Structure of a Neuron Types of Neurons and their basic structures.

The Neuron  A Neuron is a specialized type of cell that carries messages throughout the nervous system.  Message are transmitted through an electrochemical process called neurotransmission.  Neurons have structures similar to other cells.  They have a cell membrane  They have a nucleus containing DNA  And organelles such as Ribosomes and Mitochondria.

Three basic types of Neurons  Sensory Neurons carry signals from the sensory organs to the central nervous system along afferent nerve fibers.  Inter Neurons carry signals from one neuron to another either within the central nervous system or from sensory to motor neurons.  Motor Neurons carry signals from the Central Nervous System to the motor cells or muscles along efferent nerve fibers.

Basic Structure of a Neuron Soma (cell body) Dendrites Axon Terminal Buttons Myelin Sheath (Schwann Cells) Image: Biological Neuron Schema. Wikimedia Commons. Nicolas.Rougier

Parts of a Neuron  Soma or Cell body - contains cytoplasm and the nucleus, which includes the chromosomes. Mitochondria in the cell body perform metabolism. Ribosomes synthesize proteins.  Dendrites – receive input from previous neurons.  Axon – Carries the electrical impulse (action potential) to the terminal buttons.  Terminal Buttons – Contains vesicles that release chemical messengers (neurotransmitters) across the synaptic gap to other neurons.

Image of real neurons

Neurotransmission

The Synapse  The Synapse defines the neural pathway.  The type of neurotransmitter used ensures that specific neural functions occur.

Neurotransmitters

Specificity of Neurotransmission  If we only hade a single neurotransmitter then the only way to ensure specificity would be through strictly delineated pathways.

Stimulus - Response  A specific stimulus:  Light  Sound  Pressure  Chemical  Yields a specific response:  Color  Pitch  Texture  Odor

Neurotransmission  The complexity of our nervous system allows us to not only experience the world around us, but contemplate it’s meaning even it’s very existence.  “If our brains were simple enough for us to understand them, we'd be so simple that we couldn't.”  Ian Stewart