Autonomic Nervous Systen Flashcards
What is the autonomic nervous system?
Sub division of the peripheral nervous system
Not under conscious control
Controls non skeletal peripheral function: cardiac muscle, smooth muscle, internal organs, skin
What controls the ANS?
Afferent neurones (sensory) - somatic sensory and visceral sensory
—> PNS in cranial/spinal neurones
—> CNS (brain and spinal cord) (not necessarily always brain)
—> efferent neurones (motor) - somatic motor and visceral motor
Visceral motor: in the body mainly. Contains sympathetic and parasympathetic arms
What are the parasympathetic and sympathetic nervous systems?
Para: rest and digest - routine maintenance
Sympathetic: fight or flight - mobilisation and increased metabolism
These often innervate the same tissues and have antagonistic effects
What are the effects of the parasympathetic and sympathetic nervous systems on the pupil, heart and stomach?
Pupil: P-constriction S-dilation
Heart: P-rate and contractility down S-rate and contractility up
Stomach: P-motility and secretions up S:motility and secretions down
What is an example where the para and sympathetic nervous systems don’t have directly opposing effects?
In the Liver
P: increase bile release
S: increase glucose release
Where do the visceral motor neurones come from?
The visceral motor nuclei originate in the hypothalamus
These project go the brainstem or the spinal cord where they synapse with autonomic neurones
What do almost all autonomic neurones consist of?
Two neurones - A pre and a post ganglionic neurone
Parasympathetic: long preganglionic fibres with the ganglionic very close to the effector tissue. Short post ganglionic fibres
Sympathetic: short pre ganglionic fibres, ganglionic gloss to spinal cord. Long post ganglionic fibres
What is an exception for the two neurone set up of the ANS?
The adrenal gland
All it has is one fairly short sympathetic neurone
It looks like a preganglionic neurone, it is not. But it’s kinda similar
What neurotransmitter is released by preganglionic nerves?
Acetylcholine
What neurotransmitter do the post ganglionic nerves of the parasympathetic system use?
Acetyl choline
What is the only neurotransmitter concerning PARAsympathetic nerves?
Acetylcholine
What neurotransmitter do the post ganglionic nerves of the sympathetic use?
Noradrenaline
Which neurotransmitters are concerned with the sympathetic nervous system?
Acetylcholine- pre ganglionic
Noradrenaline - post
What does the adrenal gland release?
Adrenaline (and some noradrenaline and dopamine) into the blood
How are a drop in blood pressure, the smell of food and bright sunlight recepted?
Low BP: fewer baroreceptors firing, less inhibition of the sympathetic NS, heart rate and BP increase
Smell of food: parasympathetic NS turned on, and stomach is prepared for contraction and secretions. Btw the guy has its own little nervous system called the enteric nervous system
Bright light: parasympathetic NS causes the pupil to constrict
What is the unusual situation in the lungs?
NO SYMPATHETIC NEURONS
But there are parasympathetic nerves
It’s is the adrenal gland that allows bronchodilation of the lungs (adrenaline in the blood)
What is the micturition reflex?
In the bladder
Pressure in the bladder builds up as it fill with urine
This info is relayed down the efferent nervous system
The parasympathetic system can constrict the detrusor muscle
The sympathetic can relax and contract the internal sphincter
Once pressure reaches a certain point the para is activated contracting the bladder, the sympathetic is turned off so the sphincter relaxes
The somatic motor system also gives you some voluntary control
Which receptors mediate the effects within the autonomic nervous system? (Pre ganglionic)
Ion channel receptor That has a fast response
nicotinic acetylcholine receptor
These are present In all ganglion and also are the adrenal gland
Which receptors mediate the effects of post ganglionic neurotransmitters?
G protein coupled receptors, slower
Muscarinic (acetylcholine) it adrinergic receptors (noradrenaline)
What is the general way in which neurotransmitters are biosynthesised?
- Precursor enzymatically converted to neurotransmitter
- Packaged into vesicles
- Action potential causes Ca2+ influx and exocytosis
- Exocytosis and neurotransmitter release
- Receptor activation
- Removal of neurotransmitter from synapse (into presynaptic cell or glial cells)
How does biosynthesis and metabolism work when ACh is the NT?
Precursor is Choline and acetyl CoA
Receptor is nicotinic it muscarinic
The ACh is metabolised by acetylcholineesterase and the products of this are taken up into the presynaptic terminal or glial cells
The rest is all the same basic pathway
How does biosynthesis and metabolism work when Noradrenaline is the NT?
Precursor is tyrosine, converted to DOPA by tyrosine hydroxylase. DOPA converted to dopamine by DOPA carboxylase
Dopamine packaged into vesicles with dopamine beta hydroxylase. Noradrenaline is the product
Binds to adrinergic receptors
NT is removed from synapse by MOA-O and COMP enzyme
The rest is all the same as the basic model
How does biosynthesis and metabolism work when Noradrenaline is the NT in the adrenal glands?
No synapse
Tyrosine to DOPA, DOPA to dopamine. Dopamine packaged into vesicles with soma pine beta hydroxylase. Noradrenaline formed
Noradrenaline converted to adrenaline in the cytoplasm by phenylethanol methyl transferase
Action potential causes Ca2+ influx and exocytosis
Adrenaline is released and diffuses into capillary
