Autonomic nervous system (6) Flashcards
What is the autonomic nervous system?
NOT under conscious control
- sub division of the peripheral nervous system
- hypothalamus= where sensory/afferent info is relayed
- efferent output split into PARASYMPATHETIC (rest and digest) and SYMPATHETIC neurons (fight and flight) –> often innervate same tissue and have antagonistic effects
- controls non-skeletal peripheral function: heart, smooth muscle, internal organs, skin
What effect does the PNS have on main areas of the body?
parasympathetic: pupil- constriction salivary glands- ^ secretions heart- down rate lungs- constriction GIT- ^ motility and secretions liver- ^ bile release bladder- contraction
What effect does the SNS have on main areas of the body?
sympathetic: pupil- dilation salivary glands- down secretions heart- ^rate/contractility lungs- dilation GIT- down motility and secretions liver- ^glucose release bladder- relaxation
What happens when high blood pressure is detected by baroreceptors–> parasympathetic/sympathetic control systems?
high bp baroreceptor firing rate goes up switches on ParaNS to slow heart rate down slow SNS activity in order to decrease HR
What is a ganglion?
a nerve cell cluster/ group of nerve cell bodies
What do autonomic neurons consist of in general?
and what is the exception…
2 neurons- pre ganglionic and post ganglionic neuron
adrenal gland- only 1 sympathetic nerve (no pre/post)
How are the pre- and post- ganglionic neurons arranged in the PNS?
- long pre-ganglionic fibres
- ganglions close to (or embedded within) effector tissues
- short post-ganglionic fibres
How are the pre- and post- ganglionic neurons arranged in the SNS?
- short pre-ganglionic fibres
- ganglions not close to effector tissues (v early)
- long post- ganglionic fibres
Which neurotransmitters are released at each autonomic synapse?
–> ACh at both PNS synapses
- -> ACh at pre- ganglionic/ganglion synapse in SNS
- -> Noradrenaline (NA) at SNS post- ganglionic/effector organ synapse
*adrenaline HORMONE released by adrenal gland- secreted into bloodstream NOT synapse
What is special about the lung in its regulation of function?
there are parasympathetic nerves innervating the lung tissue, but NO sympathetic neurons
–> so sympathetic nervous system influences lung function via adrenaline (hormone)
What type of receptor mediates the response to ACh released from pre-ganglionic fibres at ALL autonomic ganglia?
nicotinic acetylcholine receptor (nACh) coupled to ion channel- FAST
(these also mediate the response to ACh released by sympathetic nerves innervating the adrenal medulla)
What type of receptor mediates the effect of NTs released from post-ganglionic fibres?
G protein-coupled receptors: muscarinic–> PNS
or adrenergic–> SNS
SLOW response
What is the process of biosynthesis and metabolism of acetylcholine at synapses?
- choline and acetyl coA enzymatically–> into acetylcholine by choline acetyl transferase
- packaged into vesicles
- action potential causes Ca2+ influx and exocytosis
- exocytosis and NT release from pre-synaptic terminal
- receptor activation (muscarinic/G-protein coupled OR nicotinic/ion channel)
- acetylcholine rapidly uptaken from synapse into pre-synaptic terminal or glial cell (or metabolised first by acetylcholinesterase)
What is the process of biosynthesis and metabolism of noradrenaline at synapses?
- tyrosine hydroxylase converts tyrosine–> DOPA, then DOPA decarboxylase converts DOPA to dopamine
- dopamine packaged into vesicles with dopamine b- hydroxylase, becoming noradrenaline
- action potential causes Ca2+ influx and exocytosis
- exocytosis and NT release
- receptor activation (adrenergic/G protein-coupled)
- removal of NT from synapse by uptake into pre-.. or glial cell (metabolised after reuptake)
What is the process of biosynthesis and metabolism of adrenaline at the adrenal glands?
- tyrosine converted to DOPA by tyrosine hydroxylase, then DOPA converted to dopamine by DOPA decarboxylase
- dopamine packaged into vesicles with dopamine beta hydroxylase and noradrenaline is the product
- noradrenaline converted to adrenaline in cytoplasm by phenyl ethanol methyl transferase
- AP causes Ca2+ influx and exocytosis
- exocytosis and NT release
- adrenaline diffuses into capillary and is transported to tissues in blood
