Cerebral hemispheres and cells Flashcards
Which sulcus separates the parietal and temporal lobes?
Lateral sulcus
What is the 5th cerebral cortex?
The insula cortex
Sits behind the lateral sulcus (oberculum)
Visceral sensation
Which lobe is Broca’s area in?
Frontal
What do the pre and postcentral gyri do?
Precentral gyrus: motor
Postcentral gyrus: sensory
Which lobe is Wernicke’s area in?
Temporal
Which lobe is the auditory cortex in?
Temporal
What occurs at the angular gyrus?
Visual interpretation
Sits at the occipital end of lateral sulcus
What does the uncus do?
Relays olfactory fibres
What occurs at the cingulate gyrus and fornix?
Limbic system
Part of autonomic nervous system
Where is the somatosensory association cortex?
Posterior to the postcentral gyrus
Which parts of the body are represented in the medial side of the precentral and postcentral gyri?
Foot, knee and genitals (sensory)
What is the blood supply of the medial and lateral post and precentral gyri?
Lateral: middle cerebral artery
Medial: anterior cerebral artery
What are the three types of white matter?
Commissural fibres (corpus callosum) Association fibres (different parts of one hemisphere) Projection fibres (connect higher centres to spinal cord)
What does the corpus collosum connect?
The right and the left hemispheres
What is the difference between the superior and inferior longitudinal fasciculus?
Superior: Connects frontal lobe to occipital
Inferior: Connects anterior temporal lobe to posterior temporal lobe
What is significant about the uncinate fasciculus?
Does not develop until age 30 Connects temporal (emotions) to frontal (personality)
Where is the pineal gland?
Inferior and posterior to the thalamus
Superior to the superior colliculi
What connects the two thalami within the 3rd ventrical?
Interthalamic adhesions
Where does the hypothalamic sulcus run?
From intreventricular foramen to the entrance of the aquaduct posteriorly
What enters the medial geniculate body?
Auditory pathway
What is the difference between the VPL and the VML nuclei of the thalamus?
VPL contains sensory information for body and VML contains sensory information for the head and neck
At what level does the common carotid divide into internal and external carotid arteries?
C4
Which arteries does the internal carotid split into in the head?
Ophthalmic artery Posterior communicating Anterior choroidal anterior cerebral Middle cerebral artery
Where does the vertebral artery run?
Up the transverse foramina of the cervical vertebrae usually from C6
Then enters foramen magnum and combines into basilar artery which forms posterior cerebral arteries
What does the anterior choroidal arteries supply?
Choroidal plexus which makes CSF
What are the branches of the vertebral arteries?
Anterior spinal Posterior spinal Posterior inferior cerebellar artery Basilar artery Anterior inferior cerebellar artery Pontine arteries Superior cerebellar artery Posterior cerebral arteries Meningeal branches
What do the anterior, middle and posterior cerebral arteries supply?
Anterior: medial anterior 2/3
Posterior: inferior hemispheres and posterior 1/3 of medial
Middle: outer surface
There are anastomoses between these
What is the most common location of the aneurysms in the circle of willis?
Between Anterior communicating and anterior cerebral arteries
What is the blood supply of the thalamus?
Posterior communicating
Basilar
Posterior cerebral
Which veins drain into the great vein of Galen?
Basal vein of Rosenthal
Internal cerebral vein
What are the cells in grey matter?
Neuronal cell bodies Neuropil Axons and dendrites Enveloping glial cells and glial processes Capillaries
What are the cells in white matter?
Axonal processes
Supporting glial cells
Blood capillaries
No neuronal cell bodies
What are the features of a typical neuron?
Large centrally located nucleus Prominent nucleolus Nissl bodies (Free ribosomes and RER which stain dark) Single axon-pale as not much RER Multiple dendrites Mitochondria Neurotubules Secondary lysosome Golgi apparatus/stacks
Why are neurotubules and neurofilaments so prevalent in dendrites?
Neurofilament: maintains extended form of dendrites
Neurotubules: act in rapid axonal transport
What are the two types of dendritic synapses?
Grey’s type 1: Round vesicles with asymmetric synapse
Grey’s type 2: Ellipsoidal vesicles with symmetric synapse
In pyramidal cells , type 1= mainly dendritic spines and smaller branches. Type 2 =perikaya and dendritic trunks
What is the most common site of synapse?
Dendritic spines
Each dendrite is contacted by multiple axon terminals
Where does collateral branching for axons occur?
For myelinated nerves, collateral branches occur at the node of Ranvier (Never at a point of myelination)
Towards their end, axons pass out of the myelin sheath to form the pre-terminal axon
Which cells maintain myelin sheaths?
CNS: oligodendrocytes
Peripheral nervous system: Schwann cells
How do axons terminate?
In a synaptic filled terminal bouton
How to tell the difference between axons and dendrites?
Axons: Axon hillock lacking in RER, neurotubules in clumps, myelinated, synaptic vesicles
Dendrites: Larger, unmyelinated, irregular, spines on surface
How big is a central synapse compared to a neuromuscular junction synapse?
90nm neuromuscular junction
20nm synaptic cleft
What holds pre and post synaptic junctions together?
Adherens junctions
What is contained within small clear vesicles and large dense core vesicles?
Small, clear vesicles,: acetylcholine
Dense core vesicles: dopamine, serotonin or noradrenaline
What is the difference between an electrical synapse and a gap junction?
They are the same
What are connexons?
Pore like structures between 2 membranes which allow passage of ions
What are the two types of astrocytes?
Fibrous (more common in white matter)
Protoplasmic (more common in grey matter)
or
Type 1 and type 2 depending on surface antigens and embryological origin
What are the two types of oligodendrocytes?
Interfasicular-aligned in rows between nerve fibres forming myelin. Each oligodendrocyte may wrap around a node of 15 axons
Satellite- function not clear
Why are glial cells important in the CNS?
CNS does not contain fibrous investing tissue
Filling space is done by glial cells
Play a role in nutritive support, soak up excess K+ ions
What are the morphological features of astrocytes?
Star shaped
Small nucleus and dense chromatin
Contains intermediate filaments with glial fibrillary acidic protein (GFAP)
Vesicles filled with glycogen
Terminal expansions of cell processes form end feet which form glial limiting membrane
What are the functions of astrocytes?
Endfeet stimulate endothelial cells to form tight junctions and maintain blood brain barrier
Astrocytes transmit nourishment from capillaries to neuronal cell bodies and dendrites
Astrocytes linked by gap junctions so form continuous transport chain. Remove K+ ions by passing them along towards blood vessels
What is the difference between fibrous astrocytes and protoplasmic astrocytes?
Fibrous: more common in white matter, cyclindrical processes, weaving at right angles, provides physical support to tissue, high density of GFAP
Protoplasmic: more common in grey matter, shorter, fewer glial filaments, envelop neuronal bodies and absorb K+ ions
What are microglia?
Originate from mesenchymal cells
Reside in CNS in resting state
In tissue injury they transform into large phagocytic cells
5-15% of glial cells
What are ependymal cells?
Line the ventricles and form cuboidal epithelium with cillia and microvilli
Loose epithelium allowing substances to pass freely from tissue spaces into CSF
No endothelium, just rests on endfeet of astrocytes
What are the 6 layers of the cerebral cortex?
I. Molecular/plexiform: synaptic layer with few cells, dendrites are branches of pyramidal cells
II External granular layer: stellate cells and small pyramidal cells
III External pyramid layer: pyramidal cells, slender axons which run up and down towards deeper layer of the cortex
IV: Internal granule layer: stellate cells
V: Internal pyramidal layer: Large pyramidal neurons include giant Betz cells of primary cortex
VI: multiform layer: small pyramidal cells, cells of Martinotti and stellate cells
Describe the fibres within the layers of cerebral cortex
Axial and tangential
Radial bundles=small + include axons both entering and leaving the cortex
Tangential= originate from afferent fibres in the thalamus. Often in layers 4-5 and are known as inner and outer bands of Balliarger. Outer band visible to naked eye in layer 4 ( Stria of Gennari)
