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Chapter 16 – Autonomic NS!
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Chapter 16!Neural Integration II: !The Autonomic Nervous System (ANS) and Higher Order Functions!
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SECTION 16-1!The autonomic nervous is involved in the unconscious regulation of visceral functions!!“Autonomic” refers to “automatic” because the system was first thought to work independently from the CNS. This is not the case. Higher centers can influence ANS activities.!
Chapter 16 – Autonomic NS!
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Autonomic Nervous System!
Regulates activities of:!• Smooth muscle!• Cardiac muscle!• Some glands!
Lacrimal, salivary, pancreas, adrenals, etc.!• Adipocytes!
Composed of:!• Sensory and motor neurons, integrating
centers in CNS!(Formerly classified as motor only)!
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General Organization!
Organized into:!• Nerves!• Ganglia!• Plexuses!
Controlled by brain centers!• Hypothalamus, brain stem!
Divisions!• Sympathetic division!• Parasympathetic division!• Enteric division (Chapter 24)!
Chapter 16 – Autonomic NS!
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Somatic vs. Autonomic Organization Figure 16-1!
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Here with a Loaf of Bread beneath the Bough,A Flask of wine, a book of verse—and ThouBeside me singing in the Wilderness—And wilderness is Paradise enow.
Divisions of the ANS!
Chapter 16 – Autonomic NS!
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1. Sympathetic Division Overview!
“Fight-or-flight” – some effects (see also p. 540)!• Increase mental alertness!• Increase metabolic rate!• Increase respiration rate, dilate bronchioles!• Increase HR, BP, blood flow to muscles!• Increase sweat gland activity!• Dilate pupils!• Decrease digestive and urinary functions!• Decrease blood flow to skin!How is each effect useful in an emergency? !
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2. Parasympathetic Division Overview!Vegetative, restorative functions - “anabolic
system” !“SLUDD” responses: !
• Stimulate Salivation, Lacrimation, Urination, Digestion, Defecation!
• Decrease metabolic rate, heart rate, BP!ANS dual innervation of organs!
• Most organs receive input from both divisions!• Effects usually opposite (reciprocal)!
SYMP: ↑ HR PARA: ↓ HR!SYMP: dilate pupils PARA: constrict pupils!
Chapter 16 – Autonomic NS!
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Sympathetic Division Overview Figure 16-2a!
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Parasympathetic Division Overview Figure 16-2b!
Chapter 16 – Autonomic NS!
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(The Thoracolumbar Division)
SECTION 16-2!The sympathetic division is involved in using energy and increasing metabolic rate!
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Sympathetic Division – Organization 9th edition!
Note divergence of pathway
(a.k.a. Postganglionic fibers)
*
Chapter 16 – Autonomic NS!
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Sympathetic Nerve Fibers – 1!
Pathways involve ganglia, preganglionic and ganglionic (postganglionic) fibers!
!Preganglionic fibers
Connect spinal cord to ganglion!• Cell bodies in lateral horns of cord!
Segments T1 to L2!• Axons usually short and myelinated!• Synapse with about 2 dozen postganglionic
cells!
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Sympathetic Nerve Fibers – 2!
Post-ganglionic (ganglionic) fibersConnect ganglion to target organs!
• Cell bodies in ganglion!• Axons usually long and unmyelinated!• Synapse with several target organs!
!Overall, the pathway is highly divergent.!
• Approximately 1:32!
Chapter 16 – Autonomic NS!
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Sympathetic Distribution – “Big Picture”!
Target organs!
Ganglia!
Simplified from Figure 16-4!See Netter plate 163
Postganglionic!(ganglionic)!
fibers!
Spinal cord!segments T1 - L2!
Preganglionic fibers !in white rami!
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Sympathetic Chain Ganglia – 1!
1. Sympathetic chain ganglia!a.k.a. paravertebral or lateral ganglia!• Found lateral to vertebral column!• Preganglionic fibers short, myeliinated!• Postganglionic fibers long (usually),
unmyelinated These leave ganglion via:!• Gray ramus → spinal nerves → visceral
effectors in body wall, head, limbs (refer to Fig. 13-8b)!
• Sympathetic nerves → (autonomic plexuses) → visceral organs in thoracic cavity!
Chapter 16 – Autonomic NS!
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Sympathetic Chain Ganglia – 2 Figure 16-3a!Sympathetic
chain ganglion
Note axoncollateralsSpinal nerves
Visceral effectors in:• Body wall, head, neck, limbs
Sympathetic nerves Visceral organs of:
• Thoracic cavity
Sympathetic chain
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Sympathetic Collateral Ganglia – 1!
2. Collateral ganglia - a.k.a. prevertebral ganglia!• Found just anterior to vertebral column!• Named after nearby artery (e.g. celiac,
inferior and superior mesenteric artery)!• Preganglionic fibers pass through
sympathetic ganglion to enter collateral ganglia via splanchnic nerves!
• Postganglionic fibers leave collateral ganglion, innervate visceral organs in abdominopelvic cavity!
Chapter 16 – Autonomic NS!
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Sympathetic Collateral Ganglia – 2 Figure 16-3b!
Splanchnic nerves To collateral ganglia!Collateral ganglia Innervate visceral organs of ! Abdominopelvic cavity!
Sympathetic chain
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Sympathetic Ganglia – Adrenal Medullae!
3. Adrenal (suprarenal) medullae!• Medulla is a modified sympathetic ganglion!• Preganglionic fibers!
Long (for sympathetic division)!Pass through celiac ganglion!Synapse on postganglionic cells in medulla!
• Postganglionic cells!Called neuroendocrine cells!Secrete epinephrine (E) and some!norepinephrine (NE) into blood!
Chapter 16 – Autonomic NS!
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Sympathetic Ganglia – Adrenal Medullae Fig. 16-3c!
E and NE secreted into blood• Mimic effects of sympathetic innervation!• Also affect cells not directly innervated!• Effects are wide-spread and long-lasting!
Sympathetic chain!
Splanchnic!nerve!
Celiac ganglion!
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Sympathetic Distribution Figure 16-5!Th
orac
ic c
avity!
Abdo
min
opel
vic
cavi
ty!
Chapter 16 – Autonomic NS!
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SECTION 16-3!Stimulation of sympathetic neurons leads to the release of various neurotransmitters!
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Sympathetic Neurotransmitters – 1 Figure 16-5 !
1. Preganglionic fibers!• ALL release ACh!
i.e. “Cholinergic neurons”!
• Effect is always excitatory to postsynaptic cell!
2. Postganglionic fibers!• Neurotransmitter
stored in varicosities
Chapter 16 – Autonomic NS!
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Sympathetic Neurotransmitters – 2!
2. Postganglionic fibers (continued)!A. Most release NE (adrenergic neurons)!B. A few release ACh (cholinergic neurons)!
• In skin (↑ sweat gland activity)!• In brain (dilate blood vessels)!• In skeletal muscle (dilate blood vessels)!
(Isn’t this what you’d want to happen during an emergency??)!
C. Some release NO (Nitric Oxide)!• Dilate blood vessels in brain and skeletal
muscle!
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Duration of Neurotransmitter Effects – 1!
[Neurotransmitter] at synapse affected by:!• Reuptake (into varicosities)!• Diffusion away from receptors!• Enzymatic breakdown…!!
1. Cholinergic effects brief (msec)!• High AChE activity at synapses!• Tissue cholinesterase present in tissues!
Chapter 16 – Autonomic NS!
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Duration of Neurotransmitter Effects – 2!
2. Adrenergic effects at synapse longer lasting (seconds)!• Catecholamines (E and NE) broken down by:!
1. Monoamine oxidase (MAO)!2. Catechol-O-methyltransferase (COMT)!
But…a. [MAO] and [COMT] low in synapses and
tissues!b. MAO and COMT NOT present in blood!
Big picture: Effects of circulating E and NE are very long (to several minutes). !
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Receptor Types!
Adrenergic receptors!• Alpha: α1, α2!• Beta: β1, β2, β3 !
!Cholinergic receptors!
• Nicotinic!• Muscarinic!
Chapter 16 – Autonomic NS!
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Adrenergic Receptors – 1!
Adrenergic receptor subtypes !• Alpha (α) and beta (β)!• Both are G-protein coupled receptors and act
via second messengers!Release Ca2+, affect [cAMP], change enzyme activity!
NE (released at synapses) has highest affinity for α receptors found there!• Localized (synaptic) effects!
E (from adrenals) has high affinity for both α and β!• More widespread effects on receptors
throughout body!
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Adrenergic Receptor – 2!
Effect of E and NE on target cell depends on cell type and receptor subtypes (α1, α2, β1, β2, β3)!
Alpha-1 (α1) receptors - Most common type!• Causes release of Ca2+ from SER!• Usually an excitatory effect, stimulates
metabolism, activates enzymes!• Constricts blood vessels and closes sphincters
in digestive tract, dilates pupils, ↓ secretion by salivary glands!
• Increases force of contraction in heart!(Does this make sense?)!
Chapter 16 – Autonomic NS!
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Adrenergic Receptor – 3!
Alpha-2 (α2) receptors!• Reduces [cAMP] - second messenger!• Generally an inhibitory effect!• ↓ NE release (negative feedback), ↑ blood
clotting, ↑ vasoconstriction, ↑ lipolysis!• Apparently also present in parasympathetic
division - decreases parasympathetic activity during sympathetic activation!
(Does this make sense for sympathetic stimulation?)!
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Adrenergic Receptor – 4!
Beta (β) receptors!• β1: ↑ skeletal muscle activity, ↑ heart rate and
force of contraction• β2: ↓ smooth muscle contraction in respiratory
airways, coronary vessels, and GI tract!(Why would this be useful during stress?)!
• β3: Stimulate lipolysis (?) in adipose tissue !(Why would this be useful during stress?)!
Chapter 16 – Autonomic NS!
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ACh Receptor Types!
All ACh Receptors Bind ACh
Nicotinic Receptors• Bind ACh!• Bind nicotine!• DO NOT bind
muscarine!• Ionotropic!
Muscarinic Receptors• Bind ACh!• Bind muscarine!• DO NOT bind
nicotine!• Metabotropic!
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Cholinergic Receptors – Nicotinic!
ACh receptor types!Nicotinic and muscarinic: !• BOTH TYPES OF RECEPTORS BIND ACH!
!1. Nicotinic ACh receptors are ionotropic!
• On sympathetic and parasympathetic postganglionic (ganglionic) cell bodies (i.e. in ganglia)!
• Open ligand-gated ion channels!• Always excitatory
Chapter 16 – Autonomic NS!
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Cholinergic Receptors – Muscarinic!
2. Muscarinic ACh receptors metabotropic!• On cholinergic sympathetic effectors!• On all parasympathetic effectors!!• Are G-protein coupled receptors!
↑ or ↓ enzyme activity via second messenger!
i.e. excitatory or inhibitory!Longer-lasting effects than nicotinic!
(What’s an effector?)!
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SECTION 16-4!The parasympathetic division is involved in conserving energy and lowering metabolic rate!
Chapter 16 – Autonomic NS!
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Parasympathetic Division Organization!
Less divergent than sympathetic division!
From 9th edition!
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Organization – Parasympathetic Division!
1. Preganglionic cell bodies in brainstem and sacral spinal cord (i.e. craniosacral division)!A. Midbrain, pons, medulla: CN III, VII, IX and X!B. Sacral segments S2 - S4 (lateral horns)!
2. Ganglia!• Preganglionic cells → 6 to 8 postganglionic cells
in ganglion!• Postganglionic cells → usually only one target
organ!• i.e. pathway much less divergent than
sympathetic division!
Chapter 16 – Autonomic NS!
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Parasympathetic Ganglion Types, Fiber Lengths!
A. Terminal ganglia!• Located near target organ!• e.g. Ciliary ganglion, submandibular
ganglion!B. Intramural ganglia (mural = “wall”)!
• Located in walls of target organ!• e.g. in heart, lungs!
Fiber lengths!• Preganglionic fibers long!• Postganglionic fibers short!
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Parasympathetic Distribution Figure 16-6!
Terminal ganglia!
Intramural ganglia!
Chapter 16 – Autonomic NS!
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SECTION 16-6!The sympathetic and parasympathetic divisions interact, creating dual innervation!
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Dual Innervation!
Most organs are innervated by both divisions.!Autonomic plexuses:!
• Contain both parasympathetic and sympathetic nerve fibers!
• Found in thoracic, abdominal and pelvic regions!
• Are networks of:!Sympathetic and parasympathetic nerves!Sympathetic ganglia!Sensory neuron axons!
Chapter 16 – Autonomic NS!
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Autonomic Plexuses – Examples!
Cardiac plexus!• Surrounds heart and major vessels!
Pulmonary plexus!• Posterior to each lung!
Celiac (solar) plexus!• Celiac ganglion near celiac trunk!• Distributes to digestive organs!
Superior mesenteric plexus - Small and large intestine!Inferior mesenteric plexus - Large intestine!
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Autonomic Tone!
Background level of activity by both divisions!• Allows adjustments of activity by either
increasing or decreasing background level!e.g. heart rate regulation!
• Parasympathetic input dominates at rest!• Increase heart rate by:!
Increase sympathetic input !- OR -!
Decrease parasympathetic input!
Chapter 16 – Autonomic NS!
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Differences Between the Divisions Figure 16-7!
ACh: nicotinic!
Usually NE;!Some ACh!(muscarinic);!Some NO!
ACh: muscarinic!
ACh: nicotinic!
Adrenals: NE, E!
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SYMP vs. PARA Comparison Table 16-2!
Hint: The information contained in this table and on the previous
slide is important.!
Chapter 16 – Autonomic NS!
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Functional Comparison Table 16-3!
Look over Table 16-3 for an interesting comparison of sympathetic and parasympathetic functions.!
Don’t memorize a bunch of details like receptor subtypes. !
!!!!I.e., concentrate on the “big picture.”!
Make sure that the information makes sense to you in terms of the overall functions of the two divisions.
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SECTION 16-7!Visceral reflexes play a role in the integration and control of autonomic functions!
Chapter 16 – Autonomic NS!
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Visceral Reflexes Are All Polysynaptic!
Are automatic (reflexive) responses!Can be influenced by higher centers
(especially hypothalamus)!Long Reflexes!
• Processing occurs in CNS• Affect activities of an entire target organ!
Short (local) Reflexes!• Do not involve CNS – synapse in autonomic
ganglia instead!• Affect localized area of a target organ!• Especially important in digestive system!
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Visceral Reflexes Figure 16-9!
Most visceral reflexes are
parasympathetic!
Chapter 16 – Autonomic NS!
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Visceral Reflexes Figure 24-5!
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Example of Short Visceral Reflex Figure 24-15.2!
Actions: Increased secretion by mucous, chief and parietal cells Increased stomach motility (mixing movements)
Short reflex
Chapter 16 – Autonomic NS!
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Representative Visceral Reflexes Table 16-4!
Read for understanding.!
Do not simply m
emorize this t
able.!
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Comparison of ANS and SNS Figure 16-10!
F.Y.I.!
Chapter 16 – Autonomic NS!
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Comparison of ANS and SNS Table 16-5!
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SECTION 16-10!Aging produces various structural and functional changes in the nervous system!
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Aging and the Nervous System!
1. Decreased number of neurons!2. Decreased brain size and weight!
• Wider sulci, narrower gyri!3. Decreased blood flow to brain!4. Decreased number of dendrites and synapses!5. Accumulation of plaques (extracellular proteins)!
☞ Such changes do not occur in !Clark College A&P professors. But I might be
forgetting…!End exam 2, Winter 2017!
