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Sympathetic nervous system
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The sympathetic nervous system is one of the two halves of the autonomic nervous system, the one that works without our thinking about it. Its general job is to prepare the body for physical activity.
Its nerves do not come from just anywhere: the first neurons, called preganglionic, leave the spinal cord at the level of the chest and the upper lumbar region, from T1 down to L2. There they synapse at relay points called sympathetic ganglia, that is, they hand the message off to a second neuron. Think of an order that leaves the spinal cord, switches messengers at a station and continues to the organ.
Each leg of the trip uses a different messenger. In the ganglion the neurotransmitter is acetylcholine; the second neuron, now at the organ, releases epinephrine or norepinephrine.
The result is obvious: the heart beats faster and harder, and the bronchi widen.
In brief
The sympathetic system is one of the two divisions of the autonomic nervous system and prepares the body for physical activity.
Its preganglionic neurons leave the thoracic and lumbar spinal cord, from T1 to L2, and synapse in the sympathetic ganglia.
An order that leaves the spinal cord, switches messengers at a station and continues to the organ.
In the ganglion the neurotransmitter is acetylcholine; the second neuron releases epinephrine or norepinephrine.
That is why, when it fires, heart rate and contractile force go up and the bronchi widen.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingNeuroanatomy, Sympathetic Nervous System, StatPearlsPublished
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