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Central Nervous System
Brain & Spinal Cord
Development of the CNS
Appears as neural tube on dorsal median
plane
 4th week brain formation begins at
anterior end of the neural tube
 Remaining portion of neural tube
becomes spinal cord

4 Major Regions of the Brain
Cerebrum (Cerebral hemispheres)
 Cerebellum
 Brain Stem
 Diencephalon

Cerebrum
Divided into left and right hemispheres
(What do you already know about them?)
 Surface is covered in elevated ridges and
shallow grooves

◦ Gyri- ridges
◦ Sulci- grooves
◦ Let’s think of a way to remember these!

Fissures are deep grooves that separate
large regions of the brain
Cerebrum

Gray matter:
◦ Outermost portion of the cerebral cortex
◦ Neuronal cell bodies are located here

White matter:
◦ Inner tissue of cerebrum
◦ Bundles of fiber tracts (neuronal axons!)

Basal nuclei- small islands of gray matter
within inner cerebrum
◦ Regulate voluntary motor activities
The Brain Matters 
Locate the gray matter, the white matter, and the basal nuclei.
Cerebrum separated into 4 lobes
Each lobe of the cerebrum is unique
Frontal Lobes
 Parietal Lobes
 Temporal Lobes
 Occipital Lobe

Do these names sound familiar?
Corpus Callosum
Large fiber tract
 Connects and allows
communication
between left & right
hemisphere
 “Split-Brain” patients

◦ Severed corpus
callosum
Split-Brain Patients
Article: http://www.nature.com/news/the-split-brain-a-tale-of-two-halves-1.10213
Brain Stem

Parts of the Brain Stem:
◦ Midbrain
◦ Pons
◦ Medulla oblongata
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Provides a pathway for ascending &
descending tracts from the brain to the
spinal cord
Reticular Formation
◦ Gray matter extending along brain stem involved
in motor control of organs & consciousness
Brain Stem
Diencephalon
Located on top of the brainstem
surrounded by the cerebral hemispheres
 Many structures in the diencephalon

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Thalamus
Hypothalamus
Pituitary
Pineal Body
Choroid Plexus
Amygdala
Hippocampus
Cerebellum
Located under the occipital lobe of the
cerebrum
 It has two hemispheres with an outer
cortex of gray matter and inner region of
white matter

“Let Me Pick Your Brain” Activity
Awesome 3D Brain Website:
 G2conline.com

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Pages 235-241 in your book
CNS Protection
Bones of the skull and vertebral column
 Connective tissue membranes called
Meninges
 Aqueous cushion called the cerebrospinal
fluid (CSF)
 Blood-brain barrier made by the least
permeable capillaries in the body keeps
the brain in a constant environment

◦ What would happen if the brain were
exposed to various ions?
Meninges of the Brain

Dura Mater
◦ Outermost thick, tough, double layered
membrane

Arachnoid Mater
◦ Middle layer with many projections that has CSF
flowing through it
◦ Arachnoid villi protrude through dura mater,
allowing CSF to drain into superior sagittal sinus
to the blood

Pia Mater
◦ Delicate innermost vascular layer that follows
every convolution of the brain and spinal cord
Cerebrospinal Fluid

We know where it drains… but where is
it made?
◦ Made in the choroid plexuses on roof of
ventricles in the brain
The choroid plexuses make about 20-30
mL of CSF per hour
 The body has about 150 mL of CSF at a
time
 Circulates throughout the CNS

◦ Which cells help circulate CSF?
Blood-Brain Barrier

Brain is the only body organ that cannot
handle any environmental fluctuations

Neurons are sequestered from
substances in the blood by nearly
impermeable capillaries
Spinal Cord
Continuation of the brain stem
 3 layers of Meninges
 31 pairs of spinal nerves
 Gray matter is on the inside & contains
neuron cell bodies
 White matter is on the outside &
contains axons
