1. Chapter 60: The Autonomic Nervous System and the Adrenal Medulla
Unit Eleven: The Nervous System: C. Motor and Integrative Neurophysiology
Chapter 60: The Autonomic Nervous
System and the Adrenal Medulla
Guyton and Hall, Textbook of Medical Physiology, 12 edition

2. General Organization of the ANS
Activated mainly by centers in the spinal cord, brain
stem, and hypothalamus
Often operates through visceral reflexes
Contains two major divisions
Sympathetic nervous system
Parasympathetic nervous system

3. General Organization of the ANS
Physiologic Anatomy of the Sympathetic Nervous
System
Fig Sympathetic Nervous System+

4. General Organization of the ANS
Preganglionic and Postganglionic Sympathetic Neurons
Fig. 60.2

5. General Organization of the ANS
Segmental Distribution of the Sympathetic Nerve Fibers
(Fig. 60.1)
Special Nature of the Sympathetic Nerve Endings in
the Adrenal Medullae
Secrete epinephrine and norepinephrine

6. General Organization of the ANS
Physiologic Anatomy of the Parasympathetic Nervous
System- about 75% from the vagus nerve
Fig Parasympathetic Nervous System

7. General Organization of the ANS
Preganglionic and Postganglionic Neurons
Long preganglionic fibers
Short postganglionic fibers
Postganglionic neuron located very close to or in
the wall of the affected organ or tissue
d. a, b, and c are the opposite in sympathetic neurons

8. Basic Characteristics of Sympathetic and Parasympathetic Function
Preganglionic Neurons
Cholinergic
Postganglionic Neurons
Mostly cholinergic
Mostly adrenergic
Terminal Nerve Endings
Secrete acetylcholine
Secrete norepinephrine

9. Basic Characteristics of Sympathetic and Parasympathetic Function
Mechanisms of Transmitter Secretion and
Subsequent Removal
Secretion of AcH and norepinephrine by post-
ganglionic nerve endings
Synthesis of AcH, its destruction after secretion
and duration of action

10. Basic Characteristics of Sympathetic and Parasympathetic Function
Mechanisms of Transmitter Secretion and
Subsequent Removal
Acetylcholinesterase-splits AcH into acetate and
choline
Synthesis of norephinephrine, its removal, and its
duration of action

11. Basic Characteristics of Sympathetic and Parasympathetic Function

12. Basic Characteristics of Sympathetic and Parasympathetic Function
Receptors on the Effector Organs
Excitation or inhibition of the effector cell by
changing its membrane permeability
Receptor action by altering intracellular
“second messenger” cAMP

13. Basic Characteristics of Sympathetic and Parasympathetic Function
Two Principle Types of Acetylcholine Receptors
Muscarinic-found on all effector cells stimulated by
postganglionic cholinergic neurons from either the
sympathetic or parasympathetic divisions
Nicotinic-found in the autonomic ganglia at the
synapses between pre- and postganglionic neurons
of both sympathetic and parasympathetic divisions

14. Basic Characteristics of Sympathetic and Parasympathetic Function
Adrenergic Receptors-Alphas and Betas
Alpha Receptor
Beta Receptor
Vasoconstriction
Vasodilation (Beta-2)
Iris dilation
Cardioacceleration (Beta-1)
Intestinal Relaxation
Increased myocardial strength (Beta-1)
Intestinal Sphincter Contraction
Intestinal and uterine relaxation (Beta-2)
Pilomotor Contraction
Bronchodilation (Beta-2)
Bladder Sphincter Contraction
Calorigenesis (Beta-2)
Inhibits Neurotransmitter Release
(Alpha-2)
Glycogenolysis and Bladder Wall Relaxation
(Beta-2)
Lipolysis (Beta-1)
Thermogenesis (Beta-s)

15. Basic Characteristics of Sympathetic and Parasympathetic Function
Excitatory and Inhibitory Actions of Sympathetic
and Parasympathetic Stimulation
Sympathetic stimulation causes excitatory effects
in some organs but inhibitory effects in others
Parasympathetic likewise is excitatory or inhibitory
depending on the organ affected
c. See Table 60.2 in the textbook

16. Basic Characteristics of Sympathetic and Parasympathetic Function
Function of the Adrenal Medullae
Stimulation of the sympathetic nerves causes large
quantities of epinephrine and norepinephrine to be
released into the blood.
Typically, 80% of the secretion is epinephrine and
20% norepinephrine
Have the basic same effect as direct sympathetic
stimulation except it lasts 5-10 times longer

17. Basic Characteristics of Sympathetic and Parasympathetic Function
Epinephrine have almost the same effects but
differences do occur in
Epinephrine has a greater effect on cardiac
stimulation because it stimulates beta receptors
Epinephrine causes weaker constriction of
blood vessels but increases CO
Norepinephrine greatly increases the total
peripheral resistance and elevates arterial
pressure

18. Basic Characteristics of Sympathetic and Parasympathetic Function
Epinephrine as 5-10 greater metabolic effect
Value of the Adrenal Medullae to the Function
of the Sympathetic Nervous System
Epinephrine and norepinephrine are generally
released at the same time as sympathetic stimulation
Also stimulate areas that do not have sympathetic
innervation

19. Basic Characteristics of Sympathetic and Parasympathetic Function
Relation of Stimulus Rate to Degree of Sympathetic
and Parasympathetic Effect
Only a low frequency of stimulation is required for
full activation of autonomic effectors
Sympathetic and Parasympathetic Tone
Normally, both systems are continually active
Allows a single nervous system to both increase and
decrease the activity of a stimulated organ

20. Sympathetic System Sometimes Responds by Mass Discharge
Stimulation of Discrete Organs in Some Instances and Mass Stimulation in Other Instances by the Sympathetic and Parasympathetic Systems
Sympathetic System Sometimes Responds by Mass
Discharge
Parasympathetic System Usually Causes Specific
Localized Responses
Alarm or Stress Response of the Sympathetic
Nervous System
Increased arterial pressure
Increased blood flow to active muscles and
decreased blood flow to GI tract and kidneys

21. Increased rates of cellular metabolism throughout the body
Stimulation of Discrete Organs in Some Instances and Mass Stimulation in Other Instances by the Sympathetic and Parasympathetic Systems
Increased rates of cellular metabolism throughout
the body
Increased blood glucose concentration
Increased glycolysis in the liver and muscle
Increased muscle strength
Increased mental activity
Increased rate of blood coagulation

22. Medullary, Pontine, and Mesencephalic Control of the ANS
Stimulation of Discrete Organs in Some Instances and Mass Stimulation in Other Instances by the Sympathetic and Parasympathetic Systems
Medullary, Pontine, and Mesencephalic Control
of the ANS
Fig Autonomic control areas in the brain stem and hypothalamus