Autonomic Nervous System Flashcards
General facts about the autonomic nervous system
Sub division of the peripheral nervous system
Not under conscious control
Examples of things controlled by the autonomic nervous system
Cardiac muscle ( heart)
Smooth muscle
Internal organs
Skin
Somatic sensory
Responds to external sensory
Visceral sensory
Controls internal environment
What does the autonomic nervous system consist of
Sympathetic and parasympathetic branches of the visceral motor system
Which horn does sensory information enter the spinal cord through
Dorsal horn
Where does motor information leave the spinal cord through
Ventral horn
What does the parasympathetic nervous system do
Routine maintenance ( ‘rest and digest’)
What does the sympathetic response do
‘Fight and flight’ response
Effect parasympathetic nervous system has on pupil
Constricts
Effect sympathetic nervous system has on pupil
Dilation as during fight or flight you want to be receiving as much sensory info as possible so dilate the pupil
What does Parasympathetic/Sympathetic do on heart
Parasympathetic; decreases rate and contraction to
Sympathetic; increases rate and comtractility
What does parasympathetic and sympathetic do on stomach
Parasympathetic : increased motility and secretion
Sympathetic ; decreased motility and secretions
What does parasympathetic / sympathetic do on lungs
Sympathetic : dilation , during fight or flight more O2 is needed
Parasympathetic; constriction
What does parasympathetic / sympathetic do on liver
Parasympathetic; increased bile release
Sympathetic; increased glucose release - fight or flight so need more glucose
What does parasympathetic/sympathetic do on bladder
Parasympathetic; contraction of bladder and stimulate bladder emptying
Sympathetic; relaxation
Baroreceptors and blood pressure
Baroreceptor firing rate is directly proportional to pressure.
Increase in blood pressure-> increase in baroreceptor firing rate
High blood pressure
Parasympathetic is switched on and decreases BP, heart rate is controlled and doesn’t go higher, sympathetic is switched off as you don’t want the BP to increase and go higher.
Low Blood pressure
Baroreceptor firing rate decreases, so stimulus to inhibit sympathetic nervous system decreases, and the sympathetic nervous system is turned on
Where do visceral motor nuclei originate and the what path do they follow
Originate in the hypothalamus and these visceral motor neurone project to the brain stem or the spinal cor where they synapse with autonomic neurone ( parasympathetic or sympathetic)
Pre and post ganglionic neurones in the Parasympathetic NS
Long preganglionic fibres
Ganglions are close to / embedded within the effector tissues
Short post ganglionic fibres
Pre and post ganglionic neurones in the Sympathetic nervous system
Short pre ganglionic fibres
Ganglions close to spinal cord
Long post ganglionic fibres
Advantage of having a short pre ganglionic fibres in the sympathetic nervous system
Normally lots of sympathetic nerves in sympathetic trunks which are long and run parallel to spinal cord- allows for mass activation of neurones. So if you want an increased heart rate at same time as lung dilates
Exception to two neurone arrangement in ANS
Adrenal gland - only have sympathetic nerve that innervates the adrenal gland - basically pre ganglionic fibre
Neurotransmitters released at both synapses of parasympathetic nerve
Acetylcholine from presynaptic and postsynaptic ganglion
Neurotransmitter release at ore ganglion
ACh
Neurotransmitter released at post ganglionic fibre
Noradrenaline
What is released at sympathetic nerve of adrenal gland
Adrenal gland secretes a hormone not a transmitter. Adrenaline ( and some noradrenaline) , and a bit of dopamine is released into bloodstream not synapse as only one ganglion
What effect would the smell of food have on the gut
Parasympathetic’rest and digest’ would be activated and would tell stomach to start contracting and producing secretions .
What is the enteric nervous system
Control system in gut which can occur independently of brain . The autonomic nervous system is the central control
How does the sympathetic nervous system affect the lung function
There are no sympathetic neurones innervating the lung tissue. There are only parasympathetic .
So adrenal glands release adrenaline which passes into blood into lungs and causes bronchodilation as neurotransmitter can’t be used
Micturition reflex
Sensory information received within the bladder is that the pressure within the bladder is high and so the bladder slowly fills with urine. Info goes to the brain and down the NS again.
You don’t want the bladder to contract until full so moderate pressure in bladder actually leads to internal sphincter being in change and contracted and so bladder closes ( SYMPATHETIC IN CHARGE)
Once pressure gets to full the detrusor muscle contracts and the PARASYMPATHETIC SYSTEM IS IN CHARGE
What type of receptor would be at an autonomic pre ganglionic fibre and adrenal gland
Ion channel receptor - nicotinic acetylcholine receptor
What receptor mediates the response from neurotransmitter released from post ganglionic fibre
Muscarinic or adrenegric fibres ( G protein coupled receptor - slow response )
Type of receptor in post ganglionic fibre in parasympathetic
Muscarinic
What type of receptor would be in post ganglionic fibre in sympathetic system
Adrenergic
Biosynthesis and metabolism of acetylcholine in synapses
1) choline and acetyl CoA enzymatically converted by choline acetyl transferase
2) packages into vesicles
3) AP , Ca influx, exocytosis
4) transmitter release
5) receptor activation ( muscarinic or nicotinic )
6) ACh rapidly degraded by acetylcholinesterase in synapse. Choline taken up into presynaptic terminal by choline uptake protein
What would happen if you block acetylcholinesterase
The ACh would accumulate in neurone and so you would have a much more powerful ACh response
Biosynthesis and metabolism of noradrenaline
1) tyrosine converted to DOPA by tyrosine hydroxylase . DOPA converted to dopamine by DOPA decarboxylase
2) dopamine is packaged into vesicles with dopamine b hydroxylase . Produces noradrenaline,
3) stuff happens
5 ) adrenergic receptor is activated.
6) removal of neurotransmitter from synapse via uptake into pre- synaptic terminal or glial cell..
What two enzymes break down noradrenaline
Monoamine oxidase in pre synaptic terminal
Ciatachole O methyl transferase in Glial cell ( COMT)
Biosynthesis and metabolism of adrenaline
1) tyrosine converted to DOpA by tyrosine hydroxylase
DOPA converted to dopamine by DOPA decarboxylase
2) Dopamine packaged into vesicles with dopamine B hydroxylase . Noradrenaline is the product
3) noradrenaline coverted to adrenaline in the cytoplasm by phenylethanol methyl transferase in adrenal gland
4) action potential causes calcium influx and exocytosis
5) exocytosis and neurotransmitter release
6) adrenaline diffuses into capillary and is transported to tissues in blood
Where do the sympathetic nerves exit the spinal cord from
From T1 to L2 or L3
Where does the parasympathetic nerves exit the spinal cord from
Emerges from cranial outflow in cranial nerves 3 , 7 , 9 and 10 or from the sacral outflow
Which organ does not have direct sympathetic innervation
Lungs- goes via adrenal gland and then release of adrenaline
Which organ does not have direct parasympathetic innervation
Adrenal gland
