s t a r t h e r e c h16 l e c t u r e
TRANSCRIPT
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Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
C h a p t e r
16
Neural Integration II: The Autonomic Nervous System
and Higher-Order Functions
PowerPoint® Lecture Slides prepared by Jason LaPres
Lone Star College - North Harris
Copyright © 2009 Pearson Education, Inc.,publishing as Pearson Benjamin Cummings
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An Introduction to the ANS
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 system functions: cardiovascular, respiratory,
digestive, urinary, reproductive
The Organization of the Somatic and Autonomic Nervous Systems
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An Introduction to the ANS
Figure 16-1 An Overview of Neural Integration.
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Autonomic Nervous System
Organization of the ANS
Integrative centers
For autonomic activity in hypothalamus
Neurons comparable to upper motor neurons in
SNS
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Autonomic Nervous System
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
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Autonomic Nervous System
Visceral Motor Neurons (cont’d)
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
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Autonomic Nervous System
Figure 16-2a The Organization of the Somatic and Nervous Systems.
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Autonomic Nervous System
Figure 16-2b The Organization of the Autonomic Nervous Systems.
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Divisions of the ANS
The autonomic nervous system
Operates largely outside our awareness
Has two divisions
Sympathetic division
– increases alertness, metabolic rate, and muscular
abilities
Parasympathetic division
– reduces metabolic rate and promotes digestion
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Divisions of the ANS
Sympathetic Division
“Kicks in” only during exertion, stress, or emergency
“Fight or flight”
Parasympathetic Division
Controls during resting conditions
“Rest and digest”
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Divisions of the ANS
Two divisions may work independently
Some structures innervated by only one
division
Two divisions may work together
Each controlling one stage of a complex
process
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Divisions of the ANS
Sympathetic Division
Preganglionic fibers (thoracic and superior lumbar;
thoracolumbar) 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
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Divisions of the ANS
Seven Responses to Increased Sympathetic Activity
Heightened mental alertness
Increased metabolic rate
Reduced digestive and urinary functions
Energy reserves activated
Increased respiratory rate and respiratory passageways dilate
Increased heart rate and blood pressure
Sweat glands activated
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Divisions of the ANS
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
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Divisions of the ANS
Parasympathetic Division
Rest and repose
Parasympathetic division stimulates visceral activity
Conserves energy and promotes sedentary activities
Decreased metabolic rate, heart rate, and blood pressure
Increased salivary and digestive glands secretion
Increased motility and blood flow in digestive tract
Urination and defecation stimulation
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Divisions of the ANS
Enteric Nervous System (ENS)
Third division of ANS
Extensive network in digestive tract walls
Complex visceral reflexes coordinated locally
Roughly 100 million neurons
All neurotransmitters are found in the brain
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The Sympathetic Division
Preganglionic neurons located between
segments T1 and L2 of spinal cord
Ganglionic neurons in ganglia near vertebral
column
Cell bodies of preganglionic neurons in lateral
gray horns
Axons enter ventral roots of segments
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The Sympathetic Division
Figure 16–3 The Organization of the Sympathetic Division of the ANS.
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The Sympathetic Division
Ganglionic Neurons
Occur in three locations
Sympathetic chain ganglia
Collateral ganglia
Suprarenal medullae
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The Sympathetic Division
Ganglionic Neurons
Sympathetic chain ganglia
Are on both sides of vertebral column
Control effectors:
– in body wall
– inside thoracic cavity
– in head
– in limbs
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The Sympathetic Division
Figure 16–4a Sites of Ganglia in Sympathetic Pathways
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The Sympathetic Division
Ganglionic Neurons
Collateral ganglia
Are anterior to vertebral bodies
Contain ganglionic neurons that innervate tissues
and organs in abdominopelvic cavity
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The Sympathetic Division
Figure 16–4b Sites of Ganglia in Sympathetic Pathways.
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The Sympathetic Division
Ganglionic Neurons
Suprarenal (adrenal) medullae
Very short axons
When stimulated, release neurotransmitters into
bloodstream (not at synapse)
Function as hormones to affect target cells
throughout body
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The Sympathetic Division
Figure 16–4c Sites of Ganglia in Sympathetic Pathways.
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The Sympathetic Division
Fibers in Sympathetic Division
Preganglionic fibers
Are relatively short
Ganglia located near spinal cord
Postganglionic fibers
Are relatively long, except at suprarenal medullae
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Organization and Anatomy of the Sympathetic Division
Ventral roots of spinal segments T1–L2 contain
sympathetic preganglionic fibers
Give rise to myelinated white ramus
Carry myelinated preganglionic fibers into
sympathetic chain ganglion
May synapse at collateral ganglia or in suprarenal
medullae
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Organization and Anatomy of the Sympathetic Division
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)
Postganglionic Fibers
Paths of unmyelinated postganglionic fibers depend on
targets
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Organization and Anatomy of the Sympathetic Division
Sympathetic Chain Ganglia
Postganglionic fibers control visceral effectors In body wall, head, neck, or limbs
Enter gray ramus
Return to spinal nerve for distribution
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
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Organization and Anatomy of the Sympathetic Division
Each sympathetic chain ganglia contains
3 cervical ganglia
10–12 thoracic ganglia
4–5 lumbar ganglia
4–5 sacral ganglia
1 coccygeal ganglion
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Organization and Anatomy of the Sympathetic Division
Sympathetic Chain Ganglia
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
Chain ganglia provide postganglionic fibers
Through gray rami (unmyelinated postganglionic fibers)
To cervical, lumbar, and sacral spinal nerves
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Organization and Anatomy of the Sympathetic Division
Sympathetic Chain Ganglia
Only spinal nerves T1–L2 have white rami
Every spinal nerve has gray ramus
That carries sympathetic postganglionic fibers for distribution
in body wall
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
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Organization and Anatomy of the Sympathetic Division
Figure 16–5 The Distribution of Sympathetic Innervation.
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Organization and Anatomy of the Sympathetic Division
Figure 16–5 The Distribution of Sympathetic Innervation.
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Organization and Anatomy of the Sympathetic Division
Figure 16–5 The Distribution of Sympathetic Innervation.
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Organization and Anatomy of the Sympathetic Division
Figure 16–5 The Distribution of Sympathetic Innervation.
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Organization and Anatomy of the Sympathetic Division
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
Originate as paired ganglia (left and right)
Usually fuse together in adults
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Organization and Anatomy of the Sympathetic Division
Collateral Ganglia
Postganglionic fibers
Leave collateral ganglia
Extend throughout abdominopelvic cavity
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
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Organization and Anatomy of the Sympathetic Division
Collateral Ganglia
Preganglionic fibers from seven inferior thoracic
segments
End at celiac ganglion or superior mesenteric ganglion
Ganglia embedded in network of autonomic nerves
Preganglionic fibers from lumbar segments
Form splanchnic nerves
End at inferior mesenteric ganglion
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Organization and Anatomy of the Sympathetic Division
Collateral Ganglia
Celiac ganglion
Pair of interconnected masses of gray matter
May form single mass or many interwoven masses
Postganglionic fibers innervate stomach, liver,
gallbladder, pancreas, and spleen
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Organization and Anatomy of the Sympathetic Division
Collateral Ganglia
Superior mesenteric ganglion
Near base of superior mesenteric artery
Postganglionic fibers innervate small intestine and
proximal 2/3 of large intestine
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Organization and Anatomy of the Sympathetic Division
Collateral Ganglia
Inferior mesenteric ganglion
Near base of inferior mesenteric artery
Postganglionic fibers provide sympathetic
innervation to portions of large intestine, kidney,
urinary bladder, and sex organs
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Organization and Anatomy of the Sympathetic Division
Suprarenal Medullae
Preganglionic fibers entering suprarenal gland
proceed to center (suprarenal medulla)
Modified sympathetic ganglion
Preganglionic fibers synapse on neuroendocrine cells
Specialized neurons secrete hormones into
bloodstream
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Organization and Anatomy of the Sympathetic Division
Suprarenal Medullae
Neuroendocrine cells of suprarenal medullae
Secrete neurotransmitters epinephrine (E) and
norepinephrine (NE)
Epinephrine:
– also called adrenaline
– is 75–80% of secretory output
Remaining is norepinephrine (NE)
– noradrenaline
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Organization and Anatomy of the Sympathetic Division
Suprarenal 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
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The Sympathetic Division
Sympathetic Activation
Change activities of tissues and organs by
Releasing NE at peripheral synapses:
– target specific effectors: smooth muscle fibers in blood
vessels of skin
– are activated in reflexes
– do not involve other visceral effectors
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The Sympathetic Division
Sympathetic Activation
Change activities of tissues and organs by
Distributing E and NE throughout body in
bloodstream:
– entire division responds (sympathetic activation)
– are controlled by sympathetic centers in hypothalamus
– effects are not limited to peripheral tissues
– alters CNS activity
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The Sympathetic Division
Sympathetic Activation
Increased alertness
Feelings of energy and euphoria
Change in breathing
Elevation in muscle tone
Mobilization of energy reserves
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Various Sympathetic Neurotransmitters
Stimulation of Sympathetic Preganglionic
Neurons
Releases ACh at synapses with ganglionic neurons
Excitatory effect on ganglionic neurons
Ganglionic Neurons
Release neurotransmitters at specific target organs
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Various Sympathetic Neurotransmitters
Ganglionic Neurons Axon terminals
Form branching networks of telodendria instead of synaptic
knobs
Telodendria form sympathetic varicosities:
– resemble string of pearls
– swollen segment packed with neurotransmitter vesicles
– pass along or near surface of effector cells
– no specialized postsynaptic membranes
– membrane receptors on surfaces of target cells
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Various Sympathetic Neurotransmitters
Figure 16–6 Sympathetic Varicosities.
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Various Sympathetic Neurotransmitters
Ganglionic Neurons
Axon terminals
Release NE at most varicosities:
– called adrenergic neuron
Some ganglionic neurons release ACh instead:
– are located in body wall, skin, brain, and skeletal muscles
– called cholinergic neurons
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Various Sympathetic Neurotransmitters
Sympathetic Stimulation and the Release of NE
and E
Primarily from interactions of NE and E with two types
of adrenergic membrane receptors
Alpha receptors (NE more potent)
Beta receptors
Activates enzymes on inside of cell membrane via G
proteins
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Various Sympathetic Neurotransmitters
Sympathetic Stimulation and the Release of NE
and E
Alpha-1 (1)
More common type of alpha receptor
Releases intracellular calcium ions from reserves in
endoplasmic reticulum
Has excitatory effect on target cell
Alpha-2 (2)
Lowers cAMP levels in cytoplasm
Has inhibitory effect on the cell
Helps coordinate sympathetic and parasympathetic activities
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Various Sympathetic Neurotransmitters
Sympathetic Stimulation and the Release of
NE and E
Beta () receptors
Affect membranes in many organs (skeletal
muscles, lungs, heart, and liver)
Trigger metabolic changes in target cell
Stimulation increases intracellular cAMP levels
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Various Sympathetic Neurotransmitters
Three main types of beta receptors:
Beta-1 (1)
Increases metabolic activity
Beta-2 (2)
Triggers relaxation of smooth muscles along respiratory tract
Beta-3 (3)
Leads to lipolysis, the breakdown of triglycerides in
adipocytes
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Various Sympathetic Neurotransmitters
Sympathetic Stimulation and the Release
of ACh and NO
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
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Various Sympathetic Neurotransmitters
Sympathetic Stimulation and the Release
of ACh and 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
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The Parasympathetic Division
Autonomic Nuclei
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
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The Parasympathetic Division
Ganglionic Neurons in Peripheral Ganglia
Terminal ganglion
Near target organ
Usually paired
Intramural ganglion
Embedded in tissues of target organ
Interconnected masses
Clusters of ganglion cells
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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
The Distribution of Parasympathetic Innervation
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Organization and Anatomy of the Parasympathetic Division
Figure 16–7 The Organization of the Parasympathetic Division of the ANS.
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Organization and Anatomy of the Parasympathetic Division
Oculomotor, Facial, and Glossopharyngeal
Nerves
Control visceral structures in head
Synapse in ciliary, pterygopalatine,
submandibular, and otic ganglia
Short postganglionic fibers continue to their peripheral
targets
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Organization and Anatomy of the Parasympathetic Division
Vagus Nerve
Provides preganglionic parasympathetic innervation
to structures in
Neck
Thoracic and abdominopelvic cavity as distant as a distal
portion of large intestine
Provides 75% of all parasympathetic outflow
Branches intermingle with fibers of sympathetic division
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Organization and Anatomy of the Parasympathetic Division
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, and the
sex organs
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Organization and Anatomy of the Parasympathetic Division
Figure 16–8 The Distribution of Parasympathetic Innervation.
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Organization and Anatomy of the Parasympathetic Division
Figure 16–8 The Distribution of Parasympathetic Innervation.
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The Parasympathetic Division
Parasympathetic Activation
Centers on relaxation, food processing, and
energy absorption
Localized effects, last a few seconds at most
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The Parasympathetic Division
Major effects of parasympathetic division include
Constriction of pupils
Restricts light entering eyes
Secretion by digestive glands
Exocrine and endocrine
Secretion of hormones
Nutrient absorption and utilization
Changes in blood flow and glandular activity
Associated with sexual arousal
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The Parasympathetic Division
Major effects of parasympathetic division include
Increase in smooth muscle activity along digestive
tract
Defecation: stimulation and coordination
Contraction of urinary bladder during urination
Constriction of respiratory passageways
Reduction in heart rate and force of contraction
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The Parasympathetic Division
Anabolic System
Stimulation increases nutrient content of
blood
Cells absorb nutrients
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Parasympathetic Neurons Release ACh
Neuromuscular and Neuroglandular Junctions
All release ACh as neurotransmitter
Small, with narrow synaptic clefts
Effects of stimulation are short lived
Inactivated by AChE at synapse
ACh is also inactivated by pseudocholinesterase (tissue
cholinesterase) in surrounding tissues
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Parasympathetic Neurons Release ACh
Membrane Receptors and Responses
Nicotinic receptors
On surfaces of ganglion cells (sympathetic and
parasympathetic):
– exposure to ACh causes excitation of ganglionic neuron
or muscle fiber
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Parasympathetic Neurons Release ACh
Membrane Receptors and Responses Muscarinic receptors
At cholinergic neuromuscular or neuroglandular junctions (parasympathetic)
At few cholinergic junctions (sympathetic)
G proteins:
– effects are longer lasting than nicotinic receptors
– response reflects activation or inactivation of specific enzymes
– can be excitatory or inhibitory
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Parasympathetic Neurons Release ACh
Membrane Receptors and Responses Dangerous environmental toxins
Produce exaggerated, uncontrolled responses Nicotine:
– binds to nicotinic receptors– targets autonomic ganglia and skeletal neuromuscular
junctions – 50 mg ingested or absorbed through skin– signs:
» vomiting, diarrhea, high blood pressure, rapid heart rate, sweating, profuse salivation, convulsions
– may result in coma or death
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Parasympathetic Neurons Release ACh
Dangerous Environmental Toxins (cont’d) 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)
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Parasympathetic Neurons Release ACh
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Parasympathetic Neurons Release ACh
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Dual Innervation
Sympathetic
Widespread impact
Reaches organs and tissues throughout body
Parasympathetic
Innervates only specific visceral structures
Most vital organs receive instructions from both
sympathetic and parasympathetic divisions
Two divisions commonly have opposing effects
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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
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Dual Innervation
Figure 16–9 Summary: The Anatomical Differences between theSympathetic and Parasympathetic Divisions.
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Dual Innervation
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Dual Innervation
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Dual Innervation
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Dual Innervation
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Dual Innervation
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Dual Innervation
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
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Dual Innervation
Anatomy of Dual Innervation
Cardiac plexus
Pulmonary plexus
Esophageal plexus
Celiac plexus
Inferior mesenteric plexus
Hypogastric plexus
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Anatomy of Dual Innervation
Cardiac and Pulmonary Plexuses
Autonomic fibers entering thoracic cavity
intersect
Contain
Sympathetic and parasympathetic fibers for heart and
lungs
Parasympathetic ganglia whose output affects those
organs
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Anatomy of Dual Innervation
Esophageal Plexus
Contains
Descending branches of vagus nerve
Splanchnic nerves leaving sympathetic chain
Parasympathetic preganglionic fibers of vagus nerve
enter abdominopelvic cavity with esophagus
Fibers enter celiac plexus (solar plexus)
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Anatomy of Dual Innervation
Celiac Plexus
Associated with smaller plexuses, such as
inferior mesenteric plexus
Innervates viscera within abdominal cavity
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Anatomy of Dual Innervation
Hypogastric Plexus
Contains
Parasympathetic outflow of pelvic nerves
Sympathetic postganglionic fibers from inferior mesenteric
ganglion
Splanchnic nerves from sacral sympathetic chain
Innervates digestive, urinary, and reproductive
organs of pelvic cavity
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Anatomy of Dual Innervation
Figure 16–10 The Autonomic Plexuses.
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Dual Innervation
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
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Dual Innervation
Autonomic Tone
Autonomic motor neurons
Maintain resting level of spontaneous activity
Background level of activation determines
autonomic tone
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Dual Innervation
Autonomic Tone
Significant where dual innervation occurs
Two divisions have opposing effects
More important when dual innervation does
not occur
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Dual Innervation
The heart receives dual innervation
Two divisions have opposing effects Parasympathetic division
Acetylcholine released by postganglionic fibers slows heart rate
Sympathetic division NE released by varicosities accelerates heart rate
Balance between two divisions Autonomic tone is present
Releases small amounts of both neurotransmitters continuously
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Dual Innervation
The heart receives dual innervation
Parasympathetic innervation dominates under
resting conditions
Crisis accelerates heart rate by
Stimulation of sympathetic innervation
Inhibition of parasympathetic innervation
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Dual 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
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
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Visceral Reflexes Regulate Autonomic Function
Somatic Motor Control
Centers in all portions of CNS
Lowest level regulatory control
Lower motor neurons of cranial and spinal visceral reflex
arcs
Highest level:
Pyramidal motor neurons of primary motor cortex
Operating with feedback from cerebellum and basal nuclei
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Visceral Reflexes Regulate Autonomic Function
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
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Visceral Reflexes Regulate Autonomic Function
Visceral Reflexes
Long reflexes
Autonomic equivalents of polysynaptic reflexes
Visceral sensory neurons deliver information to CNS along
dorsal roots of spinal nerves:
– within sensory branches of cranial nerves
– within autonomic nerves that innervate visceral effectors
ANS carries motor commands to visceral effectors
Coordinate activities of entire organ
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Visceral Reflexes Regulate Autonomic Function
Visceral Reflexes Short reflexes
Bypass CNS Involve sensory neurons and interneurons located
within autonomic ganglia Interneurons synapse on ganglionic neurons Motor commands distributed by postganglionic
fibers Control simple motor responses with localized
effects One small part of target organ
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Visceral Reflexes Regulate Autonomic Function
Figure 16–11 Visceral Reflexes.
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Visceral Reflexes Regulate Autonomic Function
Visceral Reflexes
Regulating visceral activity
Most organs:
– long reflexes most important
Digestive tract:
– short reflexes provide most control and coordination
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Visceral Reflexes Regulate Autonomic Function
Visceral Reflexes
Enteric nervous system
Ganglia in the walls of digestive tract contain cell
bodies of:
– visceral sensory neurons
– interneurons
– visceral motor neurons
Axons form extensive nerve nets
Control digestive functions independent of CNS
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Visceral Reflexes Regulate Autonomic Function
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Visceral Reflexes Regulate Autonomic Function
Higher Levels of Autonomic Control Simple reflexes from spinal cord provide rapid and
automatic responses
Complex reflexes coordinated in medulla oblongata Contains centers and nuclei involved in:
– salivation
– swallowing
– digestive secretions
– peristalsis
– urinary function
Regulated by hypothalamus
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Visceral Reflexes Regulate Autonomic Function
The Integration of SNS and ANS Activities
Many parallels in organization and function
Integration at brain stem
Both systems under control of higher centers
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Visceral Reflexes Regulate Autonomic Function
Figure 16–12 A Comparison of Somatic and Autonomic Function.
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Visceral Reflexes Regulate Autonomic Function
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Higher-Order Functions
Require the cerebral cortex
Involve conscious and unconscious
information processing
Not part of programmed “wiring” of brain
Can adjust over time
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Higher-Order Functions
Memory Fact memories
Are specific bits of information
Skill memories Learned motor behaviors
Incorporated at unconscious level with repetition
Programmed behaviors stored in appropriate area of brain
stem
Complex are stored and involve motor patterns in the basal
nuclei, cerebral cortex, and cerebellum
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Higher-Order Functions
Memory
Short–term memories
Information that can be recalled immediately
Contain small bits of information
Primary memories
Long-term memories
Memory consolidation: conversion from short-term to long-
term memory:
– secondary memories fade and require effort to recall
– tertiary memories are with you for life
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Higher-Order Functions
Figure 16–13 Memory Storage.
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Higher-Order Functions
Brain Regions Involved in Memory Consolidation
and Access
Amygdaloid body and hippocampus
Nucleus basalis
Cerebral cortex
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Higher-Order Functions
Amygdaloid body and hippocampus
Are essential to memory consolidation
Damage may cause
Inability to convert short-term memories to new
long-term memories
Existing long-term memories remain intact and
accessible
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Higher-Order Functions
Nucleus Basalis
Cerebral nucleus near diencephalon
Plays uncertain role in memory storage and retrieval
Tracts connect with hippocampus, amygdaloid body,
and cerebral cortex
Damage changes emotional states, memory, and
intellectual functions
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Higher-Order Functions
Cerebral cortex Stores long-term memories
Conscious motor and sensory memories referred to
association areas
Occipital and temporal lobes Special portions crucial to memories of faces, voices, and
words
A specific neuron may be activated by combination of
sensory stimuli associated with particular individual; called
“grandmother cells”
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Higher-Order Functions
Cerebral cortex
Visual association area
Auditory association area
Speech center
Frontal lobes
Related information stored in other locations
If storage area is damaged, memory will be incomplete
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Higher-Order Functions
Cellular Mechanisms of Memory Formation and
Storage
Involves anatomical and physiological
changes in neurons and synapses
Increased neurotransmitter release
Facilitation at synapses
Formation of additional synaptic connections
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Higher-Order Functions
Increased Neurotransmitter Release
Frequently active synapse increases the
amount of neurotransmitter it stores
Releases more on each stimulation
The more neurotransmitter released, the
greater effect on postsynaptic neuron
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Higher-Order Functions
Facilitation at Synapses Neural circuit repeatedly activated
Synaptic terminals begin continuously releasing
neurotransmitter
Neurotransmitter binds to receptors on postsynaptic
membrane
Produces graded depolarization
Brings membrane closer to threshold
Facilitation results affect all neurons in circuit
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Higher-Order Functions
Formation of Additional Synaptic Connections
Neurons repeatedly communicating
Axon tip branches and forms additional synapses on
postsynaptic neuron
Presynaptic neuron has greater effect on
transmembrane potential of postsynaptic neuron
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Higher-Order Functions
Cellular Mechanisms of Memory Formation and
Storage
Basis of memory storage
Processes create anatomical changes
Facilitate communication along specific neural circuit
Memory Engram
Single circuit corresponds to single memory
Forms as result of experience and repetition
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Higher-Order Functions
Cellular Mechanisms of Memory Formation and
Storage
Efficient conversion of short-term memory
Takes at least 1 hour
Repetition crucial
Factors of conversion
Nature, intensity, and frequency of original stimulus
Strong, repeated, and exceedingly pleasant or unpleasant
events likely converted to long-term memories
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Higher-Order Functions
Cellular Mechanisms of Memory Formation and Storage Drugs stimulate CNS
Caffeine and nicotine are examples:– enhance memory consolidation through facilitation
NMDA (N-methyl D-aspartate) Receptors:– linked to consolidation– chemically gated calcium channels– activated by neurotransmitter glycine– gates open, calcium enters cell– blocking NMDA receptors in hippocampus prevents long-
term memory formation
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Higher-Order Functions
States of Consciousness
Many gradations of states
Degree of wakefulness indicates level of
ongoing CNS activity
When abnormal or depressed, state of
wakefulness is affected
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Higher-Order Functions
States of Consciousness
Deep sleep
Also called slow-wave sleep
Entire body relaxes
Cerebral cortex activity minimal
Heart rate, blood pressure, respiratory rate, and
energy utilization decline up to 30%
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Higher-Order Functions
States of Consciousness
Rapid eye movement (REM) sleep
Active dreaming occurs
Changes in blood pressure and respiratory rate
Less receptive to outside stimuli than in deep sleep
Muscle tone decreases markedly
Intense inhibition of somatic motor neurons
Eyes move rapidly as dream events unfold
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Higher-Order Functions
States of Consciousness
Nighttime sleep pattern
Alternates between levels
Begins in deep sleep
REM periods average 5 minutes in length;
increase to 20 minutes over 8 hours
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Higher-Order Functions
Sleep
Has important impact on CNS
Produces only minor changes in physiological
activities of organs and systems
Protein synthesis in neurons increases during sleep
Extended periods without sleep lead to disturbances
in mental function 25% of U.S. population experiences sleep disorders
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Higher-Order Functions
Figure 16–14 Levels of Sleep.
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Higher-Order Functions
States of Consciousness
Arousal and the reticular activating system (RAS)
Awakening from sleep
Function of reticular formation:
– extensive interconnections with sensory, motor, integrative nuclei,
and pathways along brain stem
Determined by complex interactions between reticular formation
and cerebral cortex
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Higher-Order Functions
Reticular Activating System (RAS) Important brain stem component
Diffuse network in reticular formation
Extends from medulla oblongata to mesencephalon
Output of RAS projects to thalamic nuclei that
influence large areas of cerebral cortex
When RAS inactive, so is cerebral cortex
Stimulation of RAS produces widespread activation of
cerebral cortex
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Higher-Order Functions
Arousal and the Reticular Activating
System
Ending sleep
Any stimulus activates reticular formation and RAS
Arousal occurs rapidly
Effects of single stimulation of RAS last less than a
minute
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Higher-Order Functions
Arousal and the Reticular Activating System
Maintaining consciousness
Activity in cerebral cortex, basal nuclei, and sensory and
motor pathways continue to stimulate RAS:
– after many hours, reticular formation becomes less responsive
to stimulation
– individual becomes less alert and more lethargic
– neural fatigue reduces RAS activity
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Higher-Order Functions
Arousal and the Reticular Activating System
Regulation of awake–asleep cycles
Involves interplay between brain stem nuclei that use
different neurotransmitters
Group of nuclei stimulates RAS with NE and maintains
awake, alert state
Other group promotes deep sleep by depressing RAS
activity with serotonin
“Dueling” nuclei located in brain stem
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Higher-Order Functions
Figure 16–15 The Reticular Activating System.
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Brain Chemistry
Huntington Disease
Destruction of ACh-secreting and GABA-secreting
neurons in basal nuclei
Symptoms appear as basal nuclei and frontal lobes
slowly degenerate
Difficulty controlling movements
Intellectual abilities gradually decline
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Brain Chemistry
Lysergic Acid Diethylamide (LSD)
Powerful hallucinogenic drug
Activates serotonin receptors in brain stem,
hypothalamus, and limbic system
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Brain Chemistry
Serotonin
Compounds that enhance effects also
produce hallucinations (LSD)
Compounds that inhibit or block action cause
severe depression and anxiety
Variations in levels affect sensory
interpretation and emotional states
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Brain Chemistry
Serotonin
Fluoxetine (Prozac) Slows removal of serotonin at synapses
Increases serotonin concentrations at postsynaptic
membrane
Classified as selective serotonin reuptake
inhibitors (SSRIs)
Other SSRIs:
– Celexa, Luvox, Paxil, and Zoloft
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Brain Chemistry
Parkinson Disease
Inadequate dopamine production causes motor
problems
Dopamine
Secretion stimulated by amphetamines, or “speed”
Large doses can produce symptoms resembling
schizophrenia
Important in nuclei that control intentional movements
Important in other centers of diencephalon and cerebrum
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Aging and the Nervous System
Anatomical and physiological changes
begin after maturity (age 30)
Accumulate over time
85% of people over age 65 have changes
in mental performance and CNS function
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Aging and the Nervous System
Reduction in Brain Size and Weight
Decrease in volume of cerebral cortex
Narrower gyri and wider sulci
Larger subarachnoid space
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Aging and the Nervous System
Reduction in Number of Neurons
Brain shrinkage linked to loss of cortical
neurons
No neuronal loss in brain stem nuclei
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Aging and the Nervous System
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
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Aging and the Nervous System
Changes in Synaptic Organization of Brain
Number of dendritic branches, spines, and
interconnections decreases
Synaptic connections lost
Rate of neurotransmitter production declines
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Aging and the Nervous System
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
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Aging and the Nervous System
Intracellular and Extracellular Changes in
CNS Neurons
Plaques
Extracellular accumulations of fibrillar proteins
Surrounded by abnormal dendrites and axons
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Aging and the Nervous System
Intracellular and Extracellular Changes in
CNS Neurons
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
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Aging and the Nervous System
Anatomical Changes
Linked to functional changes
Neural processing becomes less efficient with
age
Memory consolidation more difficult
Secondary memories harder to access
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Aging and the Nervous System
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
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Aging and the Nervous System
Incapacitation
85% of elderly population develops changes
that do not interfere with abilities
Some individuals become incapacitated by
progressive CNS changes
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Aging and the Nervous System
Senility
Also called senile dementia
Degenerative changes
Memory loss
Anterograde amnesia (lose ability to store new memories)
Emotional disturbances
Alzheimer disease is most common
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Nervous System Integration
Monitors all other systems
Issues commands that adjust their
activities
Like conductor of orchestra
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Nervous System Integration
Neural Tissue
Extremely delicate
Extracellular environment must maintain
homeostatic limits
If regulatory mechanisms break down,
neurological disorders appear
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Nervous System Integration
Figure 16–16 Functional Relationships between the Nervous System and Other Systems.
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Nervous System Integration
Figure 16–16 Functional Relationships between the Nervous System and Other Systems.
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Nervous System Integration
Figure 16–16 Functional Relationships between the Nervous System and Other Systems.
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Disorders of Nervous System
Infections
Rabies, polio
Congenital disorders
Spina bifida, hydrocephalus
Degenerative disorders
Parkinson disease, Alzheimer disease
Tumors of neural origin
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Disorders of Nervous System
Trauma
Spinal cord injuries, concussions
Toxins
Heavy metals, neurotoxins
Secondary disorders
Strokes
Demyelination disorders
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Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Disorders of Nervous System
Neurological Examinations
Physicians trace source of specific problem
Evaluate sensory, motor, behavioral, and
cognitive functions of nervous system