© Richard Goldman October 4, 2006 Module 5 Neurons: The Basic Elements of Behavior Chapter 2 Essentials of Understanding Psychology- Sixth Edition PSY110 Psychology © Richard Goldman October 4, 2006

Structure of the Neuron Cell Body (soma) Axon – single, long, sending arm Dendrite – many, short, receiving arm Myelin sheath – insulating coverings of axon Terminal Buttons – bulge at end of axon containing neurotransmitters

Neuron Myelin Sheath Body (Soma) Axon Nucleus Dendrites Terminal Buttons

How Neurons Fire Stimuli from dendrites produce action potential Action potential (electrical nerve impulse) - Positive to negative reversal that prorogates down axon Action potential speed – 2mph-225mph (thicker sheathed neuron transmit faster)

Neuron to Neuron Synapse – gap between terminal button on axon and the dendrite (or body) of another neuron Nerve impulse triggers the release of neurotransmitter chemicals into the synapse Neurotransmitters (> 100 different chemicals) tend to behave as either excitatory or inhibitory (their effect varies at different sites) Dendrites have specialize receiving sites for both excitatory and inhibitory neurotransmitters Enough excitatory neurotransmitters will trigger an action potential in the dendrite Inhibitory neurotransmitters mediate the potential of triggering the dendrite Reuptake: Synaptic neurotransmitters are either neutralized by enzymes or reabsorbed into the axon

Major Neurotransmitters Acetylcholine (ACh) (Excitatory) – Muscle & Cognitive Glutamate (Excitatory) – Memory Gamma-amino butyric acid (GABA) (Inhibitory) – Eating, Aggression, & Sleeping Dopamine (DA) (Inhibitory or Excitatory) – Muscle & Mental Disorders Serotonin (Inhibitory) – Sleeping, eating, mood, pain, depression Endorphins (Mostly Inhibitory) – Pain suppression, pleasure, appetite