Week 1- Autonomic Nervous System Flashcards
What is the autonomic nervous system?
A subdivision of the peripheral nervous system, not under conscious control, controls heart, smooth muscle, internal organs and skin
How does the autonomic nervous system work?
Via visceral motor effects which can be parasympathetic or sympathetic: both part of EFFERENT arm of nervous system
What does the parasympathetic system do?
Rest and digest ie routine maintenance/ basal control
TIP: P for potato couch
What does the sympathetic system do?
Fight or flight ie mobilisation and increased metabolism
TIP: S for Spider-Man
How do parasympathetic and sympathetic work together?
They innervate the same tissue but often have opposing effects
What do the parasympathetic and sympathetic do to the pupil?
Sympathetic: dilates it to allow as much visual info to come in as possible
Parasympathetic: constricts pupils
What do the parasympathetic and sympathetic do to the stomach?
Parasympathetic: increases motility and secretions
Sympathetic: decreases motility
How does autonomic control affect blood vessels?
Only sympathetic nerves, they can both dilate and constrict vessels as they go to different receptors
What are baroreceptors and what do they do during high/low BP?
They measure blood pressure in blood vessels, sending info to the brain.
High BP: high parasympathetic activity to reduce BP, negatively affects sympathetic nervous system
Low BP: Baroreceptors fire a lot less, less signal to brain, less parasympathetic stimulation and less surpression of sympathetic
What is the main integrating center of the autonomic nervous system?
The hypothalamus (receives all the signals)
Where are visceral motor neurons found?
They project to the brainstem or spinal chord where they synapse with autonomic neurons
What is the structure of autonomic neurons?
There are 2 neurons: pre ganglionic and post ganglionic neuron
PNS: longer pre fibers, shorter post
SNS: short pre, long post
In both cases, pre ganglionic fibres are close to or embedded within effector tissues
Because sympathetic responses are a lot more co ordinated so pre ganglionic synapse near spine
What is the exception to the two neuron rule?
The adrenal gland- there is just one nerve, no pre or post, adrenal gland almost acts as the post
What neurotransmitters are involved?
Acetylcholine is released from: pre ganglionic parasympathetic, pre ganglionic sympathetic, post ganglionic parasympathetic
Noradrenaline is released from: post ganglionic sympathetic
Difference in release from post ganglionic is why para and symp work differently
How does the adrenal gland work?
Secretes a hormone (adrenaline) not a neurotransmitter, into bloodstream not synapse
What is the enteric nervous system?
Has a lot of influence on gut function, more than parasympathetic and sympathetic systems
How does the lung work?
Only receives parasympathetic neurones, sympathetic function is carried out via a hormone (adrenaline release causes dilation)
What is the micturition reflex?
Controls the bladder- parasympathetic innervates the detrusor muscle (during constriction forces urine out of the bladder) and sympathetic innervates the sphincter muscle (stops urine flowing out of bladder). As urine fills bladder, the pressure increases and this is relayed to the brain so parasympathetic increases and sympathetic falls
What type of receptor would you want at an autonomic ganglia?
Acetylcholine receptor and a receptor that mediates a v fast response- use an ion channel linked receptor
What receptors are required post ganglion?
There are new neurotransmitters e.g. noradrenaline for sympathetic so we need a G protein coupled receptor (much slower in response and gives more control) either muscarinic (for acetylcholine) or adrenergic (for noradrenaline).
How are neurotransmitters produced?
- A precursor (often from diet) is enzymatically covered to transmitter
- Packaged into vesicles
- Ca 2+ influx causes release
How are neurotransmitters removed?
- Metabolise transmitter in synapse
2. Remove via transport protein then break it down
How is acetylcholine removed from synapses?
Acetylcholinesterase metabolises ach and breakdown products are taken to glial cells (if enzyme is blocked there is over accumulation/stimulation)
How is noradrenaline produced?
Tyrosine is converted to DOPA (by tyrosine hydroxylase) then to dopamine (by DOPA decarboxylase), this is packed into vesicles with dopamine beta hydroxylase allowing it to become noradrenaline
How is noradrenaline removed from synapses?
- Can be taken into presynaptic terminal via transport proteins and converted by mono-amine oxidase
- Taken into glial cell and converted via COMT
How would adrenaline have an effect?
4 enzyme conversions to create it, released directly into blood then removed by adrenal gland from bloodstream
