 What Do Neurons Have to Do With Psychology?  How Do Neurons Communicate?  How Can Neurons Produce Complex Processes?  How is the Nervous System Organized?

 Every perception, thought, emotion, and action is related to activity in the nervous system.  The nervous system is made up of neurons in the brain, spinal cord, and throughout the body.

 Every time you think something or do something, neurons are communicating.  It’s not possible to understand some issues about Psychology without knowing how neurons work  Example: Advances in the treatment of psychological disorders

 Cells that are specialized for communication  Glial cells are cells that support, insulate, nourish, and regulate neurons  The human brain has about 100 billion neurons and 900 billion glial cells.  Neurons generally are not replaced after they die

 An electrochemical process  Neurons receive input from other neurons and from sensory organs  Each neuron summarizes the input it receives; this determines what message (if any) will be sent to other neurons

 A neuron in its resting state has a negative electrical charge called the resting potential.

 Input from other neurons and/or sensory organs results in electrical changes  These changes are graded potentials  Vary in strength  Excitatory potentials bring the neuron closer to threshold  Inhibitory potentials take the neuron farther away from threshold

 The threshold is the electrical charge at which a neuron will send an outgoing message  If the neuron receives sufficient excitatory graded potentials, it will reach threshold  This triggers a chain reaction of electrochemical changes

 The action potential is the outgoing message, sent along the neuron’s axon  The action potential is all-or-none  A wave of electrochemical change  Travels faster when the axon is myelinated

 When the action potential reaches the tips of the axon, it causes the release of neurotransmitter molecules  The neurotransmitters travel across the synapse to the dendrites of another neuron  The neurotransmitters fit into receptor sites on the dendrites, causing graded potentials

 Neurons are arranged into neural circuits.  The neural circuits are connected into larger neural networks.  How did our brains get this way?

 Somatic Nervous System - voluntary behavior  Autonomic Nervous System - mostly involuntary  Sympathetic - increases arousal  Parasympathetic - decreases arousal

 Spinal Cord  Brain