Lecture 8 - Introuction To The Autonomic Nervous System Flashcards
Divisions of the nervous system
Central nervous system and the peripheral nervous system
Main function of the autonomic nervous system
To carry output from the CNS to the whole body, except skeletal muscle
What does the ANS regulate
Visceral functions that are largely involuntary, exocrine and certain endocrine functions, the heartbeat and aspects of metabolism
Divisions of the ANS
Sympathetic and parasympathetic
What does the parasympathetic division coordinate
The body’s basic homeostatic functions
What does the sympathetic division coordinate
The body’s response to stress and is associated with flight, fright and fight reactions
Travel path of an efferent signal
Travels from the CNS, along preganglionic neurones, to the synapse of the neurone causing neurotransmitter to be released. This is taken up by the associated cell body of the post ganglionic neurone. It travels down the post ganglionic neurone to the effector cell.
CNS -> synapse -> neurotransmitter released -> taken up by Post ganglionic neurone -> travels to effector cell.
What is the autonomic ganglion
Where the end of the neurone from the CNS and the start of the neurone of the ANS meet
Examples of effector cells
Cardiac cell, smooth muscle cell, secretory cell
Functions of the sympathetic system
Constricts many blood vessels but dilates those of skeletal muscles, erects hair, stimulates sweat glands, dilates pupils, dilates bronchi, decreases mucus production, increases heart rate + contractility, slows gut motility, stops secretions of the gut, shut sphincter, stimulates the liver to export fatty acid + glucose, increases renin secretion and causes adrenaline to be released
How does the sympathetic system dilate the bronchi
Through the release of adrenaline
A decrease in mucus production causes
A decrease in airway resistance
Functions of the parasympathetic system
Constricts pupils, stimulates tears, stimulates salivation, constricts bronchi, stimulates mucus secretion, decreases the heart rate, constricts the gall bladder, stimulates pancreatic secretion, increases gut motility + secretions, relaxes sphincters and contracts the bladder
What does an increase in mucus production cause
An increase in airway resistance
What is the transmitter in the pre ganglionic neurones of the ANS
Acetylcholine
Transmitter in the post ganglionic neurone for the sympathetic system
Noradrenaline
What type of transmitter is noradrenaline
Adrenergic
Transmitter in the post ganglionic neurone for the parasympathetic system
Acetylcholine
What type of transmitter is acetylcholine
Cholinergic
What does the uptake of a precursor in the synapse cause
The synthesis of a transmitter
Where is the transmitter stored
Within vesicles
An AP causes what effect on the synapse
It causes the synapse to depolarise
Depolarisation of the synapse causes
Ca2+ voltage-gated channels to open so there is an influx of Ca2+
What does an influx of Ca2+ into the synapse cause
For the transmitter to be released
What is the release of neurotransmitter known as
Exocytosis
What does the release of transmitter cause
The activation of the receptors on the post synaptic membrane
Once the receptors on the post synaptic membrane are activated what happens
The neurotransmitter is degraded by enzymes or reabsorbed by the synapse
What channels does the release of ACh from the preganglionic neurone open
Ligand-gated ion channels
What type of receptors are ligand-gated ion channels
Nicotinic ACh receptors
Where are nicotinic receptors found
Post ganglionic neurone
What does noradrenaline activate
G-protien-coupled adrenoceptors
Where does noradrenaline act upon
The target cell
What does ACh in the post ganglionic neurone activate
G-protein-coupled muscarinic acetylcholine receptors
In cholinergic transmission, what is taken up by the transporter
Choline
What does the uptake of choline cause
The synthesis of ACh
Through what mechanism is ACh synthesised from choline
Choline acetyltransferase (CAT)
What degrades ACh
Acetylcholinesterase
ACh causes the activation of what subtypes of ACh muscarinic receptors
M1, M2 and M3
In noradrenic transmission what causes the synthesis of noradrenaline
L-tyrosine
What are the transporters known as that reabsorb noradrenaline
Uptake 1 (U1) and uptake (U2)
What metabolises noradrenaline
Monoamine oxidase (MO) and catecholo-o-methlytransferase (COMT)
Associated M1 g-protien
Gq
What does the M1-Gq coupling cause
The stimulation of phospholipase C which causes an increase in acid secretion
The associated M2 G-protien
Gi
What does the M2-Gi coupling cause
Inhibition of adenyly cyclase which opens the K+ channels which causes a decreased heart rate
The associated M3 G-protein
Gq
What does the M3-Gq coupling cause
The stimulation of phospholipase C which causes an increase in the secretion of saliva and contraction of the bronchi
What indirectly effect does M3 receptor activation have
The relaxation of vascular smooth muscle due to the release of nitric oxide from neighbouring cells
The two main classes of adrenoceptors
Alpha-adrenoceptors and beta-adrenoceptors
Isoforms of alpha-adrenoceptors
Alpha 1 and alpha 2
Isoforms of beta-adrenoceptors
Beta 1 and beta 2
Beta 1 associated G-protein
Gs
What does the beta 1-Gs coupling cause
The stimulation of adenyly cyclase which causes an increase in the rate and force of the heart contractions
Beta 2 associated G-protein
Gs
What does the beta 2-Gs coupling cause
The stimulation of adenyly cyclase which causes relaxation of the bronchi and vascular smooth muscle
Alpha 1 associated G-protein
Gq
What does the alpha 1-Gq coupling cause
Stimulation of phospholipase C which causes the constriction of vascular smooth muscle
Alpha 2 associated G-protein
Gi
What does the alpha 2-Gi coupling cause
The inhibition of adenyly cyclase at pre-junctional terminals which inhibits the release of noradrenaline
