Anatomy & Physiology I and II

Anatomy & Physiology Study Guide The sympathetic division consists of preganglionic neurons and ganglionic neurons involved in using energy and increasing metabolic rate: • Preganglionic fibers from the thoracic and lumbar segments form the sympathetic division, or thoracolumbar division (“fight or flight” system), of the ANS. Preganglionic fibers leaving the brain and sacral segments form the parasympathetic division, or craniosacral division (“rest and digest” system). • The sympathetic division consists of preganglionic neurons between segments T1 and L2, ganglionic neurons in ganglia near the vertebral column, and specialized neurons in the suprarenal glands. • The two types of sympathetic ganglia are sympathetic chain ganglia (paravertebral ganglia) and collateral ganglia (prevertebral ganglia). • In spinal segments T1–L2, ventral roots give rise to the myelinated white ramus which, in turn, leads to the sympathetic chain ganglia. • Postganglionic fibers targeting structures in the body wall and limbs rejoin the spinal nerves and reach their destinations by way of the dorsal and ventral rami. • Postganglionic fibers targeting structures in the thoracic cavity form sympathetic nerves, which go directly to their visceral destinations. Preganglionic fibers run between the sympathetic chain ganglia and interconnect them. • Preganglionic fibers entering a suprarenal gland synapse within the suprarenal medulla. • In a crisis, the entire sympathetic division responds—an event called sympathetic activation. Its effects include increased alertness, a feeling of energy and euphoria, increased cardiovascular and respiratory activities, a general elevation in muscle tone, and a mobilization of energy reserves. Stimulation of sympathetic neurons leads to the release of various neurotransmitters: • The stimulation of the sympathetic division has two distinctive results: the release of either ACh or norepinephrine (NE) at specific locations, and the secretion of epinephrine (E) and NE into the general circulation. • Sympathetic ganglionic neurons end in telodendria studded with varicosities containing neurotransmitters. • The two types of sympathetic receptors are alpha receptors and beta receptors. • Most postganglionic fibers are adrenergic; a few are cholinergic or nitroxidergic. • The sympathetic division includes two sympathetic chain ganglia, three collateral ganglia, and two suprarenal medullae. The parasympathetic division consists of preganglionic neurons and ganglionic neurons involved in conserving energy and lowering metabolic rate: • The parasympathetic division includes preganglionic neurons in the brain stem and sacral segments of the spinal cord, and ganglionic neurons in peripheral ganglia located within (intramural) or next to (terminal) target organs. • The effects produced by the parasympathetic division center on relaxation, food processing, and energy absorption. ©2018 Achieve Test Prep Page 180 of 367