Nervous Tissue: Nervous Tissue: Neuroglia = Support CellsNeuroglia = 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 Types of Neuroglia Neuroglia

in CNSin CNS AstrocytesAstrocytes

– 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 Types of NeurogliNeuroglia in CNSa in CNS

MicrogliaMicroglia– Spiderlike phagocytes

(white blood cells)

– Dispose of debris like dead brains cells and bacteria

Types of Neuroglia in Types of Neuroglia in CNSCNS

Ependymal cellsEpendymal 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 Types of Neuroglia Neuroglia

in CNSin CNS OligodendrocytesOligodendrocytes

– 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 Types of Neurolgia in PNSPNS

Schwann cellsSchwann cells

– Form myelin sheath in the peripheral nervous system (nerves of the body; not nerves of the CNS)

So what’s a Neuron?So what’s a Neuron? Neurons are nerve cellsNeurons are nerve cells

– Cells specialized to transmit messages

– Major parts of neurons Cell bodyCell body — nucleus and

metabolic center of the cell (main part of nerve cell)

ProcessesProcesses — 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 NeuronAnatomy of a Neuron Cell bodyCell body

– NucleusNucleus Processes outside Processes outside

the cell bodythe cell body– DendritesDendrites — send

impulses toward the cell body

– AxonsAxons — send impulses away from the cell body

Anatomy of a Anatomy of a NeuronNeuron

Axons end in axon terminals

Axonal terminals contain small sacs with neurotransmitters (chemicals)

Synapse andSynapse andSynaptic CleftSynaptic Cleft

Axonal terminals are separated from the next neuron by a gap (they never really touch)

– Synaptic cleftSynaptic cleft — gap (space) between adjacent neurons

– SynapseSynapse — junction between nerves

What happens What happens at a synapse?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 Multiple SclerosisSclerosis

MS affects the MS affects the ability of nerve ability of nerve cells in the brain cells in the brain and spinal cord to and spinal cord to communicate with communicate with each other. each other.

In MS, the body's In MS, the body's own immune own immune system attacks and system attacks and damages the damages the myelin myelin