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Which group of neurons releases the neurotransmitters epinephrine and norepinephrine?
The sympathetic nervous system is typically associated with "fight or flight" responses in the body. When you think of stressful situations, it helps to think of adrenaline (or epinephrine) being used by the body. The postganglionic neurons of the sympathetic nervous system will release the neurotransmitter epinephrine or norepinephrine, which will then attach to adrenergic receptors on the effector organ to initiate the sympathetic action.
The neurons of the parasympathetic nervous system and the preganglionic neurons of the sympathetic nervous system use acetylcholine.
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What is the primary neurotransmitter in sympathetic postganglionic neurons?
Norepinephrine is the neurotransmitter that is released by the postganglionic neuron, and stimulates sympathetic responses in effectors. Acetylcholine is the primary neurotransmitter in post ganglionic neurons in the parasympathetic nervous system. Dopamine, GABA, and glycine are other transmitters used by the nervous system, but are not the primary neurotransmitter of the postganglionic sympathetic neurons.
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Which of the following is true when moving from the transverse colon to the descending colon?
As one moves from the transverse colon to the descending colon, the sympathetic innervation changes from the thoracic splanchnics to the lumbar splanchnics.
Pelvic splanchnic nerves provide parasympathetic innervation of pelvic and genital organs, including the distal third of the transverse colon, the descending colon, the sigmoid colon, and the rectum rectum. The proximal two thirds of the transverse colon, and the rest of the proximal gastrointestinal tract receives parasympathetic innervation from the vagus nerve.
The superior mesenteric, inferior mesenteric, and iliac arteries provide blood supply for the large intestine. The celiac trunk does not provide blood supply to the large intestine. Branches of the superior mesenteric artery mainly perfuse the transverse colon, while branches of the inferior mesenteric artery mainly perfuse the descending colon. Venous drainage mirrors colonic arterial supply, with both the superior and inferior mesenteric veins joining the hepatic portal vein.
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