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nuron system
 Neurons are cells that transfer stimuli to other cells.

Structure of Neurons:  Cell Body - contains nucleus and organelles

    Dendrites - receive input , Axon - conducts impulses away from the cell body.

    Axon hillock - an enlarged region where an axon attaches to the cell body.

    Synaptic terminal - Neurotransmitters are manufactured in the cell body but released from synaptic terminals. The neurotransmitters stimulate other neurons.

    Synapse - A synapse is the junction between the synaptic terminal and another cell. The other cell is called a postsynaptic cell.

Nerves and Ganglia
    Axons and dendrites are bundled with axons or dendrites from other neurons to form nerves. Clusters of neuron cell bodies are called ganglia.    The nervous system can be divided into the central nervous system (CNS) which includes the brain and spinal cord and the peripheral nervous system (PNS) which includes everything else.

Classes of Neurons
    Sensory neurons (afferent neurons) conduct sensory information toward the CNS. Sensory neurons have a long dendrite and a short axon.

    The brain and spinal cord contain interneurons. These receive information and if they are sufficiently stimulated, they stimulate other neurons.

    Motor neurons (efferent neurons) send information from interneurons to muscle or gland cells (effectors).

Neuroglia
    Neuroglia (also called glia) are cells within the nervous system that are not neurons.

    There are different kinds of neuroglia, and they provide neurons with insulation, physical support, metabolic assistance, and protection.
    Myelination
    Some neuroglia function to provide insulation for axons or dentrites. They do so by wrapping around the long fibers.

    The insulation properties come from myelin contained within the cells.

    The layer of insulation is referred to as a myelin sheath.

    If these insulating cells are located in the peripheral nervous system, they are called Schwann cells.


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