Neurons

Parts of the Neuron Cell Body – contains the nucleus and completes the metabolic activities needed to keep the cell alive. Dendrites- short branched extensions of the cell attached to the cell body that take input from surrounding neurons.

Parts of the Neuron Axon-long fiber that carries impulses away from the cell body. Myelin sheath- insulator that speeds up impulses.

Parts of the Neuron Nodes of Ranvier – highly conductive areas that jump-start the impulses Axon Terminal- end of the axon where the impulse is converted into neurotransmitters

Parts of the Neuron Synapse – Area between neurons Neurotransmitters – chemicals that are used to transmit the impulse from one cell to another.

How a Neuron Works: At Rest: Cells pump sodium (Na+) out of the cell and potassium (K+) into the cell. K+ leave the cell easily so the axon has a negative charge.

How a Neuron Works: Threshold A neuron will only fire if a minimum level of stimulation is reached. Too little stimulus = no firing Above the level = firing

How a Neuron Works: When Fired- The neuron pumps Na+ ions into the axon. This makes a positive electrical charge which moves down the axon. The cell returns to a resting state by pumping in K+.

How a Neuron Works: At the axon terminal- The impulse triggers the release of neurotransmitters into the synapse. The neurotransmitters attach to receptors on the next nerve cell. This creates a stimulus that continues the cycle.