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CNS
Brain, Brainstem, and Spinal Cord
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Ganglion(pl. ganglia)
Collection of nerve cell bodies
o Sensory (cell bodies of primary sensory neurons), autonomic
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Sympathetic
- Fight or flight (fear, fight, flight, “sex”),
- Global (adrenal medulla produces many hormones)
- Catabolic (increased blood glucose utilization and vasodilation of vessels in brain and skeletal system)
- GI system shuts down
o Ganglia are found near the CNS from T1 – L2, but innervation is widespread
o Two sets of paravertebral ganglia(lateral to spinal cord) and one of prevertabral (in front of spinal cord)
o White ramus communicans contains the axons of the preganglionic nerves and connects segmental nerve with preganlionic chains, T1-L2 ONLY
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Parasympathetic
- Anabolic (accumulation of energy stores)
- Increase in gut motility, vasodilation of vessels in the gut (kind of opposes the sympathetic)
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Enteric: Largenumber of neurons present within the walls of the intestine that can controlthe intestinal motility independent of the CNS; regulated by sympathetic andparasympathetico In the gut, the neurons get two kinds of input, from both the parasympathetic and sympathetic
In the prevertebral region, ACh is the neurotransmitter of the preganglionic sympathetic nerves, and the postganglionic nerves release NE in the gut
The parasympathetic nerves go straight to the gut and release ACh there
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Preganglionic
Goes from origin to ganglia; (myelinated → white)
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Postganglionic
goes from ganglia to target; no myelin sheath (→ gray)
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Hollow organ
Visceral organ that is a hollow tube or pouch or that includes a cavity that serves a vital function
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Prevertebral
Found in front of the vertebra, one prevertebral sympathetic chain ganglia, innervates the gut
o Preganglionic nerves move down within the sympathetic chain and then “bolt” without innervating the paravertebral ganglion cells → innervate the prevertebral ganglia and adrenal medulla (these preganglionic nerves are called splanchnic nerves)
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Intramural
Occurring or situated within the walls of a cavity or organ
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Describe the organization of the PNS interms of somatic/autonomic components
- The somatic (voluntary) system responds to the external environment (sensory input), and its motor target is skeletal muscle.
- The autonomic (visceral) system is automatic and its sensory input is
- internal. Its efferent targets are smooth muscle, cardiac muscle, and glands; smooth muscle and cardiac muscle are associated with the hollow organs of the body
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Name the cell types and functions of cells,all or part of which are located in the PNS
Somaticmotor neurons are used to induce voluntary movement and consist of a cell bodyin the CNS, nerve in the PNS with the synapse/terminal at the target. The autonomic system has a preganglionic neuron with its cell body in the CNS. The axon extends into the PNS and synapses/terminates at a ganglion where the postganlionic neuron’s cell body resides. The axon of that postganglionic neuron then extends to the target (smooth muscle, cardiac muscle, or glands). Autonomic neurons are either sympathetic or parasympathetic, and the easiest way to tell which is which is to look at the location of the preganglionic neuron. The preganglionic neurons of the sympathetic system emerge from T1-L2/3 while the preganglionic neurons of the parasympathetic system emerge from S2-S4. Another difference is the location of the cell body of the postganglionic neurons. If it lies near the spinal cord, then it is sympathetic. Parasympathetic postganglionic neuron cell bodies, on the other hand, lie near or within the target.
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Describe all the possible cell types whoseaxons are located in peripheral nerves, their functions, and the location oftheir cell bodies
Sympathetic preganglionic: Cell body in the CNS(T1 – L2/3), regulate fight or flight
Sympathetic post-ganglionic: Cell body in the sympathetic chain ganglion, adjacent to CNS
Parasympathetic preganlionic: Cell body in the CNS (brainstem, S2-4), “relaxation”
Parasympathetic postganglionic: Cell body in the ganglia, adjacent to or in the target
Sensory neurons: Cell bodies in sensory ganglion of PNS or dorsal root ganglion in spinal cord, NOT assoc with sympathetic or autonomic
Somatic motor neurons: Cell body in the CNS with nerves that extend in the PNS to the target
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Describe the transmitters used bypreganglionic neurons and by ganglion cells in the sympathetic andparasympathetic divisions of the autonomic nervous system
- Acetylcholine is released by the preganglionic cells of both the parasympathetic and sympathetic nerves as well as the postganglionic parasympathetic nerves. The postganglionic sympathetic nerves,
- on the other hand, release norepinephrine
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