Neurological Conditions Flashcards
What is the blood brain barrier
The BBB helps to isolate the brain from the circulatory system
Protects against: toxins, pathogens, blood components
Where is the blood brain barrier absent or ‘leaky’ in?
Choroid plexus (where CSF if produced)
Posterior pituitary and neurohypophysis (where hormones are released)
What is bacterial meningitis?
Inflammation of the meninges - particularly in the arachnoid mater and the pia mater
How does bacterial meningitis begin?
Bacteria invades the subarachnoid space, spreading to the ventricles of the brain.
Infection spreads to brain parenchyma and the spinal cord. Results in neuronal damage, particularly in the hippocampus.
Highly activated leukocytes in the cerebrospinal fluid.
How does bacteria gain access to cerebral spinal fluid?
Through local defects, sites of infection or the choroid plexus
What are the physiological consequences of menningitis?
Bacteria releases toxins that can cause immediate cell death, causing the inflammatory response.
This results in: edema, intracranial pressure and neuronal damage.
What are the effects of inflammatory mediators being released in the brain?
Toxic inflammatory mediators trigger dangerous inflammatory responses, resulting in edema in tissues, pus in the subarachnoid space, spreading over the cerebrum, cerebellum and spinal cord.
What is Cushing’s Triad?
The 3 main symptoms indicating extreme intracranial pressure =
Rising blood pressure
Bradycardia
Periodic or slow respiration rate
How does the brain compensate for increased intracranial pressure?
Increase the venous drainage (reducing amount of blood)
Increase in the CSF drainage.
What is the Monro-Kellie Doctrine?
A doctrine that describes the relationship between the contents of the cranium and intracranial pressure.
Tissue + Blood + CSF = Total volume
What pathologies change tissue volume?
Meningitis
Brain tumour
Inflammation/oedema
Trauma
What pathologies change CSF volume?
Choroid plexus tumour
Blockage retarding CSF flow
Reduced drainage into venous sinus
What pathologies change blood volume?
Hypercapnia (local vasodilation)
Heart failure (leads to increased venous pressure)
What is Alzheimer’s disease?
A cognitive impairment leading to dementia.
How does Alzheimer’s disease present itself?
With deficits in:
Sensation Processing speed Perception Motor skills Memory Language Executive functioning
What does the sulki/gyri look like in a brain with AD?
Sulki widens
Gyri thins
What are the anatomical features of cortical atrophy?
Loss of parenchyma
Narrow gyri & widened sulci
Atrophy of parahippocampal cortex
What are two key ultrastructural features of AD?
Senile plaques (i.e. amyloid plaques or neuritic plaques)
Neurofibrillary tangles (formed from tau proteins)
What are Amyloid plaques?
Extracellular deposits of beta-amyloid accumulating in areas of the brain.
Why are Amyloid plaques dangerous?
There is a recruitment of activated astrocytes and microglia (involved in inflammatory response)
Behaves in a way as if there is some damage in the tissue, and inflammatory response is developing.
True or False - the number and distribution of the amyloid disposition in the tissue is not well correlated with clinical signs.
True
You may present signs of Alzheimer’s, yet an MRI may not show any clinical signs of degeneration
What make up the amyloid plaques that sits in brain tissue?
Fibrils.
Proteins will fold, sometimes incorrectly in the intracellular space and bind into protofibrils
What is the Amyloid Cascade hypothesis?
amyloid accumulation may be the initial step in Alzheimer’s pathogenesis, leading to deposition of Tau protein (neurofibrillary tangles).
Tauopathy is linked to neuronal decline and synaptic loss. These in turn result in classical cognitive decline
What is Tau protein?
A very soluble protein, encoded by MAPT gene.
What is the Tau hypothesis of AD?
Tau pathology is the primary driver of neurodegeneration.
The spread of tau pathology correlated with cognitive decline and neuron loss.
What does tauopathy do to neurons?
Disrupts functioning of cytoskeleton
Disrupts to receptor protein trafficking inside the cell
Disrupts to synapse function and formation.
In the end, these issues lead to neuronal death.
What affects does ageing have on the brain?
Degeneration of neurons
Increase size of ventricles as we age
Develop pigmentation of neural tissue
What is the dura mater?
Makes up the periosteal and meningeal layers.
Has a tough, outer layer that lines the skull that protects the brain
What is the arachnoid mater?
The subarachnoid space is beneath the arachnoid mater and contains the cerebrospinal fluid
What is the pia mater?
The nutritive layer that hugs the surface of the brain
