1. AUTONOMIC
SYSTEM
NERVOUS

2. THE AUTONOMIC NERVOUS SYSTEM
Innervates smooth muscle, cardiac muscle and glands
Helps to maintain homeostasis
Also called the involuntary or visceral motor system

3. THE AUTONOMIC NERVOUS SYSTEM
Regulation
By brainstem, spinal cord, hypothalamus and parts of the cerebrum

4. AUTONOMIC GANGLIA AND CIRCUITS
The motor units of the ANS consist of two neurons:
Preganglionic Neuron
Cell body is in the CNS
Synapses with another neuron before reaching the effector
The synapse occurs in an autonomic ganglion outside the CNS
(The somatic motor unit consists of one neuron with its cell body in the CNS and its axon extending to the effector)
Postganglionic Neuron
Extends from the autonomic ganglion in the PNS to the effector

5. AUTONOMIC GANGLIA AND CIRCIUTS
CNS
PNS
Effector

6. THE AUTONOMIC NERVOUS SYSTEM
PARASYMPATHETIC
SYMPATHETIC

7. DIVISIONS OF THE ANS: The Sympathetic System (see table 14.4)
Fight or flight system activated in emergency situations
Effects:
Increases heart rate
Dilates bronchial tubes and pupils
Constricts blood vessels
Stimulates secretion of epinephrine and norepinephrine from the adrenal gland
Stimulates sweat glands
Inhibits digestion
Aids in ejaculation in males

8. THE SYMPATHETIC SYSTEM
Neurons
Emerge through the ventral roots of spinal nerves T1 through L2 (thoracolumabar outflow)

9. THE SYMPATHETIC SYSTEM
Preganglionic Sympathetic Neurons
Preganglionic bodies are in the lateral horns of the spinal cord at the T1 through L2 levels
Preganglionic sympathetic axons are short
Preganglionic fibers pass through the ventral root into the white rami communicantes

10. THE SYMPATHETIC SYSTEM
Preganglionic Sympathetic Neurons
Preganglionic sympathetic neurons synapse with a postganglionic neuron in the paravertebral chain ganglia
Paravertebral chain ganglia run lateral to the spinal cord on both sides
There are 22 to 23 pair of paravertebral ganglia on both sides of the vertebral column

11. THE SYMPATHETIC SYSTEM
Preganglionic Sympathetic Neurons
Preganglionic fibers may ascend or descend within the chain to synapse within a ganglion at a different level
Some sympathetic preganglionic fibers pass through the chain ganglion without synapsing
These are called sympathetic splanchnic nerves

12. THE SYMPATHETIC SYSTEM
Preganglionic Sympathetic Neurons
Sympathetic splanchnic nerves synapse in ganglia anterior to the vertebral column (near the aorta)
These ganglia are called prevertebral or collateral ganglia
Sympathetic splanchnics innervate smooth muscles of the abdominal and pelvic viscera and their blood vessels

13. THE SYMPATHETIC SYSTEM
Postganglionic Sympathetic Neurons
Post ganglionic sympathetic axons are long
Post ganglionic sympathetic neurons exit the paravertebral ganglia via the gray rami communicantes (unmyelinated) and re-enter the spinal nerve
From here they continue on to the effector (viscera, blood vessels, sweat glands)

14. THE SYMPATHETIC SYSTEM
All sympathetic preganglionic neurons release acetylcholine as a neurotransmitter (cholinergic)
Sympathetic postganglionic neurons release norepinephrine (adrenergic) with the exception of neurons to blood vessels and sweat glands (cholinergic)

15. THE SYMPATHETIC SYSTEM
Adrenal Medulla
Preganglionic sympathetic neurons innervate the adrenal medulla
Cause release of epinephrine and norepinephrine into the bloodstream
Has the same effect as the sympathetic system only lasts 5 to 10 times longer

16. THE SYMPATHETIC SYSTEM
Norepinephrine & Epinephrine
Norepinephrine and epinephrine both have similar effects on the body
Epinephrine has a greater effect on cardiac stimulation, raising B.P. and increasing metabolic rate
Both are secreted by the adrenal medulla in response to sympathetic stimulation
Same effect as stimulating organs via sympathetic nerves only lasts 5 to 10 times longer

17. THE PARASYMPATHETIC SYSTEM
Effects:
Constricts the pupils and bronchi
Restores gland and digestive system activity
Slows heartrate

18. THE PARASYMPATHETIC SYSTEM
Neurons:
Emerge with the cranial nerves (III, VII, IX and X)
Some emerge with the sacral spinal nerves
Craniosacral outflow
C.N. III
C.N. VII
C.N. IX
Neuron cell bodies for the fibers traveling with cranial nerves are in the brainstem
Cell bodies for the fibers traveling with the sacral spinal nerves are in the lateral gray horns of spinal levels S2-S4
C.N. X

19. THE PARASYMPATHETIC SYSTEM
Preganglionic Parasympathetic Neurons
Preganglionic neurons are long
Preganglionic neurons travel from the CNS almost all the way to the effector before synapsing with a postganglionic neuron

20. THE PARASYMPATHETIC SYSTEM
Postganglionic Parasympathetic Neurons
Postganglionic parasympathetic neurons are short
Postganglionic neurons synapse with preganglionics on or near the effector organ in terminal ganglia (collectively called intramural ganglia)
Postganglionic neurons travel from the terminal ganglia to the effector cells

21. THE PARASYMPATHETIC SYSTEM
Cranial Outflow
With C.N. III, VII, IX and X
Preganglionic fibers travel with each cranial nerve
Postganglionic fibers for C.N. III, VII and IX travel with C.N. X for distribution to the face
C.N. III
C.N. VII
C.N. IX
Vagus nerve accounts for 90% of all preganglionic parasympathetic fibers in the body
Parasympathetic fibers from the Vagus nerve supply almost every thoracic and abdominal organ
C.N. X

22. THE PARASYMPATHETIC SYSTEM
Sacral Outflow
Axons run from the spinal cord with the ventral rami of S2-S4
Fibers branch into pelvic splanchnic nerves
Most fibers go on to synapse in intramural ganglia near the effector organ
Pelvic splanchnics innervate the distal large intestine, urinary bladder, ureters and reproductive organs

23. Cholinergic Receptors
ANS RECEPTORS
Cholinergic Receptors
Activated by acetylcholine (Ach)
Two types:
Muscarinic
Found on all effector cells stimulated by postganglionic cholinergic fibers (all parasympathetic target organs and some sympathetic)
Nicotinic
Found on motor end plates of skeletal muscle
Found on all postganglionic neurons (sympathetic and parasympathetic)
Found on the hormone producing cells of the adrenal medulla

24. ANS RECEPTORS

25. ANS RECEPTORS Adrenergic Receptors
Activated by epinephrine and norepinephrine
Two types:
Alpha ()
Epinephrine has a greater effect on these than norepinephrine
Found on all sympathetic target organs except the heart
Usually stimulatory when NE or Epinephrine binds to them
Beta ()
Found in the heart, adipose tissue and most sympathetic organs
Usually inhibitory when either hormone binds to them (except in the heart)
Cause dilation of blood vessels

26. ANS RECEPTORS

27. VISCERAL REFLEXES
Visceral Reflex Arcs