Chapter 1. Chapter 29: Central Nervous System

1.1 Introduction

Welcome to the Interactive Study Guide for Chapter 29: Central Nervous System! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

DRIVING QUESTIONS

• How is the nervous system organized?
• How do cells in the nervous system transmit signals?
• Why are some drugs (and some behaviors) addictive?

1.2 Driving Question 1:

Why should you care?

The nervous system is the primary way we interact with both our internal and external environment. It allows us to receive, process, and act on information, sometimes consciously and sometimes subconsciously. As with all other organisms that possess one, our nervous system has been shaped by millions of years of evolution to maximize our ability to respond in adaptive ways to the information our environment provides us.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Distinguish between the central nervous system (CNS) and peripheral nervous system (PNS).
2. Trace the flow of information through the nervous system from the time a stimulus is received to the action that results from the stimulus.
3. Identify the major parts of the brain and describe their functions.
4. List the parts of the brain primarily involved in addiction.

Infographic Focus

The Infographics most pertinent to the Driving Question are 29.2 and 29.5.

Identify the major parts of the brain and describe their functions.

Question 1.7

In your notebook, draw the figure below and label each major brain region. In the spaces below, write a description of the function of each major brain region.

Major brain regions to label:

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• Spinal cord transfers information from the body to the brain and vice versa.
• Cerebellum processes sensory information; also participates in movement, balance, and coordination.
• Diencephalon includes the thalamus and hypothalamus and regulates homeostatic functions (e.g., body temperature, hunger).
• Cerebrum controls intelligence, learning, perception, and emotion.
• Brain stem controls vital (often involuntary) functions such as breathing, heart rate, and blood pressure.

1.3 Driving Question 2:

Why should you care?

As is generally the case, we need to understand neuron structure if we are to understand neuron function. The two together help us understand at least the basic problems involved in such conditions and diseases as multiple sclerosis, Parkinson’s disease, and Alzheimer’s disease.

Proper chemical communication between neurons and between neurons, muscles, and glands controls everything from your fight-or-flight response to your ability to move your arms and legs, from memory to the regulation of mood. Many animal venoms work by interfering with this chemical communication process; understanding how it works is also key to developing better treatments for a number of conditions, including Parkinson’s disease and clinical depression.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Identify the parts of a neuron and explain their functions.
2. Describe the process by which an action potential is generated.
3. Describe the process by which an action potential travels down a neuron.
4. Diagram a nerve synapse and explain the function of each of its components.
5. Outline transmission of an action potential either between two neurons or between a neuron and another cell, such as a muscle or gland.

Infographic Focus

The Infographics most pertinent to the Driving Question are 29.3, 29.4, and 29.6.

Correctly identify the parts of a neuron and explain their functions.

Question 1.15

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Question 1.16

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Cell body: contains most of the organelles, including the nucleus.
Nucleus: the command center of the cell, located in the cell body.
Dendrites: extensions of the cell body that carry incoming signals toward the cell body itself.
Axon: nerve cell process that transmits the signal from the cell body to the axon terminals.
Myelin sheath: fatty covering wrapped around axon; insulates the axon and makes signal transduction more efficient.
Axon terminals: processes where signal exits neuron; tips of axon that communicate to the next cell in the signaling pathway.

Diagram a nerve synapse and explain the function of each of its components.

Question 1.24

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Axon terminal: Where the signal is transmitted to a receiving cell

Vesicles: Packages of neurotransmitters that will fuse with the membrane of the axon terminal and release the neurotransmitters into the synaptic cleft

Neurotransmitter: Signaling molecule

Neurotransmitter receptors: Receptors on the receiving cell that recognize and bind to the neurotransmitter, which in turn generates a signal in the receiving cell

Neurotransmitter reuptake receptors: Receptors on the signaling cell’s axon terminals that remove neurotransmitter from the synaptic cleft and stop the signal

Receiving cell: The target of the signal from the nerve cell’s axon terminals

1.4 Driving Question 3:

Why should you care?

Addiction is a complex process that takes enormous tolls on individuals, families, public health, and more. Scientists are working hard to pinpoint how addictive substances—and even behaviors—affect the brain; their hope is that by doing so they will contribute to the development of more effective ways to help people recover. The good news is that whether the addiction is to nicotine, food, gambling, or illegal drugs, the same areas of the brain and the same underlying mechanisms seem to be involved. The bad news is that the mechanisms are very complex, so much work remains to be done before we understand addiction as well as we need to.

Although details of the individual mechanisms vary, all addictive drugs ultimately affect dopamine signaling the same way: they initially increase the amount of dopamine produced by the neurons of the ventral tegumental area (VTA). This kicks the pleasure centers of our brains into high gear, resulting in feelings of mild to strong euphoria. This simple result isn’t the end of the story, though. Our bodies are the ultimate Goldilocks machines, keeping the levels of critical chemicals in our bodies not too high and not too low, but just right. When a body detects too much dopamine, it responds with mechanisms to reduce it. In the absence of the addictive drug, then, dopamine levels fall below normal. The person starts to feel anxiety, depression, and the urge for more of the drug. To add insult to injury, if a person who uses the drug long enough will need to keep increasing the amount to get the same feeling of pleasure. This is the heart of addiction.

What should you know?

To fully answer this Driving Question, you should be able to:

1. Identify the primary chemical (neurotransmitter) involved in addiction, where it is produced, and its role in addiction.
2. Discuss the effects of exposure to addictive drugs on the synaptic structure and function of dopamine neurons.
3. Explain how these changes in the structure and function of neurotransmitter synapses can lead to long-term addiction.

Infographic Focus

The Infographics most pertinent to the Driving Question are 29.1, 29.5, 29.7, 29.8 and Table 29.1.