1. Unit 10 Autonomic Nervous System (ANS)

2. Objectives: Comparison of Somatic & Autonomic Nervous Systems
Structure of the Autonomic Nervous System
Anatomical Components

3. Functions of the Somatic and Autonomic Nervous Systems

4. Comparison: SomaticNS vs AutonomicNS
SNS
Controls skeletal muscle
Conscious, voluntary control
Motor pathway: one neuron from CNS to effector
Does include sensory neurons (from skin, skeletal muscles, and special sense organs)
All release the neurotransmitter ACh
ANS
Controls viscera: smooth and cardiac muscle, and glands
Unconscious, involuntary
Motor pathway: series of two neurons from CNS to effector
Does include sensory neurons (monitors viscera)
Two divisions: sympathetic, parasympathetic
Release either ACh or NE

5. Somatic Nervous System
Copyright 2010, John Wiley & Sons, Inc.

6. Introduction to the ANS
Somatic nervous system (SNS) + ANS  peripheral nervous system (PNS)
ANS
Is regulated by hypothalamus, brainstem
The ANS supplies nerves to viscera
Smooth muscle (stomach, blood vessels)
Cardiac muscle (heart)
Glands (sweat and digestive glands)

7. ANS Motor Pathways Autonomic motor pathway includes two motor neurons
CNS  (Autonomic ganglion) Preganglionic  Postganglionic neuron  to effector

8. Autonomic Nerve Fibers
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Copyright 2010, John Wiley & Sons, Inc.

9. Autonomic Nervous System
Two Divisions
Sympathetic – prepares body for fight or flight situations
Parasympathetic – prepares body for resting and digesting activities

10. Divisions of the ANS Sympathetic (S) + parasympathetic (P)
Most viscera supplied with nerves of both S and P divisions: dual innervation
S and P have opposite (antagonistic) effects
Heart rate: S stimulates, P inhibits
Digestive organs: S inhibit, P stimulate
Some viscera receive only S (not P) nerves:
Sweat glands, many blood vessels, hair muscles

11. Control of Autonomic Activity
Largely CNS
Medulla oblongata
cardiac, vasomotor and respiratory activities
Hypothalamus
regulates balance between sympathetic and parasympathetic activity
visceral functions
Limbic system & cerebral cortex
emotional responses
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12. ANS Motor Pathways
Copyright 2010, John Wiley & Sons, Inc.

13. Objectives: Organization of the Sympathetic Division
Organization of the Parasympathetic Division

14. Sympathetic (S) Preganglionic
Cell bodies located in lateral gray of spinal cord segments T1-T12 + L1-L2
called “thoracolumbar”
Axons pass through ventral roots of spinal nerves
May branch many times
May ascend or descend (from cervical to sacral)
Can synapse with 20 or more postganglionic cell bodies
Results: widespread effects (viscera respond with one another)

15. Sympathetic Division
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Copyright 2010, John Wiley & Sons, Inc.

16. Sympathetic (S) Postganglionic
Cell bodies located
“Trunk ganglia”
2 long chains lateral to vertebrae
“Prevertebral ganglia”
Anterior to 3 large abdominal arteries

17. “Trunk ganglia” From cervical to sacral regions  widespread effects
Many axons pass back into spinal nerves to reach skin
sweat glands, hair muscles, blood vessels

18. “Prevertebral ganglia”
Named celiac, superior and inferior mesenteric ganglia
Supply abdominal viscera: stomach, intestine, kidneys, liver, spleen
Axons pass from ganglia to viscera in S nerves

19. Sympathetic Division
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Copyright 2010, John Wiley & Sons, Inc.

20. Sympathetic Division
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Copyright 2010, John Wiley & Sons, Inc.

21. Parasympathetic (P) Preganglionic
Cell bodies located in brainstem + in spinal cord segments S2-S4
“Craniosacral”

22. Parasympathetic Preganglionic
Axons in cranial nerves III, VII, IX and X and in pelvic nerves from S2-S4
Vagus nerves (cranial nerves X) carry 80% of all P nerve impulses.
Vagus nerves carry both motor and sensory neurons to/from viscera within the thorax and most of the abdominal cavity.
Axons do not branch or pass though S trunk ganglia but pass directly almost to viscera

23. Parasympathetic Division
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Copyright 2010, John Wiley & Sons, Inc.

24. Parasympathetic (P) Postganglionic
Cell bodies lie in terminal ganglia
Located within or near the innervated organ
cause precise, localized (not widespread) effects
S nerves supply all viscera but P nerves do not reach some
sweat glands, arrector pili muscles, kidneys, spleen, adrenal medullae, and the walls of most blood vessels.
Axons pass from ganglia to viscera in P nerves

25. Parasympathetic (P) Division
Copyright 2010, John Wiley & Sons, Inc.

26. Objectives: Functions of the Autonomic Nervous System
ANS Neurotransmitters
Activities of the ANS
Sympathetic Activities
Parasympathetic Activities

27. ANS Neurotransmitters: Comparison
Acetylcholine (ACh)
More common
Released by:
All S and P preganglionic axons
All P postganglionic axons
Some S postganglionic axons (to sweat glands)
Destroyed by enzyme ACh-ase
Short-lived response
Norepinephrine (NE)
Less common
Released by:
Almost all S postganglionic axons
Longer lasting effects
Enhanced by epinephrine + NE from adrenal medullae

28. Sympathetic Effects Fight-or-flight activities
Increase heart rate and contraction, and blood pressure (BP)
Dilate pupils
Dilate airways
Dilate vessels to skeletal muscles, heart, liver and adipose tissue
Constrict blood vessels to nonessential organs: skin, GI tract, kidneys
Mobilize nutrients for energy: glucose and fats

29. Parasympathetic Effects
Rest-and-digest activities
SLUDD
Salivation
Lacrimation
Urination
Digestion
Defecation
Decrease
Heart rate,
Airway diameter,
Pupil diameter

30. Aging and Autonomic Nervous System