The Central Nervous System Central nervous system – the brain and spinal cord Directional terms unique to the CNS Rostral – toward the nose Caudal – toward the tail

Embryonic Development of the Brain Figure 13.2a-e

Embryonic Development of the Brain Figure 13.2a-e

Embryonic Development of the Brain Figure 13.2a-e

Embryonic Development of the Brain Figure 13.2a-e

Embryonic Development of the Brain Brain arises from the rostral part of the neural tube Three primary brain vesicles in 4-week embryo Prosencephalon – the forebrain Mesencephalon – the midbrain Rhombencephalon – the hindbrain

Embryonic Development of the Brain Secondary brain vesicles Prosencephalon Divides into telencephalon and diencephalon Mesencephalon – remains undivided Rhombencephalon Divides into metencephalon and myelencephalon

Embryonic Development of the Brain Structures of the adult brain Develop from secondary brain vesicles Telencephalon  the cerebral hemispheres Diencephalon  thalamus, hypothalamus, and epithalamus Metencephalon  pons and cerebellum Myelencephalon  medulla oblongata

Embryonic Development of the Brain Brain stem includes: The midbrain, pons, and medulla oblongata Ventricles Central cavity of the neural tube enlarges

Embryonic Development of the Brain Brain grows rapidly, and changes occur in the relative position of its parts Cerebral hemispheres envelop the diencephalon and midbrain Wrinkling of the cerebral hemispheres More neurons fit within limited space

Brain Development from Week 5 to Birth Figure 13.3a-d

Basic Parts and Organization of the Brain Divided into four regions Cerebral hemispheres Diencephalon Brain stem: midbrain, pons, and medulla Cerebellum

Basic Parts and Organization of the Brain Figure 13.4

Basic Parts and Organization of the Brain Organization Centrally located gray matter Externally located white matter Additional layer of gray matter external to white matter Due to groups of neurons migrating externally Cortex – outer layer of gray matter Formed from neuronal cell bodies Located in cerebrum and cerebellum

Basic Parts and Organization of the Brain Figure 13.5

Ventricles of the Brain Expansions of the brain’s central cavity Filled with cerebrospinal fluid Lined with ependymal cells Continuous with each other Continuous with the central canal of the spinal cord

Ventricles of the Brain Lateral ventricles – located in cerebral hemispheres Horseshoe-shaped from bending of the cerebral hemispheres Third ventricle – lies in diencephalon Connected with lateral ventricles by interventricular foramen

Ventricles of the Brain Cerebral aqueduct – connects 3rd and 4th ventricles Fourth ventricle – lies in hindbrain Connects to the central canal of the spinal cord

Ventricles of the Brain Figure 13.6a, b

Protection of the Brain – Cerebrospinal Fluid (CSF) Provides a liquid cushion for the brain and spinal cord The brain “floats” in CSF Formed in choroid plexuses in the brain ventricles

Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27a

Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27b

Protection of the Brain – Blood-Brain Barrier Prevents most blood-borne toxins from entering the brain Impermeable capillaries Not an absolute barrier Nutrients such as oxygen pass through Allows alcohol, nicotine, and anesthetics through