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Chapter 16: Neural Integration II:
The Autonomic Nervous System and Higher-Order
Functions
Somatic Nervous System (SNS)
• Operates under conscious control
• Seldom affects long-term survival
Autonomic Nervous System (ANS)
• Operates without conscious instruction
• Coordinates systems functions:– cardiovascular– respiratory– digestive– urinary– reproductive
Figure 16–2
Organization Similarities of SNS and ANS
Organization Similarities of SNS and ANS
• Are efferent divisions • Carry motor commands:
– SNS controls skeletal muscles– ANS controls visceral effectors
The Organization of the Somatic and Autonomic Nervous SystemsPLAYPLAY
Figure 16–2a
The SNS
The SNS
• Motor neurons of central nervous system
• Direct control over skeletal muscles
Figure 16–2b
The ANS
The ANS
• Motor neurons synapse on visceral motor neurons in autonomic ganglia
• Ganglionic neurons control visceral effectors
Integrative Centers
• For autonomic activity in hypothalamus
• Neurons comparable to upper motor neurons in SNS
Visceral Motor Neurons
• In brain stem and spinal cord, are known as preganglionic neurons
• Part of visceral reflex arcs
Preganglionic Fibers
• Axons of preganglionic neurons
• Leave CNS and synapse on ganglionic neurons
Autonomic Ganglia
• Peripheral ganglia• Contain many ganglionic neurons• Ganglionic neurons innervate visceral
effectors: – cardiac muscle– smooth muscle– glands– adipose tissues
Postganglionic Fibers
• Axons of ganglionic neurons
• Begin at autonomic ganglia:– extend to peripheral target organs
Somatic or Visceral Sensory Information
• Trigger visceral reflexes
• Motor commands of reflexes distributed by ANS
Motor Commands
• May control activities of target organs
• May alter ongoing activity
• Changes in visceral activity: – postganglionic fibers release
neurotransmitters
Sympathetic Division
• Does not “Kick in” only during exertion, stress, or emergency (common misconception)
• Some aspects of the system are functioning in visceral reflexes for normal activity. (pupil dilation and water balance, for instance)
Parasympathetic Division
• Controls during resting conditions
• Tends to conserve energy
• Allows for “quiet functions” (e.g. digestion, defecation, etc.)
Divisions of the ANS
• 2 divisions may work independently:– some structures innervated by only 1 division
• 2 divisions may work together:– each controlling one stage of a complex
process
Sympathetic Division
• Preganglionic fibers (thoracic and superior lumbar) synapse in ganglia near spinal cord
• Preganglionic fibers are short
• Postganglionic fibers are long
Figure 16–3
ANS: Sympathetic Division
Fight or Flight
• Sympathetic division readies body for crisis
• Increase in sympathetic activity:– stimulates tissue metabolism– increases alertness
7 Responses to Increased Sympathetic Activity
1. Heightened mental alertness
2. Increased metabolic rate
3. Reduced digestive and urinary functions
4. Energy reserves activated
5. Increased respiratory rate and respiratory passageways dilate
6. Increased heart rate and blood pressure
7. Sweat glands activated
Structure of 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
Figure 16–4
Ganglionic Neurons
• Occur in 3 locations:– sympathetic chain
ganglia– collateral ganglia– adrenal medullae
Sympathetic Chain Ganglia
• Are on both sides of vertebral column
• Control effectors:– in body wall – inside thoracic cavity – in head – in limbs
Sympathetic Chain GangliaFigure 16–4a
Collateral Ganglia
• Are anterior to vertebral bodies
• Contain ganglionic neurons that innervate tissues and organs in abdominopelvic cavity
Figure 16–4b
Collateral Ganglia
Parasympathetic Division
• Preganglionic fibers originate in brain stem and sacral segments of spinal cord
• Synapse in ganglia close to (or within) target organs
• Preganglionic fibers are long
• Postganglionic fibers are short
Rest and Repose
• Parasympathetic division stimulates visceral activity
• Conserves energy and promotes sedentary activities
Pattern of Responses to Increased Levels of Parasympathetic Activity
• Decreased: – metabolic rate– heart rate and blood pressure
• Increased: – salivary and digestive glands secretion– motility and blood flow in digestive tract
• Urination and defecation stimulation
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
Figure 16–4c
The Adrenal Medullae
Modified Sympathetic Ganglion
• At the center of each adrenal gland in area known as adrenal medulla
• Very short axons• When stimulated, release
neurotransmitters into bloodstream (not at synapse)
• Functions as hormones affect target cells throughout body
Fibers in Sympathetic Division
• Preganglionic fibers:– are relatively short– ganglia located near spinal cord
• Postganglionic fibers:– are relatively long, except at adrenal medullae
• Ventral roots of spinal segments T1–L2 contain sympathetic preganglionic fibers
Ventral Roots
• Give rise to myelinated white ramus
• Carry myelinated preganglionic fibers into sympathetic chain ganglion
• May synapse at collateral ganglia or in adrenal medullae
Preganglionic Fibers
• 1 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
Figure 16–5
Sympathetic Innervation
The Distribution of Sympathetic InnervationPLAYPLAY
Sympathetic Chain
• 3 cervical ganglia
• 10–12 thoracic ganglia
• 4–5 lumbar ganglia
• 4–5 sacral ganglia
• 1 coccygeal ganglion
Preganglionic Neurons
• Limited to spinal cord segments T1–L2:
– white rami (myelinated preganglionic fibers)– gray rami (unmyelinated postganglionic fibers)
Rami
• 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
Abdominopelvic Viscera
• Receive sympathetic innervation via sympathetic preganglionic fibers
• Synapse in separate collateral ganglia
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
Postganglionic Fibers
• Leave collateral ganglia
• Extend throughout abdominopelvic cavity
• Innervate variety of visceral tissues and organs
Preganglionic Fibers
• From 7 inferior thoracic segments:– end at celiac ganglion or superior mesenteric
ganglion
• Ganglia embedded in network of autonomic nerves
• From lumbar segments:– form splanchnic nerves – end at inferior mesenteric ganglion
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
Superior Mesenteric Ganglion
• Near base of superior mesenteric artery
• Postganglionic fibers innervate small intestine and proximal 2/3 of large intestine
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
Neurotransmitters of the sympathetic division
Neuroendocrine Cells of Adrenal Medullae
• Secrete neurotransmitters epinephrine (E) and norepinephrine (NE)
• Since they are carried in the blood they are actually considered hormones
Epinephrine
• Also called adrenaline
• Is 75–80% of secretory output
• Remaining is noradrenaline (NE)
Sympathetic Division
• Can change activities of tissues and organs by:– releasing NE at peripheral synapses– distributing E and NE throughout body in
bloodstream
Crisis Mode
• Entire division responds (sympathetic activation)
• Are controlled by sympathetic centers in hypothalamus
• Effects are not limited to peripheral tissues
• Alters CNS activity
5 Effects of Sympathetic Activation
1. Increased alertness
2. Feelings of energy and euphoria
3. Change in breathing
4. Elevation in muscle tone
5. Mobilization of energy reserves
Stimulation of Sympathetic Preganglionic Neurons
• Releases ACh at synapses with ganglionic neurons
Cholinergic Synapses
• Use ACh as transmitter
• Excitatory effect on ganglionic neurons
Stimulation of Ganglionic Neurons
• Releases neurotransmitters at specific target organs from telodendria
• Form branching network instead of synaptic knobs
Figure 16–6
Sympathetic Varicosities
• Resemble string of pearls
• Packed with neurotransmitter vesicles
Chains of Varicosities
• Formed from postganglionic neurons
• Pass along or near surface of effector cells
• No specialized postsynaptic membranes
• Membrane receptors on surfaces of target cells
• Release NE
Adrenergic Neurons
• Use NE as neurotransmitter
Varicosities and ACh
• Some ganglionic neurons release ACh instead of NE
• Are located in body wall, skin, brain, and skeletal muscles
NE Released by Varicosities
• Affects targets until reabsorbed or inactivated
• 50–80% of NE is reabsorbed by varicosities:– is reused or broken down by MAO
• The rest diffuses out or is broken down by enzymes
Duration of Effects on Postsynaptic Membrane
• NE persist for a few seconds
• ACh only for 20 msec
Effects of NE or E Released by Adrenal Medullae Last longer because:– bloodstream does not contain MAO or COMT– most tissues contain low concentrations
2 Classes of Sympathetic Receptors
• Alpha receptors
• Beta receptors
Norepinephrine
• Stimulates alpha receptors to greater degree than beta receptors
Epinephrine
• Stimulates both classes of receptors
Localized Sympathetic Activity
• Involves release of NE at varicosities
• Primarily affects alpha receptors near active varicosities
Generalized Sympathetic Activation
• Release of E by adrenal medulla
• Affect alpha and beta receptors throughout body
Stimulation of Alpha () Receptors
• Activates enzymes on inside of cell membrane
• Alpha-1 (1)
• Alpha-2 (2)
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
Beta () Receptors
• Affect membranes in many organs (skeletal muscles, lungs, heart, and liver)
• Trigger metabolic changes in target cell• Changes occur indirectly• Each is a G protein • Stimulation increases intracellular cAMP levels
Beta Receptors
• Two types:– Beta-1 (1) Increases metabolic activity
– Beta-2 (2) • Causes inhibition• Triggers relaxation of smooth muscles along
respiratory tract
Beta-3 (3)
• Found in adipose tissue
• Leads to lipolysis, the breakdown of triglycerides in adipocytes
• Releases fatty acids into circulation
Sympathetic Postganglionic Fibers
• Mostly adrenergic (release NE)
• A few cholinergic (release ACh)
• Innervate sweat glands of skin and blood vessels of skeletal muscles and brain
• Stimulate sweat gland secretion and dilates blood vessels
ACh
• Released by parasympathetic division
• Body wall and skeletal muscles are not innervated by parasympathetic division
• Both NE and ACh needed to regulate visceral functions
Nitroxidergic Synapses
• Release nitric oxide (NO) as neurotransmitter
• Neurons innervate smooth muscles in walls of blood vessels in skeletal muscles and the brain
• Produces vasodilation and increased blood flow
Summary of Sympathetic Division (1 of 3)
• Includes 2 sets of sympathetic chain ganglia, 1 on each side of vertebral column
• 3 collateral ganglia anterior to vertebral column
• 2 adrenal medullae• Preganglionic fibers are short because
ganglia are close to spinal cord
Summary of Sympathetic Division (2 of 3)
• Postganglionic fibers are longer and stretch to reach target organs
• Single preganglionic fiber may innervate 2 dozen or more ganglionic neurons in different ganglia
Summary of Sympathetic Division (3 of 3)
• Preganglionic neurons release ACh; most postganglionic fibers release NE, few release ACh or NO
• Effector response depends on second messengers activated when NE or E binds to alpha or beta receptors
ANS: 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
Ganglionic Neurons in Peripheral Ganglia
• Preganglionic fiber synapses on 6–8 ganglionic neurons:– terminal ganglion:
• near target organ• usually paired
– intramural ganglion: • embedded in tissues of target organ• interconnected masses• clusters of ganglion cells
Pattern of Parasympathetic Division
• All ganglionic neurons in same ganglion
• Postganglionic fibers influence same target organ
• Effects of parasympathetic stimulation more specific and localized
What are the mechanisms of neurotransmitter release in
the parasympathetic division?
Parasympathetic Preganglionic Fibers
• Leave brain as components of cranial nerves:– III (oculomotor)– VII (facial)– IX (glossopharyngeal)– X (vagus)
The Distribution of Parasympathetic InnervationPLAYPLAY
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
Vagus Nerve• Preganglionic parasympathetic innervation
to structures in:– neck– thoracic and abdominopelvic cavity– distal portion of large intestine
• Provides 75% of all parasympathetic outflow
• Branches intermingle with fibers of sympathetic division
Sacral Segments of Spinal Cord
• Preganglionic fibers carry sacral parasympathetic output
• Do not join ventral roots of spinal nerves
Pelvic Nerves
• Innervate intramural ganglia in walls of:– kidneys– urinary bladder– portions of large intestine– sex organs
Parasympathetic Activation
• Centers on relaxation, food processing, and energy absorption
• Localized effects, last a few seconds at most
10 Effects of Parasympathetic Activation
1. Constriction of pupils:– restricts light entering eyes
2. Secretion by digestive glands:– exocrine and endocrine
3. Secretion of hormones
4. Changes in blood flow and glandular activity:
– associated with sexual arousal
5. Increases smooth muscle activity:– along digestive tract
6. Defecation:– stimulation and coordination
7. Contraction of urinary bladder:– during urination
8. Constriction of respiratory passageways
9. Reduction in heart rate:– and force of contraction
10. Sexual arousal:– stimulation of sexual glandsSexual arousal:– stimulation of sexual glands
Parasympathetic Neurons
• All release ACh as neurotransmitter
• Effects vary widely
• Inactivated by AChE at synapse
• Ach is also inactivated by pseudocholinesterase in surrounding tissues
2 Types of ACh Receptors on Postsynaptic Membranes
• Nicotinic receptors
• Muscarinic receptors
Nicotinic Receptors
• On surfaces of ganglion cells (sympathetic and parasympathetic)
• At neuromuscular junctions of somatic nervous system
Action of Nicotinic Receptors
• Exposure to ACh causes excitation of ganglionic neuron or muscle fiber
• Open chemically gated channels in postsynaptic membrane
Muscarinic Receptors
• At cholinergic neuromuscular or neuroglandular junctions (parasympathetic)
• At few cholinergic junctions (sympathetic)
• G proteins
Action of Muscarinic Receptors
• Effects are longer lasting than nicotinic receptors
• Response reflects activation or inactivation of specific enzymes
• Can be excitatory or inhibitory
Toxins• Produce exaggerated, uncontrolled
responses
• Nicotine:– binds to nicotinic receptors– targets autonomic ganglia and skeletal
neuromuscular junctions
• Muscarine:– binds to muscarinic receptors– targets parasympathetic neuromuscular or
neuroglandular junctions
Nicotine Poisoning
• 50 mg ingested or absorbed through skin
• Symptoms: – vomiting, diarrhea, high blood pressure, rapid
heart rate, sweating, profuse salivation, convulsions
• May result in coma or death
Muscarine Poisoning
• Symptoms: – salivation, nausea, vomiting, diarrhea,
constriction of respiratory passages, low blood pressure, slow heart rate (bradycardia)
ANS: Adrenergic and Cholinergic Receptors
Comparing Sympathetic and Parasympathetic Divisions
• Sympathetic:– widespread impact– reaches organs and tissues throughout body
• Parasympathetic:– innervates only specific visceral structures
Figure 16–9
Differences between Sympathetic and Parasympathetic Divisions
Table 16-2
Summary: Sympathetic and Parasympathetic Divisions
Dual Innervation
• Most vital organs receive instructions from both sympathetic and parasympathetic divisions
• 2 divisions commonly have opposing effects
Table 16-3 (1 of 2)
Summary: Comparing
Sympathetic and Parasympathetic
Divisions
Table 16-3 (2 of 2)
Summary: Comparing Sympathetic and
Parasympathetic Divisions
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
Structure: 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
6 Autonomic Plexuses
1. Cardiac plexus
2. Pulmonary plexus
3. Esophageal plexus
4. Celiac plexus
5. Inferior mesenteric plexus
6. Hypogastric plexus
Figure 16–10
The Autonomic Plexuses
Autonomic Motor Neurons
• Maintains resting level of spontaneous activity
• Background level of activation determines autonomic tone
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
Autonomic Tone and Dual Innervation
• Significant where dual innervation occurs:– 2 divisions have opposing effects
• More important when dual innervation does not occur
Visceral Reflexes
ANS
• Simple reflexes from spinal cord provide rapid and automatic responses
• Complex reflexes coordinated in medulla oblongata
Medulla Oblongata
• Contains centers and nuclei involved in:– salivation– swallowing– digestive secretions– peristalsis– urinary function
• Regulated by hypothalamus
Hypothalamus
• Interacts with all other portions of brain
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
Characteristics of Higher-Order Functions
• Require cerebral cortex
• Involve conscious and unconscious information processing
• Not part of programmed “wiring” of brain
• Can adjust over time
MemoriesStored bits of information gathered through
experience
• Declarative memory– Facts
• Skill Memory– Learned motor behaviors– Incorporated at unconscious level with
repetition– Programmed behaviors stored in appropriate
area of brain stem
Short & Long Term Memories
Short Term
• Information that can be recalled immediately
• Contain small bits of information
Long Term
• Can last a life time
2 Types of Long-Term Memory
• Secondary memories fade and require effort to recall
• Tertiary memories are with you for life
Long-Term Memories
• Most stored in cerebral cortex
• Conscious motor and sensory memories referred to association areas
Memory Storage
Brain Structures and Memory
• Amygdaloid body and hippocampus:– are essential to memory consolidation
Damage to the Hippocampus
• Inability to convert short-term memories to new long-term memories
• Existing long-term memories remain intact and accessible
Occipital and Temporal Lobes
• Special portions crucial to memories of faces, voices, and words
“Grandmother cells”
• Specific neuron activated by combination of sensory stimuli associated with particular individual (grandmother)
Memories Stored In
• 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
Memory Consolidation at Cellular Level
• Involves anatomical, physiological changes in neurons, synapses
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
Facilitation at Synapses (1 of 2)
• Neural circuit repeatedly activated
• Synaptic terminals begin continuously releasing neurotransmitter
• Neurotransmitter binds to receptors on postsynaptic membrane
Facilitation at Synapses (2 of 2)
• Produce graded depolarization
• Brings membrane closer to threshold
• Facilitation results affect all neurons in circuit
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
Memory Engram
• Single circuit corresponds to single memory
• Form as result of experience and repetition
Factors of Conversion of short to long term memory
• Nature, intensity, and frequency of original stimulus
• Strong, repeated, and exceedingly pleasant or unpleasant events likely converted to long-term memories
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
States of Consciousness
• Many gradations of both states
• Degree of wakefulness indicates level of ongoing CNS activity
• When abnormal or depressed, state of wakefulness is affected
Figure 16–14a
2 types of Sleep
• Characteristic patterns of brain wave activity– deep sleep– REM
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%
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
Nighttime Sleep Pattern
Significance of Sleep
• Has important impact on CNS
• 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
Arousal
• Awakening from sleep
• Function of reticular formation
Reticular Activating System (RAS)
• Important brain stem component
• Diffuse network in reticular formation
• Extends from medulla oblongata to mesencephalon
Figure 16–15
Reticular Activating
System (RAS)
Ending Sleep
• Any stimulus activates reticular formation and RAS
• Arousal occurs rapidly
• Effects of single stimulation of RAS last less than a minute
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
Drugs and Clinical Considerations
Lysergic Acid Diethylamide (LSD)
• Powerful hallucinogenic drug
• Activates serotonin receptors in brain stem, hypothalamus, and limbic system
Serotonin
• Compounds that enhance effects also produce hallucinations
• Compounds that inhibit or block action cause severe depression and anxiety
• Variations in levels affect sensory interpretation and emotional states
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
Parkinson’s Disease
• Inadequate dopamine production causes motor problems
Huntington’s 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
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
Aging
• 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
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– reduce blood flow through arteries– increase chances of rupture
• Cerebrovascular accident (CVA), or stroke:– may damage surrounding neural tissue
Intracellular and Extracellular Changes in CNS Neurons
• Neurons in brain accumulate abnormal intracellular deposits
• Including lipofuscin and neurofibrillary tangles
Incapacitation
• 85% 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– emotional disturbances
• Alzheimer’s disease is most common
That’s it(phew!)