Flashcards in Lecture 14 Deck (11):
What are the basic features of the anatomy of the autonomic nervous system?
A preganglionic neuron which exits out of the spinal cord, then interacts at a ganglion with a postganglionic neuron which will signal the target tissue
The sympathetic nervous system has ganglions close to the spinal cord while the parasympathetic ganglion are further removed
What organs only receive signalling from one of the autonomic nervous systems?
Structures in the head and neck, the adrenal medulla, liver, blood vessels and sweat glands are only signalled by the sympathetic nervous system
What is the general mechanism of a neuronal transmission?
Precursor is transported into the nerve terminal
Enzymes then convert this into the transmitter
The transmitter is transported into synaptic vesicles where it is stored until release
An action potential moves down the axon to the nerve terminal
Calcium channels are then opened
The vesical and nerve membranes fuse releasing transmitter into the synaptic space
Transmitter then acts on receptors at the pre-synaptic membrane (autoinhibitory) and the post synaptic membrane (to signal cell)
It may also be reuptaken as the transmitter through transporter molecules or degraded by enzymes and then the degraded product is used as the precursor to enter as step one
What are the 10 potential places for a drug to act which can change the events of synaptic transmission?
Prevention of the precursor molecule being taken up by the neuron
Prevention of the precursor being converted to the transmitter
Preventing the transmitter from being sotred in vesicles
Inhibitors of action potentials and Ca2+ channel release
Preventing the fusion of the synaptic vesicle and the nerve membranes
Blocking the transporters for reuptake of the transmitter
Blocking the enzymes which degrade the transmitter
Blocking both pre and post synaptic membrane receptors that the transmitter acts on
What are the features of the Parasympathetic nervous system chemistry?
ACh is used at both pre and post ganglionic junctions
Uses nicotenic receptors (Nn, Nm) for communication between pre and post ganglionic neurons
Uses muscarinic (M1, M2, M3) receptors for communication between post ganglionic neuron and target tissue
What are the features of the sympathetic nervous system chemistry?
Preganglionic neurons use ACh while post ganglionic neurons use NA (except sweat glands)
Nicotenic receptors are used for communication between the post and preganglionic neuron
Uses alpha 1,2 and beta 1,2 receptors to communicate between post ganglionic neurons and target tissue
What is neuromodulation?
When other mediators act to change synaptic transmission, despite the fact they do not act as transmitters themselves
Typically a much slower process than neurotransmission
What is homotropic presynaptic inhibition?
The transmitter acts on a presynaptic receptor to inhibit further transmitter release (autoinhibition)
What is heterotropic presynaptic inhibition?
The transmitter acts on a presynaptic receptor to inhibit the release of a second neurotransmitter
What evidence suggests the existence of neurotransmitters outside of ACh and NA?
When the responses to ACh and NA are blocked, autonomic transmission does not completely stop suggesting things such as non-peptides (ATP, Nitric Oxide) and peptides (Neuropeptide Y, vasoactive intestinal peptide) may also act as neurotransmitters