The Autonomic Nervous System And The CVS Flashcards
What is the general organisation of the two different autonomic nervous systems?
There are two neurones arranged in series,
the on that originates in the central is the pre ganglionic neurone
The one that originates in the peripheral nervous system in the post ganglionic neurone where they both target n effector cell.
How is the sympathetic division of the nervous system organised?
Pregangloic neurones arise from segments T1 to L2 (thoracolumbar origin).
Most syncope with the postgangolic neurones in the paravertebral chains of the ganglia.
How is the parasympathetic division of the autonomic nervous system organised?
Craniosacral origin
Synapse in neurones with ganglia close to the target tissue.
Short post ganglionic fibres.
Pregangloic fibres travel in cranial nerves or the cranial outflow tract.
What is the neurotransmitter released in preganglonic neurones of the parasympathetic nervous system.
Actelycholine (acts on nictonic receptors)
What is the neurotransmitter released in the postganloic neurones of the paracympatheic nervous system?
Acteylcholine (acting on Muscarinic, g protein coupled, receptors)
What is the neurotransmitter released by the postgangolic neurones of the sympathetic nervous system?
Noradrenaline
What are the different subtypes of Adrenoreceptors?
B- Adrenoreceptors (B1 and B2), and a-adrenoreceptors, a1 and a2
Why is sympathetic control to different tissues independently regulated?
Allows, for example, sympathetic activity of heart to be increased without increasing sympathetic activity of the GI tract, and there is potential for coordinated response such as fight of flight.
Describe how the sympatheic nervous system effects the pupil of the eye?
Dilatation, by contracting the radial muscles and acting on A1 receptors.
How does the parasymptheic nervous system effect the pupil of the eye?
Contracts the pupil by causing contraction of the spinchter muscle, acting on the M2 Muscarinic receptors.
What does the ANS effect in the heart?
The heart rate, force of contraction of heart and the peripheral resistance of the blood vessels.
What does the ANS not control in the heart?
Does not initiate electrical activity, without nervous control the heart continues to beat but at a faster rate.
What nerve controls the Parasympathetic input to the heart?
Preganloic fibres include the 10th cranial nerve, also known as the vagus.
Where do Parasympatheic fibres act on the heart?
They synapse on the epicardial surface on within the heart at the AV and the SA node
What receptros are involved in the parasympathetic response of the heart and what response do they create?
The M2 receptors for ACh, decreasing the heart rate and having a negative chronotrophic response.
What nerves are involved in the sympathetic response of the heart?
The postgangloinic fibres from the sympathetic trunk.
What receptors does noradrenaline act on in the sympathetic response of the heart?
mainly on the b1 Adrenoreceptors, which increases the heart rate by a positive chronotrophic effect.
What effect would having autonomic nervous system activity have on the SA node action potential graph?
Sympathetic activity would increase the slope of the pacemaker potential, parasympathetic activity would decrease the slope of the pacemaker potential.
How is the parasympathetic effect on the pacemaker potential mediated?
M2 recpetors, that are g protein coupled, increase the K+ conductance, and decrease cAMP.
How is the sympathetic effect on the pacemaker potential mediated?
Mediated by B1 receptors, G protein coupled receptors, increase cAMP which speeds up the pacemaker potential.
What is the mechanism by which noradrenaline increases the force of contraction of the heart?
NA acts on B1 receptors in the myocardium, cause an increase in cAMP, activates PKA, and causes phosphorylation of the Ca2+ channels which increases the Ca2+ entry during the action potential. It also increases the Ca2+ concentration in the sacroplasmic reticulum.
What sort of innervation do the blood vessels have?
Sympatheic innervation only.
What sort of receptors do aterties and veins have?
A1 Adrenoreceptors
What are three types of drugs that act on the autonomic nervous system?
Sypathomelcis, adrenoreceptor Agnoists, cholingerics.
What are some of the cardiovascular uses of sympathemlics?
Administration of ardelinaine during a cardiac arrest, adrenaline in a anapthlic shock, B1 agnoists are given in cariogenic shock, B2 Agnoists include subutamla for treting asthma.
What are sympthamelics?
Adrenoreceptor Agnoists
What can you use a adrenreeptor anatgnoists for?
Anti hypertensive agent, and to inhibit Na action on vascular smooth muscle.
What would you use B receptor antagonists for?
Slows heart rate and the force of contraction
What are the issues of using non selctive b1/B2 atnagnoists?
Can cause brochocontrictision.
What would you use muscarnic Agnoists for?
Pilapine, used in the treatment of glaucoma.
what would you use cholgineric muscarinic anatgnoists for?
Increasing the heart rate, used to dilate the pupils in certain treatments.
What are the two divisions of the ANS?
Parasympatheic and Sympathetic
