Neuroanatomy Flashcards
Components of CNS
Brain and spinal cord
Components of PNS
Cranial nerves - 31 pairs
Ganglia outside of the CNS
Somatic
Proving sensation to the body wall
When do additional vesicles appear in the primary vesicle?
Around 6-8 weeks
Autonomic
Not present outside and maintains the internal environment of the body
3 swellings of primary vesicle
Prosencephalon, Mesencephalon and Rhombencephalon
What does the prosencephalon develop into?
Telencephalon and Diencephalon
What does the mesencephalon develop into?
It remains as the mesencephalon
What does the rhombencephalon develop into?
Metancpehalon and mylencephalon
Embryological division of cerebral hemispheres
Telencephalon
Embryological division of thalamus and hypothalamus
Diencephalon
Embryological division of midbrian
Mesencephalon
Embryological division of pons and cerebellum
Metancephalon
Embryological division of medulla oblongata
Myelencephalon
What makes up the brain stem?
Midbrain, pons and medulla
Descibe the horizontal plane
Superior and inferior portions of the brain
Describe the coronal plane of the brain
Anterior and posterior portions of the brain
Describe the sagittal plane of the brain
Right and left portions of the brain
Functional divisions of the nervous system
Sensory - afferent division
Motor - efferent division
Sensory afferent division of NS
Carries sensory information to the CNS
Motor efferent division of NS
Carries motor commands from the CNS to muscles and glands
Major structures and regions of the CNS
Brain: Cerebrum, cerebellum and brain stem
Spinal cord: Cervical, Thoracic, Lumbar, Sacral and Coccygeal segments
Commissural tracts
Connect corresponding regions of the two cerebral hemispheres
Association tracts
Connect different regions within the same cerebral hemisphere
Projection white matter tract
Connects the cortex with the spinal cord and brain stem
Cranial Nerve I
oLFACTORY
CNII
Optic
CNIII
Oculomotor
CNIV
Trochlear
CNV
Trigeminal
CNVI
Abducens
CNVII
Facial
CNVIII
Vestibulocochlear
CNIX
Glossopharyngeal
CNX
Vagus
CNXI
Accessory
CNXII
Hypoglossal
Acquiring neuroanatomical understanding
Reading current literature, dissections, reviewing radiological images
Grey matter
Outer part of cerebral hemisphere, large number of neurons, cell processes, synapses and supporting cells (microglia)
White matter
Inner part of the cerebral hemispheres, axons are myelinated
Myelinated cells in the CNS
Myelin sheath fromed by oligodendrocytes
Myelinated cells in PNS
Myelin sheath formed by Schwann cells
What do sulci and gyri do in the brain in terms of surface area?
Increase
Lobes of cerebral hemisphere
Frontal, Occipital, Parietal and Temporal
Blood supply in cranial cavity
Arterial and venous
Arterial supply in cranial cavity
Circle of Willis
Circle of Willis
R. and L. vertebral arteries join to create basilar artery and then the posterior cerebral artery.
Basilar artery forms the R. and L. posterior cerebral arteries which will form the R. and L. internal carotid arteries. They maintain contact via the posterior communicating artery.
R. and L. internal carotid go on to become the R. and L. anterior cerebral arteries respectively. These arteries communicate via the anterior communicating artery.
Cortical branches
Supplying arterial blood to the cortex
Central branches
Supplying arterial blood to the deep surfaces of the brain
Venous supply to the brain
Does not contain valves
They are called sinuses.
Present in two layers of dura mater - endosteal and meningeal
Dural venous sinuses
meningeal layer appears through gaps in the endosteal layer forming small gaps
Confluence of sinus
Present in the posterior part of the skull in cranial cavity. This is the area where the sinuses meet and drain into the internal jugular vein
Pathway of sinuses into internal jugular
Transverse sinus drains into sigmoid sinus drains into internal jugular vein
Types of veins
Superficial and deep
Superficial veins
Superior cerebral vein, superficial middle cerebral vein and inferior cerebral vein
Deep veins
Thalmostriate vein and choroidal vein which unite to create the internal cerebral vein and the great cerebral vein
Meninges - 3 layers
Dura mater
Arachnoid mater
Pi mater
Dura mater
Outer tough layer of CT
Arachnoid mater
relatively thin later that is usually apposed to the dura mater. Thin wispy cords of CT connect this layer to the pia
Pia mater
Very thin inner layer that is opposed to the surface of the brain. A layer of pia mater accompanies arteries penetrating into the brain
CSF
Cerebrospinal fluid
Where is CSF produced?
Choroid plexus in ventricles produces CSF
Journey of CSF
Circulates around the brain and spinal cord from the 4 ventricle to the subarachnoid space
Absorption of CSF
Reabsorbed into the dural venous sinuses by specialised structures called arachnoid granulations
Function of CSF
Cushions the brain both internally and externally
Cells of the nervous system and their roles
Neurons and glial cells
Neurons
transmit electrical signals
Glial cells
support and nourish neurons, maintain homeostasis and provide insulation
Cytoarchitecture of the cerebral and cerebellar cortices
Cerebral cortex - 6 layers
Cerebellar cortex - 3 layers
Layers of cerebral cortex
Molecular (plexiform) layer
External granular layer
External pyramidal layer
Internal granular layer
Internal pyramidal layer
Multiform (fusiform) layer
Diverse cell types which are organised into gyri and sulci
Layers of cerebellar cortex
Molecular layer
Purkinje cell layer
Granular layer
Highly folded structures
Basic development of nervous system
Neurulation - results in the formation of the neural tube from the ectoderm of the trilaminar germ disc.
Differentiation - neuroepithelial cells give rise to neurons and glial cells
Migration - neurons migrate to their final destinations
Synaptogenesis- formation of synapses between neurons
Myelination- glial cells wrap axons with myelin sheaths which will enhance signal transmission
Singalling factors acting as ligands
GDF
Groups of GDF
Fibroblast growth factors (FGF)
WNT
hedgehog
Transforming growth factor-b (TGF-b)
Mammals have 3 hedgehog genes - what are the names?
Desert
Indian
Sonic
WNT gene properties
15 different genes that are related to the segment polarity gene. The receptors of these genes are members of the frizzled family of proteins
TGF-b protein properties
More than 30 members, the mone morphogenetic proteins (BMP), the Mullerian inhibiting factor (MIF, anti-Mullerian hormone)
BMP inhibitory or non-inhibitory signal?
Inhibitory
BMP role
Critical molecules for preventing neural induction
Presence of BMP
inhibits the formation of neural tissue
Absence of MBP
allows for the formation of neural tissue
Cells closely packed together will form….
the epidermis
Cells disassociated and not closely packed together will…
not form epidermis but form neural tissue
Does presence of BMP allow the epidermis to form?
Yes
Mesoderm dorsal to the blastopore….
secretes moelciles that inhibits BMPs located in overlying ectoderm and will convert it to neuroderm
Types of BMP receptors
Type I and Type II
How do BMP molecules bind do a receptor?
They form a dimer and interact with the receptor which leads to the formation of 2 pathways
Pathways of bound BMP to receptor
SMAD and MAPK
Activation of the pathways after BMP has reacted with the receptor leads to
Phosphorylation.
Types of SMAD pathways which are a result of phosphorylation.
SMAD 1,5 and 8 which will combine to form complexes with SMAD4 and enter the nucleus to regulate the transcription of specific target cells
Fibroblast growth factor (FGF) will react with tyrosine kinase which leads to…
Activation of MAPK pathway.
Wnt proteins binds to only
proteins in the frizzled family, this occurs within the cell membrane and will activate another reaction in the cytoplasm
Interaction of Wnt with frizzled family protein leads to
Activation of dishevelled family proteins which inhibits a complex of proteins including axin, glycogen synthase kinase 3 (GSK-3) and adenomatous polyposis coli (APC)
Result of absence of Wnt singalling
Lead to phosphorylation of Beta-catenin which is degraded proteolytically.
Adding Wnt to the medial part of epiblast in experiment will
inhibit the formation of neural tisse
Adding Wnt to the lateral part of the epiblast will
no markers found
Addition of FGF to the medial explant
overrides the Wnt signalling and inhibts the formation of the neural tissue allowing the epidermis to continue to form
Addition of FGF to the lateral explant
no formation of neural tissue but the epidermis will develop
BMP inhibitor
Inhibits the formation of neural tissue
Neuroectoderm
Sheet that consists of neural cells. Cranial part of the ectoderm will form from the neural tube and form the brain and the spinal cord
Factors to consider when looking at neural patterning
Positional information and morphogens
Regionalisation…
involves long-range signalling that provides cells with information about their location in the neural epithelium. This information is known as positional information
Cells close to the source of cell
Very high levels of cell signalling
Cells far away from the source of cell
Very low levels of cell signalling
Signal that provokes more than one cellular response
Morphogen
