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: White 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 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 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 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 Arachnoid Mater Pia 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