1/20/15 – Lecture 3 – Cell Structure and Function in the Nervous System … Neurons and Glia Cells- Cells: the smallest unit of life that can survive on its owno Cell membrane surrounds the cell and separates itself from other cellso Aqueous interior called Cytoplasm, outer surrounding Extracellular Fluido Most cells have a Nucleus that store DNA, also have organelles with their own functions Mitochondria: the powerhouse of the cell- Cells of the Nervous Systemo Neurons: the main functioning cells of the Nervous System, electrically sending messages to communicate with one another Structures of the neurons- Dendrites: branching processes coming off the cell body to receive information from other neuronso Have 100s and 1000s of synapses to receive information from other neurons- Cell Body/ Soma: where the nucleus and most organelles are found and where the information is processed- Axon and Axon Terminals: the long process(es) that come off the cell body and send information toother neurons- Synapse: space between the sending neuron’s axon and the receiving neuron’s dendriteo Presynaptic Neuron: neuron on the axon side of the synapse (SENDING)o Postsynaptic Neuron: neuron on the dendrite side of the synapse (RECEIVING)o Neurotransmitters: chemicals that jump the synaptic gap after being created by the electrical impulse sent down the axon  3 Structural Categories of Neurons - Unipolar: both the axon and thedendrite are apart of the samestem/process- Bipolar: the axon and the dendritecome off opposite sides of the cellbody- Multipolar: neurons with multiple dendrites o MOST neurons have this structure, especially in the brain 3 of the Main Functional Categories of Neurons- Motor Neurons: neuronsthat send signals to themuscles and other bodystructures from the CNS- Sensory Neurons: neuronsreceiving sensoryinformation and relayingit to the CNS- Interneurons: neuronsthat link 2 other neuronstogethero Interneurons havethe largestnumber in thehuman body Neurons were created from stem cells- Stem cells: unspecialized cell that can form new cells through cell proliferation, these generalized cells become specialized later ono Cell Proliferation: cell division/ cell replication/ mitosis … one cell grows and replicates its DNA and then splits into two daughter cells, 2 -> 4 -> 8 -> 16 -> 32 -> 64 -> 128 -> ecto Differentiation: process by which neurons take on their complex adult forms by activating specific genes Adult neurons cannot divide again – post-mitotic No stem cells are found in the adult CNS so neurons thatdie cannot be replaced in the brain, same with the hearto Glial Cells: the support, protectors, nutrient givers, ect of the Nervous System 4 Types of Glial Cells- Astrocytes: star shaped cells that provide structure and nutritive supportto neurons while helping create the blood brain barrier and strengthen it- Oligodendrocytes and Schwann Cells: insulate neuronal axons (myelination) and improve electrical transmission along themo Myelin: fatty sheath surrounding the neuronal axons and speedsup the Axonal Conduction for sending messageso Oligodendrocytes: found in the CNSo Schwann Cells: found in the Peripheral NS Multiple Sclerosis: defect in the myelin sheath by the body’s own immune system that causes electrical messages to have interruptions- Microglia: immune like cells in the CNS that remove damaged neuronso Phagocytose or eat invading microorganisms such as bacteria and damaged or dead neurons Go from branching (non-activated) to ameboid (blobish)to the phagocytic macrophage If chronically activated it can malfunction and actually cause chronic pain and neuronal death- Ependymal Cells: produce cerebrospinal fluid constantly in the choroid plexus, so if there is a blockage it can result in hydrocephaluso Brain Tumors: large mass of abnormally over proliferating cells Usually from glial cells because neurons are post-mitotic (PRIMARY TUMORS) Tumor cells formed elsewhere in the body then invade the brain (SECONDARY