1. THE AUTONOMIC NERVOUS SYSTEM
PART I

2. Neural Control of Involuntary Effectors
The autonomic nervous system helps regulate cardiac, smooth muscle and glands
Impulses are conducted from the CNS to a second autonomic neuron. And then the second neuron innervates the involuntary effector.

3. Visceral Effector Organs
The autonomic nervous system regulates all the organs. Common features of organs regulated autonomically: 1) a built-in muscle tone – they maintain a resting ‘tone’ 2) denervation hypersensitivity – they may become more sensitive to regulation when nerves are damaged 3) They may contract without autonomic input 4) The autonomic system is like an accelerator or brake

4. Divisions of the Autonomic Nervous System
Sympathetic - thoracolumbar division – preganglionic fibers exit spinal cord at spinal nerves T1-L2 - synapse with paravertebral ganglia (sympathetic chain)

5. Fig. 9.2 The Sympathetic Chain of Paravertebral Ganglia

6. Sympathetic Neuron Pathways

7. Sympathetic Division
Divergence – preganglionic fibers branch out to postganglionic fibers at different levels of the chain Convergence – a postganglionic neuron can receive info from many pre- ganglionic nerves.
Mass activation – all postganglionic sympathetic neurons can be activated simultaneously for fight or flight

8. Sympathetic Collateral (prevertebral) Ganglia
These are places where pre- ganglionic neurons synapse if they do not synapse in the paravertebral chain; they form splanchnic nerves
E.G. celiac, superior, mesenteric, inferior mesenteric ganglia which innervate digestive, urinary, reproductive

9. Note: dual innervation of organs by both systems

10. Adrenal Glands
Two functionally different glands: medulla and cortex
Medulla – originates from neural crest; innervated by preganglionic sympathetic fibers which trigger the secretion of epinephrine into the blood
Cortex – secretes steroid hormones
Sympathoadrenal system – stimulation of adrenal medulla by mass activation of sympathetic nervous system

11. Question
What happens to blood vessels of the digestive tract during sympathetic activation? What happens to skeletal muscles? Lungs?

12. Parasympathetic Division
Craniosacral Division Preganglionic fibers originate in the brain (midbrain, pons, medulla) and in sacrum; they extend to terminal ganglia, which are inside the organs they stimulate. Terminal ganglia supply postganglionic fibers to synapse with effector cells.

13. Functions of the Autonomic Nervous System
Sympathetic: Fight or flight Epinephrine/norepi released from postganglionic neurons Can be regulated as a “mass system” or finely tuned Purpose: increase ATP
Parasympathetic
Rest and digest
Acetylcholine released from postganglionic neurons
Not activated as a whole
Opposite of sympathetic