Intermediate Pharmacology (PHAR0009) Notes - Autonomic Nervous System
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Course
Intermediate Pharmacology (PHAR0009)
Institution
University College London (UCL)
Explore Intermediate Pharmacology at UCL with a focus on the Autonomic Nervous System. Delve into the nuanced world of adrenergic pharmacology, adrenoceptors, and cholinergic pathways. Please note that these materials are intended for personal use only and should be used in accordance with academic...
Autonomic Nervous System – Summary
Peripheral Nervous System
Nervous system = CNS + PNS
o CNS
Brain + spinal cord – receives, processes, outputs
o PNS
Somatic nervous system – sensory system + somatosensory system
Autonomic nervous system – sympathetic + parasympathetic + enteric systems
Autonomic nervous system
o Sympathetic nervous system
Dilates pupil
Inhibits flow of saliva
Accelerates heartbeat
Dilates bronchi
Inhibits peristalsis and secretion
Conversion of glycogen to glucose
Secretion of adrenaline and noradrenaline
Inhibits bladder contraction
o Parasympathetic nervous system
Constricts pupil
Stimulates flow of saliva
Slows heartbeat
Constricts bronchi
Stimulates peristalsis and secretion
Stimulates release of bile
Contracts bladder
o Enteric nervous system
Innervation from autonomic system – via vagus nerve + prevertebral ganglia
Neurons control motor functions of the system + secretion of gastrointestinal
enzymes
Structure
Embedded in the lining of the gastrointestinal system
Neurons are collected in two types of ganglia = myenteric + submucosal plexuses
o Myenteric plexus
Provides motor innervation to both layers of the muscular layer of
the gut
Activation increases tonic contraction + intensity of rhythmic
contraction + rate of rhythmic contractions + velocity of conduction
o Submucosal plexus
Activation increases secretory activity + modulates intestinal
absorption
Brain processes can alter autonomic events
o Hypothalamus
Provide large hormonal output through pituitary
Innervated by limbic system = emotional part of the brain
o Brain stem nuclei
Controls autonomic outflow
o Nucleus solitary tract
Receives and sends information to the brain stem nuclei and limbic system
Acetylcholine and noradrenaline in the autonomic nervous system
o Structure = preganglionic neuron ganglion postganglionic neuron effector organ
,Autonomic Nervous System – Summary
o Sympathetic
Short cholinergic preganglionic neuron + long adrenergic postganglionic neuron
ACh at ganglion – acts on fast cholinergic nicotinic receptors
o Fast nicotinic excitation at ganglion
NA at target – acts on slow adrenergic alpha and beta receptors
o Excitatory alpha 1 receptor inhibitory alpha 2 receptor excitatory beta
1 receptor inhibitory beta 2 receptor
o Parasympathetic
Long cholinergic preganglionic neuron + short cholinergic postganglionic neuron
ACh at ganglion – acts on fast cholinergic nicotinic receptors
o Fast nicotinic excitation at ganglion
ACh at target – acts on slow cholinergic muscarinic receptors
o Excitatory muscarinic 1 receptor inhibitory muscarinic 2 receptor
excitatory muscarinic 3 receptor
Synaptic transmission
o Stages
Action potential arrival in axon of presynaptic neuron depolarises nerve terminal
Opening of voltage-gated Ca2+ channels in terminal membrane
Ca2+ enters cell binds to vesicles containing neurotransmitter
Secretion of neurotransmitter from vesicles by exocytosis
Diffusion of neurotransmitter across synaptic cleft
Neurotransmitter binds to post-synaptic receptors resulting in change in membrane
potential
Removal of neurotransmitter from synapse
Degraded by enzymes
Endocytosed into pre-synaptic cell
Diffuses away from synaptic cleft
o Transmission at the ganglion
For every preganglionic neuron – 20 postganglionic neurons
Acetylcholine – fast depolarisation
Opioid peptides – slow hyperpolarisation
LHRH – slow hyperpolarisation
o Transmission at the target
Parasympathetic – muscarinic receptors
, Autonomic Nervous System – Summary
Sympathetic – alpha and beta receptors
o Autoreceptors
Alpha-2 autoreceptor (sympathetic) + muscarinic-2 autoreceptor (parasympathetic) –
controls release of transmitter
Endothelium derived relaxation factor – nitric oxide
o NO acts as a transmitter in the endothelium
Precursor = arginine
Enzyme = nitric oxide synthase
o NO production in the endothelium release works on guanylyl cyclase relaxes smooth
muscle
Adrenergic Pharmacology
Adrenoceptors
Sympathetic Activity
Sympathetic nervous system
o Sympathetic outflow
Short preganglionic axons release
acetylcholine in the sympathetic ganglia
stimulates nicotinic receptors on the
long postganglionic axons
Long postganglionic axons release
noradrenaline from nerve terminals =
stimulates adrenoceptors on the target tissues
o Exception = sweat glands
Postganglionic axons release acetylcholine from nerve terminals stimulates muscarinic
receptors on sweat glands
o Innervation of adrenal medulla
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