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How is the Nervous System Organized?

Chapter 2-Neuroscience: The Brain and Behavior

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Module Objectives:

Identify and define the structures of the neuron

Identify and discuss the role of neurotransmitters on behavior

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Ancient cultures believed the heart was the center of all

thoughts and emotions. But we now know that the brain and the rest of the nervous

system are the power behind our psychological life and

much of our physical being.

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This chapter introduces you to the field of neuroscience and

biopsychology

the scientific study of the biology of behavior and

mental processes

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This amazingly complex nervous system controls

some of our most sophisticated

psychological behaviors

We will begin by examining the most basic elements of the

human nervous system. Let’s look at our foundation!

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The Neuron

The neuron is the basic building block of the nervous system‐ Each one is a tiny information-

processing system with thousands of connections for receiving and sending electrochemical signals to other neurons.

Each human body may have as many as one trillion neurons.

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Look at the following pictures and make a list

of words that best describe the picture

Pretend that you’re describing the picture to a friend who

cannot see it.

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Did you notice a web-like appearance in those

neurons?

We will see that neurons do create a neural network crucial to

communication…what you will also learn is that as much as they

look like a web, neurons do not actually touch

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4 parts of the neuron

1. 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

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The Neuron

2. The Cell body contains the cell nucleus

The cell body relays the information down to the axon

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The structure of a neuron3. Axon: A thin, long structure that

transmits signals from the cell body to the axon terminal.

4. Axon Terminal is the last step for the relay of information inside the neuron.

Axon

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The cell body is covered

with Axon Terminals

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Once the information hits the terminal, it is

transmitted outside the cell by

neurotransmitters, which reside in the axon

terminal.

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-Electrical Communication-Chemical Communication

How do Neurons Communicate?

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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…a neuron never firs half way. It either fires or it doesn’t.

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Action potentials travel down the axon like a wave of energy

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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

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Notice how the neurons don’t physically touch

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Let’s Review!

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Presynaptic Neuron

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Neurotransmitters

Neurotransmitters are chemical substances that reside in the axon terminals

• They communicate to other neurons by binding to receptors on neighboring neurons

-The communication between neurons is chemical

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Chemical Communication

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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 (reuptake)

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Neurotransmitters

At least 50 different types of neurotransmitters have been identified

‐ Acetylcholine‐ GABA‐ Serotonin‐ Dopamine‐ Norepinephrine‐ Endorphins

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Acetylcholine

Activates motor neurons controlling skeletal muscles

Contributes to the regulation of attention, arousal and memory

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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, eating and aggression‐ Abnormal levels may contribute to

depression and OCD

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Dopamine

Contributes to control of voluntary movements, feelings of reward and pleasure

‐ Too much dopamine has been associated with schizophrenia

‐ Too little dopamine has been associated with ADD and Parkinson’s Disease

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Norepinephrine

Involved in arousal reactions, especially important for vigilance

‐ A heightened sensitivity to your surroundings

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How do drugs effect behavior?

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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.

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Agonists versus Antagonists

Agonists mimic or facilitate the actions of a neurotransmitter

Antagonists oppose/block the actions of a neurotransmitter

AntagonistAgonist

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What’s Next?

The BrainHow do the neurons work together?‐ The Central Nervous System‐ The Peripheral Nervous System