The Autonomic Nervous System Flashcards
How to calculate blood pressure and TPR?
Blood pressure = cardiac output/ total peripheral resistance.
TPR= 1/r^4
Describe how the sympathetic nervous system exerts control over the trachea and bronchi.
The trachea and bronchi have no sympathetic nerve fibres. They are affected by the release of catecholamines from the adrenal medulla.
Describe the response of blood vessels to skeletal muscle during a period of increased sympathetic discharge. What causes this response?
Blood vessels supplying the skeletal muscle dilate. This is caused by circulating catecholamines.
Describe the role of the adrenal medulla in the sympathetic nervous system.
Adrenal medulla is innervated by sympathetic pre-ganglionic nerve fibres, which release acetyl choline that binds to the nicotinic acetyl choline receptors and causes release of catecholamines from the chromaffine cells.
What is special about the sympathetic innervation of the sweat glands?
The sympathetic nerves to the sweat glands release acetylcholine instead of noradrenaline.
What are the two outflows of the parasympathetic nervous system?
Craniosacral
What inhibits bladder contraction>?
Sympathetic nervous system
State the four cranial nerves that form part of the parasympathetic nervous system and explain their functions?
Oculomotor - 3
pupil constriction
Facial - 7
innervates glands that are higher up in the body e.g. tears and salivary
Glossopharyngeal - 9
influences activity in the tissues that are higher up in the body
Vagus – 10
outflow from the CNS via the vagus goes to many organs e.g. lungs, heart, stomach, pancreas, small intestine.
Which parasympathetic nerves come out of the sacral region?
Pelvic spanchnic nerves
Describe the outflow of the sympathetic nervous system. State the vertebral levels that define the limits of this outflow.
Thoracolumbar (T1 - L3)
-have NO cranial nerve
Describe the relative lengths of sympathetic and parasympathetic pre-ganglionic fibres.
Sympathetic nerves have a short preganglionic and a long post ganglionic
Parasympathetic has a long preganglionic and a short post ganglionic
what is a key difference between sympathetic nervous and parasympathetic nervous system?
in sympathetic the post ganglionic neurone is outside ( in the sympathetic chain)the organs in parasympathetic is inside the target organ
what is ganglia?
where cell body exists.
How does innervation happen in sympathetic pathways?
The pre-sympathetic neurone going down the spinal cord and synapsing the preganglionic neurone and then goes through he sympathetic chain and synapses the postganglionic neurone which then innervates the target organ.
How does innervation happen in parasympathetic neurone
Come out of the CNS. Target and innervate the target organ, the post-ganglionic neurone is inside the target organ.
Monosynaptic connection, only 1 synapse there.
What neurotransmitters to parasympathetic neurone mainly use/
is cholinergic.
releases acetylcholine at its presynpase and post synapse.
if vagus nerve in heart is stimulated leads to bradycardia
What neurotransmitter do sympathetic use?
the pre-ganglionic neurone that comes down the spinal cord uses glutamate ( excitatory)
these pre-ganglionic neurone releases acetylcholine in the ganglia, and the post ganglionic neurone usually releases noradrenaline but there are differences e.g. sweat glands
How is noradrenaline biosynthesised?
- Using phenylalanine ( get this through diet )
- converted to tyrosine
- then DOPA: dihydroxyphenylalanine (tyrosine hydroxylase)
- then dopamine(dopamine decarboxylase)
- noradrenaline(Dopamine hydroxylase)
1-4 happens in the cytoplasm and 4-5 happens on the pre-synaptic vesicles.
how is acetylcholine synthesised and what breaks it down?
What would happen if you inhibit acetylcholinestrase
Add acetate and choline using choline acetyltransferase.
-acetylcholinesterase breaks it down.
Inhibiting acetylcholinesterase would result in a build up of acetylcholine in the synaptic cleft and a decrease in the responsiveness of the post synaptic neurone receptors to acetylcholine and you will become paralysed. This how botulinum toxin works.
where do all the sympathetic nerves emanate from in the vertebrae?
intermediolateral cell column
How does the ANS control blood pressure
In the heart there are baroreceptors ( mechanoreceptors, respond to physical distention)
There is 1 aortic baroreceptors and 2 carotid baroreceptors which are in the neck.
These aortic baroreceptors communicate to the brain via the afferent vagus nerve (10th cranial nerve)
Carotids communicate via glossopharyngeal nerves. (9th cranial nerve)
These communicate the pressure.
Once the baroreceptors are activated due to blood pressure increasing, this is communicated back to the heart via the vagus nerve (efferent) which cause parasympathetic activity to innervate the heart and reduce stroke volume, reduce cardiac output and via inhibition of sympathetic nervous system you increase the blood vessels diameter so blood pressure decreases.
What is the relationship between the baroreceptor firing and the
blood pressure?
Baroreflex
It is a S phase. The baroreceptor firing is the number of action potentials being fired as a result of blood pressure changes.
We have a set point, and it is controlled by the brain.
A slight increase in blood pressure is met by increased baroreceptor firing to move the blood pressure back to normal.
How is this relationship in hypertension patients?
Baroreflex
The S shape graph is shifted to the right, so the set point is higher, therefore the brain thinks it should be defended at a higher blood pressure.
How is the GI function regulated and what type of response is this?
It is regulated by the vagus nerve.
Even before ingestion, stimuli’s such as smell can stimulate the release of enzymes in your intestine.
All of these sensory input enter the hypothalamus, enter the spinal cord which regulate these responses.
This is the cephalic response: pancreas primes the body by releasing insulin into the blood even before ingestion.
2nd phase of insulin spike is glucose mediated.
This is mediated by the 10th cranial nerve.
