Miscellaneous Flashcards
What are the 3 fluid filled compartments we can consider the brain to consist of
what are they separated by
Extracellular space
blood vessels
ventricles
selectively permeable barriers
What is the Monro-Kelly Doctrine
If any of the brain fluids changes in volume, one or both of the other two must also change, otherwise intracranial pressure will rise and brain tissue will become compressed
How much blood does the brain require per min
800ml/min
Why is cerebral blood flow so regulated
too much blood flow can lead to raised intra-cranial
pressure (normal range, 5-15 mmHg),
too little blood flow (ischaemia and resulting hypoxia) can lead to loss of neuronal function.
If blood flow is interrupted for a few seconds, unconsciousness results; after a few minutes infarction may occur
What is a ‘stroke’
a rapid onset of neurological dysfunction due to impaired blood supply to brain tissue
What are the causes of interrupted blood flow to the brain?
What % of strokes does each count for
- Thrombotic strokes (~50% of strokes)
- Embolic strokes (~30%)
- Haemorrhagic strokes (~20%)
What is a haemorrhagic stroke
Leaking or ruptured blood vessels, eg due to high blood pressure, aneurysm, trauma
What is a TIA
‘transient ischaemic attack’ - a stroke that lasts for < 24 hours.
Although blood supply is restored, a TIA can indicate the risk of a major stroke
What do the arteries from the ICA in the circle of Willis supply
anterior cerebral
arteries (ACA) supply medial aspects of the cortical hemispheres forward of the parietal-occipital border,
middle cerebral arteries (MCA) supply lateral parts of the hemispheres, the basal ganglia and the internal capsule (sensory and motor axonal tracts conveying information to and from the cerebral cortex).
A choroidal artery branch supplies part of the choroid plexus
What do the most common strokes in the Circle of Willis arise from
occlusion of MCA branches, notably ‘striate‘ branches
What does the Post. cerebral artery supply
occipital lobe,
posterior-inferior surface of the temporal lobe,
diencephalon and midbrain,
the choroid plexus.
What do branches of the basilar and vertebral arteries supply
midbrain, pons, medulla, cerebellum and spinal cord.
2 ways of doing a cerebral angiograph
what does this allow
X-ray/CT or MRI angiography
allows visualisation of cerebral blood flow following introduction of a radio-opaque substance (‘contrast medium’) into the anterior or posterior systems. This allows obstructions or leaks to be located.
Magnetic Resonance Angiography can be used (rather than x-rays) to image the vessels, although this depends on MRI availability and cost.
True or false
cerebral blood vessels have some independence from systemic blood pressure
true
Cerebral blood vessels can alter their diameter, autoregulating blood flow to a given brain region despite changes in systemic blood pressure. For example, increased pCO2 or decreased pH or pO2 cause vasodilatation, increasing blood flow
What makes fMRI possible
autoregulation of cerebral blood vessels
Increased neuronal activity demands an increase in regional blood flow
What is the BBB formed from
formed in the walls of the blood vessels that penetrate into brain tissue, whose endothelial cells have specialised tight junctions between them and this is covered by astroglial foot processes
what are the 3 functions of the BBB
(i) Prevent harmful substances in the body reaching the brain.
(ii) Prevent exogenous toxins from the external environment reaching the brain.
(iii) Allow essential substances, such as glucose and amino acids, to reach neurones and glia.
How do substances required by the brain cross the BBB (3)
passive diffusion, either across the tight junctions (small hydrophilic substances), or across the endothelial cells membranes (small lipophillic substances);
carrier-mediated facilitated diffusion (eg glucose, amino acids)
vesicular movement (eg adsorptive endo/transcytosis of plasma proteins, receptor-mediated endo/transcytosis of insulin).
Give an example of a drug that can cross the BBB
L-DOPA, used to treat Parkinson’s disease, is carried across endothelial cells by a facilitated diffusion system normally used to transport essential amino acids
Where is the BBB absent in the brain
(i) In circumventricular organs - secretory/receptive structures at the interface of the brain and endocrine system eg the pineal gland.
(ii) In choroid plexus
(iii) In certain neurological disorders. For example brain tumours often contain ‘leaky’ blood vessels. A leaky BBB may allow toxins into the brain and can lead to vasogenic oedema (increased ECF volume).
Where is CSF found (4)
(i) The ventricles of the brain.
(ii) The central canal of the spinal cord.
(iii) The subarachnoid space (between the arachnoid & pia membranes in brain and spinal cord).
(iv) The cisterns (expansions of the subarachnoid space- eg cisterna magna and lumbar cistern).
What is the purpose of the CSF
acts as a cushion against physical trauma and displacement of the brain, and removes
harmful metabolites from ECF.
How much CSF is secreted each day, what secretes it, and what is it secreted into
Around 500ml per day is secreted by choroid plexus in the lateral, third and fourth ventricles
What does the choroid plexus consist of
branches of the choroidal arteries surrounded by a specialised epithelium called choroid epithelium
Give a function of choroid epithelium
another mechanism for limiting the entry of toxins - choroid endothelium allows free movement like a normal blood vessel so the epithelium’s tight junctions stop movement out of the choroid plexus
Describe choroid endothelium
Inside the choroid plexus the blood vessel walls have normal (fenestrated) spaces between endothelial cells, allowing free movement of substances out of the blood vessel.
What does the choroid epithelium consist of
it is a fusion of pia materand ependyma (the epithelium lining the ventricles).
Why is the choroid epithelium considered a blood-CSF barrier
Essential substances cross the choroid epithelium (into the ventricles, forming CSF) by specialised transport mechanisms similar to those in the BBB (facilitated diffusion/ ion exchange and active transport/ ion exchange)
Give 4 key differences between CSF and blood composition
why can this difference happen
(i) CSF has much lower protein content
(ii) CSF contains no red blood cells
(iii) CSF contains <5 lymphocytes per ml under normal conditions
(iv) CSF contains about 50% of the [glucose] found in blood.
the choroid epithelium acting as a barrier
Name a disease that requires a lumbar puncture
In bacterial meningitis, CSF becomes cloudy, and contains more protein and blood cells.
CSF can be sampled by lumbar puncture
How is CSF removed to the systemic circulation per day
how much?
why is CSF removed?
via arachnoid villi, one-way valves formed from arachnoid mater in the walls of dural sinuses
400ml
to maintain constant CSF volume
What happens in hydrocephalus
excess of CSF in the brain:
either too much production or too little removal or a blockage in the flow of CSF (eg in the cerebral aqueduct).
The outcome (after the cerebral sutures are fused) may be an increase in intracranial pressure, and tissue damage
How does blood drain from different parts of the brain
Superficial cerebral veins from cortex and white matter drain into the superior and inferior sagital sinuses and then into the transverse or straight sinuses, while deep veins e.g. from basal ganglia and diencephalon, drain into the great cerebral vein and then into the straight sinus. The sinuses meet at the confluens.
From the straight sinus, venous blood drains into the sigmoid sinus and then into the internal jugular vein, which removes exhausted blood and CSF from the brain
What are the 3 types of psychological research
the first concerns identification and description of psychological phenomena by means such as classifying types of mental illness, measuring distributions of behavioural phenomena and observing reliable behavioural phenomena.
The second looks for relationships between between data sets and attempts to distill statistical regularities that might then inform further research to explain these relationships.
The third is experimental research which attempts to characterize the causal, explanatory mechanisms underlying psychological phenomena
What is the purpose of classifying complex issues like stigma
that further research can be conducted asking questions such as whether different types of stigma have different consequences, for example on whether people will seek help for addiction, social isolation of those with addictions, reluctance by health providers to treat addictions, decisions regarding public spending on addiction services and so on.
What does mentalise mean
when does this ability appear
infer the mental states of others
sudden onset around the age of 4
Give an example of how mentalisation is useful socially
involves an appreciation that the other person’s mental states could be the same as one’s own but could also be different. If they are different, mentalizing allows you to adjust your communication to accommodate to the other person’s perspective, allowing smooth and more efficient interaction.
Give an example of a task to assess a person’s ability to mentalise
2 characters: A and B
A puts a ball in a box and leaves the room with B still in the room
B puts ball into the basket
Examiner asks where A thinks the ball is
From the child’s perspective, the true location of the ball is in the new location. If the child is able to represent the mental states of the first character, they can infer that the character does not have access to this new information and now has a false belief based on where she originally placed the ball.
how does value placed on social responsibility change through development
steadily declines through childhood and adolescence
Are developmental changes always linear?
no some are quadratic
shift in who influences adolescents, where unlike children and adults, adolescents are more influenced by their same age peers.
Why are observations of U shaped curves when looking at psychological developmental changes useful
there could be a fundamental restructure of a process during adolescence or the change may reflect the influence of two processes, one which operates in childhood and then declines in adolescence and a second but different one which begins in adolescence and matures in adulthood.
How did empathy vary with stress and social support in the Park et al. study (2015)
Empathy correlated negatively with perceived stress levels (more empathy, less stress) and positively with perceived levels of social support (more empathy, more support).
Park et al advocated that medical programmes should include training on resilience towards stress and means to enhance social support networks in order to optimize levels of empathy. Why may this be misleading?
assumes a causal direction where stress lowers empathy and social support enhances it. But it is equally possible that having higher levels of empathy produces resilience to stress and fosters good social networks. So in order to establish whether medical programmes should invest in training resilience to stress and means of increasing social support, we would need further research
How could we to establish whether medical programmes should invest in training resilience to stress and means of increasing social support
we could run an experiment where we have four groups of participants matched for levels of empathy and then give each group different types of experience as they go through their training. One group gets some resilience training, another help in strengthening social support networks, a third gets both types of training and the control group gets nothing. If there are effects of either resilience or social support, we might see changes in empathy scores over time in group 1 or group 2 compared to the control group 4, or perhaps resilience and social support are themselves related in which case we might see the greatest difference in empathy scores between group 3 and group 4.
What is factor analysis
identifies superordinate correlations among subordinate correlations.
