Autonomic Nervous System Flashcards
Where in the spinal cord do the nerves which form the sympathetic nervous system originate?
The thoracolumbar region, from T1 to L2/3
Where on the spinal cord are the nerve origins for the parasympathetic nervous system?
The cranial and sacral regions.
Where do nerves from the sympathetic division synapse?
In paravertebral ganglia
What molecule is secreted by preganglionic neurones?
This is acetylcholine and it acts on nicotinic ACh receptors.
In the sympathetic nervous system, what type of transmission occurs at the post ganglionic synapse?
Noradrenaline is the neurotransmitter released and this acts on adrenocreceptors.
What is the neurotransmitter responsible for the sympathetic innervation Of sweat glands?
Acetylcholine which acts on muscarinic receptors.
What is the action of an adrenoceptor?
These are G-protein coupled receptors and do not have integral ion channels.
What is the significance of adrenoceptor subtypes?
This means that there can be a more specific response as each different tissue has a slightly different receptor. This is a good target for drugs.
What is a co-transmitter?
These are transmitters such as neuropeptide Y and ATP which are release with adrenaline/noradrenaline at the post ganglionic synapse with the effector cell.
What molecule acts on muscarinic receptors?
Acetylcholine
What type of receptor is a cholinergenic receptor?
These are G protein coupled receptors
What can be said about the combined action of the sympathetic and parasympathetic nervous systems?
They are both opposite responses to each other but together they maintain a balance.
Where are B2 receptors found?
In the lungs
What type of adrenoceptor is found in the heart?
B1.
State where muscarinic receptors M2/m3 are found.
M2 is found in the heart and M3 is found in the lungs
Name three features of the cardiovascular system which are controlled by the autonomic nervous system.
Heart rate, force of contraction, total peripheral resistance.
At rest, what influences the heart?
The Vagal system
What is the major effect of the parasympathetic nervous system on the heart?
Reduction in heart rate.
Where on the heart does the parasympathetic nervous system act?
Post ganglionic fibres synapse at the SA and AV node, and they release acetyl choline which acts on M2 receptors.
How does the parasympathetic nervous system slow the pulse?
At the SA node it reduces heart rate and at the AV node it reduces conduction velocity.
Where on the heart does the sympathetic nervous system act?
It acts on both the SA, AV nodes and the myocardium. It releases noradrenaline which acts on B1 receptors.
What changes does the sympathetic nervous system stimulation have on the heart?
It increases pulse and force of contraction.
What is the name for increase in pulse rate?
Chronotropic effect.
What is inotropic effect?
Increase in force of contraction of the heart.
What change does the sympathetic nervous system have on the SA node action potential?
It increases the slope making it short. It achieves this because it’s Gprotein causes increased cAMP and so there are more HCN channels open and quicker Na influx.
How does the parasympathetic nervous system slow pulse rate?
The m2 receptor G proteins increase K+ conductance meaning that the starting potential has a greater magnitude and so there is further for the pacemaker potential to depolarise. There is also reduced cAMP and so less HCN channels are open.
How does the action of noradrenaline on the myocardium increase force of contraction?
B1 adrenoreceptor activation leads to cAMP increase and more calcium influx during the plateau of the action potential.
What effect does more activation of protein kinase A have on calcium channels?
This means that they are phosphorylated and so there is greater influx of calcium.
What effect does increased uptake of Ca into the SR have on a cell?
It makes the contractile machinery more sensitive to Ca and so there is increased force of contraction
What part of the autonomic nervous system controls vasomotor tone? What is the name of the receptor?
Sympathetic, actin on a1 adrenoreceptors
What effect does B2 adrenoreceptor activation have on vascular smooth muscle tone?
This leads to increased cAMP and PKA which phosphorylates MLCK and means that there is less contraction - vasodilation.
Describe the effect of a1 adrenoreceptor activation on vasomotor tone.
Vasoconstriction. a1 receptors lead to increased IP3 and so cystolic calcium increases and muscle contracts.
What local molecules have a vasodilation effect?
Local metabolites such as K+, H+, pCO2.
Where are baroreceptors found?
Aortic arch and carotid sinus.
What do baroreceptors measure?
These are sensitive to stretch and so detect increases in blood pressure
What is a sympathomimetic?
This is a drug which mimics the action of the sympathetic nervous system.
What is dobutamine?
This is a B1 agonist which is given in cardiogenic shock.
What is salbutamol?
This is a B2 agonist which acts on smooth muscle in the respiratory system.
What action do a1 antagonists have on the CVS?
They prevent NA action on smooth muscle and so they lead to reduced vasomotor tone and reduced blood pressure.
When are muscarinic agonists used?
Treatment of glaucoma as they activate constrictor pupillary muscles.
What do B adrenoreceptor antagonist do in the CVS?
These slow heart rate and force of contraction.
