© 2015 Pearson Education, Inc. Lecture Presentation by Lee Ann Frederick University of Texas at Arlington Chapter 16 The Autonomic Nervous System and Higher-Order.

© 2015 Pearson Education, Inc.

Lecture Presentation by Lee Ann Frederick

University of Texas at Arlington

Chapter 16

The Autonomic Nervous System and

Higher-Order Functions


An Introduction to the ANS and Higher-Order Functions

• Learning Outcomes• 16-1 Compare the organization of the autonomic

nervous system with that of the somatic nervous system.

• 16-2 Describe the structures and functions of the sympathetic and parasympathetic

division of the autonomic nervous system.• 16-3 Describe the mechanisms of sympathetic

and parasympathetic neurotransmitter release and their effects on target organs and tissues.



• Learning Outcomes.• 16-4 Describe the hierarchy of interacting levels of

control in the autonomic nervous system, including the significance of visceral reflexes.

• 16-5 Summarize the effects of aging on the nervous system and give examples of interactions between the nervous system and other organ systems.



• Somatic Nervous System (SNS) • Operates under conscious control• Seldom affects long-term survival• SNS controls skeletal muscles

• Autonomic Nervous System (ANS)• Operates without conscious instruction• ANS controls visceral effectors• Coordinates vitals system functions

• Cardiovascular, respiratory, digestive, urinary, reproductive

• 5 year survival after heart attack: increased since 1960


16-1 Autonomic Nervous System

• Organization of the ANS• Integrative centers ViscMotN (PreGN) G PostGN

Efec

• Integrative centers• For autonomic activity in hypothalamus• Neurons here are comparable to upper motor

neurons in SNS• Synapses with ganglionic neurons



• Organization of the ANS• Visceral motor neurons

• In brain stem and spinal cord, are known as preganglionic neurons

• Preganglionic fibers• Axons of preganglionic neurons • Leave CNS and synapse on ganglionic neurons



• Visceral Motor Neurons• Autonomic ganglia

• Contain many ganglionic neurons• Ganglionic neurons innervate visceral effectors

• Such as cardiac muscle, smooth muscle, glands, and adipose tissue

• Postganglionic fibers• Axons of ganglionic neurons


Figure 16-1a The Organization of the Somatic and Autonomic Nervous Systems.

Brain

a

Upper motorneurons in

primary motorcortex

Somatic motornuclei of brain

stem

Skeletalmuscle

Lowermotor

neurons

Skeletalmuscle

Spinal cord

Somatic motornuclei ofspinal cord

Somatic nervous system

Motor neurons ofthe CNS exertsdirect control overskeletal muscles


Figure 16-1b The Organization of the Somatic and Autonomic Nervous Systems.

b

Visceral motornuclei in

hypothalamus

Preganglionicneuron

Visceral Effectors

Smoothmuscle

Glands

Cardiacmuscle

Adipocytes

Preganglionicneuron

Ganglionicneurons

Autonomicganglia

Autonomicnuclei inbrain stem

Spinal cord

Autonomicnuclei inspinal cord

Brain

Autonomic nervous system

Motor neurons ofthe CNS synapse onvisceral motor neuronsin autonomic ganglia, andthese ganglionic neurons control visceral effectors


16-1 Divisions of the ANS

• The Autonomic Nervous System • Operates largely outside our awareness

• Control activities of target organs• Modify or alter some ongoing activity

• Two divisions1. Sympathetic division

• Increases alertness, metabolic rate, and muscular abilities

• Kicks in only during exertion, stress, or emergency (F or F)

2. Parasympathetic division• Reduces metabolic rate and promotes digestion• Controls during resting conditions (R and D)



• Sympathetic and Parasympathetic Division1. Most often, these two divisions have opposing

effects (antagonist)• If the sympathetic division causes excitation, the

parasympathetic causes inhibition

2. The two divisions may also work independently• Only one division innervates some structures

3. The two divisions may work together, with each controlling one stage of a complex process



• Sympathetic Division –Preganglionic fibers originates in thoracic and superior lumbar; (thoracolumbar, between T1 – L2 segments)

• Synapse in ganglia near spinal cord• Preganglionic fibers are short• Postganglionic fibers are long• Prepares body for crisis, producing a “fight or

flight” response• Stimulates tissue metabolism• Increases alertness



• Seven Responses to Increased Sympathetic Activity

1. Heightened mental alertness2. Increased metabolic rate3. Reduced digestive and urinary functions4. Energy reserves activated5. Increased respiratory rate and respiratory

passageways dilate6. Increased heart rate and blood pressure7. Sweat glands activated



• Parasympathetic Division • Preganglionic fibers originate in brain stem and

sacral segments of spinal cord; craniosacral• Synapse in ganglia close to (or within) target

organs• Preganglionic fibers are long• Postganglionic fibers are short• Parasympathetic division stimulates visceral

activity• Conserves energy and promotes sedentary

activities



• Five Responses to Increased Parasympathetic Activity

1. Decreased metabolic rate2. Decreased heart rate and blood pressure3. Increased secretion by salivary and digestive

glands4. Increased motility and blood flow in digestive

tract5. Urination and defecation stimulation


Figure 16-2 Overview of the Autonomic Nervous System (Part 1 of 2).

Preganglionic fibers

Postganglionic fibers

KEY

“Fight or flight” response

Sympathetic activation

Most postganglionic fibersrelease norepinephrine (NE) atneuroeffector junctions.

Target Organs

Ganglia are located near thespinal cord. Preganglionic fibersrelease acetylcholine (Ach),stimulating ganglionic neurons.

Ganglia

Preganglionic Neurons

Preganglionic neurons arelocated in the lateral gray hornsof spinal segments T1–L2.

Sympathetic Division (Thoracolumbar)


Figure 16-2 Overview of the Autonomic Nervous System (Part 2 of 2).

Preganglionic fibersPostganglionic fibers

“Rest and digest” response

All postganglionic fibersrelease Ach at neuroeffectorjunctions.

Target Organs

Ganglia are in or near the targetorgan. Preganglionic fibersrelease acetylcholine (Ach),stimulating ganglionic neurons.

Ganglia

Preganglionic Neurons

Preganglionic neurons in brainstem and in lateral portion ofanterior gray horns of S2–S4.

Parasympathetic Division (Craniosacral)

KEY

Parasympathetic stimulation



• Enteric Nervous System (ENS) • Third division of ANS• Extensive network in digestive tract walls• Complex visceral reflexes coordinated locally plus

influence of sympathetic and parasympathethic divisions

• Neurotransmitters are the same found in the brain


16-2 The Sympathetic Division

• Ganglionic Neurons • Occur in three locations

1. Sympathetic chain ganglia• On both sides of vertebral column (paravertebral)• Control effectors:

• In body wall • Inside thoracic cavity • In head, and limbs

2. Collateral ganglia• Are anterior to vertebral bodies (prevertebral)• Innervate tissues and organs in abdominopelvic cavity


Figure 16-3a Sites of Ganglia in Sympathetic Pathways.

Preganglionic neuronsGanglionic neurons

KEY

Gray ramus

Spinal nerve Preganglionicneuron

Autonomic ganglionof left sympathetic chain

Sympathetic nerve(postganglionic

fibers)

Innervates visceralorgans in thoracic

cavity bysympathetic nerves

Note: Both innervation patternsoccur on each side of the body.

Autonomic ganglion ofright sympathetic chain

Innervatesvisceral

effectors byspinal nerves

Whiteramus

Ganglionicneuron

SYMPATHETIC CHAIN GANGLIAa


Figure 16-3b Sites of Ganglia in Sympathetic Pathways.

b

White ramus

COLLATERAL GANGLIA

Lateral gray horn

Splanchnic nerve(preganglionic

fibers)

Postganglionicfibers

Collateralganglion

Innervatesvisceral organs inabdominopelvic

cavity



• 3. Adrenal Medullae (Suprarenal Medullae) • Modified sympathetic ganglia• Center suprarenal medulla• Very short axons• When stimulated, release neurotransmitters into

bloodstream (not at synapse)• Neurotransmitters then function as hormones to

affect target cells throughout body


Figure 16-3c Sites of Ganglia in Sympathetic Pathways.

c


THE ADRENAL MEDULLAE

Endocrine cells(specialized ganglionic

neurons)

Adrenalmedullae

Secretesneurotransmitters

into generalcirculation



• Fibers in Sympathetic Division • Preganglionic fibers

• Are relatively short• Ganglia located near spinal cord

• Postganglionic fibers• Are relatively long• Except at adrenal medullae



• Organization and Anatomy of the Sympathetic Division

• Ventral roots of spinal segments T1–L2 contain sympathetic preganglionic fibers

• Carry myelinated preganglionic fibers into sympathetic chain ganglion

• May synapse at collateral ganglia or in adrenal medullae



• Sympathetic Chain Ganglia• Preganglionic fibers

• One preganglionic fiber synapses on many ganglionic neurons

• Fibers interconnect sympathetic chain ganglia• Each ganglion innervates particular body segment(s)

• Preganglionic neurons• Limited to spinal cord segments T1–L2

• White rami (myelinated preganglionic fibers)• Innervate neurons in:

• Cervical, inferior lumbar, and sacral sympathetic chain ganglia



• Sympathetic Chain Ganglia • Postganglionic fibers control visceral effectors

• In body wall, head, neck, or limbs

• Postganglionic fibers innervate effectors • Sweat glands of skin• Smooth muscles in superficial blood vessels

• Postganglionic fibers innervating structures in thoracic cavity form bundles

• Sympathetic nerves



• Sympathetic Chain Ganglia • Postganglionic sympathetic fibers

• In head and neck leave superior cervical sympathetic ganglia

• Supply the regions and structures innervated by cranial nerves III, VII, IX, X


Figure 16-4 The Distribution of Sympathetic Innervation (Part 2 of 4).

Pons



KEY

T1

T2

T3

T4

Lung

Heart

Sympathetic nerves

Cardiac andpulmonaryplexuses

Eye

Salivaryglands


Figure 16-4 The Distribution of Sympathetic Innervation (Part 3 of 4).

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

T12

L1

L2

L3

L4

L5

S1S2

S3S4

S5

Uterus Ovary Penis Scrotum Urinary bladder

Kidney

Adrenalmedulla

Small intestine

Large intestine

Pancreas

Spleen

Stomach

Liver and gallbladder

Celiac ganglion

Inferiormesentericganglion

Sacralsplanchnic

nerves

Lumbarsplanchnic nerves

Lessersplanchnic

nerve

Superiormesenteric

ganglion

Greatersplanchnic

nerve

Coccygealganglia (Co1)

fused together(ganglion impar)



KEY



• Collateral Ganglia• Receive sympathetic innervation via sympathetic

preganglionic fibers• Splanchnic nerves

• Formed by preganglionic fibers that innervate collateral ganglia

• In dorsal wall of abdominal cavity



• Collateral Ganglia • Postganglionic fibers

• Innervate variety of visceral tissues and organs• Reduction of blood flow and energy by organs

not vital to short-term survival• Release of stored energy reserves



• Collateral Ganglia • Preganglionic fibers from inferior thoracic

segments• End at celiac ganglion or superior mesenteric

ganglion

• Preganglionic fibers from lumbar segments• Form splanchnic nerves • End at inferior mesenteric ganglion


16-2 The Sympathetic Division• Collateral Ganglia

• Celiac ganglion• Postganglionic fibers innervate stomach, liver,

gallbladder, pancreas, and spleen

• Superior mesenteric ganglion • Postganglionic fibers innervate small intestine and

proximal 2/3 of large intestine

• Inferior mesenteric ganglion • Postganglionic fibers provide sympathetic innervation to

portions of: • Large intestine • Kidney • Urinary bladder • Sex organs



• Adrenal Medullae • Preganglionic fibers entering adrenal gland proceed

to center (adrenal medulla)• Modified sympathetic ganglion• Preganglionic fibers synapse on neuroendocrine

cells• Specialized neurons secrete hormones into

bloodstream



• Adrenal Medullae• Neuroendocrine cells

• Secrete neurotransmitters epinephrine (E) and norepinephrine (NE)

• Epinephrine• Also called adrenaline • Is 75–80 percent of secretory output

• Remaining is norepinephrine (NE)• Noradrenaline



• Adrenal Medullae• Bloodstream carries neurotransmitters through

body• Causing changes in metabolic activities of

different cells • Including cells NOT innervated by sympathetic

postganglionic fibers• Effects last longer

• Hormones continue to diffuse out of bloodstream



• Sympathetic Activation• Change activities of tissues and organs by:

• Releasing NT at peripheral synapses• Distributing E and NE throughout body in

bloodstream• Target specific effectors, smooth muscle fibers in

blood vessels of skin• Are activated in reflexes • Do not involve other visceral effectors



• Changes Caused by Sympathetic Activation• Increased alertness• Feelings of energy and euphoria• Change in breathing• Elevation in muscle tone • Mobilization of energy reserves


16-3 Various Sympathetic Neurotransmitters

• Stimulation of Sympathetic Preganglionic Neurons

• Releases ACh at synapses with ganglionic neurons • Excitatory effect on ganglionic neurons

• Ganglionic Neurons• Release neurotransmitters (NE, ACh) at specific

target organs



• Ganglionic Neurons • Axon terminals

• Release NE at most varicosities• Called adrenergic neuron• Monoamine oxidase (MAO) • Catechol O methyltransferase (COMT)

• Some ganglionic neurons release ACh instead• Are located in body wall, skin, brain, and skeletal

muscles• Called cholinergic neurons• AChe


Figure 16-5 Sympathetic Varicosities.

Ganglion

Preganglionic fiber(myelinated)

Ganglionicneuron

Postganglionic fiber(unmyelinated)

Vesicles containingnorepinephrine (NE)

Varicosities

Mitochondrion

Schwann cellcytoplasm

5 μm

Smooth muscle cells Varicosities



• Sympathetic Stimulation and the Release of NE and E• Effects occurs primarily from interactions of NE and E

with:1. Alpha receptors

- NE more potent- E same potency

2. Beta receptors- NE less potent- E same potency

1.Two types of adrenergic membrane receptors2.Activates enzymes on inside of cell membrane via G

proteins (2nd messengers)



• Alpha receptors• Alpha-1 (1)

• More common type of alpha receptor• Releases intracellular calcium ions from reserves

in endoplasmic reticulum• Has excitatory effect on target cell• In smooth muscles

• Vessels constriction• Closing sphincters



• Alpha receptors• Alpha-2 (2)

• Lowers cAMP levels in cytoplasm• Has inhibitory effect on the cell• Helps coordinate sympathetic and parasympathetic

activities• When sympathetic division is active:

• NE is released

• Binds to 2, on parasympathetic efectors (neuromuscular and neuroglandular) and inhibits their activity


16-3 Various Sympathetic Neurotransmitters• Beta () receptors

• Affect membranes in many organs (skeletal muscles, lungs, heart, and liver)

• Trigger metabolic changes in target cell via G proteins• Stimulation increases intracellular cAMP levels

• Three Main Types of Beta Receptors

• Beta-1 (1)

• Beta-2 (2)

• Beta-3 (3)



• Three Main Types of Beta Receptors1. Beta-1 (1)

• Increases metabolic activity, skeletal muscle• Heart, increase heart rate and force of contraction

2. Beta-2 (2) (inhibition)

• Triggers relaxation of smooth muscles along respiratory tract

• Easier breathing, respiratory therapy

3. Beta-3 (3)

1.Leads to lipolysis, the breakdown of triglycerides in adipocytes

2.Make fatty acids available for other tissues



• Sympathetic Stimulation and the Release of Ach

• Cholinergic (ACh) sympathetic terminals• Innervate sweat glands of skin and blood vessels of

skeletal muscles and brain• Stimulate sweat gland secretion and dilate blood

vessels



• Sympathetic Stimulation and the Release of NO• Nitroxidergic synapses

• Release nitric oxide (NO) as neurotransmitter• Neurons innervate smooth muscles in walls of

blood vessels in skeletal muscles and the brain• Produce vasodilation and increased blood flow


Summary: Sympathetic Division

• Includes:• 2 sets of chain ganglia• 3 collateral ganglia • two adrenal ganglia

• Preganglionic fibers shorts, post ganglionic are long• ganglia are near spinal cord

• Adrenal: very short fibers direct to bloodstream

• Extensive divergence: • a single sympathetic motor neuron can control a

variety of visceral effectors producing a complex and coordinated response.


Summary: Sympathetic Division

•All preG neurons release ACh at synapses with ganglionic neurons

•Most postG neurons release NE• a few release Ach or NO

•The effector response depends on the 2nd messenger triggered by activation of G proteins by NE o E to α or β receptors.


16-4 The Parasympathetic Division

• Autonomic Nuclei • Preganglionics neurons

• Are contained in the mesencephalon, pons, and medulla oblongata

• Associated with cranial nerves III, VII, IX, X

• In lateral gray horns of spinal segments S2–S4



• Ganglionic Neurons in Peripheral Ganglia• Terminal ganglion

• Near target organ• Usually paired

• Intramural ganglion • Embedded in or within tissues of target organ



• Organization and Anatomy of the Parasympathetic Division

• Parasympathetic preganglionic fibers leave brain as components of cranial nerves

• III (oculomotor)• VII (facial)• IX (glossopharyngeal)• X (vagus)

• Parasympathetic preganglionic fibers leave spinal cord at sacral level

• S2-S4



• Oculomotor(III), Facial(VII), and Glossopharyngeal Nerves(IX)

• Control visceral structures in head• Synapse in ganglia;

• ciliary• pterygopalatine,• submandibular• otic ganglia

• Short postganglionic fibers continue to their peripheral targets



• Vagus Nerve(X)• Provides preganglionic parasympathetic

innervation to structures in:• Neck• Thoracic and abdominopelvic cavities • as distant as a distal portion of large intestine

• Provides 75 percent of all parasympathetic outflow


Figure 16-6 The Distribution of Parasympathetic Innervation (Part 1 of 2).

Heart

Lungs

Pterygopalatine ganglion

N III

N VII

N IX

N X (Vagus)

Ciliary ganglion

Submandibularganglion

Otic ganglion

Lacrimal gland

Eye

Salivary glands

Pons

Oculomotor(III)Facial(VII)Glossopharyngeal Nerves(IX)Vagus (X)



• Sacral Segments of Spinal Cord• Preganglionic fibers carry sacral parasympathetic

output• Do not join ventral roots of spinal nerves, instead

form pelvic nerves• Pelvic nerves innervate intramural ganglia in walls of:• kidneys• urinary bladder• portions of large intestine• sex organs


Figure 16-6 The Distribution of Parasympathetic Innervation (Part 2 of 2).

Liver and gallbladder

Stomach

Spleen

Pancreas

Large intestine

Small intestine

Rectum

Kidney

Urinary bladderScrotumPenisOvaryUterus

Pelvicnerves

Spinalcord S2

Autonomic plexuses

(see Figure 16-8)

S3

S4



KEY

Lungs



• Parasympathetic Activation • centers on relaxation • food processing• energy absorption• localized effects• last a few seconds at most• Anabolic system

• Raisin up nutrient content in the blood



• Major Effects of Parasympathetic Division • Constriction of the pupils

• To restrict the amount of light that enters the eyes

• Focusing of the lenses of the eyes on nearby objects

• Secretion by digestive glands • Salivary, gastric glands, intestinal glands• the pancreas (exocrine and endocrine)• the liver



• Major Effects of Parasympathetic Division• Secretion of hormones

• Promote the absorption and utilization of nutrients by peripheral cells

• Changes in blood flow and glandular activity • Associated with sexual arousal

• Increase in smooth muscle activity • Along the digestive tract, peristalsis



• Major Effects of Parasympathetic Division • Stimulation and coordination of defecation• Contraction of the urinary bladder during

urination• Constriction of the respiratory passageways• Reduction in heart rate and in the force of

contraction


16-5 Parasympathetic Neurons Release ACh

• Neuromuscular and Neuroglandular Junctions • All PS fibers release ACh as neurotransmitter• Effects of stimulation are short lived

• Inactivated by acetylcholinesterase (AChE) at synapse

• ACh is also inactivated by tissue cholinesterase in surrounding tissues



• Two Types of Membrane Receptors and Responses• Nicotinic receptors

• On surfaces of ganglion cells (sympathetic and parasympathetic)

• On neuromuscular junction of Somatic Nervous System

• Exposure to ACh causes excitation of ganglionic neuron or muscle fiber

• Open Na+ channels in post sinaptic membrane



• Muscarinic receptors• At cholinergic neuromuscular or neuroglandular

junctions (parasympathetic)• At few cholinergic junctions (sympathetic)• G proteins

• Effects are longer lasting than nicotinic receptors• Can be excitatory or inhibitory• Response reflects activation or inactivation of

specific enzymes



• Dangerous Environmental Toxins• Produce exaggerated, uncontrolled responses• Nicotine

• 3mg/g on tobacco• Binds to nicotinic receptors• Targets autonomic ganglia and skeletal

neuromuscular junctions • Poisoning with 50 mg ingested or absorbed through skin• Signs and symptoms:

• Vomiting, diarrhea, high blood pressure, rapid heart rate, sweating, profuse salivation, convulsions

• May result in coma or death



• Dangerous Environmental Toxins • Produce exaggerated, uncontrolled responses• Muscarine

• Binds to muscarinic receptors• Targets parasympathetic neuromuscular or

neuroglandular junctions• Signs and symptoms:

• Salivation, nausea, vomiting, diarrhea, constriction of respiratory passages, low blood pressure, slow heart rate (bradycardia)

• Sweating• Amanita muscaria


Amanita muscaria


Table 16-1 Adrenergic and Cholinergic Receptors of the ANS.


16-6 Dual Innervation: S y PS interaction

• Sympathetic Division• Widespread impact• Reaches organs and tissues throughout body

• Parasympathetic Division• Innervates only specific visceral structures

• Sympathetic and Parasympathetic Division• Most vital organs receive instructions from both

sympathetic and parasympathetic divisions• Dual innervation• Two divisions commonly have opposing effects


Figure 16-7 Summary: The Anatomical Differences between the Sympathetic and Parasympathetic Divisions.

Bloodstream

Sympatheticganglion

PNS

CNS

Sympathetic Parasympathetic

Preganglionicneuron

Preganglionicfiber

Ganglionicneurons

Postganglionicfiber

TARGET

Parasympatheticganglion

KEYNeurotransmitters

Acetylcholine

Norepinephrine

Epinephrineor


Table 16-2 A Structural Comparison of the Sympathetic and Parasympathetic Divisions of the ANS.


16-6 Dual Innervation

• Anatomy of Dual Innervation • Parasympathetic postganglionic fibers accompany

cranial nerves to peripheral destinations• Sympathetic innervation reaches same structures

• By traveling directly from superior cervical ganglia of sympathetic chain


Table 16-3 A Functional Comparison of the Sympathetic and Parasympathetic Divisions of the ANS (Part 1-2 of 4).


Table 16-3 A Functional Comparison of the Sympathetic and Parasympathetic Divisions of the ANS (Part 3-4 of 4).



• Anatomy of Dual Innervation• Autonomic plexuses

• Nerve networks in the thoracic and abdominopelvic cavities

• Are formed by mingled • sympathetic postganglionic fibers and

parasympathetic preganglionic fibers

• Travel with blood and lymphatic vessels that supply visceral organs



• Anatomy of Dual Innervation • Cardiac plexus• Pulmonary plexus• Esophageal plexus• Celiac plexus• Inferior mesenteric plexus• Hypogastric plexus


Figure 16-8 The Autonomic Plexuses and Ganglia (Part 1 of 2).

Aortic arch

Right vagus nerve

Autonomic Plexusesand Ganglia

Cardiac plexus

Pulmonary plexus

Thoracic sympatheticchain ganglia

Esophageal plexus

Celiac plexusand ganglion

Inferior mesentericplexus and ganglia

Hypogastric plexus

Pelvic sympatheticchain

Superior mesentericganglion


Figure 16-8 The Autonomic Plexuses and Ganglia (Part 1 of 2).

Aortic arch

Right vagus nerve

Autonomic Plexusesand Ganglia

Cardiac plexus

Pulmonary plexus

Thoracic sympatheticchain ganglia

Esophageal plexus

Celiac plexusand ganglion

Inferior mesentericplexus and ganglia

Hypogastric plexus

Pelvic sympatheticchain

Superior mesentericganglion

Trachea

Left vagus nerve

Thoracic spinal nerves

Esophagus

Splanchnic nerves

Diaphragm

Superior mesenteric artery

Inferior mesenteric artery



• Autonomic Tone • Is an important aspect of ANS function

• If nerve is inactive under normal conditions, can only increase activity

• If nerve maintains background level of activity, can increase or decrease activity

• Significant where dual innervation occurs• Two divisions have opposing effects• Heart

• More important when dual innervation does not occur

• Blood vessels



• The Heart Receives Dual Innervation• Two divisions have opposing effects on heart

function1. Parasympathetic division

• Acetylcholine released by postganglionic fibers slows heart rate

2. Sympathetic division• NE released by varicosities accelerates heart rate

• Balance between two divisions• Autonomic tone is present• Releases small amounts of both neurotransmitters

continuously



• The Heart Receives Dual Innervation • Parasympathetic innervation dominates under

resting conditions• Crisis accelerates heart rate by:

• Stimulation of sympathetic innervation• Inhibition of parasympathetic innervation



• Autonomic Tone • Blood vessel dilates and blood flow increases• Blood vessel constricts and blood flow is reduced• Sympathetic postganglionic fibers release NE

• Innervate smooth muscle cells in walls of peripheral vessels



• Autonomic Tone • Background sympathetic tone keeps muscles

partially contracted• To increase blood flow:

• Rate of NE release decreases• Sympathetic cholinergic fibers are stimulated• Smooth muscle cells relax• Vessels dilate and blood flow increases


16-7 Visceral Reflexes Regulate the ANS

• Visceral Reflexes• Provide automatic motor responses• Can be modified, facilitated, or inhibited by higher

centers, especially hypothalamus• Visceral reflex arc

• Receptor• Sensory neuron• Processing center (one or more interneurons)

• All polysynaptic

• Two visceral motor neurons



• Visceral Reflexes• Long reflexes

• Visceral sensory neurons deliver information to CNS• ANS carries motor commands to visceral effectors• Coordinate activities of entire organ

• Short reflexes • Bypass CNS• Control simple motor responses with localized effects• One small part of target organ


Figure 16-9 Visceral Reflexes.

Stimulus

Receptors inperipheral tissue

Afferent (sensory)fibers

CENTRAL NERVOUSSYSTEM

Longreflex

Processing centerin spinal cord

Preganglionicneuron

Autonomic ganglion(sympathetic orparasympathetic)

Postganglionicneuron

Peripheraleffector

Shortreflex

Response



• Visceral Reflexes• Regulating visceral activity

• Most organs • Long reflexes most important

• Digestive tract • Short reflexes provide most control and coordination


Table 16-4 Representative Visceral Reflexes (Part 1 of 2).



• The Integration of SNS and ANS Activities• Many parallels in organization and function• Integration at brain stem• Both systems under control of higher centers


Table 16-5 A Comparison of the ANS and SNS.


16-10 Effects of Aging on the Nervous System

• Effects of Aging• Anatomical and physiological changes begin after

maturity (age 30)• Accumulate over time• 85 percent of people over age 65 have changes in

mental performance and CNS function



• Reduction in Brain Size and Weight • Decrease in volume of cerebral cortex• Narrower gyri and wider sulci • Larger subarachnoid space

• Reduction in Number of Neurons• Brain shrinkage linked to loss of cortical neurons• No neuronal loss in brain stem nuclei



• Decrease in Blood Flow to Brain • Arteriosclerosis

• Fatty deposits in walls of blood vessels• Reduces blood flow through arteries• Increases chances of rupture

• Cerebrovascular accident (CVA), or stroke• May damage surrounding neural tissue



• Changes in Synaptic Organization of Brain • Number of dendritic branches, spines, and

interconnections decreases• Synaptic connections lost• Rate of neurotransmitter production declines



• Intracellular and Extracellular Changes in CNS Neurons

• Neurons in brain accumulate abnormal intracellular deposits

• Lipofuscin • Granular pigment with no known function

• Neurofibrillary tangles• Masses of neurofibrils form dense mats inside cell

body and axon




• Plaques • Extracellular accumulations of fibrillar proteins• Surrounded by abnormal dendrites and axons




• Plaques and tangles • Contain deposits of several peptides• Primarily two forms of amyloid ß (Aß) protein • Appear in brain regions specifically associated with

memory processing



• Anatomical Changes • Linked to functional changes• Neural processing becomes less efficient with age• Memory consolidation more difficult• Secondary memories harder to access



• Sensory Systems • Hearing, balance, vision, smell, and taste become

less acute• Reaction times slowed• Reflexes weaken or disappear

• Motor Control• Precision decreases• Takes longer to perform



• Incapacitation • 85 percent of elderly population develops changes

that do not interfere with abilities• Some individuals become incapacitated by

progressive CNS changes



• Senility • Also called senile dementia• Degenerative changes

• Memory loss• Anterograde amnesia (lose ability to store new

memories)• Emotional disturbances• Alzheimer’s disease is most common


16-10 Nervous System Integration

• The Nervous System• Monitors all other systems• Issues commands that adjust their activities• Like conductor of orchestra


16-10 Nervous System Integration

• Neural Tissue • Extremely delicate• Extracellular environment must maintain

homeostatic limits• If regulatory mechanisms break down,

neurological disorders appear


Figure 16-14 diagrams the functional relationships between the nervous system and other body systems we have studied so far.

SYSTEM INTEGRATOR

The Nervous System

Body System Nervous System

Provides sensations of touch, pressure,pain, vibration, and temperature; hairprovides some protection and insulationfor skull and brain; protects peripheralnerves

Nervous System Body System

Provides calcium ions for neuralfunction; protects brain and spinal cord

Facial muscles express emotionalstate; intrinsic laryngeal musclespermit communication; musclespindles provide proprioceptivesensations

Controls skeletal muscle contractions;coordinates respiratory andcardiovascular activities

Controls skeletal muscle contractionsthat results in bone thickening andmaintenance and determine boneposition

Controls contraction of arrector pilimuscles and secretion of sweat glands

The nervous system is closely integrated with other body systems. Every moment of your life, billions of neurons in your nervous system are exchanging information acrosstrillions of synapses andperforming the mostcomplex integrativefunctions in the body. Aspart of this process, thenervous system monitors allother systems and issuescommands that adjust their activities. However, thesignificance and impact ofthese commands variesgreatly from one system toanother. The normal functions of the muscular system, for example, simply cannot be performed without instructions from the nervous system. By contrast, the cardiovascular system is relatively independent—the nervous system merely coordinates and adjusts cardiovascular activities to meet the circulatory demands of other systems. In the final analysis, the nervous system is like the conductor of an orchestra, directing the rhythm and balancing the performances of each section to produce a symphony, instead of simplya very loud noise.

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© 2015 Pearson Education, Inc. Lecture Presentation by Lee Ann Frederick University of Texas at Arlington Chapter 16 The Autonomic Nervous System and Higher-Order.

Documents

autonomic nervous systems

ans visceral motor neurons

upper motor neurons

pearson education

hypothalamus neurons

autonomic activity

b visceral motor nuclei

higherorder functions