CHAPTER 16: AUTONOMIC NERVOUS SYSTEM
I. INTRODUCTION
A. P. N. S. - EFFERENT BRANCH
- SOMATOMOTOR vs. A.N.S. (KNOW Tab. 16.1, p. 559)
1. SOMATOMOTOR: 1 Neuron, C.N.SèSkeletal muscle
2. A.N.S.: 2 Neurons, C.N.S èSmooth mus., cardiac mus., glands
- Figure 16.1, p. 565
a. PREGANGLIONIC - C.N.S.èGANGLION
- MYELINATED
b. POSTGANGLIONIC: - GANGLION èEFFECTOR
- UNMYELINATED
B. 2 DIVISIONS OF A.N.S.
1. SYMPATHETIC DIVISION
2. PARASYMPATHETIC DIVISION
(3. ENTERIC - walls of G.I. tract - both SYM & PARA)
II. SYMPATHETIC DIVISION = THORACOLUMBAR (T1-L2) (Fig. 16.2, p. 560)
A. 4 PATHWAYS (Fig. 16.3, p. 561)
- ALL have Preganglionic bodies in LATERAL HORNS
1. SPINAL NERVES (A)
a. PREGANGLIONIC N. è VENTRAL ROOT è SPINAL NERVE è
WHITE RAMUS COMMUNICANS èSYNAPSE @ SYMPATHETIC CHAIN è POSTGANGLIONIC N. è GRAY RAMUS è
SPINAL NERVE èEFFECTOR
b. May synapse at same level, ascend or descend.
c. Effectors = SKIN BELOW NECK: sweat glands, vessels, arrector pili
2. SYMPATHETIC NERVES (B)
a. PREGANGLIONIC N.è VENTRAL ROOT è SPINAL NERVE è
WHITE RAMUS COMMUNICANS èSYNAPSE @ SYMPATHETIC
CHAIN è POSTGANGLIONIC N. è SYMPATHETIC NERVE è
EFFECTOR
b. May synapse at same level, ascend or descend
c. Effectors = Head & neck sweat glands, salivary glands,
heart, thoracic vessels, esophagus, lungs & eye
3. SPLANCHNIC NERVES (C) GK = VISCERA
a. PREGANGLIONIC N.è VENTRAL ROOT è SPINAL NERVE
è WHITE RAMUS COMMUNICANS è THROUGH
SYMPATHETIC CHAIN è SPLANCHNIC NERVES è
SYNAPSE @ COLLATERAL GANG. è
POSTGANGLIONIC N. èEFFECTOR:
1. CELIAC Ganglion (“solar plexus”)
2. SUPERIOR MESENTERIC Ganglion
3. INFERIOR MESENTERIC Ganglion
b. Pregang. may pass through same level, ascend or descend
c. Effectors = Abdominopelvic organs, vessels & glands
4. ADRENAL NERVES (D)
a. PREGANGLIONIC N.è VENTRAL ROOT è SPINAL NERVE
è WHITE RAMUS COMMUNICANS è THROUGH
SYMPATHETIC CHAIN è SPLANCHNIC NERVES è
THRU/BY COLLATERAL GANGLIA è POSTGANG. N. è
SYNAPSE @ ADRENAL MEDULLA èPOLYHEDRAL
CELLS (= POST-GANGLIONIC CELLS) è
é EPINEPHRINE/N.E.
b. Pregang. may pass through same level, ascend or descend
c. Effectors = Adrenal medulla
B. NOTE/REMINDER:
1. PREGANGLIONIC N. = MYELINATED
2. POSTGANGLIONIC N. = UNMYELINATED
III. PARASYMPATHETIC DIVISION (CRANIOSACRAL) (Fig. 16.4, p. 562)
A. PATHWAY:
1. PREGANGLIONIC BODIES IN EITHER:
a. CRANIAL NUCLEI IN BRAINSTEM
b. LATERAL GRAY HORNS OF S2 è S4
2. GO OUT TO CRANIAL OR PELVIC NERVES
3. VERY LONG PREGANGLIONIC AXON
4. TERMINAL GANGLIA IN, ON OR NEAR EFFECTORS
B. CRANIAL NERVES - III, VII, IX & X
1. III (Oculomotor) to eyes
2. VII (Facial) to salivary & lacrimal glands
3. IX (Glossopharyngeal) to salivary glands
4. X (Vagus) to heart, lungs & viscera
a. Carries 3/4 of all PARASYMPATHETIC N. in body
C. PELVIC NERVES - S2 è S4
1. To colon, rectum, bladder & genitals
IV. STRUCTURAL COMPARISON - (KNOW Tab. 16.2, p. 563)
SYMPATHETIC PARASYMPATHETIC
A. PREGANGLIONIC BODIES THORACOLUMB. BRAINSTEM & SACRAL
B. C.N.S.èP.N.S. OUTFLOW SPINAL, SYMP. CRANIAL & PELVIC N.
& SPLANCHNIC
C. GANGLIA SYMP. CHAIN & TERMINAL GANGLIA
COLLATERAL; NEAR/AT Effector
FAR from Eff.
D. PRE/POST GANG. RATIO 1:17 more divergent 1:2 less divergent
(more general) (more specific, local.)
E. PREGANG. NEURON SHORT LONG
F. POSTGANGLIONIC NEURON LONG SHORT
V. NEUROTRANSMITTERS & RECEPTORS (Fig. 16.6, p. 566)
A. NEUROTRANSMITTERS - 2 TYPES
1. CHOLINERGIC FIBERS - secrete ACETYLCHOLINE (ACh)
2. ADRENERGIC FIBERS - secrete NOREPINEPHRINE (NE)
3. ALL PREGANGLIONIC FIBERS = CHOLINERGIC
a. SYMPATHETIC
b. PARASYMPATHETIC
4. ALL POSTGANG. PARASYMPATHETIC FIBERS = CHOLINERGIC
5. MOST POSTGANG. SYMPATHETIC FIBERS = ADRENERGIC
(A few are cholinergic - sweat glands & some vessels)
B. RECEPTORS - 2 TYPES
1. CHOLINERGIC (ACh) – 2 categories:
a. NICOTINIC - bind to & stim. by NICOTINE
i. ALL POSTGANG. NEURONS (SYMP & PARA)
ii. EXCITATORY
b. MUSCARINIC - bind to & stim. by MUSCARINE
i. ALL EFFECTORS that respond to ACh (SYM. & PARA)
ii. EXCITE or INHIBIT EFFECTOR
2. ADRENERGIC (NE) – 2 categories:
- ONLY in EFFECTORS OF SYMPATHETIC neurons
a. ALPHA - greater affinity for N.E.
b. BETA - less affinity for N.E.
c. EXCITE or INHIBIT
d. EPINEPHRINE binds EQUALLY to ALPHA & BETA
e. EFFECTORS may have varying #s of ALPHA & BETA rec.
VI. A. N. S. REGULATION
A. UNCONSCIOUS MAINTENANCE OF HOMEOSTASIS
1. AUTONOMIC REFLEXES - MANY
a. BARORECEPTORS - B.P. (Fig 16.7, p. 570)
b. RESPIRATION
c. TEMPERATURE
d. pH
2. BRAIN PARTS INVOLVED (Fig 16.8, p. 571)
a. CEREBRUM
b. HYPOTHALAMUS - LIMBIC SYSTEM
*c. BRAINSTEM - KEY - esp. MEDULLA OBLONGATA
d. SPINAL CORD
VII. FUNCTIONAL GENERALIZATIONS - MANY EXCEPTIONS
A. SYMP & PARA can both STIMULATE & INHIBIT
B. DUAL INNERVATION - MOST EFF./ORGANS served by SYMP & PARA
(Fig. 16.9, p. 573 & Fig. 16.5, p. 564)
C. OPPOSITE EFFECTS (Tab. 16.3, p. 567)
1. SYMPATHETIC - USUALLY EXCITATORY
a. PREPARE FOR PHYSICAL ACTIVITY
b. é blood to skel. muscle, é metabolism
c. “Fight or flight”
d. MORE GENERAL, LESS SPECIFIC
2. PARASYMPATHETIC - USUALLY INHIBITORY TO PHYS. ACT.
a. STIM. TO “VEGETATIVE” FUNCTIONS, at REST
b. Eating, digestion, urination, defecation
c. MORE SPECIFIC & LOCALIZED
D. COOPERATIVE EFFECTS
1. REPRODUCTION – male
a. PARA - Erection
b. SYMP - Ejaculation
V. NEUROTRANSMITTERS & RECEPTORS (Fig. 16.6, p. 566)
A. NEUROTRANSMITTERS - 2 TYPES
1. CHOLINERGIC FIBERS - secrete ACETYLCHOLINE (ACh)
2. ADRENERGIC FIBERS - secrete NOREPINEPHRINE (NE)
3. ALL PREGANGLIONIC FIBERS = CHOLINERGIC
a. SYMPATHETIC
b. PARASYMPATHETIC
4. ALL POSTGANG. PARASYMPATHETIC FIBERS = CHOLINERGIC
5. MOST POSTGANG. SYMPATHETIC FIBERS = ADRENERGIC
(A few are cholinergic - sweat glands & some vessels)
B. RECEPTORS - 2 TYPES
1. CHOLINERGIC (ACh)
a. NICOTINIC - bind to & stim. by NICOTINE
i. ALL POSTGANG. NEURONS (SYMP & PARA)
ii. EXCITATORY
b. MUSCARINIC - bind to & stim. by MUSCARINE
i. ALL EFFECTORS that respond to ACh (SYM. & PARA)
ii. EXCITE or INHIBIT EFFECTOR
2. ADRENERGIC (NE)
- ONLY in EFFECTORS OF SYMPATHETIC neurons
a. ALPHA - greater affinity for N.E.
b. BETA - less affinity for N.E.
c. EXCITE or INHIBIT
d. EPINEPHRINE binds EQUALLY to ALPHA & BETA
e. EFFECTORS may have varying #s of ALPHA & BETA rec.