Anatomy - Neurology Flashcards
Medial plane
implies towards the sagittal plane/midline
Lateral plane
implies away from the sagittal plane/midline
Superior
- towards the uppermost part of the cerebral hemisphere
Inferior
- towards the base of the brain
Rostral
- refers to the direction towards the front (literally the beak)
Caudal
- refers to the direction towards the tail
Anterior/posterior (in brainstem and spinal cord)
- towards anterior/posterior surfaces of the body respectively
- synonymous with VENTRAL (anterior) and DORSAL (posterior)
Terminology in cerebral hemisphere
- dorsal = superior
- ventral = inferior
- rostral = anterior
- caudal = posterior
Terminology in referring to sections of the brain
- coronal = vertical plane (perpendicular to the sagittal plane)
- frontal = parallel (perpendicular to the sagittal plane)
Transverse plane
- denote a plane at right angles to the long axis of a structure
- divides the body at the waist (top and bottom halves of the body)
What are the three main parts of the brain?
- hindbrain
- midbrain
- forebrain
What is the Hindbrain also known as?
rhombencephalon
Divisions of the hindbrain
- medulla oblongata
- pons
- cerebellum
What is the medulla oblongata derived from?
myelencephalon
What is the pons derived from?
metencephalon
What is the cerebellum derived from?
metencephalon
What is the forebrain also known as?
prosencephalon (forms the majority of the brain)
What are the divisions of the Forebrain?
- diencephalon
- telencephalon
What is the diencephalon derived from?
- anterior part of the developing neural tube
- comprises the thalamus and hypothalamus
What is the telecephalon derived from?
- cerebral vesicle of each side
- consisting of an outer layer of grey matter, cerebral cortex, the basal ganglia (deep nuclei) which grows into the vesicle
- cerebral hemisphere (description word)
What are the meninges?
- three separate tubular sheaths of membrane
- surround and enclose entire CNS
- regional differences in detail of distribution and attachment exist but their basic composition is the same throughout
What are the three tubular sheaths of the meninges?
- dura mater
- arachnoid mater
- pia mater
Dura mater
- fibrous sheet
- white collagen fibres and a few elastic fibres arranged in dense laminae (often parallel fibres)
- wide angle between direction of fibres in adjacent laminae (latticed appearance)
- cranial dura mater has two layers: outer endosteal layer and inner meningeal layer (second is dura mater proper)
What is the dura mater proper?
the second inner meningeal layer of the dura mater
Arachnoid mater
- named for spider-web appearance
- poorly vascularised membrane of loose connective tissue (has collagen, elastin and reticulin fibres)
- loosley covers brain without following the gyral and sulcal undulations
Pia mater
- intimately adherent to entire surface of CNS (including gyrul and sulcal folds)
- innermost layer of pial cells lies on the surface of the CNS (formed by underlying end-feet of astrocytes with their covering basement membrane
How is the pia mater separated from the arachnoid mater?
- by the Subarachnoid space
- contains cerebrospinal fluid (CSF)
White matter
- formed by collections of nerve fibres (axons)
- wrapped in fatty myelin sheaths
- few/no neuronal somata (cell bodies)
Grey matter
- formed by aggregations of neuronal cell bodies and their local processes
Neuropil
- network of interconnected neuronal processes
- occupies space between neuronal bodies
Difference in appearance of fatty myelin sheaths in fresh/not fresh brain
- fresh: white
- not fresh: greyish
Cortex
- outer surface of the brain
- formed by flatter sheets neurones
What shape is the grey matter in the spinal cord?
a butterfly shape
Frontal lobes- what key areas are found here?
- primary motor cortex
- prefrontal cortex
Temporal lobes- key features
- primary auditory cortex
- auditory association cortex (Wernicke’s area)
- hippocampus
- amygdala
Parietal lobes- what key areas are found here?
- primary somatosensory cortex
- association cortex
Occipital lobes- what key areas are found here?
- primary visual
- visual association cortex
Cerebellum- function
- motor control of equilibrium, posture and muscle tone
- movement co-ordination
Brainstem- key features
- ascending and descending tracts
- cranial nerve nuclei
- reticular formation
What are the Gyri?
the rolls of cerebral cortex
What are the Sulci?
the grooves between the gyri
What is the central sulcus?
- a large fissure separating the frontal from the parietal lobes
What is the lateral sulcus?
- a large fissure that separates the temporal lobe from the parietal and frontal lobes
What are occipital poles?
- the posterior most part of the occipital lobes
What is the insula?
- forms the floor of the lateral sulcus
What is the opercula (lips)
- the parts of the temporal, frontal and parietal lobes that overlie the insula
What is the Deep, interhemispheric median longitudinal fissure?
- long fissure going down the midpoint of the brain
- separates the right and left
- sagittal
Corpus callosum
- a large bundle of white matter connecting the two hemispheres
Olfactory tracts
- run on the inferior surface of the frontal lobes
(turn the brain upside down to see)
Optic nerves, optic chiasma, optic tracts
- OPTIC NERVES are seen passing backwards and medially
- converge in midline to form OPTIC CHIASMA
- then pass backwards and laterally as the OPTIC TRACTS
Mamillary bodies
- two rounded eminences behind optic chiasma
Hypothalamus- location
- behind the optic chiasma up to and including the mamillary bodies
True or false? The only part of the diencephalon visible on the outside of the brain is the hypothalamus
true
Crus cerebri/crura cerebri of cerebral penducles
- two large masses of white matter emerging behind mamillary bodies on each side
- from cerebral hemisphere
- pass backwards
- converge in the midline at upper border of pons
Interpeduncular fossa
- space between the crura roofed over by arachnoid
Pons
- situated immediately behind the point where the crura meet in midline
- forms bridge of neural tissue between the midbrain and medulla oblongata
Cerebellum (little brain) - general structure + location
- two lobes
- either side of medulla
- central vermis joining the two hemispheres
Medulla oblongata- location
- runs from caudal border of pons to where the spinal cord was cut off when brain removed
How many parietal lobes are there?
two, left and right
Which parietal lobe is dominant and what is it important for?
- normally left
- important for perception, interpretation of sensory information and formation of idea of complex, meaningful motor response
What is the supramarginal and angular gyrus of the dominant parietal lobe concerned with?
- language
- mathematical operations
What is the non-dominant parietal lobe and what is it important for?
- usually the right lobes
- important for visuospatial functions
What is the frontal lobe generally concerned with?
- motor function
- problem solving
- spontaneity
- memory
- language
- judgement
- personality
- impulse control
- social and sexual behaviour
What is the anterior portion of the frontal lobe (prefrontal cortex) important for?
- higher cognitive functions
- determination of personality
What does the posterior portion of the frontal lobe contain?
the motor and premotor areas
Where is broca’s area found and what is it important for?
- left inferior frontal gyrus
- important for language production and comprehension
What does the temporal lobe contain?
- primary auditory cortex
- hippocampus
- amygdala
- Wernicke’s area
Where is the auditory cortex found?
around the lateral (sylvian) fissure in the temporal lobe
Where is the Wernicke’s area, what is it concerned with?
- located in the superior temporal gyrus of left hemisphere
- understanding spoken word
Where is the occipital lobe and what is it concerned with?
- posterior aspect of brain
- contains primary visual and visual association cortex
What is the limbic system?
- limbic lobes surrounds medial margin of hemisphere
- includes hippocampus, fornix, amygdala
- involved in emotion, memory behaviour and olfaction
- operates by influencing the endocrine system and autonomic nervous system
- it is highly interconnected with the brains pleasure centre
What is the role of the hippocampus?
- involved in long term memory formation
What is the role of the amygdala?
- important in motivationally significant stimuli e.g. related to reward and fear
Nuclus accumbens
- role in sexual arousal and the high experienced with recreational drugs
Describe the inner meningeal layer of the dura mater
- envelopes the central nervous system
- continues as tube of dura seen around the spinal cord
- provides tubular sheaths for the cranial nerves
Why does the inner layer of the dura mater separate from the skull?
- to form dural folds which support the subdivisions of the brain
- partially divide the brain into three areas: right and left hemispheres and posterior cranial fossa (where cerebellum lies)
The dural venous sinuses
- system of communicating blood filled spaces where the DURAL FOLDS ARE ATTACHED TO THE SKULL
Falx cerebri
- arched crescent of dura lying in longitudinal fissure between the cerebral hemispheres
Superior sagittal sinus
- where the falx cerebri attaches to the cranium
Inferior sagittal sinus
- at free border of falx cerebri
Tentorium cerebelli
- dura forming a thick fibrous roof over the posterior cranial fossa and cerebellum
Straight sinus
- within tentorium cerebelli (at its attachment) to falx cerebri
Tentorial inscisure
- a horseshoe-shaped space between the free concave border of tentorium and the dorsal sellae of the sphenoid
Transverse sinuses
- along line of attachment of
- tentorium cerebelli - occipital bone
Cavernous sinus position
- lateral to the body of the sphenoid
Trigeminal cave
- next to apex of petrous part of temporal bone
- envelops the roots of the trigeminal nerve
Diaphragma sellae
- small, circular, horizontal fold of dura mater which forms the roof of the pituitary fossa
Falx cerebelli
- small, vertical, sickle-shaped reflection of dura
- separates the two lobes of cerebellum
Subarachnoid cisterns
- spaces between the arachnoid and pia mater
- found where the arachnoid spans the gyri of the brain
- full of CSF
Foramen of magendie
- midline communication between the IVth ventricle and the subarachnoid space
Foramen of Luschka
- lateral communication between the IVth ventricle and the subarachnoid space
What are the 6 cisterns of the subarachnoid cisterns?
- cerebellomedullary cistern
- pontine cistern
- interpeduncular cistern
- cistern of the lateral fissure
- superior cistern
- cisterna ambiens
Cerebellomedullary cistern
- lies in angle formed by dorsal surface of medulla and inferior surface of cerebellum
Pontine cistern
- on the ventral surface of the pons
Interpeduncular cistern
- contains the circle of willis
Cistern of lateral fissure- what does it contain
- contains the middle cerebral artery and bridges the lateral sulcus on each side
Superior cistern
- contains the great cerebral vein (of Galen)
- and the pineal gland
- found between the posterior end (selenium) of the corpus callosum and the superior surface of the cerebellum
Cisterna Ambiens
- group of subarachnoid cisterns which completely encircle the midbrain
What is the choroid plexus?
a network of blood vessels and cells in the ventricles (fluid-filled spaces) of the brain
True or false? The pia mater is indishtinguishable from the underlying nervous tissue with the naked eye
true - it also forms the blood brain barrier (acts as a barrier between the blood vessels and the neurological tissue)
Describe the blood brain barrier
- on surface of brain the arteries lie in subarachnoid space
- as vessels pass into the substance of the brain they take with them prolongations of pia mater and some of subarachnoid space
- this forms a layer around the vessel
- as it penetrates deeps into the brain tissue, tunica media thins and prolongation of subarachnoid space narrows
- at level of capillary, basement membrans of endothelial cells and of pia fuse
What are the features unique to the brain and spinal cord in the blood brain barrier that limit the ability of molecules to pass between the blood and CNS?
(protects tissue from toxic substances)
1. edges of adjacent endothelial cells that line blood vessel are bonded closely together by ‘tight junctions’ to prevent molecules passing between them
2. basement membrane of CNS blood vessels lack ‘fenestrations’ (small holes) that are present elsewhere in the body
3. pericytes are cells that are embedded in basement membrane and wrap around endothelial cells (regulate capillary blood flow, immunity and vascular permeability)
4. astrocytes extend processes called end feet that envelop C|NS capillaries and restrict the flow of molecules into the CNS parenchyma
What is the cribiform plate of the ethmoid?
the portion of the ethmoid bone that forms the roof of the nasal cavity
What does the anterior cranial fossa contain?
- frontal lobe of the brain
- orbital part of frontal bone
- ethmoid bone (cribriform plates and crista Galli)
- lesser wing of the sphenoid bone
What does the middle cranial fossa contain?
- temporal, parietal and occipital lobes of the brain
- much deeper than the anterior cranial fossa
What does the posterior cranial fossa contain?
- cerebellum, pons and medulla oblongata
- deepest of three fossae
Where do the arteries and veins on the surface of the brain lie within?
- the subarachnoid space, partially hidden by the arachnoid mater
How are the superficial cerebral veins easily distinguished?
- darker in colour
- fixed coagulated blood visible through thin fragile walls
How do the superficial cerebral arteries look compared to the veins?
- arteries look paler
- thicker, muscular walls and are not so easily torn
What are the three anatomical elements that contribute to the blood brain barrier?
- endothelial cells of capillaries
- basement membrane, which lies between the endothelial cells and astrocytic end feet and is formed from the true basement membrane and the pia
- the astrocyteic end feet themselves
What are the two pairs of vessels that supply arteriole blood to the brain?
- internal carotid arteries (80% - of P CB + anterior + medial + diencephalon)
- vertebral arteries (20% - of posterior cerebrum)
Where in the arterial blood supply to the brain is the weakest point?
- at branches
At what level does the common carotid bifurcate into the internal and external carotid?
- level of upper border of thyroid cartilage
Where does the internal carotid artery enter the brain from?
- base of the skull
- temporal bone
- lies in the carotid canal
Describe the course of the internal carotid artery in the brain
- temporal bone > carotid canal
- > pierces the dura forming the roof of cavernous sinus to enter the cranial cavity > anterior perforated substance at medial end of lateral sulcus > divides into terminal branches (anterior and middle cerebral arteries)
Terminal branches off the internal caroitd artery
- anterior cerebral artery
- middle cerebral artery
What does the anterior cerebral artery supply?
- the corpus callosum and medial aspects of the hemispheres
What does the middle cerebral artery supply?
- largest of the terminal branches of the internal carotid artery
- supplies majority of lateral surface of the hemisphere and deep structures of the anterior part of the cerebral hemisphere via its ANTERIOR PERFORATING BRANCHES
Purpose of the anterior communicating artery
- connects together the two anterior cerebral arteries
- provides anterior perforating branches
Purpose of the posterior communicating artery
- connects the internal carotid and vertebra-basilar systems
- via the posterior cerebral artery
Branches of the internal carotid artery NOT TERMINAL
Do we need to know this?
- central artery
- precentral artery
- anterior cerebral artery
- prefrontal artery
- middle cerebral artery
- anterior temporal artery
- middle temporal artery
- basilar artery
- vertebral artery
- posterior inferior cerebellar artery
- anterior inferior cerebellar artery
- superior cerebellar artery
- angular artery
- parietal artery
- postcentral artery
- temporo-occipital artery
What are the deep structures of the hemisphere, including the internal capsule supplied by?
- central branches from the circle of willis
True or false? there is no functional anastomosis between the capillary beds and the circle of willis
true (clinically important as infarction of one area does not automatically mean that supply will be taken up by other vessels
Where does the vertebral artery arise from?
the subclavian artery
True or false? the two sides of vertebral arteries have different diameters?
true
Where do the vertebral arteries enter the skull from?
through the foramen magnum
Basilar artery
- at the lower border of the pons, the two vertebral arteries unite in the midline
- lying in the anterior median fissure on the pons
What is referred to as the posterior circulation?
- vertebral and basilar arteries
- branches from them
- posterior cerebral artery
What is referred to as the anterior circulation?
- right and left internal carotid arteries and their branches
True or false? the anterior and posterior circulations are linked via the circle of willis
true
Branches of the vertebro-basilar system
- anterior spinal artery
- posterior spinal arteries
- posterior inferior cerebellar arteries
- pontine arteries
- labrinthine artery
- anterior inferior cerebellar artery
- superior cerebellar artery
- posterior cerebellar artery
True or false? cerebral veins first drain into the dural venous sinuses before draining back towards the heart
true - they are channels formed between the two layers of dura mater
What are the two groups of cerebral veins?
Internal cerebral veins:
- run within the substance of the brain tissue and end when they reach the surface of the brain where they become external cerebral veins
External cerebral veins:
- run on the surface of the brain
- cross the subarachnoid space to drain the dural venous sinuses
- there are four named groups which drain into different dural sinuses
Great Cerebral vein (of Galen)
- drains the deep structures of the brain
- drains into the straight sinus
What do the sinuses connect?
- they connect the major cerebral veins to the internal jugular veins
Name the 8 sinuses
- inferior sagittal sinus
- superior sagittal sinus
- straight sinus
- transverse sinus
- sigmoid sinus
- cavernous sinus
- superior petrosal sinus
- inferior petrosal sinus
Where can you find the inferior sagittal sinus?
at the inferior margin of the falx cerebri
Where can you find the superior sagittal sinus?
at the superior border of the falx cerebri
Where can you find the straight sinus?
in the midline of the tentorium cerebelli
Where can you find the transverse sinus?
in the posterior fixed margin of the tentorium cerebelli