Columbia University DPT Program PHYT M8105 Neuroscience Lecture Notes PDF

**COLUMBIA UNIVERSITY** **DPT PROGRAM** **PHYT M8105 Neuroscience** **[Essential Concepts -- Lecture \#3 Notes -- ]** **[Development of the Nervous System]** **FORMATION OF THE BASIC ANATOMICAL STRUCTURES** I. A. - "Zero point" of embryological development. B. - Week 1 of embryol...

**COLUMBIA UNIVERSITY** **DPT PROGRAM** **PHYT M8105 Neuroscience** **[Essential Concepts -- Lecture \#3 Notes -- ]** **[Development of the Nervous System]** **FORMATION OF THE BASIC ANATOMICAL STRUCTURES** I. A. - "Zero point" of embryological development. B. - Week 1 of embryological development. C. - 6-days post fertilization until the end of week 2 of embryological development. D. - End of week 2 through week 3 of embryological development. +-----------------+-----------------+-----------------+-----------------+ | | **Ectoderm** | **Mesoderm** | **Endoderm** | | | | | | | | **(Outer | **(Middle | **(Inner | | | Layer)** | Layer)** | Layer)** | +=================+=================+=================+=================+ | | *Nervous | Connective | Epithelial | | | Tissue* | Tissue | Lining of | | | | | | | | Adrenal Medulla | Muscle Tissue | Gastrointestina | | | | | l | | | Posterior | Epithelial | (Except Mouth & | | | Pituitary | Lining of Blood | | | | | | Anus) & | | | Cornea & Lens | Vessels, | Respiratory | | | | Lymphatic | Systems | | | Epithelial | | | | | Lining of | Vessels, Body | Epithelial | | | | Cavities, | Lining of | | | Nose, Mouth, | | Anterior | | | Anus | Kidneys, | Pituitary, | | | | Ureters, | | | | Epidermis of | | Auditory | | | Skin & | Gonads, Genital | Structures, | | | | Ducts, | Pharynx, | | | Derivatives | | | | | | Adrenal Cortex | Tonsils, | | | | | Thymus, Thyroid | | | | Dermis of Skin | Gland, | | | | | | | | | | Parathyroid | | | | | Glands, Liver, | | | | | Gall | | | | | | | | | | Bladder, | | | | | Pancreas, | | | | | Urinary | | | | | | | | | | Bladder, | | | | | Urethra, Vagina | +-----------------+-----------------+-----------------+-----------------+ E. - 1. Notochord -- A midline mesoderm derived structure. - 2. Somitomeres/Somites **--** Rounded mesoderm derived structures, lying parallel to the notochord. - - F. - 1. Steps a. The notochord induces the overlying ectoderm (a.k.a. neuroectoderm) to form the neural plate. b. The neural plate begins to crease ventrally along its midline, forming a neural groove with neural folds on each side. c. The neural folds move together and fuse, forming the neural tube. The lumen of the neural tube is the neural canal. d. A special population of cells, the neural crest, arises from the lateral margins of the neural folds. e. The neural tube separates from the surface ectoderm and sinks into the posterior body wall. 2. Histogenesis of the Neural Tube a. b. c. 3. Molecular Basis for Neural Induction +-----------------------------------------------------------------------+ | *Failure of the neural tube to close effects the development of the | | vertebral arches and the CNS.* | | | | *Spina Bifida -- Failure of the vertebral arches to form completely | | and fuse to cover the spinal cord. The defect may be covered with | | skin (occulta), not covered with skin (aperta), and/or involve a | | cystic mass (cystic) that may contain only meninges (meningocele) or | | meninges and neural tissue (meningomyelocele).* | | | | *Anencephaly -- The brain is not formed, the surrounding meninges and | | skull may be absent, and there may be facial abnormalities.* | +-----------------------------------------------------------------------+ **II. Development of the Central Nervous System** A. [Spinal Cord] - 1. A longitudinal groove, the [sulcus limitans] appears in the lateral wall of the neural tube, separating it into a dorsal and ventral half. 2. Cells migrate peripherally to form four longitudinal columns, which will become the gray matter of the spinal cord. a. b. c. 3. The neural canal will become the central canal of the spinal cord. - B. [Brain] - **Primary Vesicle** **Secondary Vesicle** **Neural Derivatives** **Cavity** --------------------------------- ----------------------- -------------------------------------------------- -------------------- **Prosencephalon (Forebrain)** Telencephalon Cerebral Hemispheres Lateral Ventricles Diencephalon Thalamus, Hypothalamus, Retina, Other Structures Third Ventricle **Mesencephalon (Midbrain)** Mesencephalon Midbrain Cerebral Aqueduct **Rhombencephalon (Hindbrain)** Metencephalon Pons, Cerebellum Fourth Ventricle Myelencephalon Medulla Fourth Ventricle 1. Brainstem -- Consists of the myelencephalon (medulla), part of the metencephalon (pons), and the mesencephalon (midbrain). a. b. 1. The alar plate gives rise to sensory cranial nerve nuclei. 2. The basal plate gives rise to motor cranial nerve nuclei. 2. Cerebellum 3. Forebrain a. The prosencephalic bulge subdivides into two rostral telencephalic swellings that expand around a caudal centrally directed diencephalon. b. As a result of the rapid telencephalic growth the basal ganglia portion folds down toward the diencephalon and the regions fuse. c. After further rapid growth, the insula, overlying the point of fusion, becomes overgrown by the cerebral cortex. Due to the disproportionate growth of the cerebral cortex, the cerebral hemispheres "rotate" into a C shape. d. Extensive folds develop on the surface of each cerebral hemisphere. 4. Ventricular System -- An elaboration of the cephalic portions of the neural canal. -------------------------------------------------------------------------------------------------------------- *Hydrocephalus -- Dilation of the ventricular system due to increased pressure from obstructed flow of CSF.* -------------------------------------------------------------------------------------------------------------- **III. Development of the Peripheral Nervous System** A. [Neural Crest] - 1. Neural Elements -- Neurons of dorsal root ganglia, autonomic nervous system, and some sensory ganglia of cranial nerves. 2. Non-Neural Elements -- Schwann cells, melanocytes, odontoblasts, satellite cells of peripheral ganglia, cartilage of pharyngeal arches, ciliary & papillary muscles, chromaffin cells of the adrenal medulla, pia & arachnoid of the meninges. B. [Placodes] -- Specialized regions of neuroepithelium in the developing head region. - C. [Neuroepithelium Lining the Neural Canal] - **CELLULAR EVENTS OF DEVELOPMENT** *The organization of the brain ultimately determines its function. Three important parameters in brain organization are (1) neuron density, (2) the formation of axonal pathways, and (3) the pattern of synaptic contacts.* I. A. [Period of Overproduction] - B. [Programmed Cell Death] - - - C. [Mature Human Brain] - - II. A. - - - B. - - - **III. Synaptogenesis** A. [Elaboration of the Postsynaptic Apparatus in the Target Cell] - - B. [Differentiation of Axon Growth Cone into a Presynaptic Nerve Terminal] - - IV. A. [Definitions] 1. Plasticity = The ability of an experience to influence neural activity in such a way that it alters neural circuitry and thus determines behavior. 2. Critical Period = The postnatal time during which a given behavior is especially susceptible to -- indeed, requires -- specific environmental influences in order to develop normally. 1. Imprinting -- Young animals learn the characteristics of their parents. 2. Language Acquisition 3. Vision - - Correlated Synaptic Increase Modify Gene May Influence: Activity Alterations Intracellular Ca++ Expression Neurotrophins In a Receptors Target Cell Cytoskeletal Elements Extracellular Matrix