Lecture 13: epilepsy and schizophrenia Flashcards
What are the different lobes of the brain?
frontal
parietal
occipital
temporal
Where is the cerebellum and what is it involved in?
located at the back of the brain, invovled in movement and balance
What is the frontal cortex?
the part of the brain that is scrunched and squeezed against the skull
-this is also broken up tino different regions
What parts of the brain are in the ‘middle’?
hippocampus- invovled in learning and memory
basal ganglia- involved in movement, initiation and control of purposeful movement
this is affected by parkinson’s
What is the function of the brain stem?
primitive control like heart rate and breathing
this runs down to the spinal cord.
How do brain cells communicate wth each other?
An AP is generated which opens V-gated calcium channels to cause the release of vesicles containing neurotransmitters
- these are released into the synaptic cleft
- the neurotransmitters then bind to receptors in the post synaptic cell, or are taken up by a transporter.
- they can also be recycled back into the presynaptic cell
what is epilepsy?
-chronic disorder characterised by recurrent seizures which affects 0.5% of the population
What are the causes of epilepsy?
- genetic (rare)
- birth/perinatal injuries
- children undergone febrile seizures
- after head injury, trauma or vascular event affecting an area of the brain
- congenital abnormalities or metabolic disorders where there are imbalances in the brain
What is the characteristic event of epileptic seizures?
-seizures which are assoc with an episodic high frequency discharge of brain cells
What are the two types of seizure activity?
- generalised
2. partial
What are generalised seizures?
- these affect both sides of the brain
- can start in one hemisphere, but seizure activity is strong enough to spread across the corpus callosum to the other side
- usually results in loss of consciousness of patients
What are partial seizures?
- one hemisphere or one localised region exhibits the seizure activity
- does not spread to the other hemisphere,
- patients do not tend to lose consciousness
What is the mechanism on the spread of seizure activity?
- not fully understood and involves multiple mechanisms
- stems from abnormal neuronal activity in an area (focus) which could be due to damage or where a pathological event has occurred
- These cells have abnormal electrical properties so the V gated (sodium and calcium) channels are abnormal
- within this focus, you get these cells firing at a very high frequency due to constant depolarisation
- can get abnormal activity of receptor gated channels resulting in the release of excitatory neurotransmitters and a reduction in the release of inhibitory transmitters
- this imbalance contributes to the high frequency discharge.
- cells then go into synhronisation resulting in full seizure activity
- abnormal v gated channels and abnormal flow of Na and Ca ions results in abnormal extracellular environment- further promoting synchronisation
- helps seizure activity spread to adjacent neurons (dependent on how many connections these neurons have made)
What is the problem with continual excitation and reduced inhibiton?
- high levels of glutamate may accumulate.
- this is toxic. -> loss of brain cells
- cells will become abnormal which spreads the focus area of the seizure
What has research suggested regarding the seizure spread?
- the seizure spread is determined by the delicate balance of excitation and inhibition.
- increased excitation and reduced inhibition results in the synchronisation and further spread of seizure activity
What are the limitations regarding the biochemical balance theory of seizure spread?
- when looking at animal models and in epileptic patients, there are no major abnormalities in the enzymes involved in the synthesis of glutamate/GABA
- there are also no significant receptor abnormalities
- but definitely considered that some of epilepsy is due to damage and repair process
What could the focal injury due to head injury or trauma represent?
surviving neurons making connections which are not successively connecting.