Exam #1: Physiology of the ANS I Flashcards
What is the ANS?
Portion of the nervous system that controls most visceral functions & accommodates coordinated responses to external stimuli.
What are the components of the CNS?
- Brain
- Spinal cord
What are the components of the PNS?
1) Somatic Nervous System
2) Autonomic Nervous System
What are the three divisions of the ANS?
1) Sympathetic
2) Parasympathetic
3) Enteric division
What is the key neuron in the somatic nervous system?
Alpha motor neuron
What is the neurotransmitter in the somatic nervous system?
ACh
How does the autonomic nervous system differ from the somatic nervous system in terms of neruons?
- In the somatic nervous system, there is one large neuron that synapses directly on the effect cell
- In the ANS, there are two neurons (preganglionic & post ganglionic, with an intervening ganglia)
How do the sympathetic & parasympathetic nervous systems differ organization of the neurons?
- Sympathetic= Short pre-ganglionic & long post-ganlgionic fiber
- Parasympathetic= Long pre-ganglion & short post-ganglionic
*Note that the the ganglia of the PNS are clustered within the walls of visceral organs
What is the alternate name for the sympathetic nervous system?
Thoraco-lumbar division
What is the intermediolateral cell column?
- Lateral horn of the spinal cord
- Location of the cell bodies of autonomic ganglia
Describe the path of sympathetic outflow.
1) Cell body in the intermediolateral column
2) Preganglionic axon exits the spinal cord via the ventral root w/ somatic motor neurons
3) Diverge from somatic & enter the white rami communicantes
What are the three modes of innervation in the SNS?
1) Preganglionic neuron goes to a) paravertebral ganglia or b) prevertebral ganglia, and then synapses with post-ganglionic neuron
2) Preganglionic neuron goes to a specialized ganglia, which then synapses with the target organs
3) Preganglionic neuron goes straight to the organ e.g. adrenal medulla
Specialized ganglia include: superior cervical ganglion, celiac ganglion, superior mesenteric ganglion, & inferior mesenteric ganglion
What is the alternate name for the PNS?
Cranio-Scaral Division
Describe cranial outflow.
- Preganglionic fibers follow certain cranial nerves
- Ganglia lie very close to target organs
Specific cranial nerves= oculumotor, fascial, glossopharyngeal, & vagus
Describe sacral outflow.
- Parasymathetic fibers emerge from the spinal cord in a bundle known as the nervi erigentes
- Synapse with pelvic ganglia
- Short postganglionic fibers to target organs
What is the enteric nervous system?
Two ganglia sandwhiched between the layers of the gut:
- Myenteric (Auerbach’s)
- Submucosal (Meissner’s)
Specifically, where is the myenteric plexus located? What does the myenteric plexus control?
- Between the external longitudinal & deep circular smooth muscle layers
- Motility
Specifically, where is the submucosal plexus located? What does the submocosal plexus control?
- Between the circular muscularis mucosae
- Ion & fluid transport
Where does the enteric nervous system receive input from? Can the enteric nervous system function without this input?
PNS & SNS
*However, the enteric nervous system can function normally without extrinsic input
What does dual innervation mean?
Most organs receive input from both SNS & PNS; thus, their action is controlled by both systems
What are the exceptions to dual innervation that only receive SNS innervation?
- Hair follicles
- Thermoregulatory sweat gland
- Liver
- Adrenal Gland
- Kidney
In what organs do the SNS & PNS produce similar effects?
Salivary glands
*Both increase the production of saliva
What NT is released from all of the preganglionic fibers?
ACh
*Regardless of system, all preganglionic fibers release ACh
What do the postganglionic fibers of the PNS release?
ACh
