Autonomic Nervous System pharmacology
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- Created by: Alex
- Created on: 15-05-13 23:05
Autonomic Nervous system
The part of the nervous system responsible for control of the bodily functions not consciously directed, such as breathing, the heartbeat, and digestive processes - senses internal changes & maintains homeostasis
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What is autonomic NS split into
Sympathetic and parasympathetic
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Autonomic NS acting selectively (what does it effect)
One Organ
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Autonomic NS acting non-selectively
Effects whole body
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When is sympathetic NS dominant?
In response to threat - prepares body for physical activity - fight or flight
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Effect of Sympathetic system
Increase 02/nutrients to skeletal muscle. increase heart rate, opens airways/alveoli, relax smooth muscle in blood vessels, release nutrients into blood(glucose form liver), start sweating/panting in anticipation of lowering body temp
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When is the parasympathetic NS dominant?
During restful periods
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What functions does the parasympathetic NS promote?
rest and digest - digestion and excretion - constricts pupil, causes erection
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what is antagonistic control of autonomic ns function?
dual innervation with opposing effects on effector organs allowing for precise and rapid control of function - sympathetic and parasympathetic work against each other to maintain balance
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How many neurons in the autonomic nerve pathway (from CNS to Effector)
2 neuron chain
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What neurotransmitters does the ANS use?
Acetylcholine and noradrenaline
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What neurotransmitter do pre-ganglionic terminals release? and are both sympathetic and parasympathetic the same?
Both release acetylcholine
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What is the sympathetic post-ganglionic neurotransmitter ?
noradrenaline?
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What in the parasympathetic post-ganglionic neurotransmitter?
acetylcholine
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Stages of chemical transmission
1. precursor uptake 2.transmitter synthesis from precursor 3.transmitter packaged into vesicles and any (4)synthesis by-products are degraded 5.electrical signal reaches terminal causing (6)Ca2+ to enter the cell and
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cont
(7)trigger the fusion of vesicle with the membrane 8.transmitter is released into synaptic cleft to then (9)bind with the post-synaptic receptor 10.neurotransmitter is then inactivated and (11) is re-uptaken into pre-synaptic terminal
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What two precursors make acetylcholine?
Choline + acetyl-coA
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What enzyme catalyses this?
choline acetyltransferase
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what then happens to the acetylcholine?
packed into vesicles to be released into the synaptic cleft
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what breaks down acetylcholine to choline and acetyl-CoA?
acetylcholinesterase
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What effect does botulinum have on cholinergic transmission?
inhibits acetylcholine release from vesicles
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What effect do pesticides have on cholinergic transmission?
irreversible inhibition of acetylcholinesterase
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Cholinergic receptor subtypes
Nicotinic and musarinic
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how are nicotinic cholinergic receptor sub types activated?
by release from autonomic preganglionic fibers
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how are muscarinic cholinergic receptor sub types activated?
release from parasympathetic postganglionic fibers
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whats a nicotinic acetylcholine receptor?
are cholinergic receptors that form ligand-gated ion channels in the plasma membranes of certain neurons and on the postsynaptic side of the neuromuscular junction.
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what structure does it have?
pentameric
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What does a pentameric structure mean?
5 protein subunit form a pore
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What type of channel is it (what goes through)
Cation (Na+, K+)
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Are all the subunits in the nicotinic pentameric structure the same?
no, 2 x alpha, 1 beta, 1 delta 1 gamma
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which subunits are anchored into the membrane?
a-helix
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Which subunits act as a gate, blocking the pore and preventing ion conductance?
alpha helices
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What causes alpha-helices to shift away from the pore?
the binding of acetylcholine to the two binding site on the exterior surface - allows ion conductance and results in excitation of post-synaptic neuron or muscle cell
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What enters and what exits the post synaptic neuron/muscle cell
(Na+ enters, K+ leaves)
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Whats a muscarinic receptor?
that form G protein-receptor complexes in the cell membranes of certain neurons[1] and other cells. They play several roles, including acting as the main end-receptor stimulated by acetylcholine released from postganglionic fibers in the PS NS
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The muscarinic receptors are categorised into 5 classes based on differences in what?
Location and signal transduction mechanisms
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Different locations of muscarinic receptors (5 locations)
1- neural (NS) 2-Cardiac(heart) 3-Glandular(glands;visceral and vascular smooth muscle) 4&5- in brain (not well characterised)
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Different signal transduction mechanisms of muscarinic receptors
M1,3&5 coupled to Gq (increase phospholipase C) M2&4 coupled to Gi (decrease adenylyl cyclase) M2 coupled to Go (open K+channels)
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Adrenergic transmission
Transmission across a synapse using Noradrenaline and adrenaline as the neurotransmitter? (from noradrenergic varicosity (swelling) to postsynaptic cell
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what is adrenergic transmission mainly terminated by?
reuptake (of noradrenaline) via noradrenaline transporter and degradation by enzyme monoamine oxidase
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How are receptor subtypes classified?
By their affinity for noradrenaline vs adrenaline
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Affinity in alpha 1
noradrenaline > adrenaline
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affinity in alpha 2
adrenaline > noradrenaline
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affinity in Beta 1
noradrenaline = adrenaline
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affinity in beta 2
adrenaline > noradrenaline
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What effect does activation of alpha 1 receptor have? and why
coupled to Gq (increases phospholipase C) activation has excitatory effects
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What effect does activation of alpha 2 receptor have? and why
Coupled to Gi (decrease adenylyl cyclase) activation has mainly inhibitory effects
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What are both B1 and B2 coupled to and what does it do?
Gs (increases adenyl cyclase)
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what does B1 receptor do and where is it found?
found in heart and activation increases contractions
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what does B2 receptor do?
activation causes smooth muscle relaxation
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Other cards in this set
Card 2
Front
What is autonomic NS split into
Back
Sympathetic and parasympathetic
Card 3
Front
Autonomic NS acting selectively (what does it effect)
Back
Card 4
Front
Autonomic NS acting non-selectively
Back
Card 5
Front
When is sympathetic NS dominant?
Back
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