brain organization
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Nervous
System
CNS PNS ANS
BRAIN
SPINAL
CORD
CRANIAL
NERVES
SPINAL
NERVES
SYMPATHETIC
PARA-
SYMPATHETIC
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Definition:
Unpaired, bilaterally symmetrical structuresextending along the longitudinal axis of the
midsagittal plane of the body.Structures arising directly from the neural tube.
Includes:
Brain
Spinal cord
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Definition:
Made up of transmission pathwayscarrying information between the CNS and
external/internal environments. Afferent (sensory) pathways:
Carry information to the CNS.
Efferent (motor) pathways:Carry information from the CNS.
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Includes:
Cranial nerves (12 pairs).
Spinal nerves (31 pairs).
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May be considered a subdivision of the PNS.
Entirely motor.
Innervates smooth muscle and glands (viscera).
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Sympathetic system (fight or flight):
Also called thoracolumbar.
Parasympathetic system (feed or breed):
Also called craniosacral.
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Cell body:
Trophic unit
Perikaryon
Dendrites:
Receptive unit
Axon:
Conductive unit
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Neuron Anatomy
Slide 7.9bCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Cell body
Nucleus
Largenucleolus
Figure 7.4a
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Neuron Anatomy
Slide 7.10Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Extensionsoutside the cellbody
Dendritesconductimpulses towardthe cell body
Axons conductimpulses awayfrom the cellbody (only 1!)
Figure 7.4a
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That part of a neuron that encloses the nucleusand other organelles necessary to maintain andrepair the neuron.
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Branches off the cell body that carryinformation to the cell body.
Usually several to many.
Relatively short.
Often branched.
Have receptors for neurotransmitters.
Conduct local potentials.
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Carries information to another neuron ormuscle cell.
Often relatively long.
Single (one per neuron).
Conducts action potential
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Ends in short branched processes calledtelodendria.
May have collateral branches.
Cell membrane (= axolemma). Cytoplasm = (axoplasm).
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Covered by neurolemma:
Made up of Schwann cells.
Often myelinated:
Myelin is formed by Schwann cells.
Note: axon is the only part of a neuron that isever myelinated.
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Nucleus:
Aggregation of dendrites and nerve cellbodies in the CNS.
Ganglion:Aggregation of dendrites and nerve cellbodies in the PNS.
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White matter:
Areas of myelinated axons.
Gray matter:
Areas of unmyelinated axons, cell bodies,and dendrites.
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Definition:
Composite structure that allows two neurons or aneuron and a muscle cell to talk to each other.
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Presynaptic membrane:
With synaptic vesicles filled withneurotransmitters.
Synaptic cleft: Postsynaptic membrane:
With receptors for neurotransmitters.
Monosynaptic pathways.
Polysynaptic pathways.
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Afferent (sensory) pathways:
Somatic.
Visceral (splanchnic).
Efferent (motor) pathways:
Somatic.
Visceral (splanchnic).
Association neurons (interneurons).
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Schwann cells
Astrocytes
Microglial cells
Oligodendrocytes
Ependymal cells
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Derived from neural crest cells.
Myelinate axons in the PNS.
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Derived from embryonic mesenchyme.
May transform into phagocytes within CNS.
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Nerve Fiber Coverings
Slide 7.12Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Schwann cellsproduce myelinsheaths in jelly-rolllike fashion
Nodes of Ranviergaps in myelinsheath along theaxon
Figure 7.5
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Structural Classification of Neurons
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Multipolar neurons many extensionsfrom the cell body
Figure 7.8a
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Structural Classification of Neurons
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Bipolar neurons one axon and onedendrite
Figure 7.8b
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Structural Classification of Neurons
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Unipolar neurons have a short singleprocess leaving the cell body
Figure 7.8c
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How Neurons Function
(Physiology)
Slide 7.17Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Irritability ability to respond to stimuli
Conductivity ability to transmit an
impulse
The plasma membrane at rest ispolarized
Fewer positive ions are inside the cell thanoutside the cell
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Starting a Nerve Impulse
Slide 7.18Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Depolarization astimulus depolarizes theneurons membrane
A deploarizedmembrane allowssodium (Na+) to flowinside the membrane
The exchange of ionsinitiates an actionpotential in the neuron
Figure 7.9ac
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The Action Potential
Slide 7.19Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
If the action potential (nerve impulse)starts, it is propagated over the entireaxon
Potassium ions rush out of the neuronafter sodium ions rush in, whichrepolarizes the membrane
The sodium-potassium pump restoresthe original configuration
This action requires ATP
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Nerve Impulse Propagation
Slide 7.20Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The impulsecontinues to move
toward the cell body
Impulses travelfaster when fibers
have a myelinsheath
Figure 7.9ce
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Continuation of the Nerve Impulsebetween Neurons
Slide 7.21Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Impulses are able to cross the synapseto another nerve
Neurotransmitter is released from a nervesaxon terminal
The dendrite of the next neuron has
receptors that are stimulated by theneurotransmitter
An action potential is started in the dendrite
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How Neurons Communicate atSynapses
Slide 7.22Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.10
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Fig. 48.20
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cerebrum corpuscallosum
thalamus
cerebellum
medullaoblongata
hypothalamus
pituitary
pons
spinal cord
Pineal gland
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Involved with higher brain functions. Processes sensory information.
Initiates motor functions.
Integrates information.
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The
cerebrum is
divided intofrontal,
temporal,
occipital,
and parietallobes.
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Frontal lobe. Contains the primary motor cortex.
Parietal lobe. Contains the primary somatosensory cortex.
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Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 48.25
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Integrative Function of the Association Areas.
Much of the cerebrum is given over to
association areas.Areas where sensory information is integrated
and assessed and motor responses areplanned.
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The brain exhibits plasticity of function.
For example, infants with intractable
epilepsy may have an entire cerebralhemisphere removed.
The remaining hemisphere can provide thefunction normally provided by both
hemispheres.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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Generatingwords
Max
Speakingwords
Hearingwords
Seeingwords
Min
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Language and Speech.
Brocas area.
Usually located in the left hemispheres frontal lobe Responsible for speech production.
Wernickes area. Usually located in the right hemispheres temporal lobe
Responsible for the comprehension of speech.
Other speech areas are involvedgenerating verbs to match nouns,grouping together related words, etc.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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Memory and Learning.
Short-term memory stored in the frontal
lobes.
The establishment oflong-term memory
involves the hippocampus.
The transfer of information from short-term tolong-term memory.
Is enhanced by repetition (remember that when you are
preparing for an exam).
Influenced by emotional states mediated by theamygdala.
Influenced by association with previously stored
information.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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Different types of long-term memories arestored in different regions of the brain.
Memorization-type memory can be rapid. Primarily involves changes in the strength of
existing nerve connections.
Learning of skills and procedures isslower.
Appears to involves cellular mechanismssimilar to those involved in brain growth and
development.
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Human Consciousness.
Brain imaging can show neural activity
associated with: Conscious perceptual choice
Unconscious processing
Memory retrieval
Working memory.
Consciousness appears to be a whole-brain phenomenon.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
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Relay center for sensory tracts
from the spinal cord to thecerebrum.
Contains centers for sensationof pain, temperature, and touch.
Involved with emotions andalerting or arousal mechanisms.
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The Reticular System, Arousal, and Sleep.
The reticular activating system(RAS)of
the reticular formation. Regulates sleep
and arousal.
Acts as asensory filter.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 48.21
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Sleep and wakefulness produces patterns
of electrical activity in the brain that can
be recorded as anelectroencephalogram (EEG).
Most dreaming
occurs duringREM (rapid
eye movement)
sleep.
Copyright 2002 Pearson Education, Inc., publishing as Benjamin Cummings
Fig. 48.22b-d
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autonomic control center- blood pressure,
rate and force of heart contraction, centerfor emotional response and behavior
body temperature water balance and thirst sleep/wake cycles
appetite sexual arousal control of endocrine functioning:Acts on the pituitary gland through the
release of neurosecretions.
Regulates:
H th l
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Hypothalamus
Midbrain
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Cerebellar peduncles
Tectum
Superior colliculi Inferior colliculi
Substantia nigra
Red nuclei
Midbrain
thalamus
Red nucleus
Substantia nigra
Posterior
Anterior
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Contains ascending and descendingtracts to the cerebrum andthalamus.
Reflex center for eye muscles. Also involved with processing visual
and auditory information (connects
head movements with visual andauditory stimuli).
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Connects the two
halves of the
cerebellum.
Regulates breathing.
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Composed of nerve tractsto and from the brain
(these tracts cross over
left to right and right to left) May be regarded as an
extension of the spinal
cord Almost all of the cranial
nerves arise from this
region
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Contains control centers formany subconscious
activities
Respiratory rate Heart rate
Arteriole constriction
Swallowing Hiccupping
Coughing
Sneezing
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On OldOlympus Towering Tops A Fat Voracious German Viewed A Hop
1. Olfactory- smell
2. Optic- vision
3. Oculomotor- 4 of the 6 extrinsic eye muscles4. Trochlear- extrinsic eye muscles
5. Trigeminal- sensory fibers to the face and motor fibers to
the chewing muscles
6. Abducens- controls eye muscles that turn the eye laterally7. Facial- facial expression
8. Vestibulocochlear- hearing and balance
9. Glosopharyngeal- tongue and pharynx
10.Vagus- parasympathetic control of heart, lungs &abdominal organs
11.Accessory- accessory part of vagus nerve, neck & throat
muscles
12.Hypoglossal- moves muscles under tongue
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Olfactory
Optic
Oculomotor
Trochlear
Trigeminal
Abducens
Vestibulocochlear
Glossopharyngeal
Vagus
Accessory Hypoglossal
Facial
P t ti f th C t l N
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Protection of the Central NervousSystem
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Scalp and skin
Skull and vertebral column
Meninges
Figure 7.16a
M i
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Meninges
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Dura mater
Double-layered external covering
Periosteum attached to surface of theskull
Meningeal layer outer covering of the
brain
Folds inward in several areas
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C b i l Fl id
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Cerebrospinal Fluid
Slide 7.46Copyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Similar to blood plasma composition
Formed by the choroid plexus
Forms a watery cushion to protect thebrain
Circulated in arachnoid space,ventricles, and central canal of thespinal cord
Ventricles and Location of the
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Ventricles and Location of theCerebrospinal Fluid
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.17a
Ventricles and Location of the
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Ventricles and Location of theCerebrospinal Fluid
SlideCopyright 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 7.17b
Bl d B i B i
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Blood Brain Barrier
Includes the least permeable capillaries
of the body
Excludes many potentially harmfulsubstances
Useless against some substances
Fats and fat soluble molecules
Respiratory gases
Alcohol
Nicotine
Anesthesia