Epilepsy Flashcards
What does neuronal transmission occur via?
The neuronal action potential
What is dysfunction of the neuronal action potential the fundamental basis of?
Epilepsy and seizure disorders
What do action potentials occur due to?
Depolarisation of the neuronal cell membrane propagating along the axon in a wave
What does the wave of depolarisation of the neuronal cell membrane lead to?
The release of neurotransmitters across the axon terminal
In what fashion do action potentials occur?
‘All or nothing’
What do action potentials occur as a result of?
Local changes in membrane potential caused by a net positive influx of ions
What does membrane potential vary with?
Activation of various ligand-gated channels
What affects the ligand-gated channels in the neurone?
Binding to neurotransmitters, or changes in the transmembrane potentials
What can a cellular hyper excitable state result from?
- Increased excitatory factors
- Decreased inhibition
- Alteration in voltage-gated ion channels
- Change in ion concentrations
All of these favour membrane depolarisation
Where are neurotransmitters released from?
The presynaptic terminal at the synapse
What happens once neurotransmitters are released from the presynaptic terminal?
They bind to specific receptors on the post-synaptic membrane for that ligand
What does ligand binding to the post-synaptic terminal cause?
Channel activation and movement of ions in or out of the cells
What are the major neurotransmitters in the brain?
- Glutamate
- Gamma-aminobutyric acid (GABA)
- Acetylcholine (ACh)
- Noradrenaline
- Dopamine
- Serotonin
What other molecules are thought to modify neurotransmission?
- Neuropeptides
- Hormones
What is the difference between neurotransmitters and molecules such as neuropeptides and hormones, in terms of neurotransmission?
Molecules such as neuropeptides and hormones are thought to modify neurotransmission over longer time periods
What is the major excitatory neurotransmitter?
Glutamate
Give 2 examples of subtypes of glutamate receptors?
- AMPA
- NMDA
What are glutamate receptors permeable to?
Sodium and potassium
What does the movement of sodium and potassium through glutamate receptors lead to?
Depolarisation and generation of the action potential
What can lead to channel dysfunction?
Situations leading to altered brain tissue physiology, such as infection, inflammation, or vascular compromise
What can situations leading to altered brain tissue physiological lead to?
Seizure activity
Often also results in various other neurological symptoms
What do genetic channelopathies cause?
Malfunction of a particular ion channel
What do genetic channelopathies often have as part of the phenotypical presentation?
Epilepsy
Give 2 examples of genetic channelopathies?
- SCN1A sodium channelopathy
- CACNA1A channelopathy
How does SCN1A sodium channelopathy present?
Often presents with a range of troublesome seizures, from frequent febrile seizures, the syndrome of generalised epilepsy with febrile seizures plus (GEFS+), as well as severe myoclonic epilepsy of infancy
What is CACNA1A channelopathy associated with?
Migraine disorders such as hemiplegic migraine
