What is the difference between a ganglion and a nucleus?
A ganglion is a cluster of cell bodies usually found outside CNS
Nucleus is usually located within the CNS
What is the difference between post and pre ganglionic neurons?
Post ganglionic neurons are neurons after synapse in the ganglion
Preganglionic are neurons before the synapse in the ganglion
What are the types of ganglia present in somatic nervous system?
Dorsal root ganglia
Where are autonomic nervous system ganglia?
Prevertebral (on anterior surface of abdominal aorta) or paravertebral ganglia (run in sympathetic trunk and chain)
Where do preganglionic fibers start in somatic nervous system?
In somatic NS: anterior horn of spinal cord
In autonomic NS: cell body is in lateral horn of spinal cord
How many neurons from CNS to effector tissue in somatic NS?
Single neuron from CNS to skeletal muscle
How many neurons from CNS to effector tissue in parasympathetic NS?
2-neuron chain from CNS to effector organs
Where are preganglionic neuron origins in Sympathetic and parasympathetic NS?
Sympathetic in lateral horn of spinal cord (T1 - L1/2) and parasympathetic in CN III, VII, IX, X In abdominal and thoracic viscera. In pelvic viscera theyc come from S2 - S4 (pudendal nerve)
How do muscles respond to sympathetic activation?
How do viscera/smooth muscles respond to autonomic NS?
Depends on what receptor is being acted on they can be either stimulatory or inhibitory
What do motor neurons of the ANS do?
Innervate smooth/cardiac muscle and glands
They maintain homeostasis completely subconsciously
Examples of glands in head run by ANS:
Lacrimal and nasal glands
What is the structural difference between axons of preganglionic and postganglionic sympathetic ANS nerves?
Preganglionic are lightly myelinated and short whereas postganglionic nerves are unmyelinated, branch out, and are much longer as they go from ganglion to target tissue.
Which autonomic fibers act directly on target tissue?
Sympathetic neurons activating adrenaline and noradrenaline release
What is the structural difference between axons of preganglionic and postganglionic parasympathetic ANS nerves?
preganglionic nerves are lightly myelinated and long.
Postganglionic nerves are short and unmyelinated and don’t branch because they are in the target organ.
Why does the skin get sympathetic innervation?
Rich in blood vessels
Goosebumps (erector pili smooth muscle)
How are sympathetic fibers arranged?
Topographically (T1-T3 head, T4 - T6 Heart, lungs, oesophagus, T7 - T9 Stomach, liver, gallbladder, pancreas, T10 - 11 appendix + colon, T12 - L2/3 Rectum bladder uterus)
Where does the superior mesenteric ganglion postganglionic fibers go?
To the same sites as the superior mesenteric artery.
Same is true for coeliac ganglion+artery and inferior mesenteric ganglion+artery
What kind of ganglia are the coeliac, sup.mesenteric, and inf.mesenteric preganglionic ganglia?
At preverterbral ganglia
What kind of ganglia are located in the sympathetic trunK?
What ganglia go back to the head for sympathetic innervation?
Superior cervical, middle cervical, and inferior cervical ganglia
What 2 ganglia combine in the stellate ganglion?
Inferior and middle cervical ganglia
What tissue do preganglionic afferent sympathetic nerve fibers travel in to reach the sympathetic trunk?
White rami communicantes
What tissue do post ganglionic efferent sympathetic nerve fibers travel in to reach grey rami communicantes
Preganglionic (myelinated) fibers travel through white communicantes to enter sympathetic trunk and synapse with postganglionic (unmyenilated) fibers which leave through grey communicantes to exit trunk and enter spinal nerves.
NOTE: Not all preganglionic fibers synapse at the same level some move upwards (eg to synapse with postganglionic nerves going to the head) and others move on to meet postganglionic neuron near target tissue.
How many paravertebral ganglia are there in the sympathetic trunk?
3 cervical (remember fusions such as the stellate ganglion)
What are the 3 possible pathways for sympathetic innervation?
1) Preganglionic fiber enters sympathetic trunk through afferent white rami communicantes and synapse with poastganglionic nerves in the sympathetic trunk ad post ganglionic fiber exits through grey ramus communicantes.
2) Preganglionic fiber travels to a different level and synapses with post ganglionic fiber somewhere else. (must be able to do so for innervation at things above T1 and below L1/2)
3) Synapse in a distant collateral ganglion anterior to the vertebral column (eg celiac, sup.mesenteric and inf.mesenteric ganglia)