14 the autonomic nervous system
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© 2011 Pearson Education, Inc.
PowerPoint® Lecture Presentations prepared byAlexander G. CheroskeMesa Community College at Red Mountain
14The Autonomic Nervous System
© 2011 Pearson Education, Inc.
Section 1: ANS Functional Anatomy and Organization
• Learning Outcomes
• 14.1 List the divisions of the ANS and the general functions of each.
• 14.2 Describe the structures and functions of the sympathetic and
parasympathetic divisions of the autonomic nervous system.
• 14.3 Describe the innervation patterns of the sympathetic and parasympathetic
divisions of the autonomic nervous system.
© 2011 Pearson Education, Inc.
Section 1: ANS Functional Anatomy and Organization
• Learning Outcomes
• 14.4 Describe the various types of sympathetic and parasympathetic receptors and
their associated neurotransmitters.
• 14.5 Describe the mechanisms of neurotransmitter release in the ANS,
and explain the effects of neurotransmitters on target organs and tissues.
© 2011 Pearson Education, Inc.
Section 1: ANS Functional Anatomy and Organization
• Comparisons of somatic nervous system (SNS) and autonomic nervous system (ANS)
• SNS
• Motor neurons exert voluntary control over skeletal muscles
• Lower motor neurons may be controlled by
• Reflexes based in spinal cord
• Upper motor neurons with cell bodies in brain nuclei or at primary motor cortex
Animation: Somatic Autonomic Nervous System
© 2011 Pearson Education, Inc.Figure 14 Section 1 1
A schematic of the somatic nervous system(SNS), which provides conscious and sub-Conscious control over skeletal muscles
BRAIN
Upper motorneurons in
primary motorcortex
Skeletalmuscle
Skeletalmuscle
Lowermotor
neurons
Spinal cord
Somaticmotornuclei ofspinal cord
Somatic motornuclei of brain
stem
© 2011 Pearson Education, Inc.
Section 1: ANS Functional Anatomy and Organization
• Comparisons of somatic nervous system (SNS) and autonomic nervous system (ANS) (continued)
• ANS
• CNS motor neurons synapse with visceral motor neurons in autonomic ganglia, which control visceral effectors
• Integrative centers located in hypothalamus• Comparable to SNS upper motor neurons
• Two types of visceral motor neurons1. Preganglionic neurons (cell bodies in CNS)
• Activities represent direct reflex responses
§ Ganglionic neurons (cell bodies in autonomic ganglia)
• Innervate effectors like cardiac and smooth muscle
© 2011 Pearson Education, Inc.Figure 14 Section 1 2
Preganglionicneuron
Visceral Effectors
Smoothmuscle
Glands
Cardiacmuscle
Adipocytes
A schematic of the autonomicnervous system (ANS), whichcontrols visceral functions largelyoutside our awareness
Preganglionicneuron
Ganglionicneurons
Autonomicganglia
Autonomicnuclei inspinal cord
Spinalcord
Autonomicnuclei inbrain stem
Visceral motornuclei in
hypothalamus BRAIN
© 2011 Pearson Education, Inc.
Module 14.1: ANS divisions
• Three ANS divisions
1. Sympathetic (or thoracolumbar) division
• Axons emerge from thoracic and superior lumbar segments of spinal cord
• Innervate ganglia relatively close to spinal cord
• “Kicks in” only during periods of exertion, stress, or emergency
2. Parasympathetic (or craniosacral) division
• Axons emerge from brain stem and sacral spinal segments
• Innervate ganglia very close (or within) target organs
• Most often, effects are opposite to sympathetic
© 2011 Pearson Education, Inc.Figure 14.1 1
Autonomic Nervous System
Sympathetic Division Parasympathetic Division
In the sympathetic division, or thoracolumbar(thor-a-kō-LUM-bar) division, axons emerge from the thoracic and superior lumbar segments of the spinal cord and innervate ganglia relatively close to the spinal cord.
In the parasympathetic division, or cranio-sacral (krā-nē-ō-SĀ-krul) divions, axonsemerge from the brain stem and the sacralsegments of the spinal cord, and they innervateganglia very close to (or within) target organs.
The two main divisionsof the ANS: the sympatheticand parasympatheticdivisions
Cranial nerves(III, VII, IX, andX)
T1T2
T3
T4
T5
T6
T7
T8
T9
T10
T11
T12
L1
L2
S2
S3
S4
Sacral nerves(S2, S3, S4 only)
Lumbar nerves(L1, L2 only)
Thoracicnerves
© 2011 Pearson Education, Inc.
Module 14.1: ANS divisions
• Three ANS divisions (continued)
3. Enteric nervous system (ENS)
• Extensive network of neurons (~100 million) and nerve networks within walls of digestive tract
• Influenced by sympathetic and parasympathetic divisions
• However, many complex visceral activities are coordinated on a local level (without CNS instructions)
• Will be discussed more in Ch. 21 (Digestive System)
© 2011 Pearson Education, Inc.Figure 14.1 2
The extensive system of neurons andnerve networks of the enteric nervoussystem (ENS)
Esophagus
Stomach
Large intestine
Small intestine
© 2011 Pearson Education, Inc.Figure 14.1 3
Representative plexuses, ganglia,and nerves of the sympathetic andparasympathetic divisions
Pelvic symaptheticchain
Hypogastric plexus
Inferior mesentericplexus and ganglion
Superior mesentericganglion
Celiac plexusand ganglion
Esophageal plexus
Thoracic sympatheticchain ganglia
Pulmonary plexus
Cardiac plexus
Autonomic Plexusesand Ganglia
Right vagus nerve
Aortic arch
Trachea
Esophagus
Diaphragm
Superior mesentericartery
Inferior mesentericartery
Thoracic spinalnerves
Left vagus nerve
Splanchnic nerves
© 2011 Pearson Education, Inc.
Module 14.1 Review
a. Identify the major divisions of the autonomic nervous system.
b. What division of the ANS is responsible for the physiological changes you experience when startled by a loud noise?
c. Compare the anatomy of the sympathetic division with the parasympathetic division.
© 2011 Pearson Education, Inc.
Module 14.2: Autonomic ganglia
• Autonomic ganglia
• Sympathetic division
• Preganglionic fibers (neurons) are relatively short while postganglionic fibers (neurons) are relatively long
• Accordingly, sympathetic ganglia (where these fibers synapse) are relatively near spinal cord
• Specific ganglia
1. Sympathetic chain (on either side of spinal cord)
• Innervates visceral effectors in thoracic cavity, head, body wall, and limbs
© 2011 Pearson Education, Inc.
Module 14.2: Autonomic ganglia
• Sympathetic division (continued)
• Specific ganglia (continued)
2. Collateral ganglia (within abdominopelvic cavity)• Includes celiac, superior, and inferior mesenteric
ganglia
• Innervates visceral effectors in abdominopelvic cavity
3. Adrenal medulla• Center of adrenal gland
• Acts as endocrine gland
• Targets organs and systems throughout body
© 2011 Pearson Education, Inc.
Module 14.2: Autonomic ganglia
• Sympathetic division (continued)
• Prepares body for heightened levels of somatic activity
• Known as “fight or flight” division
• Typical responses
1. Heightened mental alertness
2. Increased metabolic rate
3. Reduced digestive and urinary functions
4. Activation of energy reserves
5. Increased respiratory rate and dilation of passageways
6. Elevated heart rate and blood pressure
7. Activation of sweat glands
© 2011 Pearson Education, Inc.Figure 14.2 1
Organization of the sympathetic division of the ANS
PreganglionicNeurons
Lateral grayhorns ofspinalsegmentsT1-L2
Ganglionic Neurons
Each sympathetic chainconsists of a series ofinterconnected ganglialocated on either side of thevertebral column.
The collateral ganglia,located within theabdominopelvic cavity,include the celiac, superiormesenteric, and inferiormesenteric ganglia.
The center of each adrenalgland contains a sympatheticganglion, the adrenalmedulla, that acts as anendocrine organ.
Ganglionic neurons inthe sympathetic chainand collateral gangliaexert their effectsthrough innervationof peripheral targetorgans.
Ganglionic neurons inthe adrenal medullaeaffect target organsthroughout the bodythrough the release ofhormones into thegeneral circulation.
Target Organs
Organs andsystemsthroughout thebody
Visceral effectorsin abdomino-pelvic cavity
Visceral effectorsin thoracic cavity,head, body wall,and limbs
KEY
Preganglionic fibers
Postganglionic fibers
Hormones releasedinto circulation
© 2011 Pearson Education, Inc.
Module 14.2: Autonomic ganglia
• Parasympathetic division
• Typical preganglionic fiber synapses on 6–8 ganglionic neurons
• May be situated in:
• Terminal ganglia (near target organ)
• Usually paired
• Ciliary ganglion (intrinsic eye muscles)
• Pterygopalatine and submandibular ganglia (nasal, tear, and salivary glands)
• Otic ganglion (parotid salivary gland)
© 2011 Pearson Education, Inc.
Module 14.2: Autonomic ganglia
• Parasympathetic division (continued)
• Typical preganglionic fiber synapses on 6–8 ganglionic neurons (continued)
• May be situated in: (continued)
• Intramural (murus, wall) ganglia (embedded in target organ wall)
• Typically interconnected masses/clusters of cells
• Innervate visceral organs of neck, and of thoracic and abdominopelvic cavities
© 2011 Pearson Education, Inc.
Module 14.2: Autonomic ganglia
• Parasympathetic division (continued)
• Concerned with regulation of visceral function and energy conservation
• Known as “rest and digest” system
• Typical responses
1. Decreased metabolic rate
2. Decreased heart rate and blood pressure
3. Increased salivary and digestive gland secretion
4. Increased digestive tract motility and blood flow
5. Stimulation of urination and defecation
© 2011 Pearson Education, Inc.Figure 14.2 2
Organization of the parasympathetic division of the ANS
KEY
Preganglionic fibers
Postganglionic fibers
PreganglionicNeurons
Ganglionic Neurons Target Organs
In sacral segments of thespinal cord, parasympatheticnuclei lie in the lateral grayhorns of spinal segmentsS2–S4.
The midbrain, pons,and medulla oblongatacontain parasympatheticnuclei associated withcranial nerves III, VII, IX,and X.
Pelvicnerves
III
VII
IX
X
Ciliary ganglion
Pterygopalatine andsubmandibularganglia
Otic ganglion
Intramural ganglia
Intramural ganglia
Visceral organs ininferior portion ofabdominopelviccavity
Visceral organs of neck,thoracic cavity,and most ofabdominal cavity
Parotid salivary gland
Nasal glands, tearglands, and salivaryglands
Intrinsic eye muscles(pupil and lens shape)
© 2011 Pearson Education, Inc.
Module 14.2 Review
a. List general responses to increased sympathetic activity and to parasympathetic activity.
b. Describe an intramural ganglion.
c. Starting in the spinal cord, trace the path of a nerve impulse through the sympathetic ANS to its target organ in the abdominopelvic cavity.
© 2011 Pearson Education, Inc.
Module 14.3: Autonomic innervation patterns
• Autonomic innervation patterns
• Sympathetic division
• Every spinal nerve has a gray ramus carrying sympathetic postganglionic fibers
• Preganglionic fibers passing to collateral ganglia form splanchnic nerves
• Postganglionic fibers innervating thoracic cavity structures form bundles or sympathetic nerves
© 2011 Pearson Education, Inc.Figure 14.3
The innervation of the sympathetic division: at left, thedistribution of nerves to the skin, skeletal muscles, andtissues of the body wall; at right, the distribution of nerves to visceral organs
PONS
Eye
Salivaryglands
Heart
Lung
Liver andgallbladder
Stomach
Spleen
Pancreas
Largeintestine
Smallintestine
Adrenalmedulla
Kidney
Urinary bladderScrotum
PenisUterus
Ovary
Inferiormesentericganglion
Superior mesentericganglion
Celiac ganglion
Cardiac andpulmonary plexuses
Sympathetic nerves
Splanchnicnerves(SEE NOTE 2)
T1T1
L2L2
Spinalcord
Superior
Middle
Inferior
Cervicalsympathetic
ganglia
Gray rami tospinal nerves(SEE NOTE 1)
Postganglionic fibers tospinal nerves (innervatingskin, blood vessels, sweatglands, arrector pilimuscles, adipose tissue)
Sympatheticchain ganglia
Coccygealganglia (Co1)
fused togetherNOTE 1
NOTE 2Every spinal nerve has a gray ramus thatcarries sympathetic postganglionic fibersfor distribution in the body wall and limbs.In the head and neck, postganglionicsympathetic fibers leaving the superiorcervical sympathetic ganglia supply theregions innervated by cranial nerves III,VII, IX, and X.
Preganglionic fibers on their way to the collateralganglia form the splanchnic (SPLANK-nik) nerves.Postganglionic fibers innervating structures in thethoracic cavity, such as the heart and lungs, formbundles known as sympathetic nerves. Preganglionic neurons
KEY
Ganglionic neurons
© 2011 Pearson Education, Inc.
Module 14.3: Autonomic innervation patterns
• Parasympathetic division
• Vagus nerve (X) alone provides ~75% of all parasympathetic outflow
• Numerous vagus nerve branches intermingle with sympathetic fibers forming nerve plexuses
• Preganglionic fibers in sacral spinal cord segments form distinct pelvic nerves
• Innervate intramural ganglia in kidneys, bladder, terminal portions of large intestine, and sex organs
© 2011 Pearson Education, Inc.Figure 14.3
Preganglionicfibers in thesacral segmentsof the spinal cord,which carry sacralparasympatheticoutput
Spinalcord
S2
S3
S4
Uterus Ovary
Penis
Scrotum
Liver andgallbladder
Stomach
Spleen
Pancreas
Largeintestine
Smallintestine
Kidney
Urinary bladder
Rectum
Eye
Salivary glands
Heart
Lungs
Hypogastricplexus
Inferior mesentericplexus
Celiac plexus
Cardiac plexus
Vagus nerve (X),which providesabout 75 percentof all parasympa-thetic outflow
PONS
Otic ganglion
Submandibularganglion
Ciliary ganglion
Pterygopalatine ganglion
IIIVII
IX
The innervation of the parasympathetic division onone side of the body; the innervation on the oppositeside (not shown) follows the same pattern
Lacrimal gland
Preganglionic neuronsKEY
Ganglionic neurons
© 2011 Pearson Education, Inc.
Module 14.3 Review
a. Define splanchnic nerves.
b. Which nerve carries the majority of the parasympathetic outflow?
c. Describe sympathetic nerves.
© 2011 Pearson Education, Inc.
Module 14.4: Autonomic neurotransmitters and receptors
• Autonomic neurotransmitters and receptors
• Sympathetic division
• Adrenergic receptors (bind “adrenaline”)
• Located in plasma membranes of target cells
• Binding of epinephrine (E) or norepinephrine (NE) activates enzymes (2nd messenger system) within cell
• Two classes
1. Alpha receptors (generally stimulated by NE & E)
• α1 receptors – generally excitatory
• α2 receptors – generally inhibitory
© 2011 Pearson Education, Inc.
Module 14.4: Autonomic neurotransmitters and receptors
• Sympathetic division (continued)
• Adrenergic receptors (continued)
• Two classes (continued)
2. Beta receptors (generally stimulated by E)
• β1 receptors – cardiac muscle stimulation and increased tissue metabolism
• β2 receptors – relaxation of respiratory passage and blood vessel smooth muscle
• β3 receptors – release of fatty acids from adipose tissue for metabolic use in other tissues
© 2011 Pearson Education, Inc.
Module 14.4: Autonomic neurotransmitters and receptors
• Sympathetic division (continued)
• Neurotransmitter release
• Epinephrine (E) and norepinephrine (NE) can be released
• Locally, involving more norepinephrine
• Effects last a few seconds
• Generally, from adrenal medulla
• 3× more epinephrine than norepinephrine
• More beta receptors activated
• Effects may last several minutes
© 2011 Pearson Education, Inc.Figure 14.4 1 – 2
The effects of sympathetic stimulation, which result primarily from the interactions of NE and E with adrenergicreceptors in the target cell’s plasma membrane
The stimulation of alpha receptors bynorepinephrine, which activates enzymeson the inside of the target cell’s plasmamembrane
The stimulation of beta receptors by epinephrine, which triggerschanges in the metabolic activity of the target cell
Epinephrine
Betareceptor
Activation ofadenylate cyclase
cAMP ATP
If β3
receptorIf β2 receptorIf β1
receptor
Cardiac musclestimulationand increasedtissuemetabolism
Relaxation of smoothmuscle in respiratorypassages and in theblood vessels of skeletalmuscle
Release of fattyacids by adiposetissue for metabolicuse in other tissues
CYTOPLASM OF TARGET CELLCYTOPLASM OF TARGET CELL
Gland cellsecretion
Smooth musclecontraction
Inhibition ofcell
Release of Ca2+
from ER
Reduction ofcAMP levels
Second messengersactivated
If α1
receptorIf α2
receptor
Plasma membraneAlpha
receptor
Norepinephrine
© 2011 Pearson Education, Inc.
Module 14.4: Autonomic neurotransmitters and receptors
• Parasympathetic division
• Receptors (all bind ACh)
1. Nicotinic receptors (also bind nicotine)• Located on ganglion cell surfaces
• Also on sympathetic ganglion cells and at SNS neuromuscular junctions
• Always excitatory
2. Muscarinic receptors (also bind muscarine toxin)• Located at cholinergic neuromuscular and neuroglandular
junctions as well as some sympathetic cholinergic junctions
• Can be excitatory or inhibitory
© 2011 Pearson Education, Inc.Figure 14.4 3 – 4
CYTOPLASM OF TARGET CELL
The action of nicotinicreceptors of theparasympathetic division
AChNa+
Nicotinicreceptor
ACh
The action of muscarinic receptorsof the parasympathetic division
CYTOPLASM OF TARGET CELL
Muscarinicreceptor
G protein(inactive)
G proteinactivated
Plasma membrane
Metaboliceffects
Activation/inactivationof specific enzymes
The effects of the binding of ACh to nicotinic and muscarinic receptors of the parasympathetic division
© 2011 Pearson Education, Inc.
Module 14.4 Review
a. Compare and contrast alpha and beta receptors.
b. Compare nicotinic receptors with muscarinic receptors.
c. An individual with high blood pressure (hypertension) is prescribed a drug that blocks beta receptors. How could this medication alleviate hypertension?
© 2011 Pearson Education, Inc.
Module 14.5: Anatomical and physiological characteristics of ANS divisions
• Characteristics of ANS divisions
• Sympathetic activation
• Can occur at:
• Local level using mainly NE
• Affect only target organs
• Generalized body using E and NE
• Have effects in many organs
• Also alters CNS activity
• Controlled by hypothalamus
© 2011 Pearson Education, Inc.
Module 14.5: Anatomical and physiological characteristics of ANS divisions
• Sympathetic activation effects
• Increased alertness through reticular activating system
• Feeling of energy and euphoria
• Increased activity in cardiovascular and respiratory centers of pons and medulla oblongata
• Increased blood pressure, heart/breathing rate, inspiration depth
• General elevation in muscle tone
• Mobilization of energy reserves
• Breakdown of liver and muscle glycogen
• Release of adipose tissue lipids
© 2011 Pearson Education, Inc.
Module 14.5: Anatomical and physiological characteristics of ANS divisions
• Parasympathetic activation
• Under normal conditions, not controlled or activated as a whole
• Active continuously as individual reflex responses
• Effects center on relaxation, food processing, and energy absorption
• Also called anabolic division (anabole, a rising up) because blood nutrients generally increase
© 2011 Pearson Education, Inc.
Module 14.5: Anatomical and physiological characteristics of ANS divisions
• Parasympathetic activation effects
• Constrictions of pupils and focusing of eye lenses for nearby objects
• Secretion of digestive glands
• Secretion of hormones that promote nutrient absorption and utilization
• Blood flow and glandular activity changes associated with sexual arousal
© 2011 Pearson Education, Inc.
Module 14.5: Anatomical and physiological characteristics of ANS divisions
• Parasympathetic activation effects (continued)
• Increased digestive organ smooth muscle activity
• Stimulation and coordination of defecation
• Contraction of urinary bladder during urination
• Constriction of respiratory passageways
• Reduction in heart rate and force of contraction
© 2011 Pearson Education, Inc.Figure 14.5 2 – 3
A summary of the anatomical characteristics of the sympathetic divisionof the ANS (left) and of the parasympathetic division of the ANS (right)
A summary of the anatomical characteristics of the sympathetic division of the ANS
A summary of the anatomical characteristicsof the parasympathetic division of the ANS
Sympathetic
CNS CNS
PNS PNS
Adrenalmedulla
Bloodstream
Preganglionicneuron
Preganglionicneuron
Preganglionicfiber
Preganglionicfiber
Sympatheticganglion
Ganglionicneurons
Ganglionicneurons
Postganglionicfiber
Postganglionicfiber
Parasympatheticganglion
KEY
Neurotransmitters
Acetylcholne
Norepinephrine
EpinephrineTARGET TARGET
Parasympathetic
or
© 2011 Pearson Education, Inc.
Module 14.5 Review
a. What neurotransmitter is released by all parasympathetic neurons?
b. Why is the parasympathetic division called the anabolic system?
c. What physiological changes are typical in tense (anxious) individuals?
© 2011 Pearson Education, Inc.
Section 2: Autonomic Regulation and Control Mechanisms
• Learning Outcomes
• 14.6 Discuss the relationship between the two divisions of the ANS and the significance of
dual innervation.
• 14.7 Define a visceral reflex, and explain the significance of such reflexes.
• 14.8 Explain the roles of baroreceptors and chemoreceptors in homeostasis.
• 14.9 Describe the hierarchy of interacting levels of control in the autonomic nervous
system beginning with the hypothalamus.
© 2011 Pearson Education, Inc.
Section 2: Autonomic Regulation and Control Mechanisms
• Autonomic Regulation and Control Mechanisms
• ANS output affects virtually every body system
• Unconscious ANS control can maintain homeostasis and vital physiological processes without conscious input
• Survival in a coma can continue for decades
© 2011 Pearson Education, Inc.Figure 14 Section 2
A general overview of theway the nervous systemdistributes information andissues motor commands
Central nervoussystem (CNS)processing
Processing at the consciouslevel, which can be affected bymemory, learning, or planning.
Sensory processingcenters
Motor centers operatingat the subconscious level.
Motor Responses
Motor pathways
Somatic Visceral
Sensory pathways
General sensoryreceptorsStimulus
Somatic nervoussystem (SNS)
Somatic effectors(skeletal muscles)
Autonomic nervoussystem (ANS)
Visceral effectors(smooth muscle,glands, cardiacmuscle, adipocytes)
© 2011 Pearson Education, Inc.
Module 14.6: Visceral responses to ANS control
• Visceral responses to ANS control
• Even in the absence of stimuli, autonomic motor neurons maintain continuous activity
• = Autonomic tone
• Many organs receive signals from both ANS divisions
• = Dual innervation
• Effects may be opposing or complementary
• In organs with only sympathetic innervation, response may vary with receptor type
© 2011 Pearson Education, Inc.Figure 14.6 1
© 2011 Pearson Education, Inc.Figure 14.6 1
© 2011 Pearson Education, Inc.Figure 14.6 1
© 2011 Pearson Education, Inc.Figure 14.6 1
© 2011 Pearson Education, Inc.Figure 14.6 1
© 2011 Pearson Education, Inc.
Module 14.6: Visceral responses to ANS control
• Dual innervation example: heart
• Heart consists of cardiac muscle tissue triggered by specialized pacemaker cells affected by ANS
• Parasympathetic: ACh release decreases heart rate
• Sympathetic: NE release accelerates heart rate
• Small amounts of both neurotransmitters released continuously to maintain autonomic tone
• Under resting conditions, parasympathetic dominates
© 2011 Pearson Education, Inc.Figure 14.6 2
At rest, both ANSdivisions are activeat low levels, butparasympatheticeffects predominate.
Increasedparasympatheticstimulationlowers theheart rate.
Parasympatheticinhibition or sympatheticstimulation increases theheart rate. The balancebetween these factorscan be precisely adjusted.
Increased sympatheticstimulation combinedwith parasympatheticinhibition result in anincrease in heart rate tomaximum levels.
Time
180
120
72
50
He
art
ra
te(b
ea
ts p
er
min
ute
)
The effects of both autonomic divisions on the heart, which receives dual innervation
© 2011 Pearson Education, Inc.
Module 14.6 Review
a. Define dual innervation.
b. Discuss autonomic tone and its significance in controlling visceral function.
c. You go outside in winter and blood flow to your skin is reduced, conserving body heat. You become angry, and your face turns red. Explain these changes.
© 2011 Pearson Education, Inc.
Module 14.7: Visceral reflexes
• Visceral reflexes
• Provide automatic motor responses that can be modified, facilitated, or inhibited by higher centers (especially those of hypothalamus)
• All are polysynaptic
• Components of reflex arc
1. Receptor (interoceptors such as nociceptors, thermoreceptors, baroreceptors, chemoreceptors, etc.)
2. Sensory neuron
3. Processing center (spinal cord nuclei and solitary nuclei of brain stem)
4. Visceral motor neurons (one or two)
© 2011 Pearson Education, Inc.
Module 14.7: Visceral reflexes
• Two visceral reflex types
1. Short reflexes
• Bypass CNS entirely
• Impulses relay with interneurons in ganglia
• Control simple motor responses with localized effects
• Usually just one part of an organ
• Predominate in enteric nervous system
© 2011 Pearson Education, Inc.Figure 14.7 1
A short reflex, which bypasses the CNS and involvessensory neurons and interneurons whose cell bodies arelocated within autonomic ganglia
Stimulus
Receptors inperipheral tissue
Afferent(sensory) fibers
Autonomicganglion
Ganglionicneuron
Shortreflex
Peripheraleffector
Response
© 2011 Pearson Education, Inc.
Module 14.7: Visceral reflexes
• Two visceral reflex types (continued)
2. Long reflexes
• Pathway
• Visceral sensory neurons in cranial nerves and autonomic nerves enter CNS through dorsal roots
• Interneurons process information in CNS
• ANS motor neurons carry response to visceral effectors
• Predominate over short reflexes
• Activate entire organs and coordinate responses of multiple organ systems
Animation: Sympathetic Innervation
Animation: Parasympathetic Innervation
© 2011 Pearson Education, Inc.Figure 14.7 2
A long reflex, which is the autonomic equivalentof a polysynaptic reflex
Stimulus
Receptors inperipheral tissue
Longreflex
Central nervoussystem
Processing centerin spinal cord
(or brain)
Preganglionicneuron
Autonomicganglion
PeripheraleffectorResponse
© 2011 Pearson Education, Inc.Figure 14.7 3
© 2011 Pearson Education, Inc.Figure 14.7 3
© 2011 Pearson Education, Inc.
Module 14.7 Review
a. Define visceral reflex.
b. Describe the solitary nucleus.
c. Compare short reflexes with long reflexes.
© 2011 Pearson Education, Inc.
Module 14.8: Monitoring visceral function with baroreceptors and chemoreceptors
• Baroreceptors
• Stretch receptors that monitor pressure changes
• Distortion of dendritic branches changes AP generation rate
• Free nerve endings in walls of:
• Blood vessels (monitor blood pressure and flow)
• Tubes of respiratory, digestive, and urinary tracts (monitor volume changes)
© 2011 Pearson Education, Inc.Figure 14.8 1
The sites and functions of thebody’s baroreceptors
Baroreceptors of CarotidSinus and Aortic Sinus
Baroreceptors of Lungs
Baroreceptors of Colon
Baroreceptors of Digestive Tract
Baroreceptors of Bladder Wall
Provide information onvolume of tract segments,trigger reflex movement ofmaterials along tract
Provide information on volume of urinarybladder, trigger urinationreflex
Provide information on volumeof fecal material in colon, triggerdefecation reflex
Provide information on lungstretching to respiratoryrhythmicity centers for controlof respiratory rate
Provide information on bloodpressure to cardiovascular andrespiratory control centers
© 2011 Pearson Education, Inc.
Module 14.8: Monitoring visceral function with baroreceptors and chemoreceptors
• Chemoreceptors
• Specialized neurons detecting small changes in specific chemical or compound concentration
• Reflexive control of respiratory and cardiovascular function
• Are found in:
1. Medulla oblongata and other brain areas
• Monitor pH and PCO2 in CSF
2. Carotid bodies (near origin of internal carotid arteries in neck)
• Monitor pH, PCO2, and PO2 in blood
3. Aortic bodies (between branches of aortic arch)
• Monitor pH, PCO2, and PO2 in blood
© 2011 Pearson Education, Inc.Figure 14.8 2
Chemoreceptors of Aortic Bodies
Chemoreceptors of Carotid Bodies
Chemoreceptors in RespiratoryCenters in the Medulla Oblongata
The body’s chemoreceptors, which play important roles in thereflexive control of respiration and cardiovascular function
Sensitive to changes in the pH,PCO2
, and PO2 in arterial blood
Sensitive to changes in the pH,PCO2
, and PO2 in arterial blood
Respond to the concentrations ofhydrogen ions (pH) and carbondioxide (PCO2
) in cerebrospinal fluid
Via cranialnerve IX
Via cranialnerve X
Trigger reflexiveadjustments inrespiratory andcardiovascularactivity
Trigger reflexiveadjustments indepth and rate ofrespiration
© 2011 Pearson Education, Inc.Figure 14.8 2
Blood vessel
Chemoreceptiveneurons
A photomicrograph ofa carotid body
Carotid body LM x 400
The body’s chemoreceptors, which play important roles in thereflexive control of respiration and cardiovascular function
© 2011 Pearson Education, Inc.
Module 14.8 Review
a. Define baroreceptor and chemoreceptor.
b. Which type of receptor is sensitive to changes in blood pH?
c. Where are baroreceptors located within the body?
© 2011 Pearson Education, Inc.
Module 14.9: Levels of ANS motor control
• Autonomic activities are controlled mainly in two CNS areas
1. Autonomic ganglia and spinal cord
• Simple reflexes
2. Medulla oblongata
• More complex reflexes
• Cardiovascular reflexes
• Respiratory reflexes
• Salivation
• Swallowing digestive secretions
• Peristalsis
• Urinary function
© 2011 Pearson Education, Inc.
Module 14.9: Levels of ANS motor control
• Lower CNS centers are subject to regulation by higher brain areas
• Hypothalamus
• Limbic system
• Thalamus
• Cerebral cortex
© 2011 Pearson Education, Inc.
Module 14.9 Review
a. What structure within the brain relays sensory information?
b. Identify the target structures for the SNS and ANS.
c. Harry has a brain tumor that is pressing against his hypothalamus. Would you expect this tumor to interfere with autonomic function? Why or why not?
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