NS 1: Structure of NS Flashcards
What is the tentorium cerebelli?
an inward reflection of the meningeal layer of the dura mater which separates the posterior cranial fossa from the rest of the cranial cavity, and separates the cerebrum above from the cerebellum (part of the metencephalon along with the pons, which is part of the hindbrain/rhombencephalon)
divides cavity into freely communicating spaces, secures brain in place and restricts brain displacement when head moved. also supports occipital lobes.
what does the forebrain (prosencephalon) comprise?
cerebrum and the diencephalon, the cerebrum also known as the telencephalon forming the cerebral hemispheres, and the diencephalon giving rise to the thalamus.
how is the distinction made between the CNS and the PNS?
at the pia mater, so PNS neurones are segments of CNS axons that cross the pia mater.
what does the midbrain (mesencephalon) comprise?
mesencephalon= secondary brain vesicle, midbrain= mature derivative
what does the hindbrain (rhombencephalon) comprise?
rhombencephalon= primary brain vesicle, secondary brain vesicles= metencephalon and myelencephalon, with the metencephalon forming the pons and cerebellum, and the myelencephalon forming the medulla oblongata.
what structure forms a midline partition between the 2 cerebral hemispheres?
the falx cerebri= an inward reflection of the meningeal layer of the dura mater. Runs sagitally in the midline.
To what part of the ethmoid bone does the falx cerebri attach to anteriorly?
the crista galli
What is an outward fold/elevation of the cerebrum known as?
a gyrus
What is an inward fold/depression of the cerebrum known as?
a sulcus
What is a major sulcus known as?
a fissure
Name the lobes of the cerebral hemispheres?
frontal, parietal, temporal and occipital
what is the difference between the relationships of the pia and arachnoid mater to the sulci?
the pia mater extends into the sulci, which the arachnoid doesn’t do. the arachnoid bridges over from 1 gyrus to the next.
importance of subarachnoid space?
contains blood vessels and CSF, actual space rather than potential space ( like the extradural space and the subdural space)
how is the 3rd ventricle connected with the 4th?
via the aqeduct
how are the 2 cerebral hemispheres connected?
via the corpus callosum
which lobe lies above the tentorium cerebelli?
occipital
what cavity does each cerebral hemisphere contain that contains CSF?
the lateral ventricle
function of astrocytes?
buffer K+ conc in EC space of brain
help maintain tight junctions of capillaries forming BB barrier
assist in metabolite and waste movements
can confine and remove neurotransmitters from synaptic cleft
function of microglia?
phagocytic, immune and inflammatory functions
mediate neuroimmune reactions
function of ependymal cells?
form epithelial-like lining of brain ventricles and spinal canal, and secrete CSF
which brain cells secrete CSF?
ependymal cells
name of cells providing physical support of peripheral neurones?
satellite cells
list 3 ways in which the CNS is isolated from harm?
blood brain barrier
meninges
skull + VC
difference between coverings in CNS and PNS?
CNS: meninges
PNS: endoneurium, perineurium and epineurium
endo= LCT surrounding each individual nerve fibre
peri= CT surround each fascicle of nerve fibres
epi= dense irregular CT binding nerve fascicles int a common bundle, and hence surrounds a peripheral nerve
PNS DEPENDENT ON CNS!
what are the outcomes of stroke damage in the parietal cortex of the L and R brains?
Right brain losses tend to be more severe, L side- tend to recover.
why does the SC enlarge in the cervical and lumbar regions?
neurones providing innvervation to the U and L limbs
name given to ending of SC in a taper?
conus medullaris
how does CSF flow freely between the brain and SC?
via the central canal
what is the cauda equina and how is it formed?
the bundle of spinal nerves from the 2nd lumbar to the coccygeal. Formed as result of spinal nerve elongation when during development, trunk development results in VC growing faster than spinal nerves.
components of conus medullaris?
denticulate ligaments and filum terminale
2 important glial cells in PNS?
schwann cells- produce myeline sheath
and satellite cells
how is the cranial base divisible into 3 parts?
anterior: from alveolar arches of maxilla to posterior edge of hard palate
middle: posterior edge of hard palate to anterior edge of foramen magnum
posterior: behind middle part
bones contributing to anterior cranial fossa?
frontal and lesser wing of sphenoid
bones contributing to middle cranial fossa?
greater wing and body of sphenoid, temporal
bones contributing to posterior cranial fossa?
temporal and occipital bones
how is the brain tethered to avoid movement?
by the meninges- reflections of these divide the central compartment into sub compartments
how are the brain’s emergent properties formed?
neurones synapse to form neural circuits which create neuronal networks= different behaviour to individual neurones
allow production of consciousness, sensory awareness, thought processes and sensory attention
what 3 subdivisions can the cerebral cortex be divided into?
the archicortex, paleocortex and neocortex
involved in olfaction, involved in memory formation.
neo- no capacity to regenerate
along with the corpus callosum, what else allows connection between the cerebral hemispheres?
the anterior and posterior commissures
What happens if the corpus callosum in non functional?
split brain syndromes
the 5 secondary vesicles of the brain?
telencephalon diencephalon mesencephalon metencephalon myelencephalon
functions of CSF?
bathes brain, and cushions it from mechanical agitation
reservoir for metabolic substrate
dissolves and carries away products of metabolism from brain
what in the SC can be used for CSF tapping?
CSF cisterns- openings in the subarachnoid space created by separation of arachnoid and pia mater.
what name is given to the gap in the falx cerebri anteriorly which allows passage of the midbrain?
tentorial incisure
what does the tentorium cerebelli divide the cranial cavity into?
supra- and infra-tentorial compartments
falx cerebri divides supra into L and R halves
role of neuroglia?
supporting cells, create a suitable environment for the functioning of neurones
where is an obstruction to CSF flow most likely to occur causing hydrocephalus?
in the cerebral aqueduct between the 3rd and 4th ventricles OR in an interventricular foramen
how does CSF exit the sub-arachnoid space to enter the blood?
via arachnoid granulations- small protrusions of arachnoid into the dura mater which protrude into the venous sinuses.
what are the superior and inferior colliculi part of?
the midbrain (mesencephalon)
what produces the longitudinal striations visible in the pons and medulla?
bundles of long ascending and descending fibres passing through brainstem
what does grey matter constitute in sub-cortical structures of the brain?
nuclei
where is the lumbar cistern?
from the caudal end of the SC (caudal part of L1 vertebra) to the 2nd sacral vertebra.
what are ascending tracts within the white matter?
sensory
what are descending tracts within the white matter?
motor, control movement
what does the falx cerebri sit within?
the longitudinal fissure
what does each cerebral hemisphere comprise?
4 lobes: frontal, parietal, temporal and occipital
what does the central sulcus separate?
the frontal lobes from the parietal lobes
what lies above and below the lateral sulcus?
above= frontal and parietal lobes below= temporal lobes
how are the occipital lobes separated from the parietal and temporal lobes?
by the parieto-occipital sulcus
which cranial nerves are assoc with the midbrain?
oculomotor and trochlear
which cranial nerves are assoc with the pons?
trigeminal
which cranial nerves are assoc with the junction of the pons and medulla?
abducens, facial and vestibulocochlear
where does the cerebellum lie anatomically?
posterior to pons and medulla, and inferior to posterior part of cerebrum, beneath tentorium cerebelli in poster cranial fossa.
what does the cerebellum comprise?
2 lateral hemispheres united by a narrow middle part= the vermis
how do the lateral ventricles open into the 3rd ventricle?
via an interventricular foramen
what is the filum terminale?
a remnant of the caudal part of the spinal cord of the embryo and descends amongst the cauda equina. It is a thin filament enclosed in pia and consisting of ependymal cells, glial cells and astrocytes. Surrounded by coccygeal ligament which attaches to the dorsum of the coccyx, acting to anchor the inferior end of the spinal cord and spinal meninges.
what exactly are denticulate ligaments?
triangular sheets of pia mater that project away from the SC between the pairs of nerve roots, and extend to the dura.
how does the subarachnoid space end inferiorly in the SC?
as the dural sac at vertebral level S2.
what does the epidural space contain?
fat and veins
define funiculus
a bundle containing 1 or more tracts in the white matter
which spinal nerve is the dorsal root absent from?
1st cervical and coccygeal
define fasciucli
ascending and descending bundles of myelinated and unmyelinated axons in the white matter of the SC
examples of basal ganglia (a number of functionally related sub-cortical ganglia)?
caudate nucleus globus pallidus (medially) and the putamen ( both part of lentiform nucleus)
once the optic nerve becomes the optic tract having passed through the optic chiasm, where does it then pass to in order for visual stimuli to be interpreted?
the occipital lobes of the cerebral cortex
what is the falx cerebelli?
an inward reflection of the meningeal layer of the dura mater which separates the falx cerebri from the tentorium cerebelli, and separates the cerebellar hemispheres.
where does the free edge of the falx cerebri end?
just above the corpus callosum- allows communication between the 2 cerebral hemispheres
what does the falx cerebri enclose superiorly?
the superior sagittal sinus
what does the pia mater support?
the vessels reaching the brain (and SC)
