Autonomic Nervous System 1 Flashcards
What does the ANS do?
ANS controls all involuntary functions (heart rate, blood pressure, GI motility, iris diameter)
The ANS is separate from the somatic motor system
It is entirely efferent but regulated by afferent inputs.
What systems are there in the ANS?
Sympathetic
Parasympathetic
Enteric
What is the sympathetic nervous system?
A fight or flight. Increases heart rate, force of contraction and blood pressure.
What is the parasympathetic nervous system?
Rest and digest. Regulates basal activities like basal heart rate.
What are the division of the brain stem and spinal cord?
M - medullary C - cranial T - thoracic L - lumbar S - sacral
How does the sympathetic nervous system differ to the parasympathetic structurally?
The sympathetic nervous system has a short preganglionic nerve fibre and a long postganglionic.
The parasympathetic has a long preganglionic nerve fibre and short post ganglionic.
What is the main structural difference between postganglionic and preganglionic fibres?
Preganglionic are myelinated
Postganglionic are not myelinated
What anatomical divisions connect to the PNS?
M - medullary
S - sacral
going via vagus nerve in M
Give some features of the parasympathetic nerves.
Originate in the lateral horn of the medulla and the sacral spinal cord.
Long myelinated preganglionic fibres
Short unmyelinated postganglionic fibres
Ganglia are located within the innervated tissues
Have actions that oppose the sympathetic nervous system.
Give some features of the sympathetic nerves.
Originate in the lateral horn of the lumbar and thoracic spinal cord.
Short myelinated preganglionic fibres
Long unmyelinated postganglionic fibres
Ganglia are located in the paravertebral chain close to the spinal cord (spinal nerve)
Have actions that oppose the parasympathetic nervous system.
Which are the most common neurotransmitters in the ANS?
Acetylcholine and noradrenaline
What neurotransmitters do all pre-ganglionic neurones use?
They use acetylcholine as their neurotransmitter
All pre-ganglionic neurones are cholinergic. What does this mean?
That they use acetylcholine as their neurotransmitter.
nAChR and mAChR are also cholinergic receptors.
What types of receptors are found in the post ganglionic fibres?
Nicotinic acetylcholine receptors at the neuromuscular junction for example.
What types of channels are nicotinic acetylcholine receptors?
Ligand-gated channel ions
What types of channels are muscarinic acetylcholine receptors?
GPCRs
Look at page 13.
Yup.
What types of receptors are also found in the parasympathetic post-ganglionic neurones?
Muscarinic acetylcholine receptors
What is the main types of receptors found in sympathetic post-ganglionic neurones?
Noradrenergic receptors
What are noradrenergic receptors?
GPCRs that use noradrenaline as their primary neurotransmitter.
What are the two major classes of adrenoceptors (noradrenergic)?
alpha and beta adrenoceptors: a1 a2 b1 b2 (b3)
Give examples of sympathetic post-ganglionic neurones that are cholinergic instead of noradrenergic.
Innervating sweat glands and hair follicles.
They are non-adrenergic and non-cholinergic transmitters as well in the ANS. Give some examples.
ATP
Nitric Oxide
Serotonin
Neuropeptides like VIP and substance P
How are the sympathetic postganglionic neurones in the adrenal glands different?
They differentiate to form neurosecretory chromatin cells.
Chromaffin cells can be considered as postganglionic sympathetic neurones that do not project to a target tissue.
This also means that there is no ganglion found in the spinal nerve. The chromaffin cells work as their own ganglion.
What do chromaffin cells release?
By sympathetic stimulation they release adrenaline as a hormone into the bloodstream.
Where are chromaffin cells found?
In the adrenal medulla.
Look at page 21.
Yup.
Give examples of what parasympathetic release of ACh causes.
Heart (M2) - bradycardia and reduced cardiac conduction velocity Smooth muscle: bronchial/bronchiolar contraction (M3) GI-motility Bladder contraction and relaxation Penile erection Ciliary muscle and iris sphincter Glandular: Increased sweat/salivary/lacrimal secretion (M1/M3)
Give examples of what sympathetic release of noradrenaline causes.
Heart: (b1) Tachycardia Positive inotropy Smooth muscle: Arteriolar contraction/venous contraction (a1,b2) Bronchiolar/intestinal/uterine relaxation (b2) Bladder sphincter contraction Radial muscle contraction Glandular: Increased viscous secretion Kidney: Renin release
How does vasoconstriction happen by the sympathetic nervous system?
By release of adrenaline or noradrenaline that binds to alpha1 adrenoceptors. This causes vasoconstriction.
Nor/adrenaline also causes vasodilation by the sympathetic nervous system. How does this work when it also causes vasoconstriction?
alpha1 adrenoceptors are responsible for vasoconstriction. beta2 adrenoceptors are responsible for vasodilation. These two types of adrenoceptors are not found in the same tissues and organs in the body. For example alpha1 adrenoceptors are found in the skin, sphincters, brain, GI-system, kidney etc. These are organs you don’t need to work during fight or flight.
