Session 2 Flashcards
Describe the structure and function of the blood brain barrier
Limits diffusion of substances into the brain
Brain capillaries - tight junctions between endothelial cells, basement membrane surrounding capillary, end feet of astrocytes processes, allows transport of glucose and amino acids
Describe the general morphology of a neurone and how neurotransmitters are released
Nucleus surrounded by soma, dendrites, axon (myelin sheath by Schwann cell/oligodendrocytes), axon terminal
Neurotransmission (at synapse) - depolarisation opens VG calcium channels –> vesicles move and fuse to release neurotransmitter –> diffusion across cleft to post synaptic membrane –> ligand gated ion channels or GPCR
Name the major excitatory and inhibitory neurotransmitters in the CNS and describe their action at receptors
Excitatory - glutamate, ACh, dopamine, serotonin, histamine , substance P
At receptors e.g. glutamate, NMDA, AMPA, kainate - cause depolarisation by release of sodium, potassium or calcium
Inhibitory - GABA (brain), glycine (brainstem)
At receptors e.g. GABA - cause hyperpolarisation by release of chloride ions
Understand the location of amine neurotransmitters in discrete pathways and how they may be implicated in various CNS disorders
Serotonin pathways - locus ceruleus
NA pathways - locus ceruleus
ACh pathways - nucleus basalis –> cortex, hippocampus
*degeneration associated with Alzheimer’s disease
Dopamine pathways - mesocortical, mesolimbic, nigrostriatal, tuberohypophyseal
* low dopamine associated with Parkinson’s disease, high dopamine associated with schizophrenia
Outline the blood supply of the brain
Circle of Willis
Anterior cerebral –> anterior communicating –> middle cerebral –> internal carotid –> opthalmic/posterior communicating –> basilar –> pontine –> anterior inferior cerebellar –> vertebral –> anterior spinal/posterior inferior cerebellar
Describe the location of the cranial dural sinuses (superior saggital, inferior saggital, straight, occipital, sphenoparietal, cavernous, superior petrosal, inferior petrosal, transverse, sigmoid…)
Venous channels found between the layers of the dura mater
They receive blood from internal and external veins of the brain and CSF from the subarachnoid space and empty into the internal jugular vein
Describe the meninges and explain how they protect the brain
Meninges supports and mechanically stabilises contents of the cranium
Skull, extradural space, dura mater, subdural space, arachnoid mater, subarachnoid space, pia mater, brain tissue
Describe the function and contents of the subarachnoid space
Contents - trabeculae, blood vessels, CSF
CSF bathes brain, cushions agains mechanical agitation, dissolves and carries away products of metabolism
Describe the locations of the ventricles in the brain and outline the formation, functions and circulation of cerebrospinal fluid
Lateral (L+R) - cerebrum
Third - diencephalon of forebrain, between right and left thalamus
Fourth - back of the pond and upper half of medulla oblongata
Formation - ependymal cells of the choroid plexus
Function - produces CSF
Circulation:
Lateral -foramina of Monro-> third -cerebral aqueduct-> fourth –> brainstem –> spinal cord
Consider clinical consequences of intercranial disease and head/skull injury
Le fort fractures (I, II, III)
Anterior fossa - cribriform fracture –> CSF rhinorrhea
Middle fossa - pterion –> MMA bleed
Posterior fossa - damage to brainstem –> death
Name the types of glial cells found in the CNS and describe their contributions to the normal function of the nervous system
Astrocytes - provide nutrition for neurones (glucose-lactate shuttle), remove/control concentration of neurotransmitters, maintain ionic environment (K+ buffering), help form blood brain barrier
Oligodendrocytes - responsible for myelinating axons in CNS
Microglia - immunocompetent cells, recognise foreign material –> activated phagocytosis to re,over debris and foreign material
Which arteries supply the spinal cord?
Posterior spinal artery (x2)
Anterior spinal artery
Anterior & posterior segmental medullary arteries
Explain the significance of the artery of Adamkiewicz
Largest anterior segmental medullary artery
Supplies inferior 2/3 of spinal cord (via anterior spinal artery)
Damage (e.g. during aortic aneurysm surgery) –> anterior spinal artery syndrome (incontinence, impaired motor function of legs, somewhat preserved sensory function)
Describe the blood supply of the brain
Anterior cerebral artery - medial, superior brain, frontal pole
Middle cerebral artery - lateral brain, temporal pole
Posterior cerebral artery - inferior brain, occipital pole
Describe Le Fort fracture classification
Involve separation of all or a portion of the midface from the skull base (involving pterygoid plates)
Le Fort 1 - above level of teeth (floating palate)
Le Fort 2 - at level of nasal bones (floating maxilla)
Le Fort 3 - at level of orbit (floating face)
