Principles of Neuroscience Lecture 3 Structure of the Nervous system Flashcards
Where does the cerebrospinal fluid sit?
The CSF resides in the subarachnoid space
Between the arachnoid and pia maters
What is the name for the protective layers on the brain?
Describe the layers
These are collectively called the Meninges
Pia: close
Arachnoid: spidery
Dura: hard (has its own vascularisation, fused with skull)
What are arachnoid granulations?
These are projections that release CSF back into the super sagital space for venous return
Where and what is the super sagital space?
It is within the dura mater. It contains blood for venous return
Where is CSF made?
It is made in the ventricles in the brain
How many ventricles are there?
2 lateral
3rd ventricle
4th ventricle
What is the name of the blood vessels delivering nutrients into the ventricles for the CSF?
Choroid plexus
How much cerebrospinal fluid is made per day?
Around half a litre
What is the difference between white matter and grey matter?
White matter has much more extensive myelination
The fat gives it the white colour
Describe how CSF moves from the ventricles to the subarachnoid space
Moves down into the 3rd and fourth ventricles, then into the subarachnoid space
Is the vasculature in the brain dense or no?
Is vasculature in the white or grey matter more dense?
The vasculature is very dense due to the hi energy demands of the brain
Vasculature is more dense in the grey matter
Which arteries delivery blood to the brain?
Internal carotid arteries
Vertebral arteries
Which arteries circulate blood through the brain?
What are the subdivisions?
The cerebral arteries
Posterior, Middle and Anterior.
The middle is most important
What is important about the blood supply to the four sections of the brain?
The blood supply to the four sections is discrete. This means that if there is a problem with blood flow to one area, that section is deprived of blood
What is another name for a stroke?
Cerebrovascular accident
What is responsible for most of the problems that occur in the brain?
Issues with vascularisation (CVAs)
What are the two types of cerebrovascular accidents?
Occlusive
Haemorrhagic
What is an occlusive CVA?
Give an example
Occlusive CVAs involve narrowing and blockage of the vascularisation of the brain.
Eg. Atherosclerosis, thrombosis
What is an haemorrhaging CVA?
Give an example
Haemorrhaging is bleeding, due to the rupture of vessels
Eg. Aneurysm, trauma, elevated blood pressure
What do CVAs lead to?
Tissue ischemia (lack of oxygen), leading to atrophy of the area
Is vascularisation different among individuals?
What does this mean in terms of characteristic loss of function?
Vascularisation is consistent between individuals (in such a way that function organisation of the brain is)
This means that CVAs in a particular region will lead to a characteristic loss of function
What is herniation?
Herniation is when an organ is displaced, protruding through the wall of the cavity containing it
Why is raised intra-cranial pressure dangerous?
The skull resists expansion, so there is a build up of pressure, leading to herniation
What are the four ways that intra-cranial pressure can increase
- Haemorrhage
- Vasogenic oedema : increased permeability, increased volume of CSF
- Cytotoxic oedema: swelling of cells
- Hydrocephalus : over secretion of CSF
What is haemorrhage?
Bleeding
What is cytotoxic oedema?
When cells swell, reducing the volume of ECF
What is hydrocephalus?
This is when there is over secretion of ECF
What is vasogenic oedema?
This is when there is increased permeability leading to increased volume of ECF
What is the role of the blood brain barrier?
To closely control what can get into the blood supply to the brain
What is the main requirement for molecules in order for them to be able to cross the blood brain barrier?
The must be small and lipid soluble
Receptor on the epithelium that can transport the molecule in
What structural feature means that the blood brain barrier is very selective?
The tighht junctions between the epithelial cells of the capillaries in the vasculature of the brain means that molecules cannot get through
What are the two ways that molecules can cross the BBB?
Be small and lipid soluble
Have a transporter protein
Why is the BBB problematic for drug designers?
It is hard to make the drug acceptable to the brain
Even if it gets into the brain, it may be expelled back out again
What are astroglia?
Astroglia regulate the ionic composition of the ECF and recycle neurotransmitters
What are micro glia?
Micro glia are like macrophages
They clean up detritus and dead cells
What are the two phases of micro glia?
Ameboid (active)
Ramified (resting)
What is the role of atrocytes?
They maintain the tight junctions in the capillaries of the brain
