Drugs and the Nervous System Flashcards
What constitutes the nervous system?
The brain, spinal cord and the nerves.
What are the excitatory neurotransmitters?
Noradrenaline Dopamine Serotonin (5-HT) Acetylcholine Glutamate
What are the inhibitory neurotransmitters?
GABA
glycine
What are the drugs that act on the nervous system?
Anaesthetics (local and general) Anxiolytic/ hypnotic drugs Neuromuscular blocking drugs Antidepressant drugs Antiparkinsonian drugs Anticonvulsants
Where do general anaesthetics act?
In the central nervous system.
How are general anaesthetics administered?
By inhalation or intravenously.
Why use anaesthetics?
To promote: Analgesia Unconsciousness Amnesia Loss of reflexes
How do general anaesthetics work?
- act on CNS to promote insensitivity
- usually fat soluble – can cross blood-brain barrier
- may act on membrane receptors to reduce excitability of neurones
- may affect ion channels
What are some common side-effects of general anaesthetics?
- Nausea/ Vomitting,
- Breathing difficulties ( Shallow/rapid)
- Low blood pressure,
- Low kidney perfusion,
- Loss of temperature control.
What are the stages of anaesthesia?
Stage 1 – analgesia
Stage 2 – excitement
Stage 3 – surgical anaesthesia → skeletal muscle relaxation/ loss of reflexes
Stage 4 – medullary paralysis → loss of respiratory/ vasomotor control
What are the 4 types of general anaesthetics?
- Barbiturates,
- Gases,
- Non-barbiturates,
- Volatile liquids.
Why is nitrous oxide used?
To maintain anaesthesia and as a potent analgesic.
Three types of inhaled anaesthetics?
Isoflurane, desflurane, sevoflurane.
How is the depth of anaesthesia controlled?
By varying the concentration of the vapour.
What type of general anaesthetic is Propofol?
An intravenous, non-barbiturate.
Advantages of Propofol?
- Rapid action,
2. Rapid recovery without ‘hangover’.
Disadvantage of Propofol?
May cause convulsions or anaphylaxis.
What type of general anaesthetic is Thiopental (Thiopentone)?
An intravenous, barbiturate.
Advantage of Thiopental?
Useful for brief procedures.
Disadvantage of Thiopental?
Can cause rapid awakening or long lasting sedation which may cause problems.
What are benzodiazepines?
Anxiolytics or hypnotics.
Examples of benzodiazepines…
Midazolam, Temazepam, Diazepam. All end in ‘am’.
How are benzodiazepines administered?
Orally, intravenously. intramuscularly and rectally.
Side effects of benzodiazepines?
- Hypotension,
- Constipation,
- No analgesic effect.
Disadvantages of Hypnotics?
- May lead to dependence
- May cause respiratory depression
- Benzodiazepines interact with alcohol
- Will cross the placenta in a pregnant woman.
How do neuromuscular blocking drugs work?
- They block transmission in motor nerves.
2. Relax vocal cords, to allow insertion of tracheal tube.
Disadvantages of neuromuscular blocking drugs?
- Patients require assisted respiration.
- Prolonged muscle paralysis or pain.
- May cause the release of histamine which may cause a bronchospasm.
How do Narcotic analgesics (opioid) work?
Act on opioid receptors in the central nervous system to relieve pain.
What effect do narcotic analgesics have?
Euphoric effect. (to escape from reality).
Examples of Narcotic analgesics…
Fentanyl, Alfentanil, Remifentanil. All end in the sound ‘nil’.
Disadvantages of Narcotic analgesics?
- May cause nausea/vomiting.
- Reduced breathing rate.
- Small risk of addiction.
What are local anaesthetics used for?
- Analgesia,
2. Paralysis.
How do local anaesthetics work?
They act on specific nerve pathways.
What is the mechanism of action for a local anaesthetic?
They block transmission of nerve impulses carrying pain signals from nociceptors to the brain.
What is the cellular mechanism of action in a local anaesthetic?
Inhibition of Na+ entry through very sensitive Na+ channels, this blocks transmission of nerve impulses.
Common methods of administration of local anaesthetics?
- Epidural - injection into epidural space which affects nerve roots.
- Intradermal/topical - relieves minor irritation/superficial pain.
Commonly used local anaesthetics…
Lidocaine, Prilocaine, Bupivacaine, ropivacaine and proxymetacaine. (all end in ‘caine’)
What is Lidocaine used for?
- Dental surgery.
2. To treat premature ejaculation.
What is Prilocaine used for?
It is mixed with Lidocaine and used for surface anaesthesia.
Side effects of local anaesthetics?
- Abnormal heart beat.
- Restlessness.
- Convulsions.
- In severe cases, cardiorespiratory arrest.
How do vasoconstrictors work?
They enhance potency and prolong duration of action of anaesthetics. They also reduce blow flow meaning that lesson blood is lost in surgery.
Examples of vasoconstrictors?
Adrenaline and felypressin.
Other drugs that work on the nervous system…
- Antidepressants,
- Antiparkinsonian drugs,
- Anticonvulsants.
How do antidepressants work?
Increase levels of excitatory neurotransmitters in the brain.
How do antiparkinsonian drugs work?
Increase levels of the neurotransmitter dopamine.
How do anticonvulsants work?
Treat epilepsy by reducing the conduction of excitatory nerve impulses and/or increasing GABA activity.
What are the 3 types of Antidepressants?
- Tricyclic antidepressants.
- Selective serotonin re-uptake inhibitors.
- Monoamine oxidase inhibitors.
