Drugs in Neurotransmission Flashcards
What kind of processes does the ANS control?
Involuntary processes
Name 5 involuntary processes controlled by the ANS
- Blood flow
- Temperature regualtion
- Digestion
- Metabolism
- Excretion
What is the effector organ of the somatic nervous system?
The voluntary muscles (skeletal muscle)
What are the effector organs of the autonomic nervous system?
Smooth muscle
Cardiac muscle
Glands
Gastrointestinal neurons
The somatic nervous system only contains one fibre from CNS to synpase; what is this known as?
A monosynaptic system
Where is the synpase in the somatic nervous system?
Skeletal neuromuscular junction
What two fibres are involved in the autonomic nervous system?
The preganglionic fibre and the postganglionic fibre
What is the ganglion?
The junction between neurons
What receptors are between the neurons in the ganglia of the autonomic nervous system?
Nicotinic receptors
What activates the receptors of the ganglia and is thus released by the preganglionic fibre of the ANS?
Acetylchloline
What does the post ganglionic fibre of the ANS do?
Innervates the organ
If the preganglion fibre releases acteylchloine what is it known as
Cholinergic
What do the preganglionic fibres release in the sympathetic and parasympathic divisions?
Acetylcholine
What does the post ganglionic fibre of the parasympathic division release?
Acetylcholine
What does the post ganglionic fibre of the sympathetic division release?
Noradrenaline
What does the monosynaptic system of the sensory nervous system release
Acetylchloine
What are the receptors for the sensory nervous system?
Nictotinic receptors for acetylcholine
What receptors are involved in the parasympathic division?
Muscarinic receptors for acetylchloine
what receptors are involved in the sympathetic division?
Alpha and Beta Adrenoceptors for Noradrenaline
Are the receptors of the autonomic nervous system excitatory or inhibitory?
Depends on the post-receptor mechanisms (what happens during the signal transduction)
What are the 6 things that must happen for something to be classified as a neurotransmitter?
- Must be synthesised
- Must be stored
- Must be released
- Must diffuse
- Must bind to a receptor
- Must be able to be inactivated
How are neurotransmitters synthesised?
By enzymes in the cystol
What is acetylchloline synthesised from and by what enzyme?
Synthesised from choline and acetic acid (acetyl coA) b the enzyme chloline actetyl-transferase (CAT)
What amino acid is starting point for the synthesis of noradrenaline?
Tyrosine
What enzyme converts tyrosine to DOPA and what does it do to the structures
Tyrosine hydroxylase and it adds a hydroxyl group
What enzymes converts DOPA to dopamine and what does it do the the structure?
Dopa decarboxylase which removes a carbonyl group
What enzymes converts dompamine to noradrenaline and what does it do to the structure?
Dopamine B-hydroxylase and it adds another hydroxyl group
What are neurotransmitters stored in in the nerve endings?
Vesicles
What does reserpine do?
It blocks the uptake of noradrenaline into vesicles so its not available for release
What causes the neurotransmitter to be released?
An action potential arriving at the nerve ending triggers depolarisation and opens channels causing calcium influx which triggers release of neuotransmitters
What triggers the release of noradrenaline?
Epinedrine
What blocks the release of noradrenaline
Guanethidine
What does the neurotransmitter difuse across?
The synpatic cleft
What does diffusion mean?
It goes from a high concentration to a low concentration
What drugs can affect the diffuse process?
Not many
Name an agonist for a muscarinic receptor, what neurotransmitter does it mimic?
Pilocarpine mimics acetylcholine
Name an agonist from an alpha adrenoceptor, what neurotransmitter does it mimic?
Phenylephrine mimics noradrenaline
Name an agonist for a B adrenoceptor, what neurotransmitter does it mimic?
Salabutamol mimics noradrenaline
Name an antagonist from a muscarinic receptor; what neurotransmitter does it block?
Atropine blocks acetylchloine
Name an antagonist for an alpha adrenoceptor; what neurotransmitter does it block?
Prazosin blocks noradrenaline
Name an antagonist for a beta adrenceptor; what neurotransmitter does it block?
Propranolol blocks noradrenaline
What three things can happen to cause inactivation of a neurotransmitter?
- Diffuses away
- Reuptake into the nerve
- Destroyed by enzymes
Give an example of a neurotransmitter than can be inactivated by destruction by an enzyme
Acetylchloine is destroyed by acetylchlolinesterase which hydrolyses the ester
What does neostigmine do?
It inhibits acetylchlolineesterase and prevents it breaking down acetylchloine
What percentage of the neurotransmitter is taken back up into the nerve
70-99%
Name a drug that blocks the reuptake of noradrenaline into the nerve?
Cocaine
How does cocaine block the reuptake of NA?
blocks a transporter needed to take up NA