Autonomic Physiology Flashcards
What do somatic, efferent neurones control?
Skeletal muscle
What is the structural difference between pre-ganglionic fibres and post-ganglionic fibres, in the autonomic nervous system?
Pre-ganglionic are myelinated
Post-ganglionic are unmyelinated
What muscle types of innervated by the ANS?
Smooth
Cardiac
What are the differences between the synapse junctions in the autonomic and somatic nervous system?
SNS:
Specialised NMJ
Ionotropic
Excitatory
ANS:
Can have multiple junctions (variscosities) per fibre
Metabotropic
Can be excitatory or inhibitory
What spinal regions does the parasympathetic nervous system link to?
Cranio-sacral
Cranial nerves 3, 4, 9 and 10
S2-4
What spinal regions does the sympathetic nervous system link to?
Thoraco-lumbar
T1-L2
Describe the differences between the sympathetic and para-s nervous systems in terms of pre vs post ganglionic fibre length.
P = long pre-ganglionic, short post-ganglionic
S = short pre-ganglionic, long post ganglionic
In the sympathetic nervous system, where are most of the ganglia located?
What is the exception to this?
Sympathetic trunk
Celiac ganglion and mesenteric ganglia
What are the two autonomic neurotransmitters?
Acetylcholine
Norarenaline (+adrenaline)
What are the two types of cholinergic receptors?
Nicotinic
Muscarinic
Why do drugs targeting acetylcholine receptors in the nervous system not fuck up the somatic nervous system as well?
ACh receptors in nervous system are slightly different from the ones at the NMJ
Describe how a signal is sent to receptors in the sympathetic nervous system, in terms of transmitters and receptors.
Preganglionic fibres release ACh which binds to nicotinic receptors
Postganglionic fibres release NA which binds to either alpha or beta receptors.
Or postganglionic cells release A/NA into blood which then binds to alpha or beta
Some post-ganglionic fibres do not release ACh or NA/A but instead release NANC transmitters. (Non adrenergic non cholinergic)
What are these transmitters?
Peptides
Nitric oxide (NO)
Describe the mechanism for sympathetic stimulation of the eye.
Beta 2 receptors on ciliary muscle
Relax ∴ focuses far away
Alpha 1 receptors on radial muscle of iris
Contracts ∴ pupil larger ∴ more light
Describe the mechanism for parasympathetic stimulation of the eye.
ACh ∴ muscarinic receptors on ciliary muscle
Contracts ∴ focuses close up
Muscarinic receptors on sphincter
Contracts ∴ pupil smaller
How does sympathetic stimulation of the heart work?
Beta 1 on pacemaker cells = increased heart rate
Beta 1 on muscle cells = increased strength of contraction
Describe the parasympathetic stimulation of the heart.
Muscarinic receptors on pacemaker cells = slows HR
Little effect on muscle cells
In sympathetic stimulation of the lungs, beta 2 receptors are activated in the smooth muscle of the airway.
What effect does this have?
Relax smooth muscle ∴ dilates airway
What happens in parasympathetic stimulation of the lungs?
Muscarinic receptors in smooth muscle activated
Muscle contracts ∴ airways constrict
What does a Beta 2 agonist do?
eg salbutamol
Dilates airways (sympathetic)
Does not effect heart - heart has beta 1 receptors
What does a beta 1 antagonist do?
eg atenolol
Decreases heart rate
Does not affect airways
Describe how sympathetic stimulation of the blood vessels does?
Activates both beta 2 and alpha 1 receptors in smooth muscle, to relax/contract smooth muscle and channel blood flow to areas where it is most needed
What effect does the parasympathetic system have on blood vessels?
None
except salivary + genitalia blood vessels
Sympathetic response causes the body to go into fight/flight mode, so gut motility decreases. What mediates this?
Alpha and beta receptors - smooth muscle of gut
Decrease motility
Alpha receptors in pancreas ∴ inhibit enzyme secretion
