Download Human Physiology - Maryville University

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 9
The Autonomic Nervous System
9-1
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 9 Outline
Introduction
ANS
Neurons
Divisions of ANS
ANS Neurotransmitters
ANS Innervation of Organs
Higher Control of ANS
9-2
Introduction
9-3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Overview
Autonomic
nervous system (ANS) manages our
physiology
By regulating organs & organ systems, & their
smooth muscles & glands
9-4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ANS Control of Smooth Muscle
Smooth
muscle maintains resting tone in absence of
nerve stimulation
Smooth becomes more sensitive when ANS input is
cut (=denervation hypersensitivity)
Many types of smooth are spontaneously active &
contract rhythmically without ANS input
ANS input simply increases or decreases intrinsic
activity
9-5
ANS Neurons
9-6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Autonomic Neurons
 ANS
has 2 neurons in
its efferent pathway
 1st neuron
(=preganglionic
neuron) has cell body
in brain or spinal cord
 Synapses with 2nd
neuron
(=postganglionic
neuron) in an
autonomic ganglion
Fig 9.1
9-7
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Autonomic Neurons
 Postganglionic
axon
extends from
autonomic ganglion to
target tissue
Fig 9.1
9-8
Divisions of the ANS
9-9
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Divisions of the ANS
ANS
has sympathetic & parasympathetic divisions
Usually have antagonistic effects
These coordinate physiology with what’s going on in
person's life
Sympathetic mediates "fight, flight, & stress"
reactions
Parasympathetic mediates "rest & digest"
reactions
9-10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathetic Division
 Is
also called thoracolumbar division because its preganglionics
exit spinal cord from T1 to L2
 Most then synapse on postganglionics in the paravertebral
ganglia
 Which form chain of interconnected ganglia paralleling
spinal cord
Fig 9.2
9-11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathetic Division continued
Is
characterized by divergence & convergence which
cause Symp to mostly act as a unit (mass activation)
9-12
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathetic Division continued
Divergence:
preganglionics branch to synapse with
number of postganglionic neurons
Fig 9.3
9-13
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathetic Division continued
Convergence:
postganglionics receive synaptic input
from large number of preganglionics
Fig 9.3
9-14
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathetic Division continued
 Some
postganglionics
do not synapse in
paravertebral
ganglion but go to
outlying collateral
ganglion
Fig 9.4
9-15
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathoadrenal System
The
adrenal medulla, located in adrenal gland on top
of kidney, appears to be a modified collateral ganglion
Its secretory cells appear to be modified
postganglionics
That release 85% epinephrine (Epi) & 15%
norepinephrine (Norepi) into blood in response to
preganglionic stimulation
Stimulated during mass activation
9-16
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Sympathoadrenal System continued
Epi
is made by methylating Norepi
Fig 9.8
9-17
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parasympathetic Division
Is
also called craniosacral division because long
preganglionics originate in midbrain, medulla, pons, &
S2 - S4
Synapse on postganglionic in terminal ganglia
located next to or within target organ
Postganglionic has short axon that innervates
target
9-18
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Parasympathetic Division continued
The
long vagus nerve carries most Parasymp fibers
Innervates heart, lungs, esophagus, stomach,
pancreas, liver, small intestine, & upper half of the
large intestine
Preganglionic fibers from S2-4 innervate lower half of
large intestine, rectum, urinary & reproductive systems
9-19
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ANS Overview
Fig 9.6
9-20
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
9-21
ANS Neurotransmitters
9-22
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ANS Neurotransmitters
 Both
Symp &
Parasymp
preganglionics release
ACh
 Parasymp
postganglionics also
release ACh
 Called cholinergic
synapses
 Most Symp
postganglionics
release Norepi
(noradenaline)
 Called adrenergic
synapses
 A small number
release ACh
Fig 9.7
9-23
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
ANS Neurotransmitters continued
Postganglionics
Fig 9.9
have unusual
synapses called
varicosities
Which
release NTs
along a
length of
axon
= synapses
en passant
9-24
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Adrenergic Stimulation
 Causes
both excitation & inhibition depending on tissue
 Because of different subtypes of receptors for same NT
 2 major subtypes are  &  adrenergic receptors
 Each has own subtypes: 1, 2 & 1, 2
9-25
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Adrenergic Stimulation continued
 Many
useful drugs
have been developed
to affect ANS
receptors
 Drugs that
promote actions of
a NT are agonists
 Drugs that inhibit
actions of a NT
are antagonists
Fig 9.10
9-26
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Cholinergic Stimulation
ACh
is used at all motor neuron synapses on skeletal
muscle, all preganglionics, & Parasymp
postganglionics
Cholinergic receptors have 2 subtypes:
Nicotinic which is stimulated by nicotine; blocked by
curare
& muscarinic which is stimulated by muscarine (from
poisonous mushrooms); blocked by atropine
9-27
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig 9.11
9-28
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
9-29
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Other ANS NTs
Some
postganglionics do not use Norepi or ACh
Called nonadrenergic, noncholinergic fibers
Appear to use ATP, VIP, or NO as NTs
NO produces smooth muscle relaxation in many
tissues
9-30
ANS Innervation of Organs
9-31
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Organs With Dual Innervation
Most
visceral organs receive dual innervation
(supplied by both Symp & Parasymp)
While 2 branches are usually antagonistic, such as
their effects on heart rate
Can be complementary (cause similar effects) such
as with salivation
Or cooperative (produce different effects that work
together to cause desired effect) such as with
micturition
9-32
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Organs Without Dual Innervation
Regulation
achieved by increasing or decreasing firing
rate
Adrenal medulla, arrector pili muscle, sweat glands, &
most blood vessels receive only sympathetic
innervation
9-33
Higher Control of ANS
9-34
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Control of the ANS by Higher Brain Centers
Medulla
most directly controls activity of ANS
It has centers for control of cardiovascular,
pulmonary, urinary, reproductive, & digestive
systems
Hypothalamus has centers for control of body
temperature, hunger, & thirst; & can regulate medulla
Limbic system is responsible for visceral responses
that reflect emotional states
Cerebral cortex & cerebellum also influence ANS
9-35