Wednesday February 1 y Bio Psych Studying Midterm II Lecture 8 Developmental Neurogenesis 1 Zygote Blastula and Gastrula Zygote single cell formed by reproduction from fertilization to 4 days old Blastula hollow ball of cells formed around 4 5 days after reproduction Gastrula 3 layered ball of cells formed 7 10 days after reproduction 2 Ectoderm Mesoderm Endoderm and the Nervous System Ectoderm outer layer of gastrula forms skin and nervous system Mesoderm middle layer of gastrula forms muscle blood and bone Endoderm inner layer of gastrula forms internal organs lungs liver intestines 3 Neural Plate Neural Tube and Neural Crest Neural plate part of the back ectoderm that forms the neural tube by folding in on it Neural tube hollow tube of cells that eventually forms the spinal cord and brain Neural crest cells that eventually migrate out and form the peripheral nerves Incomplete folding can result in anencephaly lack of brain formation or spina bifida 4 6 Main Processes that form the Nervous System during Neu ral Development etc self 1 Cell proliferation the formation of two new cells from one cell starts shortly after conception and is mostly complete 4 5 months post conception Wednesday February 1 y Cell migration the movement of cells from one place to another starts around 8 9 weeks post conception and is complete 2 3 months before birth Cell differentiation and maturation unspecialized stem cells or precursor cells take on their final specialized state chemical differentiation done by birth morphological differentiation continues into childhood Synaptogenesis formation of a function synapse between an axon from a presynaptic neuron and the dendrites of a postsynaptic neuron starts in prenatal development and continues into late childhood Cell death and Synaptic pruning neurons with weaker connections do not get enough support and eventually die postnatal Myelination the formation of myelin sheaths around neurons begins just after birth and continues into young adulthood prenatal prenatal postnatal postnatal postnatal 2 5 Neural Cell Migration Tangential Cell Migration moving up down or around Radial Cell Migration moving out from center Wednesday February 1 y 6 Neural Cell Migration cont Tangential migration of crest cells forms Schwann cells and neurons in peripheral nerves Radial migration of cerebral cortical neurons forms the layers of the cerebral cortex 7 Master Regulatory Genes Master Regulatory Genes genes that produce a protein that then turns on neuron specific proteins such as voltage gated ion channels neurotransmitter receptors and peptide neurotransmitters most associated with chemical differentiation 8 Processes Associated with Morphological Differentiation Grow dendrites Extend axons 9 Axonal Extension Chemoattractants and Adhesion Molecules 2 CUES 1 Secretion of chemoattractants from the target cell that guide the axon to them 2 Cell adhesion molecules then grasp the axon and adhere it to the target cell 10 Synaptogenesis IN DEPTH 3 1 Presynaptic neuron needs to synthesize and store neurotransmitter vesicles 2 Postsynaptic neuron needs to form and insert receptors into membrane Wednesday February 1 y 11 Neuronal Cell Death and Synaptic Pruning Postsynaptic cells secrete neurotrophins Neurotrophins promote the survival of neurons Neurons with a stronger connection get more support those with weaker connections don t and eventually die This leaves only neurons with strong functional connections 12 Myelination IN DEPTH Brain regions that myelinate FIRST sensory and motor parts of the brain hindbrain Brain regions that myelinate LAST problem solving decision making impulse control Lecture 9 Maturation Environment and Neural Devel opment 1 Grasping Behaviors in Infants 2 months hand orients toward objects and gropes to hold it 4 months grasps with entire hand palmer grasp 6 8 months mature grasp using fingers individually 4 Wednesday February 1 y 10 months fine pincer grasp for holding small objects Neural changes Increased dendritic maturation in motor cortex neurons Increased myelination of motor cortex neurons Decreased cortical thickness in hand region of motor cortex synaptic pruning 2 Developmental Neural Changes Associated with Language Increased cortical thickness in speech areas of cortex for the language the child is increased dendritic branching and synaptogenesis hearing and speaking increase in glial cells myelination ing heard or spoken Pruning of neurons and synapses in speech sound areas of other languages not be 3 4 Stages of Piagetian Development 1 Sensorimotor stage birth 2 years old object permanence cause and effect 2 Pre operational stage 2 6 years old form mental word and drawing representation of things 3 Concrete operations 7 11 years old mentally manipulate dimensions mathematics conservation of mass 4 Formal operations abstract reasoning 5 Wednesday February 1 y Neuronal number doesn t change we aren t adding new neurons but glial cells and synaptic density probably increase 5 Adult Neurogenesis Adult neurogenesis new neuronal formation in the hippocampus see picture caused by enriched environments neural complexity in animals and exercise 6 Autism Spectrum Disorder Autism Spectrum Disorder a family of disor ders characterized by social deficits commu nication difficulties stereotyped or repetitive behaviors and interests and in some cases cognitive delays Symptoms not able to interpret emotions and intentions of other people very accustomed to routine language deficit missing social cues obsessed with a single object or activity Autism is very different for each child and patients typically don t display the same 7 Under connectivity and Over connectivity Hypotheses Neural Changes pattern of deficits 6 Wednesday February 1 y Undergrowth under connectivity hypothesis some brain regions are smaller or less well connected in autistic brains 1 hippocampus and amygdala emotion processing 2 insular cortex social processing 3 brainstem nuclei hearing and facial expressions defective neuron proliferation defects in dendritic branching and synapse forma tion excessive pruning connected in autistic brains Overgrowth over connectivity hypothesis some brain regions are larger or overly 1 basal ganglia motor cortex repetitive movements 2 sensory cortex fixation with certain sensory stimuli 3 frontal cortex immersion in own thoughts excessive neuron or synapse formation defective pruning of cells or synapses 8 Mental Retardation Mental Retardation