Autonomic Nervous System Flashcards
what are the two arms of the autonomic nervous system?
sympathetic and parasympathetic
what does the autonomic nervous system control?
non-skeletal peripheral function: cardiac muscle, smooth muscle internal organs, skin
which part of ANS is used for ‘rest and digest’?
parasympathetic
which part of ANS is used for ‘fight and flight’?
sympathetic
is ANS under conscious control?
no
what is the exception to the rest and digest/fight or flight rule?
sympathetic nervous system both constricts and dilates blood vessels
which visceral sensory receptors determine parasympathetic/sympathetic control of heart rate?
baroreceptors
if blood pressure rises, what happens?
baroreceptors detect change and activate parasympathetic nervous system to reduce heart rate
if blood pressure falls eg. due to blood loss, what happens?
baroreceptor firing rate slows down, so brain receives less stimulation and therefore less signal to parasympathetic and less inhibition to sympathetic so sympathetic increases heart rate
which part of the brain is autonomic sensory (afferent) information relayed to?
hypothalamus in CNS
where do visceral motor neurons project to and what do they synapse with?
brainstem or spinal cord, where they synapse with autonomic neurons (parasympathetic or sympathetic)
what do autonomic neurons consist of?
pre-ganglionic and post-ganglionic neuron
what is a ganglion?
nerve cell cluster or group of nerve cell bodies
where are the ganglia located within the parasympathetic nervous system, and what is the relative length of pre-ganglionic neurons compared to post ganglionic?
close to, or embedded in the effector tissue eg. stomach and they are long in comparison to post ganglionic neurons
where are the post ganglionic neurons in the parasympathetic nervous system in comparison to pre ganglionic?
synapse in or close to effector organ eg.stomach, very short and protude out into efffector, producing the effect
where are the ganglia located within the sympathetic nervous system, and what is the relative length of pre-ganglionic neurons compared to post ganglionic?
ganglions are very close to originating site of pre-ganglionic neuron
short pre-ganglionic fibres and long post ganglionic fibres which project to various tissues and organs.
why are the pre-ganglionic fibres so short in the sympathetic nervous system?
The key is that this allows each ganglion to influence other ganglia. This is what allows the whole response to occur globally and simultaneously, which is crucial to an effective fight or flight response.
what is the exception to the two ganglia rule, and what is it?
There is only one sympathetic nerve to the adrenal gland
the adrenal gland acts like a post ganglionic fibre, releasing the HORMONE, ADRENALINE, (and some noradrenaline) into the BLOODSTREAM instead of neurotransmitter into a synapse
which neurons in the ANS release acetylcholine?
preganglionic in both parasympathetic and sympathetic
post ganglionic in parasympathetic fibres
which neurons in the ANS release noradrenaline?
post-ganglionic in the sympathetic
which part of the adrenal gland produces adrenaline?
adrenal medulla
what is the enteric nervous system?
the nervous system of the gut
what is special about the lung?
there are NO sympathetic neurons innervating the lung tissue
BUT the sympathetic system secretes a hormone - adrenaline (causing dilation) instead of innervation
which muscle of the bladder does the parasympathetic nervous system innervate?
detrusor muscle
which muscle of the bladder does the sympathetic nervous system innervate?
sphincter
what does the sphincter muscle do?
keeps the bladder closed
what does the detrusor muscle do upon contraction?
forces urine out of the bladder
which part of information about the bladder is relayed to the brain?
pressure
what happens when the bladder gets full?
parasympathetic switches on and contracts detrusor muscle and sympathetic nervous system switches off and relaxes the sphincter muscle
however, the somatic motor also has control so there is some conscious control involved
which type of receptor would you want at the autonomic ganglia and adrenal gland? What would be the speed of response?
NICOTINIC ACh receptor - a receptor coupled to ION CHANNELS producing a FAST response
which receptors would you need to detect neurotransmitters from post ganglionic fibres? What would be the relative speed of the response? What is the advantage?
parasympathetic - muscarinic (ACh) G-protein coupled receptor
or
sympathetic - adrenergic (NA) G-protein coupled receptor
SLOW responses (secs/mins)
cell has control over receptors
how are neurotransmitters biosynthesized?
precursor digested and then comes into nerve via bloodstream
nerve enzymatically converts into neurotransmitter at pre-synaptic vesicle
packaged into vesicles
why do we need to remove the neurotransmitter from the synapse?
so we don’t get an overly prolonged effect
how can you metabolise a neurotransmitter?
enzymes in synapse
remove via transport protein into pre-synaptic terminal to be recyled or glial cell
can also be metabolised in synapse prior to uptaking
which enzyme converts precursors into acetylcholine and what are the names of the two precursors?
choline acetyl transferase
choline and acetyl CoA
what are the two main types of acetylcholine receptors?
nictonic and muscarinic
which enzyme degrades acetylcholine in the synapse?
acetylcholinesterase
what happens if you block acetylcholinesterase?
overaccumulation of acetylcholine and its effects
which precursors are involved in production of noradrenaline and what is the process of conversion and enzymes involved?
tyrosine from diet is converted to DOPA in nerve cell
DOPA converted to dopamine by DOPA decarboxylase
dopamine packaged into vesicles with enzyme dopamine B hydroxylase
noradrenaline is the product (produced in vesicle)
how is noradrenaline removed from the synaptic cleft?
no enzyme in synapse (unlike ACh)
uptake into pre-synaptic terminal then broken down by MOA-O (monoamine oxidase)
OR uptaken into glial cell and metabolised by COMT
how does production and release of adrenaline into bloodstream from adrenal medulla differ to that of noradrenaline from pre-synaptic terminal into the synapse?
after dopamine B hydroxylase is used in the vesicle to convert dopamine into noradrenaline, one more enzyme is used to convert this to adrenaline
when cells are depolarised, adrenaline is released into the bloodstream
how is adrenaline removed?
in bloodstream
