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Neuroscience > Regulating neuronal excitability > Flashcards

Regulating neuronal excitability Flashcards

1
Q

Describe the difference between local and general anaesthetics?

A

Local anaesthetics produce regionalised inhibition of pain/sensory pathways, with no loss of consciousness

General anaesthetics depress cortical processing of pain/sensory signals, and result in loss of consciousness

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2
Q

What is the site of action for analgesics?

A

Peripheral nerves, spinal cord and brain cortex

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3
Q

What is the site of action for local anaesthetics?

A

Peripheral nerves and spinal cord

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4
Q

What is the site of action for general anaesthetics?

A

Brain cortex

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5
Q

What the first local anaesthetic?

A

Cocaine

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6
Q

Describe the broad action of local anaesthetics?

A

Drugs that reversibly block conduction of nerve impulses at the axonal membrane Interfere with influx of Na

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7
Q

Are local anaesthetics acidic or basic? Are they strong or weak?

A

Weak bases

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8
Q

How do the various local anaesthetic agents differ?

A

Differ in onset, duration and toxicity

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9
Q

List three classes of local anaesthetics?

A

Aminoesters Aminoamides Benzocaine

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10
Q

What is the difference in duration and metabolism between aminoesters and aminoamides?

A

Aminoesters are shorter acting and are hydrolysed by esterases Aminoamides are longer acting and undergo hepatic metabolism

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11
Q

What sorts of tissue can local anaesthetics affect?

A

Will affect all nerves and excitable tissue

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12
Q

What do local anaesthetics selectively bind to?

A

Na channels

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13
Q

How can systemic distribution of local anaesthetics be limited? Why is this important?

A

Local application Limits toxicity and makes them safer

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14
Q

Describe the difference in sensitivity to local anaesthetics between motor and sensory nerves?

A

Sensory nerves more sensitive (require less drug for same effect)

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15
Q

How can the level of nerve blockade achieved with local anaesthetics be altered?

A

Alter dose of drug

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16
Q

Which part of the Na channel do local anaesthetics interact with?

A

Transmembrane domain

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17
Q

Which part of the Na channel do toxins interact with?

A

Bind extracellular domain

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18
Q

What are the two mechanisms of action of local anaesthetics?

A

Hydrophobic Hydrophilic

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19
Q

What is the difference between the hydrophobic and hydrophilic mechanisms of local anaesthetics, in terms of speed and use dependence?

A

Hydrophobic: fast, non use dependent Hydrophilic: slow, use dependent

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20
Q

What limits the rate of onset/offset of local anaesthetics?

A

Diffusion across membranes (hydrophobic fast vs hydrophilic slow)

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21
Q

How does the size of nerves affect the rate of onset/offset?

A

Small nerves > smaller membranes > quicker access

22
Q

Are sensory nerves or motor nerves larger?

A

Motor nerves are larger

23
Q

What is the extracellular gate of the Na channel called?

A

m-gate

24
Q

What is the intracellular gate of the Na channel called?

A

h-gate

25
Q

Describe the hydrophobic mechanism for local anaesthetics?

A
26
Q

Describe the hydrophilic mechanism for local anaesthetics?

A
27
Q

Why are local anaesthetics that use the hydrophobic mechanism not use-dependent?

A

Hydrophobic > can cross membrane > doesn’t matter whether gates are open or closed

28
Q

Why are local anaesthetics that use the hydrophilic mechanism use dependent?

A

Hydrophilic> cannot cross membrane > requires gates to be open

29
Q

What is the effect of local anaesthetics on axon membrane potential?

A

Stabilises axon membrane

No change in resting membrane potential

30
Q

When is the effect of local anaesthetics more pronounced?

A

In a basic medium

31
Q

Describe the effect of a basic medium on local anaesthetics?

A

Have a more pronounced effect

32
Q

What determines the toxicity of local anaesthetics?

A

Proprtional to blood level

Dose determines effect

33
Q

Describe some of the toxic cardiovascular effects of local anaesthetics?

A

Direct myocardial depression

Depression of vasomotor centre

Hypotension

34
Q

Describe of the toxic CNS effects of local anaestheitcs?

A

Excitation

Tremor

Convulsion

Respiratory arrest

35
Q

How can we tell if a local anaesthetic is acting in the wrong location?

A

Begin to see toxic side effects

36
Q

Which side effects of local anaesthetics are not proportional to blood level?

A

Hypersensitivity reactions

37
Q

Which side effect is particularly common with local anaesthetics?

A

Hypersensitivity reactions

38
Q

Which forms of local anaesthetics are available over the counter?

A

Lozenge

Gels

39
Q

Which forms of local anaesthetics are for professional use only?

A

Eye drops

Injection

40
Q

Describe the four stages of general anaesthesia?

A

Stage 1: amnesia, euphoria

Stage 2: excitement, delirium, resistance to handling

Stage 3: unconsciousness, regular respiration, decreasing eye movement

Stage 4: respiratory arrest, cardiac depression and arrest

41
Q

At which stage of general anaesthesia is surgery commenced?

A

Stage 3

42
Q

How long does it take to progress from Stage 1 to Stage 3 once general anaesthetics are administered?

A

Seconds

43
Q

What are the main methods of administration for general anaesthetics?

A

Inhalation

Intravenous injection

44
Q

What are some of the respiratory side effects of general anaesthetics?

A

Impaired ventilation

Depression of respiratory centre

Obstruction of airways

45
Q

How can retention of secretions due to obstruction of airways be combatted under general anaesthesia?

A

Administer ant-MuscR

46
Q

List the cardiovascular side effects of general anaesthetics?

A

Decreased vasomotor centre function

Depress contracility

Peripheral vasodilation

Cardiac arrythmias

Inadequate response to fall in BP or CO

47
Q

When can the side effect of inadequate response to fall in BP under general anaesthesia become a problem?

A

If the patient must be moved upright for surgery

48
Q

What are the theories of mechanism of action of general anaesthetics?

A

Lipid theory

Receptor interaction theory

49
Q

Describe the the lipid theory of general anaesthetics?

A

Act by dissolving in the fatty fraction of brain cells and removing fatty constituents from them, thus changing activity of brain cells and inducing anaesthesia.

50
Q

Describe the receptor interaction theory of general anaesthetics?

A

Inhibit excitatory receptors (glutamate, NMDA)

Enhance effects on inhibitory receptors (GABA, glycine)

51
Q
A

Neuroscience (51 decks)

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