Topography of the Brain Flashcards
Where does neural tube develop from?
Dorsal surface ectoderm
What do the cranial end of tube form?
Vesicles which develop into different parts of the brain
What are the parts of brain in foetal development?
Forebrain, Midbrain and Hindbrain
Forebrain - diencephalon and cerebral hemispheres
Hindbrain - pons and medulla
What is included in the brainstem?
Midbrain, pons, medulla
Cranial nerves III - XII, tracts of spinal cords and vital centres (resp.)
What is the functions of the brainstem?
Pathway for fibre tracts running between higher and lower centres
10 of 12 CN so innervation of head and neck
Produce rigidly programmed automatic behaviours essential for survival
Describe the medulla oblongata
Cavity is the 4th ventricle
Continues as spinal cord at foramen magnum of cranium
Lower part of medulla looks like spinal cord in structure
What are some surface features of the medulla?
Pyramids and their decussation (crossing over)
Olives laterally
Connected to cerebellum by inferior cerebellar peduncle
Cranial nerves IX, X, XI, XII from surface
Describe the caudal and cranial end of the medulla
Caudal - closed around IV ventricle
Cranial - opens with IV ventricle posteriorly
Describe the pons
IV ventricle is posterior to it
Has middle cerebellar peduncle
Has cranial nerves V, VI, VII and VIII from its surface
Describe the midbrain
Develops from mesencephalon
Central cavity - cerebral aqueduct
What are the surface features of the midbrain?
Superior cerebral peduncle
Corpora Quadrigemina (superior and inferior colliculi)
Origin of oculomotor and trochlear nerve
What is the only nerve to originate posteriorly?
IV - trochlear nerve
What are the right and left hemispheres separated by?
Vermis
Describe the cerebellum
Has anterior, posterior and flocculonodular lobe
Surface has sulci and folia
Three cerebellar peduncles connect it to brainstem
What is included in the white and grey matter of the cerebellum?
Grey - cortex on surface and deep nucleii
White - arbor vitae and cerebellar peduncles
What is the clinical significance of the cerebellum tonsil?
Is beside posterior lobe and if swelling then can get hernia of lobe as sitting above the foramen magnum
What are the functions of the cerebellum?
Posture maintenance
Fine tuning of motor activity
Describe how the cerebellum functions
Information from pyramidal tracts (motor), ipsilateral proprioceptors from periphery and info from vestibular nucleii for balance and posture
Cerebellum calculates the best way to coordinate action
Which sends blueprint back to cerebral cortex via superior cerebral peduncle
What is abnormality of the cerebellum function?
Ataxia
Can do finer nose test, knee heel test and walking in straight line to check
Describe the diencephalon
Deep within cerebral hemispheres, around the 3rd ventricle
Develops from diencephalic vesicle
Paired structure - thalamus and hypothalamus. All mainly grey matter
What is the function of the thalamus?
For triage for sensory overload
All synapse at the thalamus
Describe the thalamus
Mainly contains group of nuclei - anterior, medial and lateral group
Lateral group involved in processing sensory information
It is a sensory relay station
Describe the hypothalamus
Lies below the thalamus separated from it by hypothalamic sulcus
Small in size
Is main visceral control centre and essential for homeostasis
What is the homeostatic role of the hypothalamus?
Autonomic control centre, body temperature regulation, regulation of food intake, water and thirst balance, sleep wake cycle, and control of endocrine system functioning
Describe the blood supply of the brain
2 ICA enter the skull through the carotid canal (foramen lacerum) to supply the brain
2 vertebral arteries (branches of subclavian arteries) enter through skull at foramen magnum and form the basilar artery
Describe the Circle of Willis
Branches of the ICA join with those of opposite side and with PCA to form the continuous circle at the base of brain
Protective feature against vaso-occlusion of large vessels
What arteries are in the Circle of Willis?
Anterior cerebral artery
Anterior communicating artery
ICA
Posterior communicating artery
Posterior cerebral artery
Basilar artery
Where is the middle cerebral?
Medial aspect of cerebral hemispheres excluding occipital lobe
Where is middle cerebral?
Lateral aspect of cerebral hemispheres
Where is posterior cerebral?
Inferior aspect of cerebral hemispheres and occipital lobe
Describe the venous drainage of the brain
Superficial and deep veins of the brain drain into venous sinuses which lie between 2 layers of dura mater
Sinuses join together to ultimately drain into IJV
What are some of the sinuses draining the brain?
Transverse, superior sagittal, inferior sagittal, petrosal sinus, cavernous sinus
Describe the contents of the cavernous sinus
Oculomotor nerve, trochlear nerve, ophthalmic nerve, maxillary nerve, abducent nerve, ICA, sinus surrounded by dura mater
