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Chapter 3 Text Notes

Chapter 3 Text Notes - Chapter 3 Biological Foundations...

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1 Chapter 3: Biological Foundations This chapter is one that students find among the “hardest” in the textbook. The problem tends to be the biology. Many students comment that they do not have any upper level high school biology, and thus, the concepts seem foreboding. Do not be alarmed. You will not need a background in biology to get through this chapter. Although we will look at biological mechanisms, we will not go into the kind of detail that you might expect from a biology course. As you begin to look at this material (or as you study for an exam), do not try to memorize all the terms . Yes, I want you to be familiar with the terminology, but I am much more concerned that you know the function and significance of the various parts of the nervous system rather than the anatomy. Try to understand how these systems work. On a test, I will not give you a diagram to label—the questions will focus more on function. 1. The Neuron The basic building blocks of the nervous systems are cells know as neurons. A neuron has three basic parts: a cell body, the dendrites and the axon. The dendrites are the receiving end of a neuron—signals come in through the dendrites. A cell might have thousands of dendrites, branching out to receive signals from various places. The signal is passed to the cell body . Many activities occur here, but for our purposes, it is relatively unimportant. The axon is the transmitting part of the neuron. Here signals will be sent to the dendrites of other neurons. Note Important Points The Neuron The Action Potential Synaptic Transmission Neurotransmitters Brain Organization The Cerebral Hemispheres Split Brain Neural Plasticity & the Immune System
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2 that a neuron has only one axon. It may be branched at the very end, and each branch terminates in a tiny swelling called the Synaptic Knob . Neurons come in various shapes, some of which are shown below. Dendrites Axon Unipolar Bipolar Multipolar Note the diagram on p. 85. The axon is covered with a thick fatty substance called Myelin. Not all neurons are myelinated, but the speed of the nervous impulse is faster in those that have this insulating cover. 2. The Action Potential This section is very important. Here we examine just how a neural signal is generated. Think of the neuron as a tiny chemical battery. When nothing is happening the neuron has a resting potential of about –70 millivolts (a negative 70 thousandths of a volt). The charge is generated by a difference in ion concentration inside the neuron relative to the outside.
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