神经元和神经胶质细胞-胶质细胞

Neuron : Supporting cells : CNS : neuroglia (glia) PNS : Schwann cells and satellite cells Functions : physical support electrical insulation metabolic exchange blood-brain barrierComposition of Nervous TissueTypes and Functions of GliaName of Glial CellFunctionAstrocyte (Astroglia)Star-shaped cells that provide physical and nutritional support for neurons: 1) clean up brain“debris“; 2) transport nutrients to neurons; 3) hold neurons in place; 4) digest parts of dead neurons; 5) regulate content of extracellular space Microglia Like astrocytes, microglia digest parts of dead neurons.Oligo-dendrogliaProvide the insulation (myelin) to neurons in the central nervous system.Satellite Cells Physical support to neurons in the peripheral nervous system.Schwann Cells Provide the insulation (myelin) to neurons in the peripheral nervous system.Neuroglia in the CNS Able to replicate! Importance in nervous system function is VASTLY underestimated! Evidence is mounting: Nurturing role Signaling role (Memory?) Inflammation Pain Many more to come!Neuroglia: Distinguishing Features1. Presence of tight junctions between the endothelial cells2. One of the notable features of endothelial cells in comparison to other cell is the lack of pinocytic vesicles3. Selective permeability to molecules based on their molecular weight and lipid solubility4. Presence of specific markers Rich in two enzymes: gamma glutamyl transpeptidase (GGTP) (for amino acid transport) and alkaline phosphatase (transport of phsopahte ions) used as marker for BBB. Others: glucose transporter (GLUT-1); endothelial barrier antigen (EBA; unknown function) and antigen recognized by the MRC OX-47 monoclonal antibody (important for cell-to-cell adhesion); transferrin receptor (transport of ferric ions).Properties of Blood Brain BarriersBBB1. Neurons have TWO “processes“ called axons and dendrites. Glial cells only have ONE. 2. Neurons CAN generate action potentials. Glial cells CANNOT, however, do have a resting potential. 3. Neurons HAVE synapses that use neurotransmitters. Glial cells do NOT have chemical synapses. 4. Neurons do NOT continue to divide. Glial cells DO continue to divide. 5. There are many MORE (10-50 times more) glial cells in the brain compared to the number of neurons.Glia are different from neurons:Nerve CellsNeurons, Glia, Extracellular Space, and BloodBidirectional Communication Partners in the CNSReceiving signals from neighboring neurons and responding to them with release of neuroactive substancesExpress receptors for almost all neurotransmitters and neuromodulatorsIncrease of intracellular calcium concentrationMembrane depolarization in astrocytes are common responses to neural activityMetabolically coupled to neural activityMetabolism of Astrocytes and their Metabolic Cooperation with Neurons Glucose Amino acid metabolism Enzymes: glutamine synthetase(glutamate-glutamine cycle); glycogen phosphorylatase (glycogen mobilization); pyruvate carboxylase (anaplerotic synthesis of oxaloacetate); cysteine sulfinate decarboxylase (synthesis of taurine); glycine cleavage system, glycine metabolism. Three Types of Metabolic Cooperation of Astrocytes and Neurons1. Supply of the energy substrate la