How is the Nervous System Organized? Chapter 3-Neuroscience: The Brain and Behavior
Class Objectives: • Identify and define the structures of the neuron • Identify and discuss the role of neurotransmitters on behavior
The Neuron • The neuron is the basic building block of the nervous system • They are often grouped in bundles called nerves.
4 parts of the neuron • Dendrites are specialized to receive signals from neighboring neurons and carry them back to the cell body • Thin, bushy-like structures that receive information from outside the neuron • Relays the information into the cell body
The Neuron • The Cell body contains the cell nucleus • The cell body relays the information down to the axon
The structure of a neuron • Axon: A thin, long structure that transmits signals from the cell body to the axon terminal. • Axon Terminal is the last step for the relay of information inside the neuron.
Once the information hits the terminal, it is transmitted outside the cell by neurotransmitters, which reside in the axon terminal.
-Electrical Communication-Chemical Communication How do Neurons Communicate?
The Electrical Part • Action potential is an electrical current sent down the axon. • The activity within the neurons is electrical. This current causes the neuron to “fire” • This is an “all-or-none” process
Synaptic transmission • The Synapse is the space between neurons • The synaptic gap or cleft • Information must be transmitted across the synapse to other neurons via the neurotransmitters. • This is an electrochemical process
Now, Let’s DANCE! Time to do the Neuron Dance
__________ Presynaptic Neuron ________ ________ ____________ ________________________
Neurotransmitters • Neurotransmitters are chemical substances that reside in the axon terminals • They communicate to other neurons by binding to receptors on neighboring neurons
Chemical Communication • The communication between neurons is chemical • Neurotransmitter are either neutralized by an enzyme or taken back up by the neuron that released it in reuptake. • At least 50 different types of neurotransmitters have been identified
Synaptic Transmission • The neurotransmitters are released from the vesicles and then attach to receptors located on the postsynaptic neuron. • These neurotransmitters are in contact with the dendrite of the postsynaptic neuron only briefly. • The chemical is almost immediately destroyed or reabsorbed
Neurotransmitters • At least 50 different types of neurotransmitters have been identified • Acetylcholine • GABA • Serotonin • Dopamine • Norepinephrine • Endorphins
Acetylcholine • Activates motor neurons controlling skeletal muscles • Contributes to the regulation of attention, arousal and memory
Examples of Neurotransmitters • Gamma-aminobutyric acid (GABA) is involved in experiences of anxiety, alcohol abuse, seizure disorders, and sleep disorders • Serotonin is involved in sleep and mood regulation and appetite (appetite for carbohydrates)
Dopamine • Involved in movement, thought processes, emotion, feelings of reward and pleasure • Implicated in schizophrenia, attention deficit disorder, and drug abuse
Norepinephrine • Involved in arousal reactions (increasing heart rate, respiration, sweating, and dilation of pupils) • May also be involved in hunger, eating, and sexual activity
Drugs Impact on the Brain • Common drugs can alter the amount of a neurotransmitter released at the synapses • Some drugs can mimic/facilitate the action of the neurotransmitters while others can block the action of the neurotransmitter.
Agonists versus Antagonists • Agonists mimic or facilitate the actions of a neurotransmitter • Antagonists oppose/block the actions of a neurotransmitter Agonist Antagonist
Next Class… The Brain • How do the neurons work together? • The Central Nervous System • The Peripheral Nervous System