Enquiry 5, Stroke Part 1 Flashcards
Why are some parts of the body depicted larger then others in the motor and sensory homunculus?
For both the motor and sensory cortex the neurons are laid out in a specific way and is generally depicted as a homunculus, with more neurons present in the areas appeared larger . For example in the motor cortex the face and hands have a larger depiction indicating there are more neurons travelling to these areas of the body as compared to the elbow.
what are the primary functions of the meninges and where are they found?
the meninges are found below the skull. their primary functions are to provide stabilisation of the brain within the skull, shock absorption and to carry the blood supply to the entire brain
what are the primary functions of the meninges?
their primary functions are to provide stabilisation of the brain within the skull, shock absorption and to carry the blood supply to the entire brain
what are the meninges made up of and where are they found?
the meninges are found below the skull. there are three layers of meninges working together: - the dura mater - arachnoid mater - pia mater
describe the dura mater and its function
is a tough fibres covering with one layer attached to the periosteum of the skull. there are spaces throughout the dura where it extends deep into the cranial cavities creating dural folds and helping to secure the brain within the skull.
describe the arachnoid mater and its function
is below the dura. this layer contains lymphatic fluid helping to decrease friction and below this is the sub arachnoid space, which contains a web like collection of collegen and elastin. in the space you will also find cerebral spinal fluid CFS.
describe the pia mater and its function
is the inner most layer. it is a delicately thin layer attached to the brain and spinal cord. the layer is highly vascularised and the blood supply to the brain runs along the top of this layer.
where and what are the sinuses within the skull?
sinuses are areas within the dura folds where large veins can be found which collect blood and circulate it back to the heart e.g. the superior sagittal sinus.
what is the function of CSF?
the cerebral spinal fluid plays a key role for shock absorption and is a transport system for dissolved gases, nutrients, chemicals and waste. the brain and spinal cord have numerous cavities (sinuses, sub arachnoid space) that are filled with csf.
In the brain the cavities, filled with csf, are interconnected and create a passage way for the csf to circulate. this passage way branches into four chambers, known as the ventricles. Explain how each ventricle is connected and their structures within the brain.
Each cerebral hemisphere has a large lateral ventricle which are connected via the third ventricle in the diencephalon (near the thalamus and hypothalamus). the third ventricle is connected to the fourth ventricle, located in the pons and medulla oblongata, via a cerebral aquaduct. these structures can be impacted by stroke. *picture
where in the brain is the blood supply found?
found along the top of the pia mater
what causes a stroke?
happens when blood flow to the brain is cut off. when brain cells are staved of oxygen they become damaged causing a stroke. (Insult within the brain).
symptoms following a stroke?
Face Arms Speech Time - drooping face - weakness in arms or legs - difficulty speaking - confusion - changes to vision - loss of balance - memory loss
what is an ischaemic stroke?
make up about 85% of all stokres. caused by a blockage in one or more of the arteries that supply blood to the brain.
how can the circle of willis help to prevent a stroke?
the circle of willis may provide collateral circulation and may help to prevent cell death (from lack of o2 in blood).
what causes an ischaemic cascade? and what damage does this cause?
as cell death occurs the ischaemic cascade begins and the amount of cell death and damage becomes evident. as cascade develops, significant swelling develops in brain causing compression to near by areas in brain like the ventricles.
what does an ischaemic stroke and lateral ventricles look like in a CT scan?
in ct scan darkened area shows the ischaemic stroke. left and right of midline is a black linear structure which is a lateral ventricle. healthy brain should present both symmetrical ventricles (looks like a butterfly). compression to the lateral ventricle (in an ischaemic stroke) causes csf to move out of the space and increases inter cranial pressure.
what causes an embolic stroke?
embolic stroke occurs when a clot is formed in another area of the body and travels to the brain. they occur in the heart or arteries of the chest and neck. they break free and travel throughout blood stream into the brain. when they reach a blood vessel they cant pass through and the clot is stuck which stops the blood flow. this blockage is called an embolus.
how to treat an embolus?
when these clots occur the use of clot busting drugs (e.g TPA), or neuro surgery (e.g Thrombectomy) can help minimise the effects.
describe the removal of an embolus through a thrombectomy.
Thrombectomy - mechanical removal of a clot. done by inserting a catheter into the femoral artery. when the clot is found it is entrapped by the catheter and then removed.
what are the negative effects of TPA
TPA can result in significant bleeding and the selection criteria to use this drug is very specific.
what is a haemorrhagic stroke?
Is when bleeding occurs within the brain. Causes lots of tissue damage as the area surrounding the bleed/haematoma have diminished blood flow and oxygen. there is an increased pressure from the haematoma itself to the local brain tissue resulting in infarction (tissue death).
what is the survival rate of an haemorrhagic stroke compared to an ischaemic stroke? How common is it?
around 1 in 10 patients who have a haemorrhagic stroke die before reaching hospital. the risk of death in the first 3 months is much higher than that of an ischaemic stroke. about 15% of all strokes are haemorrhagic.
how is a haemorrhagic stroke seen in a CT scan?
The CT scan for an intrecerebral (within brain) hemorrhage - areas in white indicate blood or fluid leaking from haemorrhagic stroke, - darkened areas indicate ishaemia or cell death as said before. Haemorrhagic stroke can also compress the lateral ventricles and increases the inter cranial pressure, limiting the flow of csf to the brain and spinal cord.
