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Muscle effectors are bundles rather than single smooth muscle cells that are connected by gap junctions which allow electrotonic spread of activity between cells. A multiplicity of transmitters are utilized by autonomic nerves, and co-transmission occurs often involving synergistic actions of the co-transmitters, although pre- and post ...
Presynaptic neurotoxins, commonly known as β-neurotoxins, affect the presynaptic regions of the neuromuscular junction. The majority of these neurotoxins act by inhibiting the release of neurotransmitters, such as acetylcholine, into the synapse between neurons. However, some of these toxins have also been known to enhance neurotransmitter ...
While intake of neurotransmitter precursors does increase neurotransmitter synthesis, evidence is mixed as to whether neurotransmitter release and postsynaptic receptor firing is increased. Even with increased neurotransmitter release, it is unclear whether this will result in a long-term increase in neurotransmitter signal strength, since the ...
Acetylcholine is a choline molecule that has been acetylated at the oxygen atom. Because of the charged ammonium group, acetylcholine does not penetrate lipid membranes. . Because of this, when the molecule is introduced externally, it remains in the extracellular space and at present it is considered that the molecule does not pass through the blood–brain
The α 2, on the other hand, couples to G i, which causes a decrease in neurotransmitter release, as well as a decrease of cAMP activity resulting in smooth muscle contraction. The β receptor couples to G s and increases intracellular cAMP activity, resulting in e.g. heart muscle contraction, smooth muscle relaxation and glycogenolysis. There ...
These neurons connect the brain to the appropriate level in the spinal cord, from which point nerve signals continue to the muscles by means of the lower motor neurons. The neurotransmitter glutamate transmits the nerve impulses from upper to lower motor neurons, where it is detected by glutamate receptors.
Comparatively, the command of visceral muscles is disynaptic involving two neurons: the general visceral motor neuron, located in the CNS, synapses onto a ganglionic neuron, located in the PNS, which synapses onto the muscle. All vertebrate motor neurons are cholinergic, that is, they release the neurotransmitter acetylcholine.
In invertebrates, depending on the neurotransmitter released and the type of receptor it binds, the response in the muscle fiber could either be excitatory or inhibitory. For vertebrates , however, the response of a skeletal striated muscle fiber to a neurotransmitter – always acetylcholine (ACh) – can only be excitatory.