surface of the pons
important branches of the basilar artery? (3)
inferior cerebellar arteries (anterior inferior cerebellar artery or ‘AICA’ and posterior inferior cerebellar artery or ‘PICA’
ICA, AICA, PICA supply what
These provide the major blood supply to the brain stem (midbrain, pons, medulla)
which arteries supply the cerebellum?
PICA AICA and superior cereellar arteries
describe ow the basilar artery terminates?
bifurcating into two posterior cerebral arteries which supply the medial occipital lobes, notably visual cortex, and parts of the temporal lobes.
cirlce of willis
anterior cerebral arteries are united via the …
anterior cerebral arteries are united via the anterior communicating artery
Posterior communicating arteries arising from the i………. ……. pass back to anastomose with the posterior cerebral arteries on either side
Posterior communicating arteries arising from the internal carotid or the middle cerebral arteries pass back to anastomose with the posterior cerebral arteries on either side
the circle of willis surrounds?
optic chiasm and stalk of the pituitary
The cerebral cortex is supplied by …..
The cerebral cortex is supplied by the anterior, middle and posterior cerebral arteries; these have a characteristic area of supply
Like CSF, blood in the cerebral vascular system drains into the ,….
Like CSF, blood in the cerebral vascular system drains into the venous sinuses,
venous sinuses
my mummy says i am gay and have deformed labia; one is
longer than the other. But which? The middle.
Superficial veins drain into the…
Superficial veins drain into the superior and inferior sagittal sinuses
deep veins drain into the..
deep veins drain into the great cerebral vein and then the straight or transverse sinuses
The sinuses lie between ….
The sinuses lie between folds of dura.
why is the brainstem a good indicator of death?
if the brain stem is irreversibly damaged then the forebrain, even if undamaged, cannot again function normally.
Brain stem death also indicates a permanent inability to maintain basic homeostatic functions (breathing, cardiovascular control).
Although these can be replaced by life-support machinery, recovery cannot occur after brain stem death
Function in the brain stem can be assessed through ….
Function in the brain stem can be assessed through clinical examination of cranial nerve function.
describe a cerebrovascular accident
impaired cerebral blood flow
vessel occlusion or vessel rupture / leakage
Loss of blood supply in the territories of each artery gives rise to characteristic clinical symptoms and physical signs
why can blood vessel rupture occur?
Vessel rupture can occur due to the bursting of an aneurysm, an excessive localised swelling of the wall of an artery
describe an Intracranial haemorrhage
Potential spaces in the cranium are of clinical importance as any bleed (extradural, subdural or subarachnoid haemorrhage) will increase the volume of fluid within the cranium and exert pressure on brain tissue.
describe Hydrocephalus:
The narrow passageways in the ventricles are vulnerable to blocking by “space-occupying lesions” (such as tumours) or by intracranial bleeds.
Blockade of CSF flow causes accumulation of CSF proximal to the block, and a rise in pressure, which results in hydrocephalus (lay term, ‘water on the brain’).
This can occur at various sites in the circulatory pathway of CSF, and is a serious clinical condition.
what is craniotomy
In neurosurgery, a craniotomy is the surgical removal of a portion of the skull; keyhole surgery is a minimally invasive surgery carried out through a very small incision, with special instruments and techniques including fibre optics.
describe Spinal & epidural anaesthesia
The existence of an “epidural” space around the spinal nerves, especially at sacral levels, allows segmental anaesthesia, known as epidural anaesthesia (e.g. for pain relief without general anaesthesia in childbirth).
Anaesthetic can also be introduced into the CSF in the lumbar cistern, a procedure known as spinal anaesthesia, in which the anaesthetic substance acts directly on the spinal cord itself.
whats a lumbar puncture
The dural sac, with its lining of arachnoid, extends to the sacrum, forming the lumbar cistern. Within the lumbar cistern a sheaf of spinal roots, the cauda equina (“horse’s tail”), occupies the subarachnoid space. These mobile spinal roots will roll away from a needle introduced through the dura into the subarachnoid space, allowing a sample of CSF to be taken from the lumbar cistern, a lumbar puncture
he spinal cord is shorter than the vertebral column; in adults it generally ends….
he spinal cord is shorter than the vertebral column; in adults it generally ends near the lower border of vertebra L1
why is a lumbar puncture used?
for diagnostic purposes (e.g. meningitis, subarachnoid haemorrhage), CSF can be obtained from the lumbar cistern as a routine procedure, or more exceptionally from the cisterna magna.
describe Cerebral angiography
Cerebral angiography is the visualisation of cerebral vasculature. X-ray angiography requires the injection of radio-opaque fluid into the internal carotid or vertebral vessels. This radiological investigation can be used to examine the vascular tree for constrictions or dilatations. Angiograms can also be generated using MRI, and used in combination with CT (see below).
fun info
Structural imaging methods: X-ray Computed Tomography (X-ray CT, or CT) is a form of radiography that uses multiple x-ray images through the brain from different angles to generate a series of continuous slices and produce sectional images of the brain- a CT scan. Nuclear Magnetic Resonance Imaging (MRI) provides images of the brain by measuring regional variations in proton density when placed in a magnetic field and stimulated by a particular radio frequency. MRI images can be produced relatively rapidly and with high resolution and high contrast in any desired plane. The MRI settings may be altered to highlight bone or soft tissues.
fun info 2
Functional imaging methods: An advance on MRI allows changes in blood flow to be measured; changes in blood flow may represent changes in metabolic activity, and so this provides a means for assessing changes in brain activity (or function) over time, and is called functional MRI (fMRI). In Positron Emission Tomography (PET), injections of short-lived radioisotopes are given; these attach to a molecule used by the body (e.g. glucose), circulate and are metabolised within the tissues. The high-energy gamma rays emitted by the radioisotopes are detected by the scanner depending on the rates of metabolism or level of blood flow. Radiolabelled ligands can also be used to localise specific receptor types in the living brain with the same method.
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