At the center of everything… but separated by layers of membranes

It’s all about connections…  Brain  spinal cord via foramen magnum  Spinal cord runs through vertebral canal, formed by vertebral foramina

Meninges mater (umm… matter)  Dura mater – “durable” tough, dense; protection from impact, friction  Arachnoid mater – cushion from impact Subarachnoid space – CSF runs here  Pia mater – in the “pits” direct contact Carries blood vessels Forms nerve sheaths Helps form CSF

More on the pia mater  Associated with choroid plexus Secretes CSF Combination of blood vessels & neuroglia ○ Remember which kind? Ependymal cells

It’s not all black and white… but it is gray!  Gray matter = unmyelinated neuron cell bodies Accumulate lipofuscin Found primarily in cortex (surface of brain) ○ Highly folded/ridged = gyri Increase surface area Small pockets of gray found in interior  White matter = myelinated axons, neuroglia Found in brain’s interior  In spinal cord, colors are reversed… outside white, inside gray

Concept check!  1. Describe the three layers of the meninges  2. What is the function of the choroid plexus?  3. Describe the locations of gray and white matter in the CNS Why are they those colors?

Three-Pound Marvel: The Brain  Billions of neurons, neuroglia Most multipolar (1 axon, many dendrites) Receive many signals, process them  Tracts of axons Information conduit  other regions of brain, body

 Largest, most anterior portion Emotions Memory Motor movement Thought  Contain basal nuclei, cerebral cortex

 4 pockets of gray matter – relay motor information to spinal cord Permit coordinated, steady body movements

 Convoluted gray matter covering brain  Large surface area (18 sq ft.)

 Cerebral cortex nourished by vessels in arachnoid layer  “Barrier” exists between bloodstream and CSF… Which neuroglia create this? Astrocytes!  Prevents harmful substances from entering brain (also medications)

 Halves of cerebrum divided by longitudinal cerebral fissure  Some division of labor… But you use both halves!

 Corpus callosum connects left and right hemispheres Contributes to plasticity of brain

Central sulcus Lateral sulcus

Areas of specialization

 Hypothalamus, thalamus, ventricles

 Sensation, spatial sense, motor signals to cortex  Surrounds 3 rd ventricle

 Link nervous system to endocrine system via pituitary gland

 4 connected cavities in the forebrain that contain CSF  Associated w/ choroid plexus, continue into spinal cord  Protect brain from trauma Internal cushion  Swelling: hydrocephaly

Midbrain  Strip of neurons, connects cerebrum to hindbrain.  Smallest region of the brain  Relay station for audio and visual info  Eye movement  Substantia nigra: dopamine neurons

Hindbrain

Pons  Attached to midbrain  Organize & transmit sensory info from the body

Medulla oblongata  Reg’s involuntary body functions BP Breathing Heart rate Swallowing

Cerebellum  Posterior to pons  Means “little cerebrum” In appearance only  Balance  Posture  Coordination of body movement

Spinal Cord  Where does it start from? (picture)  Paper towel roll  Blanket  Model of spine

 White matter 15 pairs nerve tracts Ascending tracts ○ Dorsal ○ Sensory to the brain Descending tracts ○ Lateral & ventral ○ Motor info to effectors Extrapyramidal tracts ○ Info from medulla oblongata  posture & muscle tone

Gray matter  Made of nerve cell bodies  reflexes  Transfer info to white matter  Dorsal horn sensory  Ventral horn Motor White matter  muscles  Intermediate gray matter b/t “wings” Sensory/motor for glands/muscles

Spinal nerves  31 pairs spinal nerves  Part of PNS  Reflex arcs for respective body regions