Anatomy 18 (Neuro 1) Flashcards
What is the CNS comprised of?
Brain/Encephalon
Spinal Cord
How many main parts is the brain divided into?
3
What are the 3 main parts of the brain?
Hindbrain
Midbrain
Forebrain
How many parts can the hindbrain be subdivided into?
3
What are the 3 subdivisions of the hindbrain?
Medulla Oblongata
Pons
Cerebellum
What is another name for the hindbrain?
Rhombencephalon
What is the medulla oblongata derived from?
Myelencephalon
What are the Pons derived from?
Metencephalon
What is the cerebellum derived from?
Metencephalon
How many parts can the midbrain be subdivided into?
2
What is another name for the midbrain?
Mesencephalon
What are the 2 subdivisions of the midbrain?
Tectum
Cerebral Peduncle
What is the Tectum?
Part of the midbrain lying dorsal to the central canal (cerebral aqueduct)
What does the tectum comprise of?
Superior and inferior COLLICULI, also called the corpora quadrigemina
What is the cerebral peduncle?
Midbrain ventral to the aqueduct
What is the cerebral peduncle subdivided into?
Tegmentum
Crus Cerebri
What is the tegmentum?
Dorsal part of the cerebral peduncle
Where in the cerebral peduncle is the crus cerebri located?
Ventrally
What separates the tegmentum and crus cerebri?
Substantia Nigra
What is the substantia nigra?
Narrow lamina of pigmented cell
What are the crura cerebri?
Large bundles of white matter emerging from the cerebral hemispheres, one on each side of the midline, which pass backwards and downwards, converging to meet in the midline at the upper border of the pons
What do the crura cerebri form?
Form the part of the cerebral peduncles visible on the inferior surface of the brain
What do the crura cerebri form?
Form the part of the cerebral peduncles visible on the inferior surface of the brain
What is another name for the forebrain?
Prosencephalon
How many parts is the forebrain divided into?
2
What are the 2 parts that the forebrain is divided into?
Diencephalon
Telencephalon
What does the diencephalon derive from?
Derives from the anterior part of the developing neural tube
What does the diencephalon comprise of?
Comprises of the Thalamus and the Hypothalamus (with the epi- and sub-thalamus) of each side
What does the telencephalon derive from?
Derives from the cerebral vesicle of each side
What does the telencephalon consist of?
Cerebral cortex
Basal ganglia
What is the cerebral cortex?
Outer layer of grey matter
What is the basal ganglia?
Deep nuclei
What is the cerebral hemisphere?
Used to refer to the telencephalon of each side, though it may be used to mean the telencephalon and diencephalon of each side together
What are the meninges?
3 separate tubular sheaths of membrane which surround and enclose the entire CNS
What are the 3 meninges?
Dura Mater
Arachnoid Mater
Pia Mater
What is the Dura Mater?
Fibrous sheet, with white collagen fibres and a few elastic fibres arranged in dense laminae, often of parallel fibres
How many layers does the cranial dura mater consist of?
2 layers
What are the 2 layers that the cranial dura mater consist of?
Outer endosteal layer (equivalent to the periosteum)
Inner meningeal layer, which is the dura mater proper
What is the Arachnoid Mater?
Poorly vascularised membrane of loose connective tissue, consisting of collagen, elastin and reticulin fibres
What is the function of arachnoid mater?
It loosely covers the brain without following the gyral and sulcal undulations
What is the PIA mater?
Intimately adherent to the entire surface of the CNS, including following the gyral and sulcal folds
Where does the innermost layer of pial cells lie?
On the surface of the CNS which is formed by the underlying end-feet of astrocytes with their covering basement membrane
What is the Pia separated from the Arachnoid by?
Subarachnoid space
What does the subarachnoid space contain?
Cerebrospinal Fluid (CSF)
What is white matter formed by?
Collections of nerve fibres (axons)
What is white matter wrapped in?
Fatty myelin sheaths, with few or no neuronal somata (cell bodies)
What is the grey matter of the CNS formed by?
Aggregations of neuronal cell bodies and their local processes
What are the Neuropil?
Network of intermingled and interconnected neuronal processes which occupies the space between neuronal cell bodies
What are Nuclei/Ganglia?
Clusters of nerve cell bodies (grey matter) within the brain.
What is the Cortex?
Outer surface of the brain (e.g., the cerebral hemispheres and the cerebellum)
What is the Cortex formed by?
Formed by flatter sheets of neurones
What are the Frontal lobes?
Primary motor cortex and prefrontal cortex
What are the Temporal lobes?
Primary auditory cortex, auditory association cortex (Wernicke’s area), hippocampus and amygdala
What are the Parietal lobes?
Primary somatosensory cortex and association cortex
What are the Occipital lobes?
Primary visual and visual association cortex
What is the Cerebellum?
Motor control of equilibrium, posture and muscle tone and movement co-ordination
What is the Brainstem?
Ascending and descending tracts, cranial nerve nuclei and the 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 the Occipital poles?
Ease the walls of the lateral sulcus apart
What are the Insula?
This forms the floor of the lateral sulcus
What are the Opercula?
Parts of the temporal, frontal and parietal lobes that overlie the insula
What is the Corpus Callosum?
Large bundle of white matter connecting the two hemispheres
Where are the Olfactory Tracts located?
These run on the inferior surface of the frontal lobes
Where are the Optic Nerves located?
Seen passing backwards and medially, converging in the midline to form the OPTIC CHIASMA, then passing backwards and laterally as the OPTIC TRACTS
What are the Mammillary bodies?
2 rounded eminences behind the optic chiasma
Where is the Hypothalamus located?
Behind the optic chiasma up to and including the mammillary bodies (the only part of the DIENCEPHALON visible on the outside of the brain).
Where are the Crus Cerebri located?
Behind the mammillary bodies on each side, from the cerebral hemisphere.
They pass backwards, converging in the midline at the upper border of the PONS.
What is the Interpenduncular Fossa?
Space between the crura roofed over by arachnoid
Where are the Pons located?
Situated immediately behind the point where the crura meet in the midline.
It forms a bridge of neural tissue between the midbrain and the medulla oblongata
Where is the Cerebellum located?
2 lobes, one either side of the medulla and a central vermis joining the two hemispheres
Where is the Medulla Oblongata located?
Runs from the caudal border of the pons to where the
spinal cord was cut when the brain was removed.
Where does the parietal lobe extend from?
From the central sulcus anteriorly to the imaginary parietooccipital fissure posteriorly
What does the parietal lobe contain?
Primary sensory area
How many parietal lobes are there?
2
What is the dominant lobe important for?
Perception, interpretation of sensory information and the formation of the idea of a complex, meaningful motor response.
What are the supramarginal and angular gyrus of the dominant lobe concerned with?
Language and mathematical operations
What is the non-dominant lobe important for?
Visuospatial functions
Which side is normally the dominant lobe?
Left
Which side is normally the non-dominant lobe?
Right
What is the frontal lobe involved in?
Motor function
Problem solving
Spontaneity
Memory
Language
Judgement
Personality
Impulse control
Social and sexual behaviour
What is the prefrontal cortex?
Anterior portion of the frontal lobe
What is the prefrontal cortex important for?
Higher cognitive functions and determination of personality
What does the posterior portion of the frontal lobe contain?
The motor and premotor areas
Where is Broca’s area located?
Left inferior frontal gyrus
What is the importance of Broca’s area?
Important for language production and comprehension
What does the temporal lobe contain?
Primary auditory cortex
Hippocampus
Amygdala
Wernicke’s area
Where is the Wernicke’s area located?
Superior temporal gyrus of the left hemisphere
What is the function of the Wernicke’s area?
Understanding the spoken word
Where is the auditory cortex located?
Around the lateral (Sylvian) fissure
Where is the occipital lobe located?
Posterior aspect of the brain
What does the occipital lobe contain?
Contains the primary visual and visual association cortex
What does the limbic lobe surround?
Surrounds the medial margin of the hemisphere
What does the limbic system include?
Hippocampus
Fornix
Amygdala
What is the limbic system involved in?
Emotion
Memory
Behaviour
Olfaction
What is the hippocampus involved in?
Long term memory formation
What is the amygdala important in?
Motivationally significant stimuli, such as those related to reward and fear.
How does the limbic system operate?
By influencing the endocrine system and the autonomic nervous system and is highly interconnected with the brains pleasure centre; ; the nucleus accumbens
How does the limbic system operate?
By influencing the endocrine system and the autonomic nervous system and is highly interconnected with the brains pleasure centre; ; the nucleus accumbens
What does the nucleus accumbens have a role in?
Sexual arousal and the high experienced with recreational drugs
What does the outer endosteal layer of the cranial dura mater do?
Lines the interior of the skull, adhering to, and sending blood vessels and fibrous processes into the cranial bones
What does the inner meningeal layer of the cranial dura mater do?
Envelopes the central nervous system; it continues as tube of dura seen around the spinal cord and provides tubular sheaths for the cranial nerves.
Are the two layers of dura mater always fused?
In places the inner layer separates from the skull to form dural folds which support the subdivisions of the brain and partially divide the cranial cavity into three areas, the right and left hemispheres and the posterior cranial fossa where the cerebellum lies
What is the Falx Cerebri?
An arched crescent of dura lying in the longitudinal fissure between the cerebral hemispheres
What is the Superior Sagittal Sinus?
Where the falx cerebri attaches to the cranium.
Where is the Inferior Sagittal Sinus?
At the free border of the falx cerebri
What is the Tentorium Cerebelli?
Dura forming a thick fibrous roof over the posterior cranial fossa and cerebellum
Where is the Straight Sinus located?
Within the tentorium cerebelli at its attachment to the falx cerebri
What is the Tentorial Inscisure?
A horseshoe-shaped space between the free concave border of the tentorium and the dorsum sellae of the sphenoid
Where is the Transverse Sinus located?
Runs along the line of attachment of the tentorium
cerebelli to the occipital bone
Where is the Cavernous Sinus located?
Lies lateral to the body of the sphenoid
Where is the Trigeminal Cave located?
Lies next to the apex of the petrous part of the temporal
bone and envelops the roots of the trigeminal nerve
What is the Diaphragma Sellae?
A small, circular, horizontal fold of dura mater which forms the roof of the pituitary fossa
What is the Falx Cerebelli?
A small, vertical, sickle-shaped reflection of dura separating the two lobes of the cerebellum
What is the foramen of magendie?
A midline communication between the IVth ventricle and the subarachnoid space
What is the foramen of luschka?
A lateral communication between the IVth ventricle and the subarachnoid space
Where is the Cerebellomedullary cistern located?
Lies in the angle formed by the dorsal surface of the medulla and the inferior surface of the cerebellum
Where is the Pontine Cistern located?
On the ventral surface of the pons
What does the Interpenduncular cistern contain?
The Circle of Willis
What does the Cistern of the lateral fissure contain?
Contains the middle cerebral artery and bridges the lateral sulcus on each side
What does the Superior Cistern contain?
Contains the great cerebral vein (of Galen) and the pineal gland and is found between the posterior end (splenium) of the corpus callosum and the superior surface of the cerebellum
What are the Cisterna Ambiens?
Group of subarachnoid cisterns which completely encircle the midbrain
What is the PIA Mater?
Meningeal layer that forms part of the blood brain barrier
What is the Blood brain barrier?
The blood brain barrier is a combination of features, unique to the brain and spinal cord that limit the ability of molecules to pass between the blood and the CNS
What is the purpose of the blood brain barrier?
Protect brain tissue from toxic substances
What are features of the blood brain barrier?
- Tightly bonded endothelial cells
- Lack of ‘fenestrations’ in the basement membrane of CNS blood vessels
- Presence of pericytes, which regulate capillary blood flow, immunity and vascular permeability
- Astrocytes extend processes called end feet that envelop CNS capillaries and restrict the flow of molecules into the CNS parenchyma
What is meningitis?
Inflammation of the meninges, typically caused by infection
What does the Meningism triad consist of?
Headache
Neck stiffness
Photophobia
What other symptoms are also present in Meningitis?
Nausea/vomiting
Fever
What are the differences between Viral and Bacterial Meningitis?
Viral meningitis is often mild and self-limiting
Bacterial meningitis requires urgent treatment or will lead to brain damage or death
What is an Extradural haemorrhage?
Between the skull and dura mater
- strips the dura from the bone and compresses the brain - typically after head injury
In an Extradural haemorrhage, where is the haemorrhage from?
The meningeal arteries
What is a Subdural Haemorrhage?
Blood between the dura and arachnoid - appears as crescent on CT head
- typically after high impact injury e.g., car accident
What is a Subdural Haemorrhage a result of?
Result of tears in the bridging veins (chronic subdural haematoma occurs 4-8 weeks following mild/moderate head injury in the elderly)
What is a Subarachnoid Haemorrhage?
Blood between the arachnoid and pia mater
- occurs after head injury (traumatic subarachnoid haemorrhage or after rupture of a berry aneurysm
- blood surrounds the brain and fills the sulci, predominantly near the site of injury/aneurysm
What is the Pathognomic symptom of Subarachnoid Haemorrhage?
Sudden severe headache
What is a Intracerebral Haemorrhage?
Rupture of small vessels and microaneurysms in perforating vessels leading to bleeding within the brain tissue
What is the classical location of Intracerebral Haemorrhage?
Internal capsule following rupture of the lenticulostriate artery due to high blood pressure
What is Amaurosis fugax?
Temporary loss of vision to one eye
Part of a carotid plaque breaks off and occludes the
central retinal artery
What is Amaurosis fugax a warning of?
Warning of thrombus of the internal carotid artery
- potential for an impending stroke
Where do the arteries and veins on the surface of the brain lie within?
Subarachnoid space, partially hidden by the arachnoid mater
What are the superficial cerebral veins easily distinguished by?
Dark colour
Why are the superficial cerebral veins a dark colour?
The fixed and coagulated blood being visible through their thin, fragile walls.
Describe features of the superficial cerebral arteries compared to the veins
Paler
Thicker, muscular walls
Not so easily torn
What is the function of the blood brain barrier?
Retards or prevents the passage of some substances from the circulation into the nervous tissue
What are 3 possible contributory anatomical elements of the blood brain barrier?
- The endothelial cells of the capillaries.
- The basement membrane, which lies between the endothelial cells and the astrocytic end- feet and is formed from the true basement membrane and the pia.
- The astrocytic end-feet themselves.
What are the 2 arteries that supply the brain?
Internal Carotid
Vertebral Arteries
What percentage of the brain arterial supply is from the vertebral artery?
20%
What percentage of the brain arterial supply is from the internal carotid artery?
80%
What parts of the brain does the vertebral artery supply?
Posterior cerebrum
Contents of the posterior cranial fossa
What parts of the brain does the internal carotid artery supply?
Anterior and middle parts of the cerebrum
Diencephalon
What can points of weakness of the arterial supply lead to?
The formation of ‘Berry Aneurysms’
What is the principal cause of mortality and morbidity in the Western world?
Cerebro-vascular accidents
Where does the internal carotid artery arise at?
The bifurcation of the Common Carotid at the level of the upper border of the thyroid cartilage
Where does the internal carotid artery ascend to?
Base of the skull, where it enters the temporal bone to lie in the carotid canal
How does the internal carotid artery enter the cranial cavity?
Pierces the dura forming the roof of the cavernous sinus
When does the internal carotid artery divide into its terminal branches?
When it reaches the anterior perforated substance at the medial end of the lateral sulcus
What are the terminal branches of the internal carotid artery?
Anterior and Medial Cerebral Arteries
What is the Anterior Circulation?
Part of the cerebral circulation supplied by the anterior and medial cerebral arteries
Why is the anterior circulation clinically important?
Topographically-specific regions of the precentral and postcentral gyri receive their blood supply via different arteries
What does the anterior cerebral artery supply?
Supplies the corpus callosum and the medial aspects of the hemispheres
What does the middle cerebral artery supply?
Supplies the majority of the lateral surface of the hemisphere and the deep structures of the anterior part of the cerebral hemisphere
How does the middle cerebral artery supply the deep structures of the anterior part of the cerebral hemisphere?
Via its anterior perforating branches
What is the function of the anterior communicating artery?
Connects together the two anterior cerebral arteries and provides anterior perforating branches
What is the function of the posterior communicating artery?
Connects the internal carotid and vertebro-basilar systems via the posterior cerebral artery
What do the central branches of the circle of Willis supply?
Deep structures of the hemisphere including the internal capsule
What do the vertebral arteries arise from?
First part of the subclavian artery
What do the vertebral arteries enter the skull through?
Foramen magnum
Where do the two vertebral arteries unite?
Lower border of the pons
What do the 2 vertebral arteries unite to form?
Basilar artery
Where does the basilar artery lie?
In the anterior median fissure on the PONS
What is usually referred to as the Posterior Circulation?
Vertebral arteries + branches
Basilar arteries + branches
Posterior cerebral artery
What are the anterior and posterior circulations linked by?
Circle of Willis
What is a Berry aneurysm?
A congenital sac-like out pouching of an intracranial artery
What happens when a berry aneurysm ruptures?
Results in a subarachnoid or intracerebral haemorrhage
Where do berry aneurysms most commonly occur?
On the branching points around the circle of Willis particularly the anterior communicating artery which lies in the subarachnoid space
What are the 2 different types of strokes?
Ischaemic (Intracerebral)
Haemorrhagic (Subarachnoid)
What is a stroke?
Rapid onset of focal neurological deficit lasting more than 24 hours
How long do TIAs take to resolve?
Less than 24 hours
What is the 3rd most common cause of death worldwide?
Strokes
Where do the cerebral veins first drain into?
Dural venous sinuses
What are the dural venous sinuses?
Channels formed between the 2 layer of dura mater
What are the cerebral veins divided into?
Internal and External groups
What are the internal cerebral veins?
These run within the substance of the brain tissue and end when they reach the surface of the brain where they become external cerebral veins
What are the external cerebral veins?
These run on the surface of the brain, crossing the subarachnoid space to drain into the dural venous sinuses
What is the function of the dural venous sinuses?
Connect the major cerebral veins to the internal jugular veins
Where can the major venous sinuses be easily identified?
Attached borders of the falx cerebri
The tentorium cerebelli
And the floor of the cranial cavity
Where is the inferior sagittal sinus located?
At the inferior margin of the falx cerebri
Where is the superior sagittal sinus located?
At the superior border of the falx cerebri
Where is the straight sinus located?
In the midline of the tentorium cerebelli
Where is the transverse sinus located?
In the posterior fixed margin of the tentorium cerebelli
Where is the sigmoid sinus located?
A deep groove in the mastoid part of the temporal bone
Where is the cavernous sinus located?
Beside the body of the sphenoid bone
What does the Cavernous sinus contain?
5 Cranial Nerves
Internal Carotid Artery
Where is the superior petrosal sinus located?
In the attached lateral margin of the tentorium cerebelli
Where is the inferior petrosal sinus located?
In the groove between the petrous temporal bone and the basal part of the occipital bone
How do the intracranial venous sinuses and the veins outside the skull communicate?
Via a variable number of Emissary Veins
What do the Emissary veins represent?
A possible route for infection or inflammation to spread into the cranial cavity from outside the skull
What are possible causes of Venous Sinus Thrombosis?
Rare complication of childbirth
Clotting disorders
Ear infection
What does obstruction of venous drainage cause?
Cerebral Oedema
Raised intracranial pressure
What can brain damage from venous sinus thrombosis present as?
Combination of headaches with epileptic seizures
Focal motor deficit
Deterioration in consciousness
What does the brain develop from?
Hollow neural tube
Why are the central spaces important?
Important in relation to the formation and circulation of cerebrospinal fluid
Where is the largest aggregation of choroid plexus?
In the lateral ventricles
Where is the majority of cerebrospinal fluid produced?
In the lateral ventricles
How does the IVth ventricle communicate with the subarachnoid space?
Via the median foramen of Magendie and the lateral foramen of Luschka
What is the Choroid plexus?
Vascular fold of pia mater covered by an epithelium derived from the ependymal lining of the ventricle
What do tight junctions prevent the passage of fluid from?
From the extracellular space of the choroid
plexus into the ventricle
How is fluid able to pass from the choroid plexus into the ventricle?
Via the choroidal cells
What constitutes the CSF brain barrier?
The ependyma
How does resorption of the CSF into the venous drainage of the brain occur?
Via tufts of arachnoid mater, called Arachnoid Villi
What happens to the Arachnoid Villi with advancing age?
They tend to calcify, forming Arachnoid Granulations
What does the presence of Arachnoid granulations cause?
Cause bone to be resorbed along the internal surface of the cranial vault near the midline, causing small pit-like structures
