CVS S4 - The CVS & The Autonomic Nervous System Flashcards
Describe preganglionic neurones in the sympathetic nervous system
Have their cell bodies in the CNS
Cholinergic
Nerve fibres are short
Arise from segments T1-L2 or L3
Describe pre-ganglionic neurones in the parasympathetic nervous system
Have their cell bodies in the CNS
Cholinergic
Nerve fibres are long
Describe post-ganglionic neurones in the parasympathetic nervous system
Have their cell bodies in the PNS
Noradrenergic (α and β classes, types 1 and 2)
EXCEPTION perspiration and ejaculation pathways cholinergic
Short nerve fibres
Describe post-ganglionic neurones in the sympathetic nervous system
Have their cell bodies in the PNS
Cholinergic receptors
Specifically muscarinic receptors and GPCRs
Nerve fibres are long
Give examples of effectors of the autonomic nervous system
Smooth muscle
Viscera
Secretory glands
Describe the sympathetic nervous system
Thoraco-lumbar outflow
Nerve fibres have cell bodies in all 12 thoracic sections and the first two lumbar sections
Pre-ganglionic neurones have short nerve fibres and are cholinergic
Post-ganglionic neurones have long nerve fibre and are noradrenergic EXCEPT the perspiration ejaculation pathways which are cholinergic
Describe the locations of synapses in the parasympathetic nervous system
Usually synapse close to target tissue
Describe the location of synapses in the sympathetic nervous system
Most synapse with post-ganglionic neurones at the para vertebral chain of ganglia
Some synapse in a number of prevertebral ganglia: coeliac, superior and inferior mesenteric ganglia
Describe the parasympathetic nervous system
Cranio-sacral outflow
Pre-ganglionic neurones have long nerve fibres and are cholinergic (nicotinic)
Post-ganglionic neurones have short nerve fibre and are cholinergic (muscarinic or GPCR)
Give the effect and the receptor of sympathetic stimulation to the heart
Sympathetic:
Receptor is β1
Effect is to increase the force of rate of contraction
Parasympathetic:
Receptor is M2
Effect is to decrease the rate of contraction
Give the effect and the receptor of parasympathetic stimulation to the heart
Receptor is M2
Effect is to decrease the rate of contraction
Give the effect and the receptor of sympathetic stimulation to the airways
Receptor is β2
Effect is to relax the airways
Give the effect and the receptor of parasympathetic stimulation to the airways
Receptor is α1
Effect is to contract the airways
Give the effect and the receptor of sympathetic stimulation to the pupils
Receptor is α1
Effect is to dilate the pupils
Give the effect and the receptor of parasympathetic stimulation to the pupils
Receptor is M3
Effect is to contract the pupils
Which type of GPCR stimulates adenylyl cyclase?
The s type: Gs
Which type of GPCR inhibits adenylyl cyclase?
The i type: Gi
Which type of GPCR stimulates phospholipase C?
The q type: Gq
Which type of GPCR stimulates cyclic GMP?
The t type: Gt
Which receptors cause the stimulation of adenylyl cyclase?
β1 and β2
Which receptors cause the inhibition of adenylyl cyclase?
α2 and M2
Which receptors cause the stimulation of phospholipase C?
α1, M1 and M3
Describe how the sympathetic nervous system innervates vasculature
Sympathetic NS innervates the smooth muscle of arteries, arterioles and veins
Stimulation causes vasoconstriction via α1 receptors
EXCEPT in specialised vessels eg erectile tissue
What is the effect of sympathetic stimulation on vasculature?
Stimulation causes vasoconstriction via α1 receptors
EXCEPT in specialised vessels eg erectile tissue
How is vasomotor tone controlled?
By the balance between sympathetic stimulation and vasodilator substances
This in turn controls flow around the cvs
How variable is vasomotor tone?
It varies between organs and can be changed quickly
Describe how vasomotor tone in the skin changes
Skin usually has very high vasomotor tone but for thermoregulation, tone can be reduced
Describe how vasomotor tone in skeletal muscle changes
At rest, skeletal muscle has high vasomotor tone but during exercise, this is antagonised by vasodilator metabolites
Describe how vasomotor tone in the gut changes
Before a meal, the gut has high vasomotor tone but after eating, various vasodilators are produced in the gut to antagonise sympathetic stimulation
What afferent information is used by the medulla oblongata to control heart rate?
Information from baroreceptors in the carotid sinuses and arch of the aorta
How does the medulla oblongata control heart rate?
Balance of sympathetic and parasympathetic stimulation to the SAN and AVN
Parasympathetic slows and sympathetic speeds
Parasympathetic is dominant at rest so initial increases in heart rate are due to a reduction in parasympathetic stimulation, then sympathetic stimulation will take effect too
Give the effect and the receptor of sympathetic stimulation to the sweat glands
The effect for the α1 receptor is generalised secretion
The effect for the M3 receptor is localised secretion
Give the effect and the receptor of parasympathetic stimulation to the sweat glands
There is no effect and there are no receptors
