1. Chapter 14 Autonomic Nervous System Nerve Cells of the Enteric Plexus
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2. SNS vs. ANS Somatic Nervous System (SNS)
Cell bodies of somatic neurons are located in CNS
axons extend to skeletal muscles --have an excitatory effect
Usually controlled consciously
Autonomic Nervous System (ANS)
Cell bodies of preganglionic neurons are located in CNS
axons extend to ganglia where they synapse with postganglionic neurons
The postganglionic axons can have an excitatory or inhibitory effect on
Smooth muscle
Cardiac muscle
Glands
Usually controlled unconsciously

3. Fig. 14.1

4. Tab. 14.1

5. Anatomy of the Autonomic Nervous System
Subdivided into
Sympathetic division
Parasympathetic division
Enteric nervous system
Sympathetic and Parasympathetic divisions differ structurally in
Location of preganglionic neuron cell bodies within CNS
Location of autonomic ganglia

6. The Sympathetic Division
Preganglionic cell bodies are in lateral horns of the spinal cord gray matter from T1 to L2
Preganglionic axons pass through ventral roots to white rami communicates to sympathetic chain ganglia. From there, four courses are possible
Fig. 14.2

7. The Sympathetic Division
1) Preganglionic axons synapse (at same or a different level) with postganglionic neurons, which exit ganglia through gray rami communicates and enter spinal nerves
2) Preganglionic axons synapse (at same or a different level) with postganglionic neurons, which exit ganglia through sympathetic nerves
Fig. 14.3

8. The Sympathetic Division
3) Preganglionic axons pass through chain ganglia without synapsing to form splanchnic nerves. Preganglionic axons then synapse with postganglionic neurons in collateral ganglia
4) Preganglionic axons synapse with cells of adrenal medulla
Fig. 14.3

9. The Parasympathetic Division
Preganglionic cell bodies are in nuclei in brainstem or lateral parts of spinal cord gray matter from S2 to S4
Preganglionic axons from brain pass to ganglia through cranial nerves
Preganglionic axons from sacral region pass through pelvic splanchnic nerves to ganglia
Preganglionic axons pass to terminal ganglia within wall of, or near, organ that is innervated
Fig. 14.4

10. Tab. 14.2

11. Enteric Nervous System
Consists of nerve plexuses within wall of the digestive tract
Has contributions from 3 sources:
Sensory neurons that connect digestive tract to the CNS
ANS motor neurons that connect CNS to digestive tract
Enteric neurons, which are confined to enteric plexuses

12. Distribution of Autonomic Nerve Fibers
Sympathetic, parasympathetic and sensory neurons intermingle in autonomic nerve plexuses
Sympathetic axons reach organs through spinal, sympathetic, and splanchnic nerves
Parasympathetic axons reach organs through cranial and pelvic splanchnic nerves
Sensory neurons run alongside sympathetic and parasympathetic neurons within nerves and nerve plexuses

13. Fig. 14.5

14. Neurotransmitters of the ANS
Acetylcholine is released by cholinergic neurons
All preganglionic neurons
All parasympathetic postganglionic neurons
Some sympathetic postganglionic neurons
Norepinephrine (or epinephrine) is released by adrenergic neurons
Most sympathetic postganglionic neurons

15. Receptors of the ANS Acetylcholine binds to
Nicotinic receptors
Found in all postganglionic neurons
Excitatory
Muscarinic receptors
Found in all parasympathetic effector organs
Some sympathetic effector organs
Excitatory or inhibitory
Norepinephrine and epinephrine bind to
Alpha and beta receptors
Found in most sympathetic effector organs

16. Fig. 14.6

17. Tab. 14.3

19. Regulation of the ANS
Autonomic reflexes control most of activity of visceral organs, glands, and blood vessels
Autonomic reflex activity can be influenced by hypothalamus and higher brain centers
The sympathetic and parasympathetic divisions can influence activities of enteric nervous system through autonomic reflexes
The enteric nervous system can function independently of CNS through local reflexes

20. Fig. 14.7

21. Functional Generalizations About the ANS
Both divisions of the ANS produce stimulatory and inhibitory effects
Most organs are innervated by both divisions
Usually, each division produces an opposite effect on a given organ
Either division alone or both working together can coordinate the activities of different structures
The sympathetic division produces more generalized effects than the parasympathetic division
Sympathetic activity generally prepares the body for physical activity
Parasympathetic activity is more important for resting conditions