Pharm 1: intro to ANS Flashcards
Describe the ANS control on the heart
At rest there is parasympathetic domination over the heart, parasympathetic nerves stimulate an inhibitory interneurone on the heart.
When there is increased BP, the baroreceptor firing rate increases and it is stimulatory to the parasympathetic arm and inhibitory to the sympathetic nerve.
Which branch of the ANS controls arterioles?
Sympathetic controls dilation (smooth muscle) and constriction (skin, mucous membranes and splanchnic area).
What are the simple defining features of the SNS and PNS?
SNS: coordinated and divergent
PNS: localised and discrete
What is the difference between the ANS and somatic nervous system?
Somatic has only one motor neurone innervating a muscle and releases ACh
Where do the nerves from the SNS and PNS originate?
SNS: thoracolumbar
PNS: craniosacral
What are nicotinic receptors and where are they found?
Pentameric
Found between pre and post ganglionic fibres in the SNS and PNS
Use the neurotransmitter ACh
Type 1: inotropic, fast
What are muscarinic receptors and where are they found?
Type 2, G-protein coupled receptor
Found at effector organs innervated by post ganglionic PNS fibres (including sweat glands of SNS)
What type of receptor would you find between pre and post ganglionic fibres?
Nicotinic
What type of receptor would you find at the organ innervated by PNS and SNS?
Muscarinic
What are the subtypes of muscarinic receptors?
M1: neural (stimulatory Gq), activated phospholipase C -> IP3 + DAG
M2: cardiac (inhibitory Gi), inhibits production of cAMP
M3: exocrine and smooth muscle (stimulatory)
What are adrenoreceptors and where are they found?
Type 2, g protein coupled
a1, a2, b1, b2
Found at the effector organ innervated by post ganglionic fibres of the SNS
Describe the synthesis of ACh
Acetyl coA + choline (from diet) = acetylcholine via Cholineacteyl transferase
Ach is packaged into vesicles on the presynaptic membrane
AP stimulates Ca influx and release of vesicles into synaptic cleft
ACh vesicles bind to post synaptic membrane and release contents causing an AP
Remaining ACh in the cleft is taken up and broken down by acetylcholinesterase -> choline + acetate
Describe the synthesis of ACh
Acetyl coA + choline (from diet) = acetylcholine via Cholineacteyl transferase
Ach is packaged into vesicles on the presynaptic membrane
AP stimulates Ca influx and release of vesicles into synaptic cleft
ACh vesicles bind to post synaptic membrane and release contents causing an AP
Remaining ACh in the cleft is taken up and broken down by acetylcholinesterase -> choline + acetate
Describe the synthesis of NA
Tyrosine (from diet) -> DOPA via tyrosine hydrolase
DOPA -> Dopamine via DOPA decarboxylase
Dopamine is packaged into a vesicle -> NA via dopamine beta hydroxylase
NA is released from the vesicle
AP is sent down causing CA influx
NA is released and binds to the adrenoreceptors on the effector organ
Uptake 1 protein (presynaptic neurones) -> Monoamine oxidase A
Uptake 2 protein -> Catechol o methyl transferase
