Drugs affecting nerve excitability

Question 1

T/F Both toxins and local anaesthetics bind extracellularly

Answer 1

False, local anaesthetics bind intracellularly

Question 2

Are local anaesthetics more effective in basic or acidic environments?

Answer 2

Basic

Question 3

What occurs with general anaesthetics?

Answer 3

Depression of cortal processes for pain/sensory signalling

Question 3

What are barbiturates main effect?

Answer 3

Depression of the CNS

• sedation > surgical anaesthesia > coma > death

Question 4

Which type of GABA receptors do benzodiazepines bind to?

Answer 4

GABA A receptors - Ligand gated ion channels

Question 4

Are there dependence issues/withdrawal symptoms with benzodiazepines?

Answer 4

Yes

Question 5

Why are some hydrophilic local anaesthetics dependent on nerve activity?

Answer 5

Because they bind to the inactivative state that the Na channels are in after a Na channel has been opened

Question 7

What is the mechanism of action of local anaesthetics?

Answer 7

Reversible blockage of Na channels

Question 7

What is clinical efficacy?

Answer 7

The strength of the beneficial effect

Question 8

Which is faster acting, hydrophobic or hydrophilic local anaesthetics? Why?

Answer 8

Hydrophobic because they can diffuse through membranes and reach the intracellular domain

Question 9

Which nerves will local anaesthetics affect in a given bit of tissue?

Answer 9

All of them!

Question 10

What are the side effects of benzodiazepines?

Answer 10

Drowiness

Confusion

Loss of coordination

Question 11

What is a common side effect of anxiolytics?

Answer 11

A degree of drowiness and sedation

Question 12

What are benzodiazepines used for?

Answer 12

Epilepsy

Sleep disorders

Anxiety

Pre-surgical

Acute alcohol withdrawal

Question 13

What are the physiological effects of benzodiazepines?

Answer 13

Sedation and induction of sleep

Amnesia

Muscle relaxant

Reduction of anxiety and anger

Question 13

Why are benzodiazepines generally prefered to barbiturates?

Answer 13

Less central and cardiovascular effects

No overdose

Less dependence

Question 14

How does benzodiazepine work in epilepsy?

Answer 14

It enhances the activity of GABA (inhibitory) receptors

Question 15

What is potency?

Answer 15

The dose of drug required to elicit its effect

Question 16

What is an example of a hydrophobic local anaesthetic?

Answer 16

Benzocaine

Question 17

What are the 7 aspects of synaptic transmission that can be targeted by drugs?

Answer 17

Synthesis

Storage

Release

Inactivation

• Reuptake
• Metabolism

Receptor

Question 18

What are the problems with barbiturates?

Answer 18

Toxic - low therapeutic window

• Induce liver enzymes
• Abrapt withdrawal causes death

Highly addictive

Question 20

What is anxiety?

Answer 20

The manifestation of the fear response

Question 22

Which is more sensitive to local anaesthetics, sensory or motor nerves?

Answer 22

Sensory

Question 23

Are fast or slow acting local anaesthetics dependent on the level of use of a nerve?

Answer 23

Slow

Question 25

What occurs in local anaesthetics?

Answer 25

Local inhibition of pain and sensory pathways

Question 26

Describe the level of glutamate in epilepsy

Answer 26

There is too much of it (it’s excitatory)

Question 27

Describe the level of GABA in epilepsy?

Answer 27

There is too little of it (it’s inhibitory)

Question 28

How do barbiturates act on GABA receptors?

Answer 28

Prolong opening of the receptor

Question 29

How does phenytoin act in epilepsy?

Answer 29

Blocks Na+ channels to inhibit excitability

• the channels must be open to be blocked, therefore the nerve must be active

Question 30

What do benzodiazepines do to their target GABA receptor?

Answer 30

Increase it’s rate of opening and closing

Question 31

Why are sensory nerve more sensitive than motor nerves to local anaesthetic?

Answer 31

Because they are smaller