19.5 Flashcards
In epilepsy, there is excess firing of the ___ cortex.
Motor
In treatment of epilepsy, ___ are used to enhance GABA (inhibitory) receptor activity.
Benzodiazepines!
In treatment of epilepsy, ___ is used to reduce excitatory input (glutamate) by limiting excitatory nerve activation.
Phenytoin
In treatment of epilepsy, ___ is used to reduce excitatory input (glutamate) by inhibiting T-type Ca2+ channels.
Ethosuximide
In treatment of epilepsy, ___ is used to reduce excitatory input (glutamate) by inhibiting the NMDA receptor.
Felbemate
Benzodiazepines are ___ modulators of the ___ receptor, that ___ activity.
Allosteric modulators of GABA receptor, enhances activity -> increases inhibition.
Why is phenytoin esp. effective in epilepsy?
Phenytoin selectively targets AP generation in nerves firing excessively!!!
Local anaesthetics are weak ___ that differ in onset, duration and toxicity, and include ___, ___ and ___.
Weak bases.
Aminoesters, aminoamides and benzocaine.
Aminoesters vs. aminoamides?
Aminoesters e.g. procaine are shorter acting, and is hydrolysed by esterases.
Aminoamides e.g. lignocaine, bupivacaine, ropivicaine are longer acting and is inactivated by hepatic metabolism.
Benzocaine is relatively ___ and is esp. useful in the ___.
Weak
Useful in the throat e.g. for cough suppression, etc.
Local anaesthetics selectively bind to the ___ channel, and bind ___ with no nerve damage.
Na+ channel.
Reversible binding.
The sensitivity of sensory fibres to local anaesthetics is ___ compared to motor fibres!!!
Sensitivity of sensory fibres > sensitivity of motor fibres.
Local anaesthetics bind ___ the channel, and therefore require access to the channel for effect.
INSIDE - NOT outside like toxins can!
There are two general types of anaesthetics that influence their mechanism of action: ___ and ___
Hydrophobic and hydrophilic.
Hydrophobic local anaesthetics act ___ and are NOT dependent on activity of the channel.
Fast!
Benzocaine is a ___ local anaesthetic.
Hydrophobic
Hydrophilic local anaesthetics act ___ and ARE dependent on activity of the channel.
Slow
Aminoesters and aminoamides are ___ local anaesthetics.
Hydrophilic
Why are sensory fibres more sensitive to local anaesthetics than motor fibres?
Sensory fibres are thin and motor nerves are thick and often myelinated - there is less distance for diffusion of local anaesthetics across membranes of sensory fibres!
Only the ___ form of hydrophilic local anaesthetics can cross the membrane.
Uncharged/non-charged.
After the non-charged form of a hydrophilic local anaesthetic crosses the membrane via the Na+ channel, it forms a ___ form.
Charged
The ___ form binds to the Na+ channel with higher affinity.
Charged!
The charged form of hydrophilic local anaesthetics can only bind when the Na+ channel is ___
OPEN
Local anaesthetics have a greater effect in a ___ medium.
Basic - because weak bases in a basic medium are mostly in uncharged form and can cross the membrane.
Use of local anaesthetics in ___ states may be less effective.
Acidic!
There will be more charged form - it cannot cross the membrane!
There are 2 theories for the mechanism of action of general anaesthetics: ___ theory and ___ ___
Lipid theory and receptor interaction.
Meyer Overton states that…
Anaesthesia is caused by volume expansion of membrane lipids, and the effect can be reversed by pressure.
