Organization of the autonomic nervous system Chart (Pharmacology Review)
The autonomic nervous system (ANS) controls involuntary activity
- Parasympathetic nervous system (PNS)
- Long preganglionic axons originate from neurons in the cranial and sacral areas of the spinal cord and, with few exceptions, synapse on neurons in ganglia located close to or within the innervated organ.
- Short postganglionic axons innervate cardiac muscle, bronchial smooth muscle, and exocrine glands.
- Parasympathetic innervation predominates over sympathetic innervation of salivary glands, lacrimal glands, and erectile tissue.
- Sympathetic nervous system (SNS)
- Short preganglionic axons originate from neurons in the thoracic and lumbar areas of the spinal cord and synapse on neurons in ganglia located outside of, but close to, the spinal cord. The adrenal medulla, anatomically considered a modified ganglion, is innervated by sympathetic preganglionic axons.
- Long postganglionic axons innervate many of the same tissues and organs as the PNS.
- Innervation of thermoregulatory sweat glands is anatomically sympathetic, but the postganglionic nerve fibers are cholinergic and release acetylcholine (ACh) as the neurotransmitter.
- Enteric nervous system
- Considered a third branch of the ANS.
- Highly organized, semiautonomous, neural complex localized in the gastrointestinal (GI) system.
- Receives preganglionic axons from the PNS and postganglionic axons from the SNS.
- Nerve terminals contain peptides and purines as neurotransmitters.