Autonomic nervous system Flashcards
What is homotropic presynaptic inhibition?
A transmitter acts on a presynpatic receptor to inhibiti its own relase
What does co-transmission mean?
the release and action of more than one transmitter at a nerve terminal
What’s the mechanism by which Ach signaling at the synapse is terminated>
Ach degraded by acetylcholinesterase
What are the two classes of Ach receptors?
Muscarinic and nicotinic
Which of the two classes of Ach receptors are a better target for drugs? and why?
Muscarinic as the receptors aren’t as widespread as nicotinic receptors which are found throughout the ANS
What effect do cholinergic agonists (parasympathomimetics) have on the heart?
Slows the heart rate
What is the difference between NA and Ach containing synaptic vesicles?
NA containing vesicles also contain ATP
What’s the difference between the VMAt transporter and NET transporter?
VMAT packages NA into vesicles. NET takes up NA from synapse into presynaptic nerve terminal
What does the enzyme monoamine oxidase (MAO) do and where is it found?
Metabolises NA and found in presynaptic terminals
What effect do beta-2 adrenergic agonists have on bronchial smooth muscle
Stimulates relaxation of bronchial smooth muscle
Give and example of a beta-2 adrenergic agonist
Salbutamol
Give two mechanisms by which drugs can affect NA release
Effects on a-2 receptor, effects on NA storage, effects on exocytosis, indirectly acting sympathomimeticsq
What is the effect on neurotransmisson when presynaptic receptors are activated at a muscarinic synapse?
Decreased (activate autoinhibatory feedback loop which inhibits further Ach release)
What is the effect on neurotransmission when presynaptic receptors are activated at a nicotinic synapse?
Increased (feedback loop that enhances further Ach release)
What is the rate limiting step in Ach synthesis?
Choline uptake into the nerve terminal by the transporter
What is neuromodulation?
The effect of other chemical mediators on synaptic transmission
What is homotropic presynaptic inhibition?
the transmitter acts on a presynaptic receptor to inhibit further transmitter release (auto inhibition)
What is heterotropic presynaptic inhibition?
the transmitter acts on a presynaptic receptor to inhibit the release of a second neurotransmitter
What is postsynaptic modulation?
Chemical mediators influence postsynaptic receptors to alter excitability or cell firing
What is NANC transmission?
Non-adrenergic, non cholinergic transmission. Drugs that block the responses to Ach and NA signaling does not completely block autonomic neurotransmission
What is co transmission?
Nerve terminals store and release more than one neurotransmitter
e.g. ATP & NA
What are the sites off ACh action?
released by all preganglionic neurons and post ganglionic in the parasympth
stimulates secretion of adrenaline by the adrenal medulla
What does Hemichoinium inhibit?
The Choline uptaker
What does Neo stigmine inhibit?
the AChE (inhibition of ACh breakdown enzyme) is used to treat mysanthia gravis
What does Vesamicol inhibit?
The putting of ACh into vesicles
What does botox inhibit?
The exocytosis os ACh vesicles
What does 4 aminopyrimidine do?
Enhances release of ACh vesicles
What does neostigmine do?
prevents breakdown of ACH by inhibiting AChE
used for treating myasthenia gravis
What antagonists directly block ACh?
Pilocarpine or atropine
Muscarinic antagonists …….
inhibit bronchial and gastric secretion
relax smooth muscle
increase heart rate
Nicotinic antagonists……
Are muscle relaxers
Tropicamide
drug used to dilate pupils
cholinergic antagonist
What is the rate limiting step for the release of NA?
The making of DOPA out of tyrosine (precursor)
What is the ratio of NA/ATP in NA vesicles
1:$
What receptors does ATP act on?
P2 Purgenic receptors
What do adrenoreceptors alpha 1 work on?
Smooth muscle contraction
What do adrenoreceptors alpha 2 work on?
Inhibition of transmitter release and smooth muscle contraction
What do adrenoreceptors beta work one?
heart muscle contraction B1
Smooth muscle relaxation B2
Glycogenolysis B2
What are the two major metabolites of NA?
VMA
MHPEG
