The Nervous System: Autonomic Nervous System 218/17_lecture...The Nervous System: Autonomic Nervous System ... Cranial nerves ... • Acceleration of blood flow to skeletal muscles

© 2012 Pearson Education, Inc.

17 The Nervous System:

Autonomic Nervous

System

PowerPoint® Lecture Presentations prepared by

Steven Bassett

Southeast Community College

Lincoln, Nebraska


Introduction

• The autonomic nervous system functions

outside of our conscious awareness

• The autonomic nervous system makes

routine adjustments in our body’s systems

• The autonomic nervous system:

• Regulates body temperature

• Coordinates cardiovascular, respiratory,

digestive, excretory, and reproductive

functions


A Comparison of the Somatic and Autonomic

Nervous Systems

• Autonomic nervous system

• Axons innervate the visceral organs

• Has afferent and efferent neurons

• Afferent pathways originate in the visceral receptors

• Somatic nervous system

• Axons innervate the skeletal muscles

• Has afferent and efferent neurons

• Afferent pathways originate in the skeletal muscles

ANIMATION The Organization of the Somatic and

Autonomic Nervous Systems

somatic_autonomic_nervous_sys.html


Subdivisions of the ANS

• The autonomic nervous system consists of

two major subdivisions

• Sympathetic division

• Also called the thoracolumbar division

• Known as the “fight or flight” system

• Parasympathetic division

• Also called the craniosacral division

• Known as the “rest and repose” system


Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 1 of 2)

Anatomical subdivisions. At the thoracic and lumbar

levels, the visceral efferent fibers that emerge form the

sympathetic division, detailed in Figure 17.4. At the

cranial and sacral levels, the visceral efferent fibers

from the CNS form the parasympathetic division,

detailed in Figure 17.8.

Thoracic

nerves

T1

T2

T3

T4

T5

T6

T7

T8

AUTONOMIC NERVOUS SYSTEM

THORACOLUMBAR DIVISION

(sympathetic

division of ANS)

CRANIOSACRAL DIVISION

(parasympathetic

division of ANS)

Cranial nerves

(N III, N VII, N IX,

and N X)


Figure 17.1b Components and Anatomic Subdivisions of the ANS (Part 2 of 2)

Anatomical subdivisions. At the thoracic and lumbar

levels, the visceral efferent fibers that emerge form the

sympathetic division, detailed in Figure 17.4. At the

cranial and sacral levels, the visceral efferent fibers

from the CNS form the parasympathetic division,

detailed in Figure 17.8.

Sacral

nerves

(S2, S3, S4 only)

Lumbar

nerves (L1, L2 only)

Thoracic

nerves

T10

T11

T12

L1

L2

L3

L4

L5

S1

S2

S3

S4

S5

T9




• Thoracic and upper lumbar nerves synapse in

ganglia near the spinal cord

• Sympathetic activation results in:

• Increased metabolism and alertness


• Synapses are located near the target organ

• Parasympathetic activation results in:

• Energy conservation




• All preganglionic fibers release acetylcholine.

The effects are stimulatory.

• Most postganglionic fibers release

norepinephrine.The effects are stimulatory.


• All preganglionic fibers release acetylcholine.

The effects are stimulatory.

• Postganglionic fibers release acetylcholine but

the effects can be inhibitory.


Figure 17.1a Components and Anatomic Subdivisions of the ANS

AUTONOMIC NERVOUS SYSTEM

Consists of 2 divisions

SYMPATHETIC

(thoracolumbar)

DIVISION

PARASYMPATHETIC

(craniosacral)

DIVISION

Preganglionic

neurons in

lateral gray horns of

spinal segments T1–L2

Preganglionic neurons in brain

stem and in lateral portion of anterior

gray horns of S2–S4

Send preganglionic

fibers to

Which send postganglionic

fibers to

Ganglia near

spinal cord

Ganglia in or

near target organs

Preganglionic fibers release ACh (excitatory),

stimulating ganglionic neurons

Preganglionic fibers release ACh (excitatory),

stimulating ganglionic neurons

Target organs Target organs

Most postganglionic fibers release NE at

neuroeffector junctions

All postganglionic fibers release ACh at


“Fight or flight”

response “Rest and repose”

response

Functional components of the ANS


The Sympathetic Division

• Sympathetic division consists of:

• Preganglionic neurons between T1 and L2

• Two types of ganglionic neurons near the

vertebral columns: sympathetic chain

ganglia (lateral to the vertebral column) and

collateral ganglia (anterior to the vertebral

column)

• Specialized neurons in the interior of the

suprarenal gland




• Preganglionic neurons

• Cell bodies are in the lateral gray horns

• Axons enter the ventral roots

• Sympathetic chain ganglia (paravertebral

ganglia)

• Control effectors in the body wall, head, neck,

limbs, and thoracic cavity



•Sympathetic division

• Collateral ganglia (prevertebral ganglia)

• Neurons innervate effectors in the abdominopelvic

cavity

• Specialized neurons

• Modified sympathetic ganglion in the suprarenal

gland

• Neurons release neurotransmitters that act like

hormones


Figure 17.2 Organization of the Sympathetic Division of the ANS

Preganglionic fibers

Postganglionic fibers

Hormones released

into circulation

KEY

Lateral gray

horns of spinal

segments

T1–L2

Sympathetic

chain ganglia

(paired)

Collateral

ganglia

(unpaired)

Suprarenal

medullae

(paired)

Preganglionic Neurons

Ganglionic Neurons

Innervation by

postganglionic

fibers

Through release of

hormones into

the circulation

Target Organs

Visceral effectors

in thoracic cavity,

head, body wall,

and limbs

Visceral effectors

in abdominopelvic

cavity

Organs and systems

throughout body

Sympathetic Division of ANS



• Sympathetic Chain Ganglia

• The ventral root joins a dorsal root

• Forms a spinal nerve

• Passes through an intervertebral foramen

• White ramus branches off the spinal nerve

• Goes to a nearby sympathetic chain ganglion



• Functions of Sympathetic Chain Ganglia

• Reduction of circulation to the skin

• More circulation to skeletal muscles

• Stimulates more energy production by skeletal

muscles

• Releases stored adipose

• Stimulation of arrector pili muscles

• Dilation of pupils

• Increased heart rate

• Dilation of respiratory tubes


Figure 17.3a Sympathetic Pathways and Their General Functions

Sympathetic Chain Ganglia

KEY Preganglionic neurons

Ganglionic neurons

Innervates visceral

organs in thoracic

cavity via

sympathetic nerves

Sympathetic nerve

(postganglionic

fibers)

Autonomic ganglion

of left sympathetic chain

Spinal nerve Preganglionic

neuron

Autonomic ganglion of

right sympathetic chain

Innervates

visceral

effectors via

spinal nerves

White

ramus

Ganglionic

neuron

Gray ramus

Major effects produced by sympathetic postganglionic

fibers in spinal nerves:

Major effects produced by postganglionic fibers

entering the thoracic cavity in sympathetic nerves:

• Constriction of cutaneous blood vessels, reduction

in circulation to the skin and to most other organs in

the body wall

• Acceleration of blood flow to skeletal muscles

and brain • Stimulation of energy production and use by skeletal

muscle tissue

• Release of stored lipids from subcutaneous

adipose tissue

• Stimulation of secretion by sweat glands • Stimulation of arrector pili

• Dilation of the pupils and focusing for distant objects

• Acceleration of heart rate and increasing the

strength of cardiac contractions

• Dilation of respiratory passageways



• Anatomy of the Sympathetic Chain Ganglia

• Each spinal nerve consists of:

• Preganglionic and postganglionic fibers

• There are:

• cervical sympathetic chain ganglia

• thoracic sympathetic chain ganglia

• lumbar sympathetic chain ganglia

• sacral sympathetic chain ganglia

• coccygeal sympathetic chain ganglia


Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers

Superior

Middle

Inferior

PONS

Cervical

sympathetic

ganglia

Gray rami to

spinal nerves

Greater

splanchnic

nerve

Superior

mesenteric

ganglion

Cardiac and

pulmonary

plexuses

Celiac ganglion

Sympathetic nerves

T1 T1

T2 T2

T3 T3

T4 T4

T5 T5

T6 T6

T7 T7

T8 T8

T9 T9

T10 T10

T11 T11

T12 T12

L1 L1

L2 L2

L3 L3

L4 L4

L5 L5 S1 S1 S2 S2

S3 S3 S4 S4

S5 S5


to spinal nerves

(innervating skin, blood

vessels, sweat glands,

arrector pili muscles,

adipose tissue)

Sympathetic

chain ganglia

Spinal cord

Coccygeal

ganglia (Co1)

fused together

(ganglion impar)

Preganglionic neurons

Ganglionic neurons

KEY

Uterus Ovary

Sacral

splanchnic

nerves

Lesser

splanchnic

nerve

Lumbar

splanchnic nerves Inferior

mesenteric

ganglion

Penis Scrotum Urinary bladder

Kidney

Suprarenal

medulla

Small intestine

Large intestine

Pancreas

Spleen

Stomach

Liver and

gallbladder

Lung

Heart

Eye

Salivary

glands



• Collateral Ganglia

• Preganglionic neurons originate in the inferior

thoracic and superior lumbar areas of the spinal

cord

• Fibers pass through the sympathetic chain

ganglia without synapsing

• Converge to form the greater, lesser, and

lumbar splanchnic nerves

• Splanchnic nerves converge on the collateral

ganglia



• Functions of the Collateral Ganglia

• Reduction of flow of blood to the visceral organs

• Decrease in activity of the digestive organs

• Stimulation of the release of glucose from glycogen in the liver

• Stimulates adipose cells to release energy reserves

• Relaxation of smooth muscles in the urinary bladder

• Cause ejaculation in males


Figure 17.3b Sympathetic Pathways and Their General Functions

Collateral Ganglia

Lateral gray horn

White

ramus

Collateral

ganglion Postganglionic

fibers

Splanchnic nerve

(preganglionic

fibers)

Innervates

visceral organs in

abdominopelvic

cavity

Major effects produced by preganglionic fibers

innervating the collateral ganglia:

• Constriction of small arteries and reduction in the

flow of blood to visceral organs

• Decrease in the activity of digestive glands and

organs

• Stimulation of the release of glucose from glycogen

reserves in the liver • Stimulation of the release of lipids from adipose

tissue • Relaxation of the smooth muscle in the wall of the

urinary bladder

• Reduction of the rate of urine formation at the

kidneys

• Control of some aspects of sexual function, such as

ejaculation in males



• Anatomy of the Collateral Ganglia

• Splanchnic nerves innervate:

• Celiac ganglion: fibers innervate the stomach,

duodenum, liver, gallbladder, pancreas, spleen, and

kidney

• Superior mesenteric ganglion: fibers innervate the

small intestine and the first parts of the large

intestine

• Inferior mesenteric ganglion: fibers innervate the

kidney, urinary bladder, sex organs, and terminal

ends of the large intestine



• Suprarenal Medullae

• Fibers pass through sympathetic chain and the

celiac ganglion without synapsing

• Proceed to the suprarenal medulla

• Fibers then synapse on modified neurons that

when stimulated will release neurotransmitters

that act as hormones:

• Epinephrine and norepinephrine



• Functions of the suprarenal medullae

• Increase alertness by activating the reticular

activating system

• Increase cardiovascular and respiratory activity

• Increase muscle tone

• Increase the mobilization of energy reserves

• Increased release of lipids from adipose cells

• Increased breakdown of glycogen in liver cells


Figure 17.3c Sympathetic Pathways and Their General Functions

The Suprarenal Medullae

Secretes

neurotransmitters

into general

circulation

Suprarenal

medullae


Endocrine cells

(specialized ganglionic

neurons)

• Release of epinephrine and norepinephrine into

the general circulation

Major effect produced by preganglionic fibers

innervating the suprarenal medullae:


Figure 17.5a Suprarenal Medulla

Relationship of a suprarenal gland to a kidney

Cortex

Medulla

Suprarenal

gland

Right

kidney


Figure 17.5ab Suprarenal Medulla

Relationship of a suprarenal gland to a kidney Histology of the suprarenal medulla,

a modified sympathetic ganglion

Suprarenal medulla LM 426

Capillaries Modified neurons

(sympathetic ganglion cells)

of suprarenal medulla

Nucleolus

in nucleus

Cortex

Medulla



• Sympathetic activation and neurotransmitter release

• Sympathetic ganglion fibers release acetylcholine at

the synapse with ganglionic neurons

• These are cholinergic synapses

• The stimulation of ganglionic neurons causes the

release of norepinephrine at the neuroeffector

junction

• These terminals are adrenergic

• Some ganglionic neurons also release acetylcholine

• Especially at the neuroeffector junctions of skeletal

muscles


Figure 17.6 Sympathetic Postganglionic Nerve Endings Preganglionic fiber

(myelinated) Ganglionic

neuron

Ganglion

Postganglionic fiber

(unmyelinated)

Varicosities

Mitochondrion

5 m

Vesicles containing

norepinephrine

Schwann cell

cytoplasm

Smooth muscle cells Varicosities



• Summary of the Sympathetic Division

• Consists of parallel chains on either side of the spinal

cord

• Preganglionic fibers are short and extend from the

spinal cord to the sympathetic chain

• Postganglionic fibers are long and extend from the

spinal cord to the body organs

• The sympathetic division shows considerable

divergence

• All preganglionic neurons release ACh / most

postganglionic neurons release norepinephrine


Figure 17.4 Anatomical Distribution of Sympathetic Postganglionic Fibers

Superior

Middle

Inferior

PONS

Cervical

sympathetic

ganglia

Gray rami to

spinal nerves

Greater

splanchnic

nerve

Superior

mesenteric

ganglion

Cardiac and

pulmonary

plexuses

Celiac ganglion

Sympathetic nerves

T1 T1

T2 T2

T3 T3

T4 T4

T5 T5

T6 T6

T7 T7

T8 T8

T9 T9

T10 T10

T11 T11

T12 T12

L1 L1

L2 L2

L3 L3

L4 L4

L5 L5 S1 S1 S2 S2

S3 S3 S4 S4

S5 S5


to spinal nerves

(innervating skin, blood

vessels, sweat glands,

arrector pili muscles,

adipose tissue)

Sympathetic

chain ganglia

Spinal cord

Coccygeal

ganglia (Co1)

fused together

(ganglion impar)


Ganglionic neurons

KEY

Uterus Ovary

Sacral

splanchnic

nerves

Lesser

splanchnic

nerve

Lumbar

splanchnic nerves Inferior

mesenteric

ganglion

Penis Scrotum Urinary bladder

Kidney

Suprarenal

medulla

Small intestine

Large intestine

Pancreas

Spleen

Stomach

Liver and

gallbladder

Lung

Heart

Eye

Salivary

glands



ANIMATION The Distribution of Sympathetic Innervation

sympathetic_innervation.html


The Parasympathetic Division

• Parasympathetic Division

• Preganglionic neurons are in the brain stem and

sacral segments

• Preganglionic neurons do not diverge as much

as the sympathetic division

• Therefore, the parasympathetic division is more

localized and specific as compared to the

sympathetic division

• Postganglionic neurons are near (terminal) the

target organ or within (intramural) the target

organ



• Organization and Anatomy of the

Parasympathetic Division

• Preganglionic fibers leave the brain via:

• CN III (to the intrinsic eye muscles, pupil, and lens)

• CN VII (to the tear glands and salivary glands)

• CN IX (to the parotid salivary glands)

• CN X (to the visceral organs of the thoracic cavity

and abdominal cavity)

• Preganglionic fibers leave the sacral region via:

• Pelvic nerves (to the visceral organs in the inferior

portion of the abdominopelvic cavity


Figure 17.7 Organization of the Parasympathetic Division of the ANS

Parasympathetic Division of ANS

Preganglionic Neurons Ganglionic Neurons Target Organs

Ciliary ganglion

Pterygopalatine

and submandibular

ganglia

Otic ganglion

Intramural ganglia

Intrinsic eye muscles (pupil and lens shape)

Nasal glands, tear glands, and salivary

glands

Visceral organs of neck,

thoracic cavity, and most of

abdominal cavity

N III

N VII

N IX

N X

Nuclei in brain stem

Nuclei in spinal cord segments

S2–S4

Pelvic nerves Intramural

ganglia

Visceral organs in inferior portion of

abdominopelvic cavity

KEY



Parotid salivary gland


Figure 17.8 Autonomic Distribution of the Parasympathetic Output Pterygopalatine ganglion

PONS

N III

N VII

N IX

N X (Vagus)

Ciliary ganglion

Submandibular

ganglion

Otic ganglion

Autonomic plexuses

(see Figure 17.9)

Pelvic

nerves

Lacrimal gland

Eye

Salivary glands

Heart

Lungs

Liver and

gallbladder

Stomach

Spleen

Pancreas

Large intestine

Small intestine

Rectum

Kidney

Urinary bladder Scrotum Penis Ovary Uterus

S2

S3

S4

Spinal

cord


Ganglionic neurons

KEY



• Functions of the Parasympathetic Division

• Pupil constriction

• Secretion of digestive enzymes from digestive glands

• Increased smooth muscle activity of the digestive system

• Stimulation and coordination of defecation

• Contraction of the urinary bladder

• Constriction of respiratory passages

• Reduced heart rate

• Sexual arousal



• Parasympathetic Activation and

Neurotransmitter Release

• All preganglionic and postganglionic fibers

release ACh at their synapses and


• Most stimulations are short lived due to the

immediate breakdown of ACh by

acetylcholinesterase



• Plasmalemma Receptors and Responses

• Two types of ACh receptors are found on the postsynaptic plasmalemmae: • Nicotinic receptors: respond to nicotine

• Found on surfaces of parasympathetic and sympathetic ganglionic neurons

• Muscarinic receptors: respond to muscarine

• Found on surfaces of parasympathetic cholinergic neuroeffector junctions



• Summary of the Parasympathetic Division

• Involves CN III, CN VII, CN IX, and CN X

• Involves sacral segments S2 to S4

• All parasympathetic neurons are cholinergic

• Release of ACh stimulates nicotinic receptors

on ganglionic neurons

• Release of ACh on neuroeffector junctions

stimulates muscarinic receptors



ANIMATION The Distribution of Parasympathetic Innervation

parasympathetic_innervation.html


Relationships between the Sympathetic and

Parasympathetic Divisions

• Sympathetic

• Widespread effect on visceral organs

• Parasympathetic

• Modifies the activity of structures innervated by

specific cranial nerves and pelvic nerves

• Most vital organs are innervated by both the

sympathetic and parasympathetic nerves

• The two often oppose (antagonistic) each other


Figure 17.10 A Comparison of the Sympathetic and Parasympathetic Divisions

Sympathetic Parasympathetic

CNS

PNS

KEY

Sympathetic

ganglion

Circulatory

system

Preganglionic

neuron

Preganglionic

fiber

Ganglionic

neurons

Postganglionic

fiber

TARGET

Parasympathetic

ganglion

Neurotransmitters

Acetylcholine

Norepinephrine

Epinephrine or


• Anatomy of Dual Innervation

• Head region

• The parasympathetic fibers accompany the

sympathetic fibers to the target organ

• Thoracic and abdominopelvic regions

• The parasympathetic and sympathetic fibers mingle

together forming plexuses

• Cardiac plexus

• Pulmonary plexus

• Esophageal plexus

• Celiac plexus

• Inferior mesenteric plexus

• Hypogastric plexus

Relationships between the Sympathetic and

Parasympathetic Divisions


Figure 17.9a The Peripheral Autonomic Plexuses

This is a diagrammatic view of the distribution of ANS plexuses in the

thoracic cavity (cardiac, esophageal, and pulmonary plexuses) and the

abdominopelvic cavity (celiac, inferior mesenteric, and hypogastric plexuses).

Splanchnic

nerves

Inferior mesenteric

artery

Superior mesenteric

artery

Celiac trunk

Diaphragm

Esophagus

Thoracic

spinal

nerves

Left vagus nerve

Right vagus nerve

Aortic arch

Trachea

Cardiac plexus

Autonomic Plexuses

and Ganglia

Pulmonary plexus

Thoracic sympathetic

chain ganglia

Esophageal plexus

Celiac plexus and

ganglion

Superior mesenteric

ganglion

Inferior mesenteric

plexus and ganglion

Pelvic sympathetic

chain

Hypogastric plexus


Figure 17.9b The Peripheral Autonomic Plexuses

A sectional view of the autonomic plexuses

Cardiac plexus

Autonomic Plexuses

and Ganglia

Thoracic sympathetic

chain ganglia

Esophageal plexus

Celiac plexus and

ganglion

Superior mesenteric

ganglion

Inferior mesenteric

plexus and ganglion

Pelvic sympathetic

chain

Hypogastric plexus

Urinary

bladder

Colon

Stomach

Diaphragm

Heart

Esophagus

Trachea

Vagus nerve

(N X)

Cranial nerve III

Cranial nerve VII

Cranial nerve IX


Visceral Reflexes

• Provide autonomic motor responses to:

• Modify or facilitate higher centers

• All are polysynaptic

• Reflexes can be:

• Long reflexes

• Short reflexes


Visceral Reflexes

•Long Reflexes

• Visceral sensory neurons go to the CNS via the

dorsal roots

• There are interneurons within the CNS

• Information is “interpreted” in the spinal cord or

brain

• ANS sends motor commands to the visceral

organs


Visceral Reflexes

• Short Reflexes

• Sensory nerve impulses go to the ganglionic

neurons

• Motor commands are distributed by the

postganglionic fibers

• Impulses bypass the CNS


Figure 17.11 Visceral Reflexes

Stimulus

Response

Receptors in

peripheral tissue Afferent (sensory)

fibers

Short

reflex

Long

reflex

Peripheral

effector

Ganglionic

neuron

Preganglionic

neuron

Processing center

in spinal cord

(or brain)

Autonomic ganglion

(sympathetic or

parasympathetic)

CENTRAL NERVOUS

SYSTEM

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The Nervous System: Autonomic Nervous System 218/17_lecture...The Nervous System: Autonomic Nervous System ... Cranial nerves ... • Acceleration of blood flow to skeletal muscles