ANA 303 Cerebrum & Circle of Willis Flashcards
What is the cerebrum?
The cerebrum, also called the telencephalon, refers to the two cerebral hemispheres (right and left) which form the largest part of the brain. It sits mainly in the anterior and middle cranial fossae of the skull.
What are the unique grooves and ridges of the cerebrum?
gyri and sulci
Discuss the white matter of the cerebrum
Deep to the cerebral cortex is an inner mass of white matter, which forms the bulk of the cerebrum and contains myelinated nerve fibers that convey information to or from the cerebral cortex
Discuss the grey matter of the cerebrum
The grey matter surrounding the cerebrum is known as the cortex of the brain.
It is home to
Lobes of the cerebral cortex
Frontal
Occipital
Parietal
Temporal
Function of the frontal lobe
planning
organising
learning and recalling info
reasoning
social understanding
voluntary muscle movements
personality
decision-making
Where is the primary site of motor control?
The motor cortex of the frontal lobe
Function of the parietal lobe
processing sensory info e.g. feeling hot or cold, touch sensation
proprioceptors - is the sense of self-movement, force, and body position
kinesthesia
location awareness e.g. knowing if something is left or right
Learned movements e.g. writing
Function of the temporal lobe
Processing auditory information
Processing olfactory information
Processing and development of memory
Associating visual and auditory information
What is Broca’s area, history, it’s location, arterial supply and clinical anatomy?
aka motor speech area
Discovered in 1861 by French surgeon Pierre Paul Broca
Located: frontal lobe, brodmann brease 44 and 45, ususally in th left hemisphere
Function: A region of the frontal lobe where all speech patterns are formed
It controls the complex movements with your tongue and mouth to form words by carring info to the motor cortex
Helps make gestures whilst speaking and writing
Stuttering and delayed speech could be tied to a disorder in a person’s broca’s area
Clinical anatomy:
Lesions in Broca’s zones lead to severe expressive language deficits
There are also non-linguistic difficulties that lead to problems understanding signs and gestures
Broca’s aphasia syndrome
supplied by the middle cerebral artery
What is Wernicke’s area, history, it’s location, arterial supply and colinal anatomy?
Discovered in 1874 by German Neurologist, Carl Wernicke, His patients were able to speak, but speech was meanignless, they couldn’t comprehend language
lesions were found in their ‘wernicke’s area’
An area of the parietal lobe
Interpreting speech
Leaning language and processing the meeaning of sounds
Location:
located in Brodmann area 22
in the superior temporal gyrus of left cerebrsl hemisphere
Supply:
supplied by the middle cerebral artery
Clinical Anatomy:
Aphasia: the loss or disruption of langauge skills that were already previosuly aquired and functional
It can be cuased by a brain injury, stroke, physical injury, tumor, dementia and infective brain disease
Clinical anatomy of the frontal lobe
trauma
stroke
brain tumour
dementia
degenerative brain diseases
The brain is supplied by which arteries?
The brain is supplied by:
two internal carotid
two vertebral arteries
How do these arteries form the Circle of Willis?
The four arteries lie within the subarachnoid space, and their branches anastomose on the inferior surface of the brain to form the Circle of Willis
The ICA forms from where and gives which terminal branches?
They arise in the neck from the common carotid artery
They give terminal branches which are:
Anterior cerebral arteries
Middle cerebral arteries
The anterior cerebral arteries are joined together by the______________
anterior communicating artery
The internal carotid arteries are joined by the ___________to_______________
posterior communicating arteries to the posterior cerebral arteries
In addition to supplying branches to deeper parts of the brain, the cortical branches of each cerebral artery supply_________________
a surface and a pole of the cerebrum
Describe the supply of the cortical branches (supply of the ant, mid and post cerebral artery)
Anterior cerebral artery supply most of the medial and superior surfaces of the brain and the frontal pole
Middle cerebral artery supply the lateral surface of the brain and the temporal pole
Posterior cerebral artery supply the inferior surface of the brain and the occipital pole
The vertebral arteries arise and unite where?
They arise from the subclavian arteries
They unite at the lower border of the pons to form the basilar artery
The basilar artery ends by dividing into_____________
two posterior cerebral arteries
What branches arise from the basilar artery?
Other branches such as the anterior inferior cerebellar arteries, several small pontine arteries, and the superior cerebellar arteries arise from the basilar artery
The basilar artery supply the________________
brainstem, cerebellum and cerebrum
Describe the circle of Willis
The cerebral arterial circle (of Willis) is a roughly pentagon-shaped circle of vessels on the ventral surface of the brain
It is an important anastomosis at the base of the brain between the four arteries (two vertebral and two internal carotid arteries) that supply the brain
The arterial circle is formed sequentially in an anterior to posterior direction by the:
Anterior communicating artery
Anterior cerebral arteries
Internal carotid arteries
Posterior communicating arteries
Posterior cerebral arteries
Clinical anatomy of the circle of willis
an embolism in a major cerebral artery can cause ischemic stroke
Describe the pathway for the anterior and posterior circulation of the circle of willis
Anterior circulation: internal carotid arteries, anterior cerebral arteries, anterior communicating artery and middle cerebral arteries (that supply the forebrain)
Posterior circulation: vertebral arteries, basilar artery, posterior cerebral arteries and posterior communicating arteries
The inferomedial border is divided into________
an anterior part called the medial orbital border
a posterior part called the medial occipital border.
What are the 3 pointed ends or poles can be recognized when the cerebral hemisphere is viewed from the lateral aspect?
1.the frontal pole anteriorly,
2. the occipital pole posteriorly
3. the temporal pole that lies between the frontal and occipital poles and points forward and downward.
What are the 2 other lobes apart from the main 4 lobes?
insular lobe and limbic lobe
A little anterior to the occipital pole the inferolateral border__________
shows a slight indentation called the preoccipital notch (or preoccipital incisure)
A coronal section through the cerebral hemispheres shows that each hemisphere has three borders:
(1) superomedial
(2) inferolateral
(3) inferomedial
What is the orbital part of the inferolateral border?
The orbital part of the inferolateral border is called the superciliary border (as it lies just above the level of the eyebrows)
Each cerebral hemisphere has three surfaces
- Superolateral surface between the superomedial border and the inferolateral border
- Medial surface between the superomedial border and the inferomedial border.
- Inferior surface between the inferolateral and
inferomedial borders
The inferior surface of the cerebrum is subdivided into_________
orbital and tentorial surfaces by the stem of the lateral sulcus
Types of sulci
- Limiting sulcus: Such a sulcus separates two
functionally different areas, e.g. central sulcus. - Axial sulcus: some sulci develop along the axis of a rapidly growing/developing area e.g., the posterior part of calcarine sulcus.
- Operculated sulcus: a sulcus may be between two structurally different areas and a third sulcus may lie in its wall and does not appear on the surface (e.g. lunate sulcus) e.g. the posterior part of calcarine sulcus which has a primary visual area in its
depth and has peristriate and parastriate areas, secondary visual surface areas. - Complete sulcus: A sulcus, which is deep enough to produce an elevation on the ventricular wall is complete, e.g. collateral sulcus which produces collateral eminence in the floor of the inferior horn of
lateral ventricle
Parts of the frontal lobe
- motor cortex
- pre-motor cortex
- prefrontal cortex
- Broca’s area
What are the sulci of the brain?
lateral sulcus
central sulcus
parieto-occipital sulcus
Describe the lateral sulcus
Separates the temporal lobe from the frontal and parietal lobe
Describe the central sulcus
serves as the posterior boundary of the frontal lobe
It separates the frontal and parietal lobe
Describe the parieto-occipital sulcus
On the medial surface of the hemisphere, there is a “Y” shaped sulcus posteriorly. The upper limb of the “Y” shaped sulcus is called the parieto-occipital sulcus.
Separates the parietal and occipital lobe
The lateral sulcus is also known as
Sylvian sulcus
Broca’s area and Wernicke’s area are functionally interrelated because they can communicate with each other through
a pathway referred to as the arcuate fasciculus
The anterior cerebral circulation supplies_______
Each gives rise to branches that supply the cortex and branches that penetrate the basal surface of the brain, supplying deep structures such as the basal ganglia, thalamus, and internal capsule
Describe the supply of the posterior circulation
It supplies the posterior cortex, the midbrain, and the brainstem
•Midline arteries supply medial structures, lateral arteries supply the lateral brainstem, and dorsal-lateral arteries supply dorsal-lateral brainstem structures and the cerebellum
Clinical correlates of the circle of willis
(Intracerebral) anuerysms ischemic and hemorhagic stroke
Describe an aneurysm
an aneurysm is the dilatation of an artery or vein (resulting in a bulge and weakening of the vessel wall) which is greater than 50% of the normal diameter.
They are most likely to occur in the vessels contributing to the Circle of Willis
They are particularly dangerous producing a few symptoms until they rupture
Upon rupture (e.g. due to head trauma ( results in extravasation of blood into the subarachnoid space. blood typically accumulates in the subarachnoid space with a subsequent increase in ICP.
Once the artery has ruptured, it is a medical emergency, patient is likely to die unless treated swiftly.
Treatment is surgical
Describe an ischemic and hemorrhagic stroke
A stroke can be caused by blockage of blood vessels ( occlusive/ischemic stroke )
or by bleeding from vessels ( hemorrhagic stroke ).
Ischemic strokes are generally caused by atherosclerotic lesions or thrombosis in blood vessels supplying the brain.
Hemorrhagic strokes are generally caused by long-standing high blood pressure or aneurysms in the vessels supplying the brain.
When bleeding occurs at the surface of the brain, it is called an extraparenchymal hemorrhage
What are the main causes of cerebrovascular accidents?
Thrombosis: obstruction of blood vessels by a locally forming clot (thrombus)
Embolism: obstruction of blood vessels by an emobolus (any foreign material)
Hyperfusion: lack of blood supply to the brain due to low bp
Hemorrhage: accumulation of blood within the cranial cavity
What is a cerebral herniation
A cerebral herniation or brain herniation is a serious medical condition that happens when brain tissues, blood and CSF, move from their normal postion within the skull.
It is usually caused when another condition (such as brain tumour, extradural or subdural haematoma, or abscesses in the supratentorial space)
Cerebral herniations are severe and need immediate treatment, if not treated immediately, it could be fatal
Function of the insular lobe (island of Reil)
Lies in the depth of the lateral cortex and therefore hidden from surface view
processing and integration of taste sensation
Function of the limbic lobe
modulation of emotions
