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46 Cards in this Set
- Front
- Back
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What are the names of the 3 cerebral meninges |
1. Dura 2. Arachnoid 3. Pia |
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Where in the skull is the dura found. What are its layers called? |
Adjacent to skull, attached in places
Periosteal and Meningeal layers - they are fused together |
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What is the structure of the Arachnoid |
Compact layer of barrier cells and an inner trabecular meshwork |
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Where is the Pia found - describe it |
Thin membrane, tightly attached to the basement lamina of the brain |
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What is the name of the fold of dura mater that separates the hemispheres? |
The falx cerebri (the separation is called the falx) |
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Describe the falx |
Long, strong, arched fold of dura mater. It descends vertically in the longitudinal fissure between the cerebral hemispheres |
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What is the tentoria |
A pair of transverse sheets of dura - extend laterally below the base of the occipital cerebrum - divide cerebrum above from cerebellum below |
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What structure does the brainstem pass through |
The brainstem passes through the gap between the 2 sides of the tentorium |
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What is the gap between the 2 sides of the tentorium known as |
The tentorial incisure |
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What are the 3 types of cerebral haemmorhage |
Epidural haemmorhage - bleeding outside the dura
Subdural haemmorhage - bleeding between dura and arachnoid
Subarachnoid - bleeding in arachnoid space |
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Patient presents with a haemmorhage increasing rapidly in size. Lens shaped on MRI Regain conciousness for lucid interval and then lose conciousness Has had a severe headache |
Epidural Haemmorhage |
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Patient presents with a haemmorhage increasing rapidly in size - spread out widely. Patient has had signs and symptoms of headacehe and vomiting following severe whiplash in a road traffic accident about a week ago |
Subdural haemmorhage (venous blood so slower onset) |
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What are the cerebral ventricles |
Fluid filled spaces in the brain - CSF fills these ventricles |
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Which ventricles are known as the lateral ventricles |
1 and 2 |
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How is CSF formed |
Formed by the choroid plexus - meshwork of capillaries which are covered by ependymal cells protruding in the ventricles of the brain |
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Where is the majority of CSF made in the brain |
There is choroid plexus found in all ventricles however the majority is in the lateral ventricles |
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In what way is the choroid plexus similar to the glomeruli in the kidneys |
Both produce a protein free filtrate from blood |
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What feature of choroid capillaries regulates the flow of blood |
They are fenestrated - this means that the blood is ultrafiltrated as it passes between the ependymal cells into the subependymal layer. |
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What is the rate of blood flow per day in the brain |
500ml per dy |
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Why can small changes in pCO2 cause such large changes in CSF in comparison to the blood |
Healthy CSF contains little protein and no cells. It is not pH buffered in the same way as blood.
Small changes in pCo2 causes large changes in pH |
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How is CSF drained |
It is drained primarily in the blood through arachnoid granulations in the superior sagittal sinus |
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What is the percentage of plasma proteins in CSF |
0.3-1% |
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What is the percentage of plasma glucose in CSF
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60% |
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What is the range of CSF pressures - what is a cause of pressure change |
4.4-7.3mmHg
Coughing
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Describe the flow of CSF through the brain |
1. From the lateral ventricles to the third ventricle 2. From third ventricle to fourth ventricle 3. From fourth ventricle to cisterna magna 4. From cisterna magna to subarachnoid space 5. Arachnoid granules to Sagittal sinus |
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How do arachnoid granules allow CSF to drain into the superior sagittal sinus |
They penetrate the dura at the top of the brain
Diploic veins also run in the skull - large, thin walled valveless veins channel between the inner and outer skull |
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What are the 4 functions of CSF |
1. Bouyancy 2. Protection 3. Chemical stability 4. Prevention of ischaemia |
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How does CSF create bouyancy |
Human brain is around 1400g - mainly lipid so floats in CSF (Water) Without this the brain would cut off its blood supply |
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How does the CSF provide chemical stability |
Flows through the inner ventricular system - before being absorbed back into the blood stream. Rinses the metabolic waste from the CNS through the blood brain barrier. Allows homeostasis and distribution of neuroendocrine factors |
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How does CSF prevent ischaemia |
If there is decrease in CSF can reduce total intercranial pressure and preven ischaemia due to reduced perfusion |
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What is the name of the condition caused by accumulation of CSF in the ventricular system. |
Hydrocephalus |
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How is hydrocephalus diagnosed |
Usually due to blockage in cerebral aquaduct- repaired by a shunt in 3rd ventricle leading to subarachnoid space
Detected by translucent skull - no brain matter to block light |
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Why are most tumours of the brain gliomas |
Neurones cannot undergo mitosis therefore cannot produce tumours |
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What is the cause of epilepsy |
Malfunction of the glial cells in an area where insult has occured |
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What is the role of astrocytes |
1. Maintain pH and glucose levels 2. Get rid of debris 3. Secrete growth factors (and cytokines to regulate immune system under attack) 4. Form a glial scar after nerve damage |
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What type of astrocytes are found in grey matter |
Protoplasmic astrocytes |
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What type of astrocytes are found in white matter |
Fibrous astrocytes |
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What type of tumour in the brain is most common |
Astrocytomas |
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What is the role of astrocyte end feet around the capillary |
Form a continous wall around capillary (Capillaries also have tight junctions) prevent exit of proteins |
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How is the blood brain barrier formed |
Continous wall around capillary by astrocyte end feet
Tight junction system - between endothelial cells |
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How do amino acids cross the BBB |
special transport mechanisms - (transporters) There are 3 amino acid transporters one for acidic neutral and basic amino acids |
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How do lipid soluble molecules pass the BBB give an example of one |
They are able to pass the BBB unaided, opiates are able to cross the BBB (eg Heroin) |
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What is the significance of antibiotics used to treat pathological conditions of the brain |
Normally the antibiotics are not able to cross the BBB |
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Name a condition where the BBB breaks down |
Meningitis |
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What is significant about the treatment of meningitis |
Penecillin can be used as the meningeal inflammation breaks down the BBB allows penecillin to penetrate the brain tissue. |
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How can a neoplasm be differentiated from normal tissue on an MRI |
In a neoplasm there is lack of tight junctions in the BBB. This affects the relative hydration of the tissue and enables it to be seen on an MRI |
