The Autonomic Nervous System Flashcards
Name the two functional divisions of the autonomic nervous system.
Sympathetic
Parasympathetic
Name the nervous system which acts on the gut.
The enteric nervous system
What is the parasympathetic system important for?
Digestion, excretion, visual accomodation.
‘Rest and digest’
Less widespread innervation and effects.
What is the sympathetic system important for?
Ongoing control of the cardiovascular system.
‘Fight, flight, fright’
More widespread innervation and effect.
Which branch of the autonomic nervous system has more widespread innervation and effect?
The sympathetic system.
Which spinal nerve roots do the sympathetic nerves arise from?
T1 to L2
Which spinal nerve roots do the parasympathetic nerves arise from?
Cranial nerves III, VII, IX, X
S2-S4
How many neurons make up an autonmic nerve track?
Always 2.
Synapse in ganglia (except in adrenal medulla)
Where do parasympathetic neurons in series synapse?
Ganglia in the tissue of effector.
Where do sympathetic neurons synapse?
In sympathetic chain ganglia OR at adrenal medulla (not in ganglion)
What neurotransmitter is released at parasympathetic synapse?
Acetylcholine
What sort of receptor is present in the post-synaptic neuron in parasympathetic ganglia?
Nicotinic receptor.
What sorts of receptor do acetyl choline bind to?
Nicotinic receptorat ganglia.
Muscarinic receptor at effector.
What neurotransmitter does a parasympathetic post-ganglionic neurone release?
Acetylcholine
What sort of receptor is found on parasympathetic effectors?
Muscarinic
Outline a parasympathetic efferent pathway.
Pre-ganglionic neuron releases acetylcholine at synapse in ganglia.
Acetylcholine binds to nicotinic receptors on post-ganglionic neuron.
Post-ganglionic neuron releases acetylcholine at neuro-effector junction.
Acetylcholine binds to muscarinic receptors on effector cell surface.
What sort of receptor does noradrenaline bind to?
Adrenergic receptors
alpha, beta
What neurotransmitter is released at all sympathetic synpases?
Acetylcholine
In most sympathetic pathways what neurotransmitter is released by the post-ganglionic neuron?
Noradrenaline
In sweat gland innervation, what neurotransmitter is released by the post-ganglionic neuron?
Acetylcholine
(very similiar to parasympathetic nerve pathway but ganglia occur in sympathetic chain)
What receptors are present on sweat glands?
Muscarinic receptors
What receptors are present on the adrenal medulla?
Nicotinic receptor
What neurotransmitter(s) do the adrenal medulla release?
Noradrenaline and adrenaline (bind to adrenergic receptors)
What are the two types of cholinergic receptors?
Nicotinic and muscarinic
Which type of cholinergic receptor is G-coupled?
Muscarinic
Where are M2 isoform muscarinic receptors found?
In the heart, regulate cardiac function.
Parasympathetic (slow heart rate)
Where are M3 isoform muscarinic receptors found?
In smooth muscle and glands act through Gproteins.
Activates phospholipase C - produces IP3 and DAG.
What are the types of adrenergic receptor?
α (1 and 2)
β ( 1, 2, 3)
What is the function of α1 receptors?
Activates Gq - stimulates IP3/Ca2+ and DAG.
Raises cellular calcium concentration
What is the function of α2 receptors?
Activates Gi - inhibits adenylate cyclase.
Reduces cAMP prodcution.
What is the function of all β receptors?
Activate Gs - increase concentration of cAMP.
Where are each β receptors found?
β1 = cardiac subtype β2 = vascular and airways subtype β3 = adipose tissue and bladder
What neurotransmitter do adrenergic receptors respond to?
Noradrenaline and adrenaline
What is non-adrenergic, non-cholinergic neurotransmission?
Neurotransmission that does not involve acetylcholine or noradrenaline.
May result in co-transmission of neurotransmitter.
Important in CNS and enteric nervous system.
Give some sympathetic effects on the body.
Increased heart rate and force of contraction.
Bronchodilation
Vasoconstriction (but dilation of arteries in heart)
Bladder relaxation
Decrease GI motility
Give some parasympathetic effects on the body.
Decreased heart rate
Increased gastrointestinal and other secretions
Bronchoconstriction
Micturition - contraction of detrusor muscles
Defaecation
Outline the baroreceptor reflex. (4 steps)
- Blood pressure increase distends arterial walls (activates stretch receptors)
- Stretch receptors signal to brain stem which compares blood pressure to set point.
- Increased parasympathetic stimulation to the heart - slows heart rate.
- Decreased sympathetic drive to the heart
What is the reaction that produce acetylcholine and what enzyme catalyses this reaction?
Acetyl-CoA + Choline > Acetylcholine
Catalyses by choline acetyltransferase
What enzyme breaks down acetylcholine?
Acetylcholinesterase
What is the enteric nervous system?
Brain of the gut, forms 2 layers of motor, sensory and interneurons in the wallls of the GI tract.
What are the two layers of the enteric nervous system?
Myenteric plexus
Submucosal plexus
What does the ENS co-ordinate?
Peristalsis, fluid transport, glandular secretions and blood flow within the GI tract.
