BIOL 4330 1st Edition Lecture 10 Outline of Last Lecture I. Signaling CentersII. Hox GenesIII. Major Themes in Vertebrate GastrulationIV. Same Molecules Same AxesOutline of Current Lecture I. Central Nervous System and Neural CrestII. NeuroblastsIII. Cerebellar OrganizationIV. Spinal CordCurrent LectureA portion of the dorsal ectoderm is specified to become neural ectoderm and the cells are columnar: thisregion of the embryo is called the neural plate – on the surface of the embryo. The process by which the neural plate forms a neural tube (rudiment of the central nervous system) is called neurulation; the embryo is called a neurula.Neural tube forms the brain anteriorly and the spinal cord posteriorly.Neural cells become specified through interactions with other cells – 4 stages through which pluripotent cells of the epiblast or blastula become neural precursor cells (neuroblasts):1) Competence – multipotent cells can become neuroblasts if they are exposed to the appropriate combination of signals2) Specification – cells have received the right signals to become neuroblasts, but progression along the neural differentiation pathway can still be repressed by other signals3) Commitment (determination) – neuroblasts enter the neal differentiation pathway and will become neurons even in the presence of inhibitory signals4) Differentiation – neurobalsts leave the mitotic cycle and express those genes characteristic of neuronsFormation of the neural tube occurs in 2 stages, primary and secondary neurulation.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.No separation of the neural tube occurs when one side of the embryo is injected with N-cadherin mRNA so that N-cadherin is expressed in the epidermal cells as well as the presumptive neural tube.1st year post birth- each cortical neuron develops enough dendrite surface – as much as 100,000 connections. Each cortical neuron connects with 10,000 synapses and neural cells.Human brain: 10^11 neurons associated with 10^12 glial cellsMicrospikes have microfilaments and are exploratory. The myelin sheath surrounds the axon to protect it. Any major disruption in the myelin sheath of the traveling axon causes electrical shorts. This can be seen during multiple sclerosis, which has a severe degradation of the myelin sheaths. 95% of your serotonin is produced by your gut, not your brain. Basic 3 Zone Pattern of Ventricula (ependymal), mantle, and marginal layers is retained throughout development – gray matter is surrounded by white matter.Sulcus limitans divides ventral and dorsal halves. Dorsal portion receives input from sensory neurons. Ventral portion is involved in effecting motor neurons.Construction of the mammalian neocortex is perhaps the most complex biological process that occurs in nature. A pool of seemingly homogenous stem cells first undergoes proliferative expansion and diversification and then initiates the production of successive waves of neurons. As these neurons are generated, they take up residence in the nascent cortical plate where they migrate into the developing neocortical circuitry. The spatial and temporal coordination of neuronal generation, migration and differentiation is tightly regulated and of paramount importance to the creation of a mature brain capable of processing and reacting to sensory input from the environment and of consciousthought. Cerebellar organization is a very highly structured part of the brain. Cross sections procure four types of cells: granule neurons, Bergmann glial cells, Purkinje neurons, Dendritic arbor of Purkinje neurons. Glial cells form a “monorail” system that guide neurons from the ventricular source. It is still debated whether the brain can create new nerve cells. It is generally accepted that substances such as alcohol and marijuana will kill the nerve cells and cannot be replaced. Into adult mice, they injected BrdU, a toxin, then used fluorescent dyes to demonstrate new neurons and fluorescent antibodies against BrdU (bromodioxyuridine). The adult mice showed evidence of adult neural stem cells that was extremely slow. The chimpanzee has a 96% genome similar to humans. Compared to the chimpanzee, the ratio of brain weight to body weight was much higher in humans due to the retention of fetal neural growth fate. Our brains continue to grow, whereas the GADD45G enhancer in chimpanzees and mice will suppress their brain growth.Sonic hedgehog separates the eye field into bilateral fields. In a study between surface-dwelling and cave-dwelling populations of Mexican tetras (Astyanax mexicanus), the cave-dwelling fish had lost their eye. Instead of having both Pax-2 and Pax-6, they lacked Pax-6.Spinal cord – central core of cell bodies (gray matter) surrounded by an outer layer of axon tracts (white