Chapter 7 : The Nervous System Central Nervous System, Anatomy

Regions of the Brain Figure 7.12 Central Nervous System: Anatomy

Protection of the Central Nervous System:  Scalp and skin  Skull and vertebral column  Meninges  Cerebrospinal fluid  Blood brain barrier Figure 7.16a Central Nervous System: Anatomy

Meninges  Dura mater  Double-layered external covering  Periosteum – attached to surface of the skull  Meningeal layer – outer covering of the brain  Folds inward in several areas Central Nervous System: Anatomy

Meninges  Arachnoid layer  Middle layer  Web-like  Pia mater  Internal layer  Clings to the surface of the brain Central Nervous System: Anatomy

Cerebral Anatomy  The surface is made of ridges (gyri) and grooves (sulci)  Deep sulci are called fissures Figure 7.13a Central Nervous System: Anatomy

 Gray matter  Outer layer  Composed mostly of neuron cell bodies  Basal nuclei – internal islands of gray matter Figure 7.13a Central Nervous System: Anatomy Cerebral Anatomy

 White matter  Fiber tracts inside the gray matter  Example: corpus callosum connects hemispheres Central Nervous System: Anatomy Cerebral Anatomy

Cerebral Hemispheres (Cerebrum)  Paired (left and right) superior parts of the brain  Include more than half of the brain mass Central Nervous System: Cerebral Anatomy

Lobes of the Cerebrum  Fissures (deep grooves) divide the cerebrum into lobes  Surface lobes of the cerebrum  Frontal lobe  Parietal lobe  Occipital lobe  Temporal lobe Central Nervous System: Cerebral Anatomy

Cerebellum  Two hemispheres with convoluted surfaces  Provides involuntary coordination of body movements Central Nervous System: Cerebellar Anatomy

Diencephalon  Sits on top of the brain stem  Enclosed by the cerebral hemispheres  Made of three parts  Thalamus  Hypothalamus  Epithalamus Central Nervous System: Anatomy

 Thalamus - Surrounds the third ventricle  Hypothalamus - Under the thalamus The pituitary gland is attached to the hypothalamus  Epithalamus – Upon the thalamus Forms the roof of the third ventricle Houses the pineal body (an endocrine gland) Includes the choroid plexus – forms cerebrospinal fluid Central Nervous System: Diencephalon

Brain Stem  Attaches to the spinal cord  Parts of the brain stem  Midbrain  Pons  Medulla oblongata Central Nervous System: Anatomy

Midbrain  Mostly composed of tracts of nerve fibers  Has two bulging fiber tracts – cerebral peduncles  Has four rounded protrusions – corpora quadrigemina Central Nervous System: Brain Stem Pons  The bulging center part of the brain stem  Mostly composed of fiber tracts  Includes nuclei involved in the control of breathing Medulla Oblongata  The lowest part of the brain stem  Merges into the spinal cord  Includes important fiber tracts

Figure 7.15a Central Nervous System: Anatomy

Ventricles and Location of the Cerebrospinal Fluid Central Nervous System: Anatomy

Figure 7.17b Central Nervous System: Ventricles and Cerebrospinal Fluid

Cerebrospinal Fluid  Similar to blood plasma composition  Formed by the choroid plexus  Forms a watery cushion to protect the brain  Circulated in arachnoid space, ventricles, and central canal of the spinal cord Central Nervous System: Ventricles and Cerebrospinal Fluid

Nervous Tissue: Supporting Cells (Neuroglia, or simply Glia)  Astrocytes  Abundant, star-shaped cells  Anchor neurons  Form barrier between capillaries and neurons  Control the chemical environment of the brain Figure 7.3a Central Nervous System: Neuroglia

 Microglia  Spider-like phagocytes  Dispose of debris  Ependymal cells  Line cavities of the brain and spinal cord  Circulate cerebrospinal fluid with beating cilia Figure 7.3b, c Central Nervous System: Neuroglia

 Oligodendrocytes Produce myelin sheath around nerve fibers in the CNS Figure 7.3d Central Nervous System: Neuroglia Function like Schwann cells in the PNS

Spinal Cord  Extends from the medulla oblongata to the region of T12  Below T12 is the cauda equina (a collection of spinal nerves)  Enlargements occur in the cervical and lumbar regions Figure 7.18 Central Nervous System: Spinal Cord

Spinal Cord Anatomy  Meninges cover the spinal cord  Nerves leave at the level of each vertebrae Dorsal root Associated with the dorsal root ganglia – collections of cell bodies outside the central nervous system Ventral root Central Nervous System: Spinal Cord

 Exterior white mater – conduction tracts Figure 7.19 Central Nervous System: Spinal Cord  Central canal filled with cerebrospinal fluid

 Internal gray matter - mostly cell bodies Dorsal (posterior) horns Anterior (ventral) horns Figure 7.19 Central Nervous System: Spinal Cord

Michelangelo’s “The Creation of Adam” from his fresco in the Sistine Chapel. Does the red cloth look familiar?