Download 9/9/2016 1 Some Basic Neuroanatomy

9/9/2016
Central Nervous System or CNS
Some Basic Neuroanatomy
The Central Nervous System
Figure 3.3: Central Nervous System Development
• Brain develops from a
fluid-filled, tubular
structure
• Upper tube develops
into
•
•
•
•
Forebrain
Midbrain
Hindbrain
At 3 weeks: all equal in
size
• At 11 weeks: forebrain
becomes the largest part
The Forebrain
• Right & left cerebral
hemispheres (seen from
above)
• The surface of
hemispheres is the very
folded cerebral cortex
• Lower tube becomes the
spinal cord
Copyright © 2009 Allyn & Bacon
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Corpus Callosum
Side View
Central
Sulcus
Lateral fissure
The Forebrain – Cortex. Figure 3.8: Lobes and Cortical Areas
Garrett: Brain & Behavior 4e
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Beyond the Motor Areas: Prefrontal Cortex
Humans: Well-developed prefrontal cortex
Frontal Lobe “Executive Functions”
• Mental representation of the world; working memory &
temporal memory (order of events in time)
• Forming goals, anticipating consequences
• Considering options; applying knowledge & past emotions &
consequences to making choices/decisions
• Choosing & initiating goal-directed behaviors
• Self-monitoring your responses
• Correcting/adapting behavior in response to feedback or
changes in context; inhibiting responses
• Attention & persistence towards goal despite distraction
The Case of Phineas Gage
• Phineas had been a
responsible, mild
mannered, church-going
family man before his
accident.
• After afterwards he not
only lost executive
functions but his behavior
& emotions were
disinhibited.
• Prefrontal lobotomy cut the connections between this executive area
and the rest of the brain/spinal cord
• https://www.youtube.com/watch?v=_0aNILW6ILk
MRI Reconstructions of Damage
• Phineas as well as many modern day
frontal patients are also likely to lose
their social sensitivity to others (lack of
tact, empathy, conscience, caring about
others)
• https://www.youtube.com/watch?v=jK1sj4JEJ2o&list=U
U943UnajVxe9SpFJpwxpLsQ&index=1
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Neocortex Has 6 Layers With Regional
Variations in Thickness
A “Processing Unit” Within the
Cortex is a Column of Cells
The Brain is Like a Tootsie Pop
• Note: as we cover the “subcortical” parts of the forebrain, I’m
including a few brain areas our chapter skips
Some forebrain areas are
hidden beneath the cortex
See 235-236
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The Basal Ganglia Motor System (see
361)
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Hypothalamus
• Plays a role in lots of different basic behaviors/motivations
necessary for survival of individual & survival of the
species
• The “four F’s”
•
•
•
•
Means “beneath the thalamus”
The Hypothalamus
Feeding
Fighting (aggression & rage)
Fleeing (fear behaviors)
Mating : )
• But also primitive parenting behaviors, temperature
regulation, hormone regulation, biorhythms & sleep,
mood/emotions
The Brainstem Areas Again
The Thalamus
works closely with
regions of cortex
• Best known for partially processing all incoming
sensations except smell before passing input on to
cortex
• Also has some motor, memory and emotional
functions.
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In Front of Hypothalamus is the
“Basal Forebrain”
• Activates cortex for consciousness and
cognitive/memory function.
Another component of the basal forebrain is the nucleus
accumbens, a hub of our pleasure/reward pathway
Ventricles Filled With CSF
CSF is continually produced in all ventricles the heads towards the hindbrain to
exit thru the 4th ventricle roof to circulate around the outer surface of cord and
brain. It is finally reabsorbed into bloodstream at the center top of the brain
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Enlarged Ventricles
Due to Hydrocephalus
Enlarged Skull
(bones not yet fused
in infants)
https://www.youtube.com/watch?v=WU
HdkP278q0&list=PLJG4HdSoAx23j8Ev
hgzuJ3sEtCiMsqNJg&index=6
Go to 20
A Shunt Tube Drains Away Excess
CSF
“Setting sun” eyes
http://www.youtube.com/watch?v=7b2JsLRanmk
The Reptilian Brain
Middle layer added emotion & memory capabilities.
Newest outer layer added judgment, reasoning, planning
and self-control.
• The brain stem, especially its core, is the most primitive
portion of our brain, relatively unchanged from the time
that dinosaurs roamed the earth. Most reptile behavior
is reflexive response to stimuli.
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The Brain Stem
Reticular Activating System
Thalamus
Hypothalamus
• The cells of the
“reticular
formation” have
many other
functions as well.
Midbrain
Cerebellum
Pons
Medulla
2 and 3 on the
“dorsal”
surface of
midbrain are
the primitive
visual (2) and
auditory (3)
processing
centers, the
superior (2) and
inferior (3)
colliculus.
Substantia Nigra Dopamine Neurons
Colliculi Primarily Handle
Visual & Auditory Reflexes
The Brainstem
Thalamus
Hypothalamus
Midbrain
Cerebellum
Pons
Medulla
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A Sadder Example
Mike, the Headless Chicken
• Anencephaly – forebrain fails to develop.
Baby has a flattened, open skull. Baby
shows basic reflexive behaviors (can nurse,
grasp, etc.) but with only hindbrain &
midbrain structures intact, survival is brief
(hours-days).
• An example of such reflexive behaviors in a
normal infant
• Survived 18 months
• Could still stand, sit on a perch,
walk clumsily, and attempt to
crow and preen.
• These basic behaviors are like
reflexes – built into the
brainstem.
http://en.wikipedia.org/wiki/Mike_the_Headless_Chicken
Afferent
Spinal Reflexes Are Triggered Before
Brain Experiences Sensation
Efferent
CNS is Protected by:
• Bone
• Meninges
• Layer of cerebrospinal fluid (CSF)
• Blood-brain Barrier
The Meninges completely
enclose the CNS and help
protect it.
Dura
Arachnoid
Pia
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“-itis” = inflammation
Meningitis= inflammation of meninges
Peripheral Nervous System (PNS)
All the nerves outside of brain &
spinal cord
Book 4.6
Divisions of the Nervous System
Structures Controlled by the ANS
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