• 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).
5. There are many MORE (10-50 times more) glial cells in the brain compared to the number of neurons.
Nerve Cells
Neurons, Glia, Extracellular Space,
and Blood
Provide the insulation (myelin) to neurons in the central nervous system.
Satellite Cells Schwann Cells
Physical support to neurons in the peripheral nervous system.
Provide the insulation (myelin) to neurons in the peripheral nervous system.
Neuroglia in the CNS
Neuroglia:
Distinguishing Features
• Able to replicate! • Importance in nervous system function is
responses to neural activity • Metabolically coupled to neural activity
3. Selective permeability to molecules based on their molecular weight and lipid solubility
4. 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.
1. Presence of tight junctions between the endothelial cells
2. One of the notable features of endothelial cells in comparison to other cell is the lack of pinocytic vesicles
VASTLY underestimated!
• Evidence is mounting:
1. Nurturing role 2. Signaling role (Memory?) 3. Inflammation 4. Pain 5. Many more to come!
Properties of Blood Brain Barriers
Types and Functions of Glia
Name of Glial Cell
Astrocyte (Astroglia)
Microglia
Oligodendroglia
Function
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 Like astrocytes, microglia digest parts of dead neurons.
• Express receptors for almost all neurotransmitters and neuromodulators
• Increase of intracellular calcium concentration • Membrane depolarization in astrocytes are common
Bidirectionathe CNS
• Receiving signals from neighboring neurons and responding to them with release of neuroactive substances
BBB
Glia are different from neurons:
1. 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.