Autonomic Pharmacology Flashcards
What is the parasympathetic pathway of the oculomotor nerve (III)?
- E-W nucleus in the midbrain
- ciliary ganglion
- ciliary muscle and iris sphincter
what is the parasympathetic pathway of the facial nerve (VII)?
- hypothalamus
- superior salivatory nucleus in the brain stem
- pre ganglionic fibres go to the sphenopalatine ganglion
- post ganglionic fibres go to the lacrimal gland
what is the sympathetic innervation pathway?
- hypothalamus
- thoracic sympathetic ganglion near the top of the spinal cord
- pre-ganglionic fibres travel to superior cervical ganglion in the neck
- post ganglionic fibres follow the internal carotid artery to the orbit
- via long and short ciliary nerves they innervate the iris dilator, ciliary muscle, ciliary epithelium and mullers muscle
know the table of parasympathetic and sympathetic nervous system components comparison
find it on the google docs
what is miosis?
constriction of the pupil and is a parasympathetic response innervated by the oculomotor nerve via cholinergic innervation of the iris sphincter
what is mydriasis?
the dilation of the pupil and is a sympathetic response via adrenergic innervation of the iris dilator
name 2 parasympathetic synapses
ganglionic synapses and neuroeffector cells
How are preganglionic synapses and neuroeffector cells similar?
they both use acetylcholine as the neurotransmitter
How do ganglionic synapses and neuroeffector cells differ?
-in ganglionic synapses, acetylcholine binds to nicotinic receptors (this can be sympathetic and parasympathetic)
-while in neuroeffector cells, ACh binds to muscarinic receptors at the junction between post ganglionic neurones and their target effector cells
Give 5 ways drugs affect cholinergic synaptic transmission
- mimic acetylcholine - parasympathomimetic e.g. pilocarpine
- block the receptor - antimuscarinic e.g. tropicamide
- block acetylcholine synthesis
- prevent acetylcholine release e.g. botulinum toxin
- inhibit acetylcholine esterase e.g. neostigmine
What are the steps to synaptic transmission in a cholinergic synapse?
- action potential arrives at the end of the neuron to the synaptic knob, depolarising the presynaptic membrane causing voltage gated ca2+ ion channels to open
- Influx of ca2+ triggers synaptic vesicles to fuse with the presynaptic membrane and release the neurotransmitter acetylcholine into the synaptic cleft by exocytosis
- Acetyl Coenzyme A combines with choline to form Acetylcholine which diffuses across the synaptic gap and binds with protein receptors in the postsynaptic membrane
- Protein receptors change shape and open a hydrophilic pore increasing membrane permeability to Na+ ions
- If enough receptors channels open, resting potential may reach threshold of -55mV causing opening of voltage gated Na+ ion channels causing depolarisation of postsynaptic membrane and an action potential is generated
- Enzyme acetylcholinesterase forms enzyme substrate complexes with acetylcholine hydrolysing the ester bond forming acetate and choline preventing further binding of the neurotransmitter to the protein receptors
- The choline is actively transported back over the presynaptic membrane via membrane bound enzymes of ChaT (choline acetyltransferase) and HACU (high-affinity choline uptake) and combines with acetyl CoA (coenzyme A) from the mitochondria enable acetylcholine to reform
how is the sympathetic ganglionic synapses similar to the parasympathetic ganglionic synapses?
they both use acetylcholine as the NT and have nicotinic receptors that receive the signal
what is the neurotransmitters used in the adrenergic nervous system?
epinephrine and norepinephrine
what are the steps to the re-uptake of norepinephrine?
- there is re-uptake of around 90% of the NE released
- some is stored in vesicles while some is degraded by enzyme MAO (monoamine oxidase) in the mitochondria
- a small proportion of NE is taken up by cells and metabolised by enzyme COMT (catechol-O-methyl-transferase)
What part if the nervous system are cholinergic synapses?
parasympathetic
