autonomic
“self-governed” and fully independent.
Autonomic nervous system (ANS)
a motor nervous system that controls smooth, cardiac muscle, and glands.
-A.K.A visceral motor system.
Primary organs of the ANS
viscera of thoracic and abdominal cavities.
Some structures of the body wall.
- cutaneous blood vessels.
- sweat glands.
- piloerector muscles.
ANS (cont.)
carries out actions INVOLUNTARILY: without our conscious intent or awareness.
Denervation hypersensitivity
exaggerated response of cardiac and smooth muscle if autonomic nerves are severed.
-spinal cord injuries
Visceral reflexes
unconscious, automatic
example of homeostatic negative feedback loop
high blood pressure detected by arterial stretch receptors (1), afferent neuron (2) carries signal to CNS, efferent (3) signals travel to the heart, then (4) heart slows reducing blood pressure.
example of homeostatic negative feedback loop
high blood pressure detected by arterial stretch receptors (1), afferent neuron (2) carries signal to CNS, efferent (3) signals travel to the heart, then (4) heart slows reducing blood pressure.
Sympathetic divison
prepares body for physical activity: exercise, trauma, arousal, competition, anger or fear.
- increases heart rate, BP, airflow, blood glucose levels, etc.
- reduces blood flow to skin and digestive tract.
Parasympathetic division
clams many body functions reducing energy expenditure and assists in bodily maintenance (rest and digest)
Parasympathetic tone
- maintains smooth muscle tone in intestines.
- hold resting heart rate down to about 70 to 80 beats per minute.
Sympathetic tone
keeps most blood vessels partially constricted and maintains blood pressure.
(Autonomic output pathways) control nucleus in the ______ and other brainstem regions.
hypothalamus
Autonomic pathway
- signal must travel across 2 NEURONS to get to target organ.
- must cross a synapse where these two neurons meet in an autonomic ganglion.
Presynaptic neuron
the first neuron has a some in the brainstem or spinal cord. (type B)
____ with a _________ whose axone extends the rest of the way to the target cell. (type C)
Synapses ; postganglionic neuron
Sympathetic division
- also called thoracolumbar division.
- relatively short preganglionic and long postganglionic fibers.
Preganglionic neurosomas
in lateral horns and nearby regions of the grey matter of spinal cord.
- fibers exit spinal corby way of spinal nerves T1 to L2.
- lead to nearby sympathetic chain of ganglia (paravertebral ganglia)
each paravertebral ganglion is connected to a spinal nerve by two branches:
communicating rami
Preganglionic fibers
small myelinated fibers that travel from spinal nerve to the ganglion by way of the white communicating ramus. (myelinated)
Postganglionic fibers
leave the ganglion by way of the gray communicating ramus (unmyelinated).
-forms a bridge back to the spinal nerve.
extend the rest of the way to the target organ.
nerve fibers leave the sympathetic chain by___, ___, and _____.
spinal, sympathetic, splanchnic nerves.
spinal nerve route
- some postganglionic fibers exit a ganglion by way of the grey ramus.
- return to the spinal nerve and travel the rest of the way to the target organ.
- most sweat glands, piloerector muscles, and blood vessels of the skin and skeletal muscles.
sympathetic nerve route
- other nerves weaver by way of sympathetic nerves that extend to heart, lungs, esophagus, and thoracic.
- these nerves form carotid plexus around each carotid artsy of the neck.
- issue fibers from there to the effectors in the head. (sweat, salivary, nasal glands, piloerector muscles, blood vessels, dilator of iris) (superior cervical)
