week 8 - nervous system Flashcards
What are the steps on how the synapse operates?
- The action potential from the pre-synaptic neuron reaches the synaptic terminal
- The synaptic vesicle releases the neurotransmitter
- The neurotransmitters travel across the synapse and bind to the receptors in the post-synaptic neurone
What do sensory neurones do?
They receive information from the environment
What do interneurones do?
They carry signals between sensory and motor neurones
What do motor neurones do?
They generate a response
What are the 4 main mechanisms of brain injury/
- Brain Contusion
- Increased Intercranial Pressure - ICP
- Diffuse Axonal Injury
- Stroke
What is a brain contusion?
It is cell death in the brain accompanied by haemorrhage/internal bleeding.
Can occur distant from point of impact
What is ICP?
Your bone does not expand, the intracranial vault is a fixed volume.
Therefore, if more material (like blood, CSF) is added, the pressure also increases
What else happens as ICP increases?
As more material is added in, substances are forced out of the cranial vault.
What is herniation?
This is when the brain is squeezed out through the foramen magnum(opening at the base of the skull) bc of increased ICP.
The brainstem becomes compressed, damaging the brain, patient stops breathing
Why is brainstem herniation the most life threatening type of herniation?
Bc the brainstem regulates unconscious processes essential to life - such as breathing
What is diffuse axonal injury/
Diffuse meaning damage is over a widespread area
Involves the shearing of axons in white matter tracts
Occurs when grey matter and white matter slide over each other, severing the axons
Causes unconsciousness and persistent vegetative state
How can mechanical pressure be put on the brain to cause diffuse axonal injury?
- Encephalitis - viral, inflammation of brain
- Rabies - from bites
- Meningitis - inflammation of the meninges
- Brain tumours
- Abscesses
What is a stroke?
It is a loss of blood supply to some or all of the brain which results in cerebral deficit that lasts for at least 24 hours - unless fatal
What are the symptoms of stroke determined by/
The areas that are damaged by the stroke. For example, right side brain injury can cause symptoms in the left side of the body - as right side controls left side of body
What is a transient ischaemic attack?
It’s like as stroke that lasts for less than 24 hours caused by inadequate cerebral blood supply
How does a loss of blood supply occur?
A lack of blood flow top brain caused by clot/rupture of blood vessel
What are the 2 classifications of stroke?
Ischaemic stroke - caused by decreased oxygen delivery to brain tissue due to swelling which compresses nearby arteries
Haemorrhagic stroke - decreased oxygen delivery because of blood leaking into the brain
What are the main things that protect the brain?
Circle of Willis - 4 main blood vessels supply blood to circle of Willis, blood leaves via 3 other blood vessels????????
What can put you at risk of stroke?
Modifiable - smoking
diabetes
hypertension
obesity etc
Uncontrollable -
Age
Genetics
Prior stroke
What is intracerebral haemorrhage
Bleeding within the brain, which leads to blood in parenchyma, causing a haematoma, causing rupture of vessels nearby.
The growth is stopped by counter pressure
What is subarachnoiud haemorrhage
Occurs when saccular aneurysms located at cerebral arteries of circle of willis rupture
Hunt Hess scale?
What is the diagnosis of hemorrhagic stroke?
- Thunderclap headache
- Xanthochromic lumbar puncture (blood in places such as CSF)
- Star pattern on CT Scan
How can you try prevent the bursting of aneurysms which can cause stroke?
- Clipping
- Endovascular coils
Compare ischaemic and haemorrhagic strokes
