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Some Basic Neuroanatomy

The Central Nervous SystemFigure 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

• Lower tube becomes the spinal cord

Central Nervous System or CNS

Copyright © 2009 Allyn & Bacon

The Forebrain• Right & left cerebral

hemispheres (seen from above)

• The surface of hemispheres is the very folded cerebral cortex

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Corpus Callosum Side View

Lateral fissure

Central

Sulcus

The Forebrain – Cortex. Figure 3.8: Lobes and Cortical Areas

10Garrett: Brain & Behavior 4e

Beyond the Motor Areas: Prefrontal Cortex

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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

• Prefrontal lobotomy cut the connections between this executive area and the rest of the brain/spinal cord

• https://www.youtube.com/watch?v=ftDGcCbkeH4

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.

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=UU943UnajVxe9SpFJpwxpLsQ&index=1

Neocortex Has 6 Layers With Regional Variations in Thickness

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A “Processing Unit” Within the Cortex is a Column of Cells

The Forebrain – Cortex. Figure 3.8: Lobes and Cortical Areas

20Garrett: Brain & Behavior 4e

The Brain is Like a Tootsie Pop

Some forebrain areas are

hidden beneath the cortex

See 235-236

The Basal Ganglia Motor System (see 361)

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1

2

3

Hypothalamus• Plays a role in lots of different basic behaviors/motivations

necessary for survival of individual & survival of the species

• The “four F’s”• Feeding

• Fighting (aggression & rage)

• Fleeing (fear behaviors)

• Mating : )

• But also primitive parenting behaviors, temperature regulation, hormone regulation, biorhythms & sleep, mood/emotions

The Hypothalamus

Means “beneath the thalamus”

The Brainstem Areas Again

The Thalamusworks 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.

In Front of Hypothalamus is the“Basal Forebrain”

• Nucleus basalis activates cortex for consciousness and cognitive/memory function.

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Another component of the basal forebrain is the nucleus accumbens, a hub of our pleasure/reward pathway 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

Ventricles Filled With CSF

Enlarged VentriclesDue to Hydrocephalus https://www.youtube.com/watch?v=WU

HdkP278q0&list=PLJG4HdSoAx23j8Ev

hgzuJ3sEtCiMsqNJg&index=6

Go to 20

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A Shunt Tube Drains Away Excess CSF

https://www.youtube.com/watch?v=WUHdkP278q0

The Reptilian Brain

• 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.

Middle layer added emotion & memory capabilities.

Newest outer layer added judgment, reasoning, planning

and self-control.

The Brain Stem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

Cerebellum

Reticular Activating System

• The cells of the “reticular formation” have many other functions as well.

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.

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Colliculi Primarily Handle

Visual & Auditory ReflexesSubstantia Nigra Dopamine Neurons

The Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

Cerebellum

Mike, the Headless Chicken

• 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

A Sadder Example• 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

https://www.youtube.com/watch?v=lw-psbNU5XA go to :45

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Gray & White Matter

• Brain areas with lots of neuron cell bodies/dendrites look darker (“gray matter”) & function like information processors – receiving & combining input

• Areas with lots of myelinated axons appear lighter (“white matter”) & function like cables connecting regions

• A group of neuron cell bodies = “nucleus” (in CNS) or “ganglion” (in PNS)

• A bundle of axons = “tract” or “pathway” (in CNS) or “nerve” (in PNS)

• The CNS has a continuous fluid filled canal (or “ventricle” system throughout its length.

Afferent

Efferent

Spinal Reflexes Are Triggered Before Brain Experiences Sensation CNS is Protected by:

• Bone

• Meninges

• Layer of cerebrospinal fluid (CSF)

• Blood-brain Barrier

• But these protections have their limits!

The Meninges completely

enclose the CNS and help

protect it.

Dura

Arachnoid

Pia

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“-itis” = inflammationMeningitis= inflammation of meninges

CTE

https://www.youtube.com/watch?v=iBLYs-pDaQY

https://www.youtube.com/watch?v=ovzQKnLXH6A

Peripheral Nervous System (PNS)

All the nerves outside of

brain & spinal cord. That

includes:

31 pairs of spinal nerves

12 pairs of cranial nerves

and their peripheral

extensions.

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Divisions of the Nervous System Structures Controlled by the ANS

Book 4.6

Miscellaneous Loose Ends (Things I Forgot to Mention)

• Symmetrical and asymmetrical functions of the hemispheres

Contralateral organization & crossing of tracts

• “Association cortex” or higher level processing regions of cortex• Posterior parietal – uses body sensations to generate body image

• If damaged person may experience “contralateral neglect”

• Integrates visual & somatosensory input

• Damage may impair locating objects

• Inferior temporal – integrates vision & memory

• Damage may cause face blindness

• Damage may cause object agnosia

• Brain stem area• Ventral tegmentum

• One more example of the plasticity of the young nervous system:

• https://www.youtube.com/watch?v=VaDlLD97CLM

• Hemispherectomy