Nervous Tissue: Neuroglia = Support Cells Support cells in the Central Nervous System (CNS) are grouped together as neuroglia Neuroglia literally means “nerve glue” The function of neuroglia is to support, insulate, and protect the delicate neurons of the brain

Types of Neuroglia in CNS Astrocytes Astrocytes – –Star-shaped cells – –Half of all brain tissue – –Brace neurons; they keep the neurons in contact with their blood supply (capillaries) – –Control the chemical environment of the brain by mopping up leaked ions

Types of Neuroglia in CNS Microglia Microglia – –Spiderlike phagocytes (white blood cells) – –Dispose of debris like dead brains cells and bacteria

Types of Neuroglia in CNS Ependymal cells Ependymal cells – –Lines the cavities of the brain and spinal cord – –Circulate cerebrospinal fluid by beating their cilia – –Cerebrospinal fluid fills the space the brain does not take up and forms a protective cushion around the brain and spinal cord

Types of Neuroglia in CNS Oligodendrocytes Oligodendrocytes – –Wrap around nerve cells in the brain and spinal chord – –Produce myelin sheaths for spinal cord and brain (CNS) – –Myelin is a fatty, insulation covering the nerve cells; allows for the electrical signal to transmit faster (like wire coating)

Types of Neurolgia in PNS Schwann cells Schwann cells – –Form myelin sheath in the peripheral nervous system (nerves of the body; not nerves of the CNS)

So what’s a Neuron? Neurons are nerve cells Neurons are nerve cells – –Cells specialized to transmit messages – –Major parts of neurons Cell body Cell body — nucleus and metabolic center of the cell (main part of nerve cell) Processes Processes — fibers that extend from the cell body (where messages sent or received) – –can be microscopic or up to 3-4 feet in length

Anatomy of a Neuron Cell body Cell body –Nucleus Processes outside the cell body Processes outside the cell body –Dendrites –Dendrites — send impulses toward the cell body –Axons –Axons — send impulses away from the cell body

Anatomy of a Neuron Axons end in axon terminals Axonal terminals contain small sacs with neurotransmitters (chemicals)

Synapse and Synaptic Cleft Axonal terminals are separated from the next neuron by a gap (they never really touch) –Synaptic cleft –Synaptic cleft — gap (space) between adjacent neurons –Synapse –Synapse — junction between nerves

What happens at a synapse? The neurotransmitter diffuses across the synaptic cleft. They bind with receptor sites on the other neurons’ dendrite.s This influences the electrical response in the neuron. If enough neurotrasmitter is released, it changes the cell's excitability This allows for the signal to move on to the next neuron For communication between neurons to occur, an electrical impulse must travel down an axon to the synaptic terminal.

Multiple Sclerosis MS affects the ability of nerve cells in the brain and spinal cord to communicate with each other. MS affects the ability of nerve cells in the brain and spinal cord to communicate with each other. In MS, the body's own immune system attacks and damages the myelin In MS, the body's own immune system attacks and damages the myelin