Nervous Systems
Brain Development
AP Biology
2007-2008
Nervous system
Central
nervous
system
Brain
Peripheral
nervous
system
Spinal
cord
 Sympathetic
arousal & energy production
“fight or flight”
 Parasympathetic
calming & back to maintenance
“rest & digest”
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Sensory
pathways
Somatic
(voluntary)
nervous system
Sympathetic
division
Motor
pathways
Autonomic
(involuntary)
nervous system
Parasympathetic
division
Types of neurons
sensory neuron
cell body
cell body
axon
dendrites
dendrites
motor neuron
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interneuron
“associative”
cell
body
Cephalization = Brain evolution
 Cephalization = clustering of neurons in “brain” at front (anterior)
end of bilaterally symmetrical animals  where sense organs are
associative
neurons
nerve cords
nerve
net
Cnidarian
Simplest
nervous system
no control of
complex
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nerve
ribs
radial
nerve
Echinoderm
More organization
but still based on nerve
nets; supports more
complex movement
Flatworm
Platyhelminthes
Simplest, defined
central nervous system
more complex muscle
control
Cephalization = Brain evolution
 increase in interneurons in brain region
central nervous system
peripheral
giant
axon
brain
brain
ventral
nerve
cords
nerves
Earthworm
Mollusk
Arthropod
More complex brains
connected to all other
parts of body by
peripheral nerves
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More complex brains
in predators
most sophisticated
invertebrate nervous
system
Further brain
development
ganglia = neuron
clusters along
CNS
Evolution of vertebrate brain
forebrain
dominant cerebrum
forebrain
Shark
hindbrain
Frog
Crocodile
Cat
Human
Spinal cord
Hind: Medulla oblongata
Hind: Cerebellum
Optic tectum
Midbrain
Fore: Cerebrum
Olfactory tract
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forebrain
Bird
Human brain
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Functional divisions of brain
 Hindbrain

evolutionary older structures of the brain
 regulate essential autonomic & integrative
functions

brainstem
 pons
 medulla oblongata
 midbrain
cerebellum
 thalamus, hypothalamus

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Brainstem
 The “lower brain”
medulla oblongata
 pons
 midbrain

 Functions
homeostasis
 coordination of movement
 conduction of impulses to higher brain
centers

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Medulla oblongata & Pons
 Controls autonomic homeostatic
functions
heart & blood vessel activity
 breathing
 swallowing
 vomiting
 digestion

 Relays information
to & from higher
brain centers
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Midbrain
 Involved in the integration of sensory
information
 regulation of
visual reflexes
 regulation of
auditory
reflexes
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Reticular Formation
 Sleep & wakefulness produces patterns
of electrical activity in the brain
recorded as an ElectroEncephaloGram
(EEG)
 most dreaming
during REM
(rapid eye
movement)
sleep

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Cerebrum
 Most highly evolved structure of
mammalian brain
 Cerebrum divided
hemispheres
 left = right side of
body
 right = left side of
body

 Corpus callosum

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major connection
between 2 hemispheres
Lateralization of Brain Function
 Left hemisphere


language, math, logic operations, processing
of serial sequences of information, visual &
auditory details
detailed activities required
for motor control
 Right hemisphere

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pattern recognition, spatial
relationships, non-verbal
ideation, emotional
processing, parallel
processing of information
Cerebrum specialization
 Regions of the cerebrum are
specialized for different functions
 Lobes
frontal
 temporal
 occipital
 parietal

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Limbic system
Mediates basic emotions (fear, anger), involved in
emotional bonding, establishes emotional memory
Amygdala
involved in
recognizing
emotional content
of facial
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expression
Simplest Nerve Circuit
 Reflex, or automatic response
rapid response
 automated
 signal only goes to
spinal cord
 no higher level
processing
 adaptive value
 essential actions
 don’t need to think or
make decisions about
 blinking
 balance
 pupil dilation
 startle

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Eye Blink or Pain Withdrawal Reflex
Gray
Interneuron
matter
White
matter
Stimulus
Sensory
neuron
Receptor
in skin
Motor
neuron
Spinal
cord
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Effector
(muscle)
cerebrum
cerebellum
spinal cord
cervical
nerves
thoracic
nerves
lumbar
nerves
femoral
nerve
Any Questions??
sciatic
nerve
tibial
nerve
AP Biology
2007-2008