Autonomic Physiology Flashcards
Function of the autonomic nervous system
To control things you dont want to think about:
* Smooth muscle: blood vessels/airways/bladder/eye/gut/sex organs
* Cardiac muscle
* Glands
How can we divide the PNS
Afferent division
Efferent division:
* Autonomic NS (sympathetic, parasympathetic, enteric NS)
* Somatic NS - voluntary (muscles)
Describe the somatic nervous system in terms of nerves/recepotors
(briefly)
Nerve emerging from ventral root and sysnapeses onto skeletal muscle (n-m junction)
see sheet
Describe the autonomic nervous system in terms of nerves/recepotors
(briefly)
Pre-ganglionic fibre (small myelinated) —> synapse and ganglion —> post-ganglionic fibbre (unmyelinated) —> synaps onto smooth/cardiac muscle, gands, GI neurons
see sheet
Breifly describe the main features of synapses in the somatic nervous system
- Specialised NMJ
- Ionotropic (nicotinic cholonergic) receptors which act as monovalent cation channels
- Graded potential called end plate potential which always ecites target
Breifly describe the main features of synapses in the autonomic nervous system
- Less specialised junction
- Metabotropic receptors - G-protein coupled
- Can be exitory or inhibitory
- Neurotransmitter released into ISF until it finds receptors, therfore 1 postganglionic fiber innervates a large tissue area
2 main divisions of the autonomic nervous system
Give key rhymes for each
- Sympathetic - fight or flight
- Parasympathetic rest and digest
Outflow of sympathetic division of NS
Thoratic (T1-T12) region of spinal cord and first 2 lumbar levels (L1-L2) - thoracolumbar outflow
Describe ganglia/fibres of sympathetic NS
Very short pre-ganglionic fibres (ganglia close to spinal cord). Most found in sympathetic chain, aka the paravertebral ganglia
And then we’ve got some in these other ganglia called the collateral (or prevertebral) ganglia.
After the synapse, there are very long post-ganglionic fibres that go all the way up to their targets.
Ganglia lie close to spina cord
see diagram
Outflow of parasympathetic division of (autonomic) NS and what does it supply
Cranial (3,7,9,10) and sacral (S2-S4) regions of spinal cord - craniosacral
Cranial nerves supplies head/eyes/salivary glands but vagus nerve goes on an adventure (e.g. lungs/hear/liver/intestine…)!
Describe ganglia/fibres of parasympathetic NS
Very long pre-ganglionic fibres and very short post-ganglionic fibres which lie within the target/very close to it.
Ganglia lie close to/within target
Neurotransmitters and receptors of somatic nervous system
Only has n-m junctions so:
* Neurotranmitter: acetylcholine
* receptors: nicotinic/muscarinic cholinergic receptors
Autonomic transmitters
- Acetylcholine: acts on cholonergic receptors: nicotinic (iontropic) and muscarinic (g-protein coupled) receptors
- Noradrenaline: acts on adrenergic receptors: a and B receptors
What neurotransmitters do sympathetic/parasympathetic release over course of efference
Key flashcard
- preganglionic fibres for both release ACh which acts on nicotinic cholinergic receptors
- parasympathetic postganglionic fibres release ACh which acts on muscarine cholinergic receptors
- Sympathetic postganglionic fibres release noradrenaline which acts on a or B adrenergic receptors
Remember that ther are a couple of exeptions
Explain “special” part of the sympathetic nervous system
Fibre goes straight out of the spinal cord, through the sympathetic chain without synapsing, goes straight through the collateral/prevertebral ganglia again without synapsing and comes all the way out to its target: adrenal medulla gland that sits above the kidney. Finally synapses his here onto the post-ganglionic cell. But it doesn’t have an axon, and instead releases its neurotransmitter into the bloodstream which then acts as a hormone.
What do sympatheticd postganglionic cells of the adrenal medulla release
Adrenaline and noradrenaline into the blood: which act on a or B adrenergic receptors - hormonal component and often allows for whole body response!!!
List 3 complexities to the sympathetic/parasympathetic NS that don’t follow previous “rules”
- Sympathetic cholinergic fibres (due to length of pre/post ganglionic fibres) innervate sweat glands - expect post-G fibre to release norarenaline but instead, releases Ach
- Some postganglionic fibres use non-adrenergic non-cholinergic (NANC) transmitters (e.g. peptides)
- Sometimes co-released with the orthodox transmitter
Point 2 and 3 linked
In what 3 ways do somatic and autonomic efferent differ
(brief)
Tragets, axons, synapses
In what ways do sympathetic and parasympathetic efferent differ
(brief)
spinal outflow, location of ganglia, transmitters used, functions
Summarise the lengths of ganglia for the sypathetic and parasympathetic branches of the autonomic NS
- Sympathetic: short pre-ganglia, long post-ganglia fibres
- Parasympathetic: long pre-ganglia, short post-ganglia fibres
List features when sympathetic NS has taken over
- Airways dilate
- Heart beats faster
- Heart beats stronger
- Blood diverts to muscle
- Gut motility decreases
- Enzyme secretion in gut generally inhibited
- Stored energy is released
- Pupils dilate
- Eye focus far way
- Hair stands on end
- Mouth becomes dry
List features when parasympathetic NS has taken over
- Airways constrict
- Heart beats slower
- Heart beats weaker
- Blood diverts to gut
- Gut motility increases
- Enzyme secretion in gut generally stimulated
- Energy is stored
- Pupils constrict
- Eyes focus close up
- Hair lies flat
- Mouth starts drooling
What determines weather the sympathetic or parasympathetic NS is more “activated”
- Neurotransmitter released
- And receptor type that it acts on
Explain how the sympathetic/parasympathetic NS is more “activated” in terms of neurotransmitters and their receptors
- Acetylcholine: Cholinergic nicotinic (sympathetic) or muscarinin (parasympathetic) receptors
- Noradrenaline/adrenaline: a or B receptors (sympathetic)
ACh—>nicotinic receptors: S and P pre-ganglionic fibres
ACh —> P post-ganglionic fibres
Noradrenaline/Adrenaline—> S post-ganglionic fibres
Describe the response of the eye in the Sympathetic NS
Include details of receptors and their effects
- Activates a1 receptors (through 2nd messenger pathway) on radial muscle of the iris: radial muscle contracts and makes pupil larger
- Activates B2 recepors on ciliary muscle around lense: ciliary muscle relaxes and eye focuses far away
Describe the response of the eye in the Parasympathetic NS
Include details of receptors and their effects
- Activates muscarinic receptors on sphincter muscle of the iris: contracts and makes pupil smaller
- Activates muscarinic receptors on ciliary muscle around the lens: muscle contracts and eye focuses close up
Describe the response of the heart in the sympathetic NS
Include details of receptors and their effects
- Activates B1 receptors on pacemaker cells: increases heart rate
- Activates B1 receptors on myocytes: inc strength of contraction
Describe the response of the heart in the parasyympathetic NS
Include details of receptors and their effects
- Activates muscarinic receptos on pacmaker cells: dec heart rate
- Little effect on myocytes: little effect on strength of contraction
Describe the response of the lungs in the sympathetic NS
Include details of receptors and their effects
- Activates B2 receptors on smooth muscles of airways: relaxes and dilates airways
Describe the response of the lungs in the parasympathetic NS
Include details of receptors and their effects
- Activates muscarinic receptors: makes smooth muscle contract and constricts airways
theraputic usefulness of drugs on lungs/heart in relation to S nervous system
Examples + explanation
- B2 agonist (salbutamol) dilate airways but little effect on heart
- B1 antagonist (atenolol) dec heart rate but limited effect on airways
This is because different organs have recepors/specificity for different neurotransitters which thus, allows us to artifcially target certain parts of the P/S nervous system.
Describe the response of the blood vessels in the sympathetic NS
Include details of receptors and their effects
- Activates a1 receptors on smooth muscle of vessels: contracts and dec blood flow
- Activates B2 receptors on smooth muscle of vessels: relaxes and blood flow inc - ex. inc cardiac and skeletal muscle
Response depend on where vessel is in body
Describe the response of the blood vessels in the parasympathetic NS
Include details of receptors and their effects
Usually no effect
- salivary glands and genetalia are exeptions
What do blood vessels have (in terms of innervation)
Single innervation from the sympathetic nervous system
What are blood vessels an example of?
And define it
The importance of tone in single innervation
Tone = the level of activation in a system when it is not doing anything
Describe the response of the salivary glands in the sympathetic NS
Include details of receptors and their effects
Activates B receptors: stimulates thick secrection rich in enzymes
Describe the response of the salivary glands in the parasympathetic NS
Include details of receptors and their effects
Activates muscarine receptors: stimulates profuse watery secretion
What are salivary glands an example of?
Dual innervation with non-antagonistic actions
Describe the response of the bladder in the sympathetic NS
Include details of receptors and their effects
- Activates B2 receptors on smooth muscle of bladder wall: relaxes smooth muscle and reduces pressure on bladder
- Activates a1 receptors on smooth muscle of sphincter: contracts smooth muscle and stops urination
Describe the response of the bladder in the parasympathetic NS
Include details of receptors and their effects
- Activates muscarinic receptors on bladder wall: contracts smooth muscle and increases pressure
- Activates muscarininc receptors on sphincter: relaxes smooth muscle and causes urination
Describe the response of the **reproductive tract ** in the both the sympathetic and parasympathetic NS
Sympathetic:
* activates a1 receptors on smooth muscle of urethra: contracts smooth muscle and causes ejaculation
Parasympathetic:
* Activates muscarinic receptors on smooth muscle of corpus cavernosum: relaxes smooth muscle and causes erection
Point and Shoot
What is the reproductive tract and example of
dual innervation with complementary effects
What controls the S/P NS
Autonomic reflexes
Explain Autonomic reflexes
- Spinal reflexes (urination in babies)
- Higher control (learned reflexes)
Explain central control for the autonomic NS
Integrated in brain (hypothhalamus, thalamus and brainstem)
Detects change, looks at info, coordinates sympathetic and parasympathetic outflow accordingly
Explain dual and single innervation
how common, effects/control/ examples
- Dual: many tissues: effects usually antagonistic (bladder/eyes/lungs) , but could be complementary (salivary glands/reproductive tract)
- Single: some tissues (blood vessels): controled by varying tone
antagonistic/complementary = between S and P NS
