Introduction to autonomic nervous system Flashcards
What are the three principal efferent outputs from the central nervous system?
Autonomic nervous system
Somatic nervous system
Neuroendocrine system
What is the autonomic nervous system involved with?
Exocrine glands, smooth muscle, cardiac muscle, metabolism and host defence
What is the somatic nervous system involved with?
Skeletal muscle including diaphragm and respiratory muscle
What is the neuroendocrine system involved with?
Growth, metabolism, reproduction, development, salt and water balance and host defence
What are the two branches of the autonomic nervous system and what are they involved in?
Sympathetic- fight or flight
Parasympathetic- rest and digest
What effect does the sympathetic have on the eye?
Pupil dilatation
What effect does the sympathetic have on the trachea and bronchioles?
Dilates
What effect does the sympathetic have on the liver?
Increases glycogenolysis and gluconeogenesis
What effect does sympathetic have on adipose?
Lipolysis
What effect does sympathetic have on kidney?
Increased renin secretion
What effect does sympathetic have on ureters and bladder?
Relaxes detrusor and constricts trigone and sphincter
What effect does the sympathetic have on the salivary glands?
Causes thick viscous secretions
What effect does the sympathetic have on the skin?
Piloerection and increased sweating
What effect does the sympathetic have on the heart?
Increase in rate and contractility
What effect does the sympathetic have on the GI tract?
Decreased motility and sphincter contraction
What effect does the sympathetic have on blood vessels?
Skeletal muscle- dilatation
Skin, mucous membranes and splanchnic area- constriction
What effect does the parasympathetic have on the eye?
Pupil constriction and ciliary muscle contraction
What effect does parasympathetic have on trachea and bronchioles?
Constriction
What effect does parasympathetic have on ureters and bladder?
Contraction of detrusor and relaxation of trigone and sphincter
What effect does parasympathetic have on salivary glands?
Copious watery secretions
What effect doe parasympathetic have on gastrointestinal?
Increases motility and tone and secretions
Where do all parasympathetic nerves originate?
In the craniosacral region
What are their pre-ganglionic and post-ganglionic fibres like in terms of length?
They project a long way out to the tissue- long pre-ganglionic and short post-ganglionic
What effect does the length of the pre and post ganglionic fibres have?
Parasympathetic has a discrete localised response with little divergence
What neurotransmitters are involved with parasympathetic?
Always acetylcholine
Where do sympathetic nerves originate?
Thoracic and lumbar regions
What are their pre-ganglionic and post-ganglionic fibres like in terms of length?
Short pre and long post
What neurotransmitters are normally involved in sympathetic?
Acetylcholine is released by pre-ganglionic and noradrenaline is released by post-ganglionic
What organs are different and why?
The adrenal gland- only has one autonomic fibre innervating it which behaves like a post-ganglionic because it releases adrenaline and noradrenaline
Sweat glands- same as parasympathetic (both acetylcholine)
How does the enteric nervous system work?
The sensory neurone is connected to mucosal chemoreceptors and stretch receptors which detect chemical substances in the lumen or tension in the gut wall caused by food
Interneurones relay information to the submucosal and myenteric plexus
Motor neurones then release acetylcholine or substance P to contract smooth muscle or vasoactive intestinal peptide or nitric oxide to relax smooth muscle
What two types of membrane bound receptors does acetylcholine bind to?
Muscarinic and nicotinic
What is a nicotinic receptor?
Ion-channel linked receptor (type 1) stimulated by nicotine and acetylcholine
What is a muscarinic receptor?
G protein coupled receptor (type 2) stimulated by muscarine and acetylcholine
Where are nicotinic receptors found?
At all autonomic ganglia
Where are muscarinic receptors found?
At all effector organs innervated by post ganglionic parasympathetic fibres
What would blockage of nicotinic acetylcholine receptors lead to?
Constipation
What are the 5 subtypes of muscarinic cholinoceptors?
M1- Neural (Forebrain- learning and memory)
M2- Cardiac (Brain- inhibitory autoreceptors)
M3- Exocrine and smooth muscle (Hypothalamus- food intake)
M4- Periphery
M5- Striatal dopamine release
What are the 4 types of adrenoceptor?
Alpha 1
Alpha 2
Beta 1
Beta 2
Where are adrenoceptors found?
At all effector organs innervated by post ganglionic sympathetic nerve fibres
What is acetylcholine is formed by?
Acetyl-coA and choline
What is acetylcholine broken down by and into what?
Acetylcholinesterase and broken down into choline and acetate
How is noradrenaline formed?
Tyrosine is converted to DOPA by tyrosine hydroxylase
DOPA is converted to dopamine by DOPA decarboxylase
Dopamine is packaged into vesicles then converted to noradrenaline by dopamine beta hydroxylase
How is noradrenaline broken down?
Not in the synapse
Uptake 1- back into neuronal tissue
Uptake 2- into extra-neuronal tissue
Once it has been taken up, it is broken down by:
Monoamine oxidase (MAO)- mainly in neuronal tissue
Catechol-O-Methyl Transferase (COMT)- mainly in extra neuronal tissue
