17. The Autonomic Nervous System Flashcards
What are the two anatomical divisions of the autonomic nervous system?
Sympathetic division, and parasympathetic division.
What is the general structure of parasympathetic neurones in the autonomic nervous system?
Two neurones in series: long myelinated pre-ganglionic neurone meeting a shorter unmyelinated post-ganglionic neurone at a ganglion.
What is the general structure of sympathetic neurones in the sympathetic nervous system?
Two neurones in series: myelinated pre-ganglionic neurone meeting an equal length unmyelinated post-ganglionic neurone at a ganglion.
Where do parasympathetic nerves originate?
In the lateral horn of the medulla and sacral regions of the spinal cord.
Where do sympathetic nerves originate?
In the lateral horn of the lumbar and thoracic spinal cord.
What are the principal neurotransmitters in the autonomic nervous system?
Acteylcholine, and noradrenaline.
What do pre-ganglionic neurones use as their neurotransmitter?
ACh, as they are cholinergic.
How do parasympathetic post-ganglionic neurones pass on signals?
They are cholinergic, and release ACh which acts on muscarinic ACh receptors in the target tissue. The muscarinic ACh receptors are G-protein coupled receptors.
What are the two major classes that noradrenaline interact with?
a-adrenoceptors and B-adrenoceptors. (Subtypes: a1, a2, B1, B2, B3).
Which sympathetic post-ganglionic neurones are cholinergic?
Specialised ones that innervate the sweat glands, and hair follicles.
What are the transmitters found in the ANS?
ACh, NA, NANC (Non-adrenergic, non-cholinergic).
How are sympathetic postganglionic neurones different in the adrenal glands?
They differentiate to form neurosecretory chromaffin cells, which release adrenaline, not noradrenaline. These are postganglionic sympathetic neurones that do not project to a target tissue. They release adrenaline into the bloodstream when stimulated by the SANS.
How does parasympathetic release of ACh affect the heart?
Acts on M2 muscarinic receptors to cause bradycardia by acting on the SA node, and reduces cardiac conduction velocity by acting on the AV node.
How does parasympathetic release of ACh affect the smooth muscle?
Acts on M3 muscarinic receptors and causes NO generation to cause bronchial contraction in the lungs, increased intestinal mobility in the GI tract, bladder contraction and relaxation and penile erection in the GU tract, ciliary muscle and iris sphincter contraction in the eyes.
How does parasympathetic release of ACh affect the glands?
Acts on M1/M3 muscarinic receptors to increase sweat, salivary and lacrimal secretion.
