Chapter 16 – Autonomic NS 1 Chapter 16 Neural Integration II: The Autonomic Nervous System (ANS) and Higher Order Functions 2 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.
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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!
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? !
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:!
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!
Chapter 16 – Autonomic NS!
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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