organization & functions of the - college of the canyons · the forebrain – cortex • do...
TRANSCRIPT
-
Organization& Functions of the Nervous SystemChapter 3 Central Nervous System Peripheral Nervous System Development and Change in the Nervous System
Gar
rett:
Bra
in &
Beh
avio
r 4e
1
-
Overview
Nervous System Peripheral Nervous System
(Nerves & Ganglia)
Somatic Nervous System
Autonomic Nervous System
SympatheticNervous System
ParasympatheticNervous System
Central Nervous System
(Tracts & Nuclei)
Brain Spinal Cord
Gar
rett:
Bra
in &
Beh
avio
r 4e
2
-
TheCentral NervousSystemTable3.1:TermsforAxonsandCell Bodies
Peripheral NS Central NS
Cranial Nerves Bundle of axons TractSpinalNerves
Group ofcell bodies Ganglion Nucleus
Gar
rett:
Bra
in &
Beh
avio
r 4e
3
-
TheCentral NervousSystemFigure 3.3: Central Nervous System Development
• Brain develops from a hollow, tubular structure • Upper tube develops into
• Forebrain • Midbrain • Hindbrain • 3 weeks: all equal in size • 11 weeks: forebrain becomes the largest part
• Lower tube becomes the spinal cord • Gray Matter consists of unmyelinated cell bodies. White matter is neurons whose axons are myelinated.
4
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.5: TheForebrain
• Largest part of the brain. • Cerebral hemispheres separated by longitudinal fissure.
• Thalamus • Hypothalamus
• Cortex is wrinkled to increase surface area. • Ridge: gyrus • Groove: Central sulcus separates it and parietal lobe.
• Layers and columns of cell bodies.
Gar
rett:
Bra
in &
Beh
avio
r 4e
5
-
TheCentral NervousSystem TheForebrain–Cortex .Figure3.6:Layers&Columns
The 6-layered structure of the cortex. Columnar arrangement. 6
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
TheCentral NervousSystem TheForebrain–Cortex
• Do intelligent individuals have bigger brains? • Brain size is mostly related to body size, because larger bodies require larger brains. • Examples: Elephants and sperm whales have brains that are 5-6 times larger than humans.
• Among humans, there is a small and highly variable correlation between brain size and intelligence (discussed later in text)
Gar
rett:
Bra
in &
Beh
avio
r 4e
7
-
TheCentral NervousSystem TheForebrain–Cortex -Figure3.7
• Two key features • Armadillo characterize more “intelligent” species. • Cortex has more convolutions.
• Cerebral hemispheres • Monkey are larger in proportionto other brain areas.
• Increasing complexity from spinal cord to hindbrain to midbrain • Chimpanzee to forebrain.
8
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
TheCentral NervousSystemTheForebrain–DirectionandOrientation.Figure3.9
• Directions (relative to other structures) • Dorsal vs. Ventral • Anterior vs. Posterior • Lateral vs. Medial • Superior vs. Inferior
• Planes of section • Coronal (L/M and D/V) • Sagittal (A/P and D/V) • Horizontal (A/P and L/ M)
Coronal Sagittal Horizontal
Gar
rett:
Bra
in &
Beh
avio
r 4e
9
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.8:LobesandCortical Areas
10
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.8: Lobes and CorticalAreas
• Frontal Lobe • Movement and complex humancapabilities.
• Motor cortex found on the precentral gyrus controls voluntary movement
• Broca’sarea is important forspeech production.
• Prefrontal cortex involvedin planning, impulse control, anddecision making
• Lobotomy is the surgicaldestruction of the prefrontal cortex
• Psychosurgery treats cognitiveand emotional disorders
• Damage here may lead todepression
Gar
rett:
Bra
in &
Beh
avio
r 4e
11
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.8: Lobes and CorticalAreas
• Parietal lobe • Important for body sensations, attention, perception, and spatial localization.
• Primary somatosensory cortex on the postcentral gyrus processesskinsenses, body position, and movement
• Know how to describe where this is located
Gar
rett:
Bra
in &
Beh
avio
r 4e
12
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.8: Lobes and CorticalAreas
• Parietal associationareas • get info from primary areas • combine information from body senses and vision;
• identify objects by touch,determine the location of the limbs, and locateobjects in space.
• Posterior parietal cortexdamage causes neglect of objects, people, and activityon the opposite side. • Usually on the right side. • The patient will beunaware of the condition.
Gar
rett:
Bra
in &
Beh
avio
r 4e
13
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.8: Lobes and CorticalAreas
• Temporal separated from frontal andparietal lobes by the lateral fissure • Contains the auditorycortex,language, auditory and visualassociation areas.
• Wernicke’sarea isinvolvedin language comprehension andproduction. • Damage results in meaninglessspeech and poorcomprehension of written andspoken communication.
• Inferior temporal cortex is concerned with visual identification. • Damage causes difficulty inrecognizing objects and familiarfaces.
Gar
rett:
Bra
in &
Beh
avio
r 4e
14
-
TheCentral NervousSystemTheForebrain–Cortex.Figure3.8: Lobes and CorticalAreas
• Occipital is posterior lobe of brain • Primary Visual cortex contains a map of visual space
• adjacent receptors in the eye send information to adjacent points in thevisual cortex
• Secondary visual areas that process individual components of a scene
• Color, movement, and
Gar
rett:
Bra
in &
Beh
avio
r 4e
form. 15
-
TheCentral NervousSystemTheForebrain.Figure3.13:OtherBrainAreas • Thalamus
• Sensory processing, arousal
• Hypothalamus • Emotions and motivations • controls endocrine systemand the Autonomic N.S.
• Pineal gland • Descartes’ “seat of the soul”
• Regulates daily rhythms (melatonin) & sleep
• Structures • Corpuscallosum • Ventricles
Gar
rett:
Bra
in &
Beh
avio
r 4e
16
-
TheCentral NervousSystemTheForebrain.Figure3.15:TheVentricles
• During development, the hollow interior of the nervous system becomes the ventricles • Filled with cerebrospinal fluid (CSF)
• carries material from the blood vessels to the CNS
• transports waste materials out of the CNS
• Hydrocephalus- too much CSF in brain
Gar
rett:
Bra
in &
Beh
avio
r 4e
17
-
TheCentral NervousSystemFigure 3.16: The Midbrain and Hindbrain
• Midbrain • Secondary roles in vision, audition, movement. Parts include the
• Superior colliculi • Inferior colliculi • SubstantiaNigra • Reticular formation (also in the hind brain), and the
• Ventral tegmental area 18
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
TheCentral NervousSystemFigure 3.16: The Midbrain and Hindbrain
• Hindbrain • Basic functions. • Medulla • Pons
• Part of the reticular formation
• Cerebellum coordinates speed and direction of body movements
19
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
TheCentral NervousSystem TheSpinal Cord:Figure3.17
• The spinalcord is a cable of sensory neurons that carrysensory information to thebrain, and motor neurons thatcarry commands to the musclesand organs. • Sensory neurons enterthrough the dorsal root (1)
• Motor neuron axons leave through the ventral root (3,4)
• Interneurons connect sensory and motor neurons,or and brain (5, 6)
• Reflex- sensory neuron tointerneuron to motor neuron. (2) 20
Gar
rett:
Bra
in &
Beh
avio
r 4e
https://Cord:Figure3.17
-
TheCentral NervousSystemFigure 3.18: Protecting the Central Nervous System
• Cerebrospinal fluid cushions and ‘floats’ the brain.
• Meninges: three layers • Dura (tough outside) • Arachnoid (BBB) • Pia (on brain surface)
• Blood-brain barrier: protective layer ofendothelial cells between the blood and the brain • Gases and fat-soluble substances can pass through,but other materials must gothrough the cells
21
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
ThePeripheral NervousSystemFigure 3.19: The Nervous System
• Contents • Cranial nerves on the underside of the brain:
• Spinal nerves that connectto the sides of the spinalcord at each vertebra;
• Subsystems • Somatic nervoussystem
• Motor and sensory neuronsthat allow us to sense and react to the environment
• Autonomic nervous system (ANS)
• Controls smooth muscle, glands, heart, and other organs.
22
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
ThePeripheral NervousSystemFigure 3.19: The Nervous System
• Two branches • Sympathetic NervousSystem (fight-flight)
• activates the body in ways that help it cope with demands, such as emotional stress and physicalemergencies
• Stimulants mimic these effects • has most of its ganglia in the sympathetic ganglionchain.
• ParasympatheticNervousSystem • Slows activity of organs, increases digestion
23
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
Development & Change in N. S.StagesofDevelopment.Figure3.23:NeuronalProliferationandMigration
1. Proliferation • Neurons divide and multiply in ventricular zone (neurogenesis)
• new cells multiply at 250,000 per minute
2. Migration • Neurons move up radial glial cells towards final locations
24
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
Development & Change in N. S.StagesofDevelopment:Figure3.24:NeuronalGrowthCone
3. Circuit formation • Developing neurons
grow towards targettissues
• Use growth cones and form functional connections
4. Circuit pruning • Synaptic plasticity
• Active synapsesstrengthened
• Inactive ones removed
• Decreases with age 25
Gar
rett:
Bra
in &
Beh
avio
r 4e
-
Development & Change in N. S.Figure 3.25: FetalAlcoholSyndrome
• Mother’s use of alcohol during brain development. A • Brain smaller and malformed with dislocated neurons
• Cortical neurons do not migrate correctly intocolumns
• Some neurons migrate too Bfar. • Exposure to ionizing radiationaffects both proliferation andmigration.
26
Gar
rett:
Bra
in &
Beh
avio
r 4e
A: mouse cortex arranged in vertical columns B: alcohol-exposed cortex fails to form columns
-
Development & Change in N. S.Figure 3.26: Brain reorganization
• Stimulation continues to shape synapticconstruction and reconstruction throughout life.
• Much of this involves reorganization. • Shift in connections that changes the area’s function
• Provides compensationfor peripheral changes
• Reorganization is notalways beneficial
Gar
rett:
Bra
in &
Beh
avio
r 4e
27
-
Development & Change in N. S.Damage and Recovery
• Stroke due to internal forces • Caused by artery blockage (ischemic) or rupture (hemorrhagic).
• Damage is due to oxygen and glucose deprivation, excitotosis, and edema (swelling).
• A leading cause of death and disability in the U.S.
• TraumaticBrain Injury (TBI) due to external forces • Caused by a blow to the head, penetration, or sudden acceleration or deceleration.
• Even trauma that does not produce concussion can result in brain changes typically seen in Alzheimer’s patients.
Gar
rett:
Bra
in &
Beh
avio
r 4e
28
-
Development & Change in N. S.Limitations on Recovery
• Regeneration is the regrowth of severed axons. • Myelin provides a guide tube for the neuron to growthrough, and the axon is guided to its destination much asin development. Myelination continues until the early 20s.
• Occurs in the amphibian brain and in the mammalian PNS. • In the mammalian CNS, glia produce scar tissue and growthinhibitors, and immune cells may also interfere.
• Neurogenesis • It appears to support learning (in the hippocampus) andodor discrimination (in the olfactory bulbs).
• No evidence neurogenesis contributes to self repair. • However, neurogenesis does increase in damaged brains,and there is some hope this could be enhanced as a meansofrecovery.
Gar
rett:
Bra
in &
Beh
avio
r 4e
29
-
Development & Change in N. S.Compensation and Reorganization
• Compensation • Uninjured tissue takes over functions of lost areas
• Presynaptic neurons sprout more terminals to form additional synapses.
• Postsynaptic neurons add more receptors. • Silent side branches from adjacent neurons become activewithin minutes of injury.
• Reorganization • Functions are taken over by other, more distant areas. • Typically, compensation is by an adjacent area, but it can involve the other hemisphere.
• Reorganization generally more effective early in life. • In the mature brain we get reorganization of existingconnections
Gar
rett:
Bra
in &
Beh
avio
r 4e
30
-
Development & Change in N. S.CNS Repair
• Possibilities • Neuron growth enhancers • Providing guide tubes or scaffolding • Counteracting regrowth inhibitors
• Stem Cells seem like they could be an ideal means of neural repair. • Embryonic stem cells can be multipurpose tools because they are pluripotent.
Gar
rett:
Bra
in &
Beh
avio
r 4e
31
-
Development & Change in N. S.Application-MendingtheBrainwithComputerChips
• Temporarily anesthetized a monkey’s arm at the elbow.
• The BrainGate device records from 96 locations in the motor cortex.
32
Gar
rett:
Bra
in &
Beh
avio
r 4e
Structure BookmarksOrganization.& .Functions .of .the Nervous. System.Chapter. 3. Central Nervous System Peripheral Nervous System Development. and Change in the Nervous System Garrett: Brain & Behavior 4e 1 Overview. Nervous System Peripheral Nervous System (Nerves & Ganglia) Somatic Nervous System Autonomic Nervous System SympatheticNervous System ParasympatheticNervous System Central Nervous System (Tracts & Nuclei) Brain Spinal Cord Garrett: Brain & Behavior 4e The.Central .Nervous.System.Table.3.1:.Terms.for.Axons.and.Cell .Bodies. Peripheral .NS Central .NS Cranial .Nerves. Bundle of axons Tract.Spinal.Nerves. Group .of.cell .bodies. Ganglion Nucleus. Garrett: Brain & Behavior 4e FigureThe.Central .Nervous.System.Figure. 3.3:. Central Nervous. System. Development • Brain develops from a. hollow, tubular structure • • • • Upper tube develops into
• • • Forebrain
• • Midbrain
• • Hindbrain
• • 3 weeks: all equal in size
• • Lower tube becomes the spinal cord
• • Gray Matter consists of unmyelinated cell bodies. White matter is neurons whose axons are myelinated.
4 Garrett: Brain & Behavior 4e • • • 11 weeks: forebrain becomes the largest. part.
The.Central .Nervous.System..The.Forebrain.–.Cortex...Figure.3.5: .The.Forebrain • • • • Largest. part. of the brain.
• • • Cerebral .hemispheres. separated by longitudinal. fissure..
• • Thalamus
• • Hypothalamus
• • • Cortex is wrinkled to increase surface area.
• • • Ridge: gyrus
• • Groove:. Central .sulcus. separates it. and parietal lobe..
• • Layers and columns of cell bodies..
FigureGarrett: Brain & Behavior 4e The.Central .Nervous.System. The.Forebrain.–.Cortex ...Figure.3.6:.Layers.&.Columns. The 6-layered structure of the cortex. Columnar arrangement. 6 Garrett: Brain & Behavior 4e The.Central .Nervous.System. The.Forebrain.–.Cortex • Do intelligent. individuals have bigger brains? • • • • Brain size is mostly related to body size, because larger bodies require larger brains.
• Examples: Elephants and sperm whales have brains that. are 5-6 times larger than humans.
• • Among humans, there is a. small and highly variable correlation between brain size and intelligence (discussed later in text)
Garrett: Brain & Behavior 4e FigureThe.Central .Nervous.System. The.Forebrain.–.Cortex -.Figure.3.7. • • • • Two key features • Armadillo characterize more “intelligent” .species..
• • • Cortex has more convolutions.
• • Cerebral hemispheres • Monkey are larger in proportionto other brain areas.
• • Increasing complexity from spinal cord to hindbrain to midbrain • Chimpanzee to forebrain.
8 Garrett: Brain & Behavior 4e The.Central .Nervous.System.The.Forebrain.–.Direction.and.Orientation..Figure.3.9. • • • • Directions (relative to other structures)
• • • Dorsal vs.. Ventral
• • Anterior vs.. Posterior.
• • Lateral vs.. Medial
• • Superior vs.. Inferior
• • • Planes of section
• • • Coronal (L/M. and D/V)
• • Sagittal (A/P and D/V)
• • Horizontal (A/P and L/ M)
FigureGarrett: Brain & Behavior 4e Coronal Sagittal Horizontal The.Central .Nervous.System.The.Forebrain.–.Cortex..Figure.3.8:.Lobes.and.Cortical .Areas 10 Garrett: Brain & Behavior 4e The.Central .Nervous.System..The.Forebrain.–.Cortex..Figure.3.8: .Lobes and .Cortical.Areas • Frontal Lobe • • • Movement. and complex humancapabilities.
• • Motor cortex found on the precentral. gyrus. controls voluntary movement.
• • • Broca’s.area. is important. for
speech production.
• • • Prefrontal .cortex. involved.in. planning, impulse control, anddecision making
• • • Lobotomy is the surgicaldestruction of the prefrontal cortex
• • Psychosurgery treats cognitiveand emotional disorders
• • Damage here may lead todepression.
FigureGarrett: Brain & Behavior 4e The.Central .Nervous.System..The.Forebrain.–.Cortex..Figure.3.8: .Lobes and .Cortical.Areas • Parietal .lobe.. • • • Important. for body sensations, attention, perception, and spatial localization.
• • Primary .somatosensory .cortex.
on the postcentral gyrus processes.skin.senses, body position, and movement. • Know how to describe where this is located Garrett: Brain & Behavior 4e FigureThe.Central .Nervous.System..The.Forebrain.–.Cortex..Figure.3.8: .Lobes and .Cortical.Areas • • • • Parietal association.areas.
• • • get. info from primary areas
• • combine information from body senses and vision;
• • identify objects by touch,determine the location of the limbs, and locateobjects in space.
• • • Posterior parietal cortexdamage causes neglect of. objects, people, and activityon the opposite side.
• • • Usually on the right. side.
• • The patient. will beunaware of the condition.
FigureGarrett: Brain & Behavior 4e The.Central .Nervous.System..The.Forebrain.–.Cortex..Figure.3.8: .Lobes and .Cortical.Areas • Temporal separated from frontal andparietal lobes by the lateral. fissure • • • Contains the auditory.cortex,.language, auditory and visualassociation areas.
• • Wernicke’s.area. is.involved.in.
language comprehension andproduction. • Damage results in meaninglessspeech and poorcomprehension of written andspoken communication. • Inferior temporal. cortex is. concerned with visual identification. • Damage causes difficulty inrecognizing objects and familiarfaces. FigureGarrett: Brain & Behavior 4e The.Central .Nervous.System..The.Forebrain.–.Cortex..Figure.3.8: .Lobes and .Cortical.Areas • Occipital is posterior lobe of brain • • • • Primary Visual .cortex. contains a. map of visual space
• adjacent. receptors in the eye send information to adjacent. points in thevisual cortex
• • Secondary visual areas that. process individual components of a. scene
• Color, movement, and Garrett: Brain & Behavior 4e form.. The.Central .Nervous.System.The.Forebrain..Figure.3.13:.Other.Brain.Areas. • • • • Thalamus
• Sensory .processing, arousal
• • • Hypothalamus
• • • Emotions and motivations
• • controls endocrine systemand the Autonomic N.S.
• • • Pineal .gland
• • • Descartes’“seat. of the soul”
• • Regulates daily rhythms (melatonin) & sleep
• • • Structures.
• • • Corpus.callosum
• • Ventricles
Garrett: Brain & Behavior 4e FigureThe.Central .Nervous.System.The.Forebrain..Figure.3.15:.The.Ventricles. • During development, the hollow interior of the nervous system becomes the ventricles • • • • Filled with cerebrospinal fluid (CSF)
• • • carries material from the blood vessels to the CNS
• • transports waste materials out. of the CNS
• • Hydrocephalus-too much CSF in brain
FigureGarrett: Brain & Behavior 4e The.Central .Nervous.System.Figure. 3.16:. The. Midbrain and. Hindbrain • Midbrain • • • Secondary roles in vision, audition, movement. Parts include the
• • Superior .colliculi
• • Inferior colliculi.
• • Substantia.Nigra
• • Reticular formation (also in the hind brain), and the
• • Ventral tegmental area.
18 Garrett: Brain & Behavior 4e The.Central .Nervous.System.Figure. 3.16:. The. Midbrain and. Hindbrain • Hindbrain. • • • Basic functions.
• • Medulla
• • • Pons
• Part. of the reticular. formation
• • Cerebellum.
coordinates speed and direction of body movements 19 Garrett: Brain & Behavior 4e The.Central .Nervous.System. The.Spinal Cord:.Figure.3.17 The.Spinal Cord:.Figure.3.17
• • • • The spinal.cord. is a. cable of sensory neurons that. carrysensory information to thebrain, and motor neurons that.carry commands to the musclesand organs.
• • • Sensory neurons enterthrough the dorsal. root. (1).
• • Motor neuron axons leave through the ventral .root (3,4).
• • Interneurons connect. sensory and motor neurons,or and brain (5, 6)
• • Reflex-sensory neuron tointerneuron to motor neuron. (2).
20 Garrett: Brain & Behavior 4e The.Central .Nervous.System.Figure. 3.18:. Protecting the. Central Nervous. System. • • • Cerebrospinal .fluid cushions .and ‘floats’ .the. brain.
• • • Meninges: three layers
• • • Dura. (tough outside)
• • Arachnoid (BBB)
• • Pia. (on brain surface)
• • Blood-brain. barrier:. protective layer ofendothelial cells between the blood and the brain
• Gases and fat-soluble substances can pass through,but. other materials must. gothrough the cells 21 Garrett: Brain & Behavior 4e The.Peripheral .Nervous.System.Figure. 3.19:. The. Nervous. System • • • • Contents
• • • Cranial nerves on the underside of the brain:
• • Spinal nerves that. connect.to the sides of the spinalcord at. each vertebra;
• • • Subsystems
• • • • Somatic .nervous.system
• Motor and sensory neuronsthat. allow us to sense and react. to the environment.
• • Autonomic nervous system (ANS).
• Controls smooth muscle, glands, heart, and other organs. 22 Garrett: Brain & Behavior 4e The.Peripheral .Nervous.System.Figure. 3.19:. The. Nervous. System. • Two branches • Sympathetic .Nervous.System (fight-flight) • • • activates the body in ways that. help it. cope with demands, such as emotional stress and physicalemergencies
• • Stimulants mimic these effects
• • has most. of its ganglia. in the sympathetic .ganglion.chain..
• Parasympathetic.Nervous.System.. • Slows activity of organs, increases digestion 23 Garrett: Brain & Behavior 4e Development &. Change. in N. S.Stages.of.Development..Figure.3.23:.Neuronal.Proliferation.and.Migration. 1. Proliferation • • • Neurons divide and multiply in ventricular zone (neurogenesis).
• • new cells multiply at. 250,000 per minute
2. Migration • Neurons move. up radial .glial .cells towards final locations 24 Garrett: Brain & Behavior 4e Development &. Change. in N. S.Stages.of.Development:.Figure.3.24:.Neuronal.Growth.Cone. 3. Circuit .formation • • • Developing .neurons. grow towards target.tissues
• • Use. growth .cones. and form functional connections
4. Circuit .pruning. • • • • Synaptic plasticity.
• • • Active synapsesstrengthened
• • Inactive ones removed
• • Decreases with age
25 Garrett: Brain & Behavior 4e Development &. Change. in N. S.Figure. 3.25:. Fetal.Alcohol.Syndrome • • • • Mother’s use of alcohol during brain development. A
• • • Brain smaller and malformed with dislocated neurons.
• • Cortical neurons do not. migrate correctly intocolumns.
• • Some neurons migrate too far. B
• • Exposure to ionizing radiationaffects both proliferation andmigration.
26 Garrett: Brain & Behavior 4e A: mouse cortex arranged in vertical columns B: alcohol-exposed cortex fails to form columns Development &. Change. in N. S.Figure. 3.26:. Brain reorganization • • • Stimulation continues to shape synapticconstruction and reconstruction throughout. life.
• • • Much of this involves reorganization...
• • • Shift. in connections that. changes the area’s. function
• • Provides compensationfor peripheral changes
• • Reorganization is not.always beneficial
FigureGarrett: Brain & Behavior 4e Development &. Change. in N. S.Damage. and. Recovery • • • • Stroke due to internal forces
• • • Caused by artery blockage (ischemic) or rupture (hemorrhagic).
• • Damage is due to oxygen and glucose deprivation, excitotosis, and edema. (swelling).
• • A leading cause of death and disability in the U.S.
• • • Traumatic.Brain .Injury .(TBI) due to external forces
• • • Caused by a. blow to the head, penetration, or sudden acceleration or deceleration.
• • Even trauma. that. does not. produce concussion can result. in brain changes typically seen in Alzheimer’s patients.
FigureGarrett: Brain & Behavior 4e Development &. Change. in N. S.Limitations. on Recovery • • • • Regeneration is the regrowth of severed axons.
• • • Myelin provides a. guide tube for the neuron to growthrough, and the axon is guided to its destination much asin development. Myelination continues until the early 20s.
• • Occurs in the amphibian brain and in the mammalian PNS.
• • In the mammalian CNS, glia. produce scar tissue and growthinhibitors, and immune cells may also interfere.
• • • Neurogenesis
• • • It. appears to support. learning (in the hippocampus) andodor discrimination (in the olfactory bulbs).
• • No evidence neurogenesis contributes to self repair.
• • However, neurogenesis does increase in damaged brains,and there is some hope this could be enhanced as a. meansof.recovery..
FigureGarrett: Brain & Behavior 4e Development &. Change. in N. S.Compensation and. Reorganization • • • • Compensation
• Uninjured tissue takes over functions of lost. areas • • • Presynaptic neurons sprout. more terminals to form additional synapses.
• • Postsynaptic neurons add more receptors.
• • Silent. side branches from adjacent. neurons become activewithin minutes of injury.
• • • Reorganization
• • • Functions are taken over by other, more distant. areas.
• • Typically, compensation is by an adjacent. area, but. it. can involve the other hemisphere.
• • Reorganization generally more effective early in life.
• • In the mature brain we get. reorganization of existingconnections
FigureGarrett: Brain & Behavior 4e Development &. Change. in N. S.CNS Repair • • • • Possibilities
• • • Neuron growth enhancers
• • Providing guide tubes or scaffolding
• • Counteracting regrowth inhibitors
• • Stem Cells seem like they could be an ideal means of neural repair.
• Embryonic stem cells can be multipurpose tools because they are pluripotent. Garrett: Brain & Behavior 4e FigureDevelopment &. Change. in N. S.Application-.Mending.the.Brain.with.Computer.Chips • • • Temporarily anesthetized a. monkey’s arm at. the elbow.
• • The BrainGate device records from. 96. locations in the motor cortex.
32 Garrett: Brain & Behavior 4e