Overview of the following:
Autonomic nervous system and parasympathetic and sympathetic nerves and associated receptors.
Acetylcholine and cholinergic neurotransmission.
Adrenaline and noradrenaline and adrenergic neurotransmission.
Drug agonists and antagonists of muscarinic and nicotinic r...
Week 4: Autonomic Pharmacology
Autonomic Nervous System
Part of the NS responsible for control of bodily functions not consciously directed, such as
heart rate, blood pressure, airway resistance, urination, pupillary response, genital erection,
digestive motility, and secretion.
Anatomy of the ANS:
o Efferent: sympathetic (spinal roots: T1-L3) and parasympathetic (cranial nerves and
spinal roots: S2-S4)
There are autonomic ganglions (“rosary beads” on image), which are
clusters of nerve cell bodies, between pre-ganglionic nerves and post-
ganglionic nerves.
o Afferent: shared between sympathetic and parasympathetic. The autonomic
sensory information is conducted by general visceral afferent fibres.
o Higher autonomic centres: located in the brainstem.
Sympathetic efferent neurons:
Parasympathetic efferent neurons: PS ganglia lie close to the target sites and post-ganglionic
fibres are often entirely within the tissue of the target organ.
,
Parasympathetic (cholinergic) Physiological function Sympathetic (adrenergic)
Muscarinic (M): constriction Pupil Alpha: dilatation
M: decreased HR Heart Beta: increased HR and
contractility
No parasympathetic Vasculature Alpha: vasoconstriction
innervation of most
vasculature, but endothelial
cells express M receptors and
release nitric oxide (NO) in
response to muscarinic
activation: vasodilatation
M: bronchoconstriction Lung (bronchial tree) Beta: bronchodilatation
M & N (nicotinic): increased GI Alpha, beta: decreased
motility and secretion motility
M: smooth muscle contraction Bladder Beta: smooth muscle
relaxation
Although adrenergic and cholinergic activity modulates the autonomic system, they are not
specific to the autonomic system. Both noradrenaline and acetylcholine are used in other
non-autonomic systems too. E.g.
o Motor system also uses ACh as the main NT in the neuromuscular junction (nicotinic
receptor)
o Both ACh and noradrenaline are involved in CNS function.
Adrenergic system in the brain: The locus coeruleus plays an important role
in mood control and synchronisation of different parts of the brain in
physiological responses to stress and pain.
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