W19-L5: Regulating Neuronal Excitability Flashcards Preview

Matt's Block 06 - Neuro block > W19-L5: Regulating Neuronal Excitability > Flashcards

Flashcards in W19-L5: Regulating Neuronal Excitability Deck (19):
1

Analgesics

Targets pain/sensory pathways

2

Local anaesthesia

Regionalised inhibition of pain/sensory pathways (primary afferent nerves) with no loss of consciousness

3

General anaesthesia

Depresses cortical processing of pain/sensory signals which is not regionalised with loss of consciousness (stops processing)

4

Local Anaesthetic Agents

Weak bases that reversibly block conduction of nerve impulses at the axonal membrane by interfering with influx of Na+, which differ in onset, duration and toxicity

5

Aminoesters

Local anaesthetics eg procaine
•Shorter acting, hydrolysis by esterases

6

Aminoamides

Local anaesthetics eg lignocaine, bupivicaine, ropivicaine
•Longer acting, hepatic metabolism

7

Lethal toxins

-tetrodotoxin (puffer fish)
– saxitoxin (dinoflagellates)

8

Benzocaine

in its own group of local anaesthetics

9

Clinical use of local anaesthetics is considered safe because

- selective binding to Na+ channel
- reversible binding with no nerve damage
- will affect all nerves / excitable tissue
-Local application to limit systemic distribution

10

Sensitivity of Nerves to Local Anaesthetics

non selective for a nerve type, by blocking sensory nerves you will also get motor nerves blocked too, which increases as you block more of the sensory nerves

11

Where do local anaesthetics bind

Transmembrane domain which is intracellular

12

Where do toxin bind

extracellular domains

13

Hydrophobic mechanism for Local Anaesthetics

fast, non use dependent
- eg benzocaine
drug is usually in mainly non-ionised form and doesn't allow the channel to conduct Na

14

Hydrophilic mechanism for Local Anaesthetics

slow, use dependent - eg aminoesters & aminoamides
intracellular environment promotes charged form and in the charged form it requires the channel to be open to access the binding pocket

15

General properties of local anaesthetics

- prevent propagation of nerve action potential
- small fibres more sensitive - (sensory > ANS > motor)
- stabilize axon membrane
- no change in resting membrane potential
- effect more pronounced in basic medium
- greater effect at high frequency

16

Local Anaesthetic Toxicity

Proportional to blood level are CV eg hypotension (except cocaine) and CNS, not proportional are allergic reactions

17

How many stages are there of general anaesthetics and what are they called?

Stage 1
Stage 2: Excitement
Stage 3: Surgical anaesthesia
Stage 4: Medullary depression

18

General anasethetics side effects

Respiratory eg impaired ventilation, retention of secretions (anti-muscarinics are used) and cardiovascular eg cardiac arrythmias

19

General Anaesthetics Theories on Mechanism of action

Lipid theory: Close correlation between anaesthetic potency and lipid solubility

Receptor Interaction:
Many anaesthetic agents inhibit excitatory receptors (glutamate, NMDA) and enhance effects on inhibitory receptors (GABA, glycine)

Decks in Matt's Block 06 - Neuro block Class (48):