chapter 8 cns. copyright © the mcgraw-hill companies, inc. permission required for reproduction or...
TRANSCRIPT
Chapter 8
CNS
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ORGANIZATION OF NERVOUS SYSTEM
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Central Nervous System (CNS)Central Nervous System (CNS)
BrainBrain Spinal CordSpinal Cord
Peripheral Nervous System (PNS)Peripheral Nervous System (PNS)
Sensory NeuronsSensory NeuronsMotor NeuronsMotor Neurons
Somatic Nervous SystemSomatic Nervous System Autonomic Nervous SystemAutonomic Nervous System
SympatheticSympathetic Parasympathetic Parasympathetic
The Nervous SystemThe Nervous System
The Spinal CordThe Spinal Cord
WhiteWhiteMatterMatter
GrayGrayMatterMatter
CentralCentralCanalCanal
DorsalDorsalRootRoot
Dorsal RootDorsal RootGanglionGanglion
DorsalDorsalRootRoot
PeripheralPeripheralNerveNerve
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DEVELOPMENT OF THE BRAIN
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Embryonic Development
Forms as a tube!
Ectoderm (skin, nervous system): neural tube by day 20
Part of ectoderm where fusion occurs becomes neural crest which then forms PNS ganglia.
by 4th week:Forebrain, Midbrain, Hindbrain
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CNS
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Embryonic Development (continued)
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TECHNIQUES
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Neurobiology:Neurons trying to understand themselves…!
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We have mapped many functions to discrete parts of the brain.
TheTheCerebralCerebralCortexCortex
FrontalFrontalLobeLobe
HigherHigherIntellectualIntellectualFunctionsFunctions
PrimaryPrimaryMotorMotorAreaArea
PremotorPremotorAreaArea
SpeechSpeechMotorMotorAreaArea
leglegtrunktrunk
armarmhandhandfaceface
tonguetongue
ParietalParietalLobeLobePrimaryPrimary
SensorySensoryAreaArea
SensorySensoryAssociationAssociation
AreaArea
OccipitalOccipitalLobeLobe
PrimaryPrimaryVisualVisualAreaArea
VisualVisualAssociationAssociation
AreaArea
TemporalTemporalLobeLobe
MemoryMemory
PrimaryPrimaryAuditoryAuditory
AreaArea
LanguageLanguageComprehensionComprehension
& Formation& Formation
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Info comes from…
SurgeriesAccidentsIllnessAnatomy (autopsies)Open brain studiesAnimalsLive Imaging
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Imaging
CAT scans:soft tissues xrays
PET scans: positron emitting fluid glucose metabolism, blood flow.
MRI and fMRI blood flow
magnets spin protons, radio waves are emitted
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Imaging
NOTE: PET and MRI look at blood flow… what might they be missing?!
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PET
Stroke DamageStroke Damage
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Live imaging
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Electroencephalogram (EEG)
Summation of brain’s electrical activity.
Used clinically to diagnose epilepsy and brain death.
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STRUCTURES OF THE BRAIN
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CNSCNS = Brain plus spinal cord
- Gray matter consists of neuron cell bodies and dendrites.- White matter (myelin) consists of axon tracts.
- Ventricles- CSF secreted by meninges, cushions brain- Skull protects
- No pain sensors!
- Blood-brain barrier.
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CNS
Cell bodies in CNS: nucleiCell bodies in PNS: ganglia
Nerves: bundles of axons!
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Brain myths
We use only 10% of our brains.
It’s all downhill after a certain age.
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Brain facts
We are concious of only a small percentage of what the brain knows!
It’s not the size, it’s the connections!
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Things you can do without a brain…
Your gut has a “mind” of it’s own… (enteric nervous system)
Reflex arcs.
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Brain
100 billion neurons.10x more glial cells!Weighs about 1.5 kg, uses 20% of blood flow.
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Brain
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Brain
Prosencephelon (Forebrain) Telencephalon (cerebrum) Diencephelon (thalamus, hypothalamus)
Mesencephalon (Midbrain)
Rhombencephalon (Hindbrain)Metencephalon (pons, cerebellum)Myencephalon (medulla)
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Brain
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BRAINSForebrainMidbrain
HindbrainEmbryonicEmbryonic
SharkShark
GooseGoose
HumanHuman
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FOREBRAIN
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CEREBRUM
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Cerebrum
Telencephalon= cerebrumLargest portion of brain (80% mass).Responsible for cognitive mental functions.
Five lobes.Cortex (2-4 mm of gray matter)White matter and basal nuclei (gray)
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Cerebrum
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Cerebral Cortex
Cerebral cortex:Characterized by numerous convolutions.
Elevated folds: gyri.Depressed groves: sulci.
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Cerebral lobes
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Cerebrum
Central sulcus= between frontal and parietal lobes.
Frontal lobe:precentral gyrus: motor neurons.
Parietal lobe: Poscentral gyrus: somatesthetic sensation (cutaneous touch, pain, heat, muscles and joints).
MAP of motor and of sensory control (homunculus)
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Cerebral Cortex (continued)
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Cerebral Cortex
Temporal lobe:auditory centers that receive sensory fibers from cochlea.Interpretation and association of auditory and visual information.
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Cerebral Cortex
Occipital Lobe: Primary area responsible for vision and
coordination of eye movements.
Insula: Implicated in memory encoding.Integration of sensory information with
visceral responses.Coordinated cardiovascular response to
stress.
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Cerebrum
Basal Nucleigray matter located deep within white matter.
Corpus striatumFunctions in the refinement of voluntary movements.
Parkinson’s: degeneration of neurons that connect caudate nucleus to substantia nigra of midbrain
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Cerebrum
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Language
Aphasia: speech and language disorder due to head injuries and strokes.
Speech impediment: vocal cord or tongue injury.
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Language
Broca’s area: articulation of speech.Damage: slow to speak, comprehension is fine
Wernicke’s area:language comprehension.Damage: rapid speech, word salad
To read, hear words: visual, auditory -> Wernicke’s (concept of words)
To speak: Werknicke’s -> arcuate fasciculus -> Broca’s -> motor
Angular gyrus:Center of integration of auditory, visual, and somatesthetic
information.
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Emotion and Motivation
Hypothalamus/ limbic system.
Limbic system:Includes amygdala and hippocampus, (and cingulate gyrus and fornix)smell
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Emotion and Motivation
Rage, aggression:Amygdala and hypothalamus.
Fear:Amygdala and hypothalamus.
Feeding:Hypothalamus (satiety centers).
Sexual drive and behavior:Hypothalamus and limbic system.
Goal directed behavior (reward and punishment):
Hypothalamus and frontal cortex.
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Memory
Many structures, including:Medial temporal lobe: HippocampusPrefrontal cortex
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Memory
Consolidation of short-term memory into long-term memory.Requires activation of genes.
growth of dendritic spines.
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Long-Term Potentiation
synaptic learning.Change in excitability.
Hippocampus (in medial temporal lobe)
Glutamate is NT.NMDA receptors (Ca++ channels),
postsynaptic changesNOS -> NO -> retrograde messenger->
presynaptic changes
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Diencephalon
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Thalamus
Thalamus:Acts as relay center through which all sensory
information (except olfactory) passes to the cerebrum.
Lateral geniculate nuclei:Relay visual information; stripes!
Medial geniculate nuclei:Relay auditory information.
Epithalamus contains:Choroid plexus where CSF is formed.Pineal gland which secretes melatonin (circadian
rhythms).
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Hypothalamus
Contains neural centers for hunger, thirst, and body temperature.
Contributes to the regulation of sleep, wakefulness, emotions, sexual arousal, anger, fear, pain, and pleasure.
Stimulates hormonal release from anterior pituitary.
Produces ADH and oxytocin.Coordinates sympathetic and
parasympathetic reflexes.
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Pituitary Gland
Posterior pituitary:Stores and releases ADH (vasopressin)
and oxytocin.
Hypothalamus produces releasing and inhibiting hormones that are transported to anterior pituitary.
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MIDBRAIN
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Midbrain
Visual, auditory reflexesSee out of corner of eye, move
head; startle at a sound
Substantia nigra:motor coordination, Parkinson’s
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HINDBRAIN
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HindbrainHindbrain: connects spinal cord to rest of brain.
Metencephalon:Pons:
Connects other parts. several nuclei associated with cranial nerves
respiratory centers.
Cerebellum:“little brain”Receives input from proprioceptors (joints, muscles, tendons).Refinement/coordination of movement.
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Hindbrain
Myelencephalon
Medulla (oblongata)All descending and ascending fiber
tracts between spinal cord and brain pass through it.
Vital centers: control of breathing, heart, blood vessels.
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RAS
Reticular Activating System (reticular formation)
network of nuclei and nerve fibers within hindbrain (medulla, pons), midbrain, forebrain (thalamus and hypothalamus).
Maintains wakefulness and alertnessTurned off (by hypothalamus) to sleepAnaesthesia, alcohol, tranquillizersComa
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Continue to engage the RAS and … onto lab!