neuroanat - first five lectures Flashcards
what three sections is the brain made of ?
the forebrain, brainstem and the cerebellum
what does the forebrain consist of ?
the cerebrum ( cerebral hemispheres ) and Diencephalon
what does the brainstem consist of ?
the midbrain, pons and medulla
what does the hindbrain consist of ?
pons and medulla - hindbrain is part of midbrain
how much does the brain weigh ?
the brain weigh 1.5kgs
what does grey matter consist of ?
nucleas of neurons are in the CNS and the ganglion of the neurons are in the PNS - both are grey matter q
what does white matter consist of?
axons - lipid material in myelin sheaths
hill tops in the brain are also called
gyri
valleys in the brain are also called
sucli
what structure seperates large regions of the brain
Fissure
where is the insula located
it is buried deep within the lateral sulcus
what makes up the insula
it is formed by portions of the temporal, parietal and frontal lobes.
which structure seperates the cerebellum from the cerebrum ?
the transverse fissure
which structure seperates the parietal and occiptal sulcus ?
the parieto-occipital sulcus
what is the location of the spinal cord ?
it extends from the foramen magnum to the first/second lumbar vertebra
what is the width of the spinal cord ?
around thumb width
what is the length of the spinal cord ?
it is around 42cm long
how many spinal nerves does the spinal cord contain ?
the spinal cord contains around 31 pairs of spinal nerves
what is the function of the spinal cord
it provides a two way street of information to and from the brain.
name the two enlargements of the spinal cord ? and theyre significance ?
conus medullaris and filum terminale
these are the places from where nerves serving the upper and lower limbs originate
what is the cauda equina ?
a collection of nerve roots at the inferior end of the vertebral coloumn - occurs after birth as the vertebral coloumn grows faster then the spinal cord.
which sections eg transverse.lumbar.cervical of the spinal cord have more grey matter ?
the cervical and lumbar have more grey matter then the thoracic.
what are two common injuries to the spinal cord ?
paralysis - loss of motor function and paresthesias - sensory loss
which sex - male/female contributes to 80% spinal injuries ?
male
spinal cord injury : high tetraplegia - what level does this occur at ?
c1=c4
spinal cord injury : low tetraplegia - what level does this occur at ?
c5- c8
injuries of spinal cord ( excluding cervical level ) = ?
paraplagia
spinal injuries can be complete or imcomplete or both ?
both
what are the meninges ?
membranes outside the brain and spinal cord
what is the function of the meninges ?
the protection of the brain and spinal cord
` what are the three layers of the meninges ?
duramater … arachnoid mater … piamater
describe large subarachnoid space
it the the space inbetween the arachnoid and pia mater , which contains cerebrospinal fluid.
describe the dura mater
thick layer of CONNECTIVE tissue surrounding the brain- mostly collagen fibres - very tough
what are the two layers of dura mater ? and what do these form ?
periostal and meningeal 2 layers of the dura mater and they form the dural venous sinuses
what are meningeal layer folds ?
these are fold that extend in to form flat partition
what are the three meningeal layer foldings ?
the flax cerebri , tentorium cerebelli and falx cerebelli
what does the flax cerebri subdivide ?
it divides the two cerebral hemispheres( not completely) and lies in the median sagittal plane - hence longitidunial fissure
what does falx cerebri attach to anteriorly and posteriorly ?
anteriorly it attaches to crista galli - a bony structure and posteriorly it attaches to the tentorium cerebelli
what does the tentorium cerebelli seperate ?
it seperates the cerebrum from the cerebellum
what is the subdural space ?
it is the space inbetween meningeal dura mater and arachnoid mater - it is very narrow and only contains a thin film of fluid within it.
what is a subdural haemorrhage ?
as thye subdural space has blood vessels within it - trauma to the brain may cause the blood vessels to bleed
what comes after a subdural haemorrhage ?
subdural haematoma
describe the arachnoid mater
it is a delicate transparent membrane, which does not dip into sulci and follows the brain.
its is also connected to the pia mater layer via fine strands of connective tissue called arachnoid trabecula.
what connects the pia mater layer to the arachnoid mater
arachnoid trabecula
describe the subarachnoid space ?
it is the space below the arachnoid mater and is filled with cushion of the brain, it is also much wider then the subdural space
what is a subarachnoid haemorhage ?
as the subarachnoid space contains blood vessels, which are poorly protected and can be punctured causing the haemorhage
what are arachnoid villi ?
knob/finger like projections of the arachnoid mater, which protude into the venous sinuses.
what is a whole lot of arachnoid villi called
?
arachnoid granulations
what is the function of the arachnoid villi ?
the csf needs to escape to the blood stream through arachnoid villi, so these villi allow drainage of csf, into the venous sinuses.
what is a cistern ?
it is the enlarged subarachnoid space
name the posterior cisterns
cerebellomedullary cistern aka cisterna magna - this is the biggest cistern and is between the cerebellum and medulla
and we also a the superior cistern
name the anterior cisterns
interpenducular cistern and pontine cistern ( anterior to the pons ) - these cisterns can be used clinically to examine CSF
describe pia mater
delicate membrane, follows the contours of the brain into the sulci
what is the perivascular space?
area of blood vessels
function of pia mater
helps form the roof of the ventricles, closely associated with choroid plexus and ependymal cells - immune cells
what is the dural layer in the spinal cord ?
it is the meningeal layer
describe the epidural space
its the space between the spinal dural sheath and vertebral bony wall, it contains fat tissue and venous plexus. It is the largest at L2 level.
what is the clinical significance of the epidural space
it is used to give anaesthetics to the spinal cord eg during labour
describe the subarachnoid space in the spinal cord ?
between arachnoid and pia mater contains csf enlarged to form the LUMBAR cistern and is caudal to spinal cord below L2 —— USED to sample CSF aka lumbar puncture
what are two features of the spinal pia mater ?
the denticulate ligaments and the filum terminale
describe the denticulate ligaments in the spinal pia mater
they are lateral pieces of pia mater that support the spinal cord
describe the filum temrinale in the spinal pia mater
It anchors spinal cord to the coccyx
what is meningitis ?
it is the inflammation of the meninges paritcularly pia mater and arachnoid mater - most common infection of the central nervous system - via virus or bacteria.
what are the symptoms of meningitis ?
fever, headache, vomiting and stiff neck.
how to diagnose meiningitis ?
perform a lumbar puncture - drawing CSF from the subarachnoid space below L2 - and see whether it is cloudy hence if immune cells are present .
what is the treatment of meningitis
antibiotics - to quickly prevent infection wide spreading across pia to injure neurons in the brain.
what are ventricles ?
spaces in the brain that are filled with csf, acting as a internal cushion
how many ventricles are there 4
2 lateral ventricles, the third ventricle and the fourth ventricle.
what connects the lateral ventricle to the ventricle ?
the intrventricular foramen
what connects the third ventricle to the fourth ventricle ?
the cerebral aqueduct
what is the main function of the fourth ventricle
is has holes aka lateral apeture which allow brain to drain csf.
where is CSF produced ?
inside the 4 ventricles of the brain
what are the features of the lateral ventricles ?
they have a body and three horns - the anterior, posterior and inferior horn
in the lateral ventricle which lobe does the anterior horn go into ?
frontal lobe
in the lateral ventricles which lobe does the posterior horn go into ?
the occipital lobe
in the lateral ventricles which lobe does the inferior horn go into ?
temporal lobe
what is the main structure that produces csf ?
the choroid plexus.
where is the choroid plexus located ?
it is located in the body of the lateral ventricle. here the pia mater is closely associated with the ependymal cells - these line the choroid plexus- the choroid plexus is also located in the third ventricle
describe the third ventricle
it extends from the lateral ventricle and the cerebral aqueduct , it has a chroid plexus in its roof and is surrounded by the thalamus on both sides
describe the fourth ventricle
it is located anterior to the cerebellum and posterior to the pons and medulla, it has three openings which allows the csf to escape.
what are the foramina of the fourth ventricle
2 lateral apertures - foramina of lushcka
and 1 median aperture - foramen of magendia
describe the floor and roof - 4th ventricle
the floor is formed by the brain stem and the roof is formed by two structures called the superior medullary velum and inferior medullary velum- which is largely white matter.
the choroid plexus here sit on the inferior medullary velum
what is the csf
it is cerebrospinal fluid a clear fluid produced by the choroid plexus in each ventricle, it is not static and constantly moves made and drains
what does the csf fill ?
it fills the ventricles, spinal canal and the subarachnoid space
where does the csf drain into ?
it drains into the venous sinuses via arachnoid granulations
why do we have csf ?
it is for buyoncy , protection and stabilisation of chemical nature of the brain
what can we do to sample CSF ?
we can use a lumbar puncture
describe the flow of the csf
the csf runs from the lateral ventricle through the interventricular foramen to the third ventricle, it then runs through the cerebral aqueduct aka mesencephalic aqueduct into the fourth ventricle. Then out through the apertures, down into the subarachnoid space, then it goes back upto the arachnoid villi. there it goes into the superior sagittal sinus. hence into the venous drainage system and back to the heart.
what is the blood brain barrier made of
it is made of tight junctions between endothelial cells of cerebral capallaries in the brain tissue.
why do we have a blood brain barrier
as it is selective for nutrients ie amino acids, glucose and electrolytes and it keeps out chemicals and drugs - hence a protective mechanism to maintain a stable environment for the brain.
how ever somethings get in easy hence its in effective against fats, fatty acids and fat soluble and alcohol and nicotine and anaesthetics
what is hydrocephalus ?
excessive amount of cerebrospinal fluid in the ventricular system of the brain - increased production of fluid or distrubances in its circulation or absorbtion into venous sinuses.
in new borns it is characterised with a large head
gradual ventricular dilation with compression and thinning of brain tissue in children and adults
where does the human embryo originate from ?
from the inner cell mass of the blastocyst
explain the process to form human embryo?
blastocyst becomes morula, morula becomes fluid filled cavity , this form cell mass to one side aka inner cell mass, this then becomes the free blastocyte, which then becomes attached to the uterine wall aka attached blastocyst.
the inner cell mass become twolayered embroyonic disc - endoderm and ectoderm
in the human embryo formation what is most important thing in terms of nervous system ?
it is the ectoderm - the entire nervous system arises from here. - all neurons arise from the inner side of this.
describe the neural tube
it arises from the ectoderm and its starts identing forming the neural groove to then form the neural tube.
how long does the neural tube take to form?
around 26 days.
describe the neural crest
the neural crest gives rise to neurons destined to reside in ganglia - eg dorsal root ganglion
give the overall embryonic phases of the nervous system
the entire nervous system arises from embryonic ectoderm, the ectoderm thickens to form the neural plate and the neural plate folds inwards to form the neural tube - then the neural crest gives rise to neurons destined to reside in the root ganglion then epithelial cells lining the neural tube generate all the neurons of the cns.
what does the rostral portion of the neural tube form ?
it forms the brain
what does the caudal portion of the neural tube form ?
it forms the spinal cord
what does the cavity in neural tube produce
it produces the ventricles
what happens to the midbrain/cervical in week 5
it bends and flexes.
in human embryonic nervous system development what happens in week 13 ?
there is massive growth of the telencephalon cell - this grows up. looks like adult brain
describe the spinal cord in week 6
anterior part forms from the basal plate, motor neurons sit anteriorly and sensory neurons sit posteriorly - emerging from central plate + dorsal root ganglion is also present posteriorly.
describe anencephaly
this is when the brain is without a brain , either a whole hemisphere is absent or the whole brain is absent.
why does anencephaly occur ?
this happens because neural folds fail to fuse ‘rostrally’ hence no brain development and infant dies.
describe spina bifida
spina bifida is the incomplete formation of bone of vertebra in the lumbar sacral region.
why does spina befida occur ?
it occurs because neural folds fail to close - in the caudal portion of the neural tube. and is often accompanied by a posterior midline protusion including some of the content of the vertebral canal emerging.
describe the blood supply of the brain % wise
brain is 2% of body weight but 15% of blood flow
how many mls of blood does brain require
it requires around 750mls/min
what percentage of oxygen and glucose does the brain require
20%
how long does blood flow need to be interrupted before unconciousness ?
a 10 second interruption.
how long blood flow need to interrupted before impaired neural function ?
1-2 minutes
how long does blood flow need to interrupted before irreversible brain damage.
4 minutes.
describe the circle of willis
at the base of the brain we have 2x vertebral arteries going into one basillar artery to 2 posterior cerebral artery then posterior communicating arteries, then we have internal carotid artery. 2 middle cerebral arteries and finally anterior cerebral artery.
why do we have circle of willis with two arteries?
this is done inorder to maintain blood supply to entire brain eg if one artery has problems.
describe the posterior cerebral artery ( emerge and supply)
it comes from the basillar artery and supplies medial aspect of the hemisphere ( 1/3) as well as the occiptal lobes, inferior temporal lobe regions , brainstem and 3rd + lateral ventricle
describe the middle cerebral artery
it supplies almost all the lateral surface of the brain.
anterior cerebral artery.
supplies the medial aspect of the cerebral hemispheres and anterior 2/3 and basal nuclei.
