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individual nerve cells

three parts of a neuron

cell body, dandrites, axons

cell body of a neuron contains:

the cells nucleus


branches that extend out from the cell body and receive messages from other neurons


branches that carry messages away from the cell body


bundle of many long neurons outside the brain and spinal chord


the particles carrying either a positive of a negative electrical charge, most ions inside neurons are negatively charged

neuron membranes

semi permiable, , only certain chemicals can permeate


theprocess by which one neuron membrane touches another, and the semi permiability goes down, allowing positively charged ions to enter

action potential

caused by depolarization, axon becomes more permeable, producing a depolarization

all or none principal

neurons transmitted signals to other neurons only when depolarization was strong enough to trigger an action potential

myelin sheath

white, fatty coating encasing many axons, increases the speed at which the axon conducts neural impulses

victims of multiple schlerosis have problems with their

myelin sheath

synaptic gap

gap between neurons

nuero transmitters

carriers of neutral message across the synaptic gap

glial cells help neurons carry out their goals in three ways

transport nutrients from blood vessels to neurons, some produce the myelin sheath, and change the chances of synaptic transmission

two divisions of the nervous system

central, peripheral

central nervous system

consists of brain and spinal chords

peripheral nervous system

composed of the nerves that branch from the brain and the spinal cord to the body

two parts of the peripheral nervous system

somatic, autonomic

somatic nervous system

carries messages from the central nervous system to the skeletal muscles that control movements of the body

autonomic nervous system

composed of nerves that carry messages to the glands and visceral organs

divisions of the autonomic nervous system

sympathetic nervous system, parasympathetic nervous system

sympathetic nervous system

prepares the body to respond to psychiological or physical stress

parasympathetic nervous system

maintains balanced regulation of internal organs

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