Jonathon Williams Flashcards
(26 cards)
What are neurotransmitters
Chemical messengers released by nerve cells
The bind to receptors on target cells
Binding causes a biological response in the target cell
What do the sensory nerves do
Take messages from the body to the CNS
What do the motor nerves do
Carry messages from the CNS to the rest o the body
What are the three principle motor nerves
Somatic motor nerve - skeletal muscle
Autonomic motor nerve (sympathetic)
Autonomic motor nerve (parasympathetic)
What happens at chemical synapses
Nerve signal travels down neurone until it reaches a synapse
Neurotransmitters released from presynaptic membrane into synaptic cleft
Neurotransmitter diffuses across cleft to bind to receptors on postsynaptic membrane
How are receptors activated
Neurotransmitter binds to receptor
Non covalent interactions cause receptors to change shape
This is known as induced fit
Change in shape of receptor binding site causes further conformational changes which ultimately result in a biological response
How are ion channel receptors activated
Ion channel complexes are made of 5 protein subunits that transverse the cell membrane
Controlled by lock gate mechanism
Resting state is closed. When a messenger binds to the receptor the induced fit causes a conformational change which opens the ion channel
How do kinase linked receptors work
Directly linked to kinase enzymes
Ligand binding causes a conformational change which opens the kinase active site inside the cell
Kinase enzymes catalyse phosphorylation reactions within the cell
How do receptor agonists work
Mimic the natural neurotransmitter
Activate the target receptor
Induce the same biological response
How to receptor antagonists work
Bind to target receptor
Do not induce biological response
Block the action of the neurotransmitter
How do reuptake inhibitors work
Bind to transport proteins that return neurotransmitters to presynaptic membrane
This increases the concentration of the neurotransmitter for longer periods of time
Prolongs biological response of neurotransmitter
How do hydrolysis inhibitors work
Prevent neurotransmitter from being hydrolysed in synaptic gap
Increases concentration of neurotransmitter
Same effect as receptor agonist
How do Biosynthesis inhibitors work
Prevent correct neurotransmitters from being synthesised
Reduces the effect of the neurotransmitter
What is acetyl choline
A neurotransmitter that acts on cholinergic receptors
What are the two main types of cholinergic receptors
Nicotinic receptor
Muscarinic receptors
How do G protein couples receptors work?
When a ligand binds to a G-protein coupled receptor there is a conformational change which exposes a new binding site within the cell
This binding site interacts with a G-protein
When the G-protein binds it releases GDP and binds GTP
The GTP breaks the G-protein into its subunits
The released subunits activate other processes within the cell
The activated G-protein coupled receptor can activate several G-proteins before the original ligand leaves allowing signal amplification
Describe the binding of propantheline
Propantheline has the same core as acetylcholine with additional binding sites so binds more strongly
What are nicotinic receptor antagonists used for?
Neuromuscular blocking agents
Give three examples of nicotinic antagonists?
Suxamethonium
Pancuronium
Atracurium
How do anticholinesterases work?
Inhibit the action of acetylcholinesterase
This prevents hydrolysis of acetyl choline which has a similar effect to that of a cholinergic agonist
Acetylcholinesterase enzyme is bound to the post-synaptic membrane close to the receptor
What do nerve gases do?
Such as dyflos and sarin
Inhibit acetylcholinesterase by irreversibly phosphorylating the serine residue in the active site
Acetylcholine cannot be hydrolysed causing the cholinergic system to be continuously stimulated. This results in permanent contraction of skeletal muscle
Describe adrenaline and noradrenaline
Both catecholamines
Adrenaline is a hormone released by the adrenal medulla and activates adrenergic receptors throughout the body
Noradrenaline is a neurotransmitter released by nerve cells that control smooth muscle and cardiac muscle
Describe noradrenaline biochemistry
Biosynthesised from L-tyrosine in the presynaptic nerve and is released upon arrival of a signal
Activates target receptor it is then transported back using a carrier protein
Some noradrenaline is metabolised by methylation and oxidation
Adrenaline is biosynthesised from noradrenaline in the adrenal medulla
How does alpha methyltyrosine work?
Inhibits the enzyme tyrosine hydroxylase preventing the synthesis of noradrenaline reducing the adrenergic response
