Topography of the Brain (Anatomy) - recap and blood supply Flashcards
What parts make up the brain?
Cerebral hemispheres
Diencephalon
Cerebellum
Brainstem:
Midbrain
Pons
Medulla Oblongata
What is white and grey matter?
White matter = myelinated axons
Grey matter = neuronal cell bodies
What does white matter in spinal cords and brain form?
various tracts
What is a tract?
fibre pathway passing through the CNS carrying a specific modality (e.g. motor fibres or pain sensation or touch sensation
What is a nucleus?
Neuronal cell body collection (grey) within CNS = nucleus
What is a ganglion?
Neuronal cell bodies outside the CNS = ganglion (e.g. dorsal root ganglion)
What are all the ventricles of the brain and where are they located?
Ventricles are spaces within the brain
Within cerebral hemispheres (x2) = lateral ventricle (x2)
Within Diencephalon = III ventricle
Within Midbrain = Cerebral aqueduct
Between Pons + medulla (in front) and Cerebellum (at the back) = IV ventricle
Where is CSF?
in the ventricles
in subarachnoid space - between pia and arachnoid mater
Where is CSF formed?
By choroid plexus in each ventricle
Where is CSF absorbed?
By Arachnoid villi into saggital sinus (venous channel in brain)
What arteries provide blood supply tot he braina and how do they enter the skull?
the 2 ICA - enter the skull through the carotid canal (foramen lacerum) to supply the brain
the 2 vertebral arteries (branches of the subclavian artery) - enter the skull through the foramen magnum
What is the circle of willis?
The circle of Willis is a circulatory anastomosis that supplies blood to the brain and surrounding structures
What are the main arteries forming the circle of willis?
formed by the anastomosis of the two internal carotid arteries with the two vertebral arteries
What is the structure of the circle of willis?
Branches of the ICA join with those of the opposite side and with the posterior cerebral arteries (branch of the basilar artery) to form a continuous circle at the base of the brain
How does the anastomoses protect against vasoocclusion
This is a protective feature against vaso-occlusion of large arteries due to other areas blood can flow through but branches supplying the cerebral hemispheres, distal to the Circle of Willis are effectively “end-arteries” so this would loead to ischemia of the brain causing a stroke
A?
anterior cerebral artery
B?
anterior communicating artery
C?
middle cerebral artery
D?
posterior communicating artery
E?
posterior cerebral artery
F?
basilar artery
G?
vertebral artery
What does the anterior communicating artery do?
connects the two anterior cerebral arteries
What branches does the ICA give off?
The ICA gives branches - the anterior (ACA), middle cerebral (MCA) and posterior communicating arteries (PComA)
The ACA and the MCA supply a large part of the cerebral hemispheres
What do the vertebral arteries make and supply?
The 2 vertebral arteries join together to form a basilar artery on the ventral surface of the brainstem
The vertebro-basilar system gives branches that supply the brainstem and cerebellum
The basilar artery finally ends at the level of the midbrain by dividing into two Posterior cerebral arteries (PCA) which supplies the posterior part of the cerebral hemispheres
What area of the brain does the anterior cerebal artery supply?
medial aspect of the cerebral hemispheres excluding the occipital lobe
What areas of the brain does the middle cerebral artery supply?
lateral aspects of the cerebral hemispheres
What areas of the brain does the posterior cerebral artery supply?
inferior aspects of the cerebral hemispheres and the occipital lobe
Describe the venous drainge of the brain?
superficial and deep veins of the brain drain into venous sinuses which lie between the 2 layers of dura mater
the dura mater sinuses join together to ultimatley drain into the internal jugular veins
A?
inferior saggital sinus
B?
superior saggital sinus
C?
transverse sinuses
D?
great cerebral vein
E?
cavernous sinus
F?
petrosal sinus:
superior
inferior
G?
internal jugular veins
What is the basic function of the cerebrum?
seat of consciousness
What is the basic function of the cerebellum?
balance and coordination
What is the function of the brain stem?
viral centres e.g. cardiorespiratory
pathway for fibre tracts
Describe brefiely how the brain is formed embryologically?
The neural tube develops from the (dorsal) surface ectoderm
The cranial end of the tube forms vesicles each of which develops into different parts of the brain
What does the neural tube devide into when it is formed?
As soon as the neural tube was formed, it divided into 3 primary vesicles (Week 4) and then into 2ry vesicles (Week 5)
these develop into the adult brain
On the brain stem what is the order of strucutre that . make it up from superior to inferior
midbrain
PONS
medulla
What cranial nerves emerge from the brainstem?
Cranial nerves 3-12
What are the functions of the brainstem?
Pathway for fibre tracts running between higher & lower centres
Brainstem nucleii are involved with 10 of the 12 cranial nerves, so innervation of head & neck
Brainstem centres produce the rigidly programmed automatic behaviours essential for survival
What is the cavity in the medulla?
IV ventircle
What does the medulla continue as?
the spinal cord at the foramen magum
What is the structure of the medulla?
has pyramids in the middle and olives laterallt
What happens between the pyramids of the medulla?
decussation - crossing over of cranial nerves to the opposite side
What connects the medulla to the cerebellum?
inferior cerebellar peduncle
Where is the IV ventricle in relation to the PONS
posterior to it
What peduncle can be seen on the PONS?
middle cerebellar peduncle
What is the central cavity of the midbrain?
cerebral aqueduct
What peduncles can be seen on the midbrain?
cerebral peduncle
superior cerebellar peduncle
What cranial nerves coem from the medulla?
Cranial nerves IX, X, XI & XII from its surface
What cranial nerves come form the PONS
Cranial nerves V, VI, VII & VIII originate from its surface
What cranial nerves come from the midbrain?
Origin of Oculomotor (CN III) & Trochlear (CN IV)
What is the only cranial nerve emerging form the back of the brainstem and where does it emerge from?
CN IV
Emerges from the midbrain
What is the dark line called if you looks at a cross section of the midbrain?
substantia nigra
What are the hemispheres of the cerebellum?
right and left seperated by vermis
What does each hemisphere of the cerebellum have?
Each hemisphere has an anterior, posterior and flocculonodular lobe
WHat is the surface strucutre of the cerebellum made of?
sulci and folia
How many cerebellar peduncles connect the cerebellum to the midbrain
3
What are the functions of the cerebellum?
posture maintenance
fine tuning motor activity
Where does the cerbellum recieve information from?
information form pyramidal tracts (motor intention of brain)
information from ipsilateral proprioceptors from periphery
information from vestibular nuclei re. balance and posture
What happens to the infromation in the cerebellum when it arrives?
Calculates best way to coordinate force, direction, extent of muscle contraction to maintain posture prevent overshoot and ensure smooth coordinated muscle contraction
What happens to the information in the cerebellum once it has decided what to do?
Sends ‘blueprint’ back to cerebral cortex via superior cerebellar peduncle
Does the cerebellum deal with information that is from the same side of the body or opposite?
Ipsilateral is on the same side so cerebellum deals with the same side of the body but the cerebral hemispheres deals with the opposite side of the body
Ipsilateral rather than contralateral
What tests can be done to test an abnorality of the cerebellum? - ataxia
Finger - nose test
Knee-heel test
Walking in a straight line
What are the 2 main parts that make up the diencephalon?
thalamus
hypothalamus
Is the diencphalon mianly white or grey matter?
grey matter
How would you describe the thalamus?
a sensory relay station
Where is the hypothalamus located?
It lies below the thalamus separated from it by the hypothalamic sulcus
What is the function of the hypothalamus?
Despite its small size, it is the main visceral control centre & is essential for overall homeostasis
What is the homeostatic role of hypothalamus?
Autonomic Control Centre
Body temperature regulation
Regulation of food intake
Regulation of water balance & thirst
Regulation of sleep-wake cycle
Control of endocrine system functioning
What is the venous drainage of the brain?
venous drainage into dural venous sinuses and then into IJV
What is the structure of the diencephalon?
Groove below thalamus is your hypothalamus sulcus then hypothalamus then pituitary stalk coming off
What is the body of grey mater lateral to the 3rd ventricle?
thalamus
Where does all sensory information pass through?
the thalamus
What does trh diencephalon develop from?
Develops from diencephalic vesicle (part of forebrain vesicle)
What is the thalamus made up of
different groups of nuclei
What is the lateral group of the nuclei?
The lateral group are involved in processing sensory information
Where does all sensory information synapse?
at the thalamus
What happens at the lateral geniculate body of the thalamus?
a relay center in the thalamus for the visual pathway
it receives a major sensory input from the retina
