Biology and Neuroscience Notes PDF

the neocortex. 5. Describe each of the major methods of neuroscientific research and what aspects of the brain they are primarily used to investigate. 3.1 Introduction: The Smart Conduit Before we begin, understand that the most important tool you will need while experiencing the concepts and...

the neocortex. 5. Describe each of the major methods of neuroscientific research and what aspects of the brain they are primarily used to investigate. 3.1 Introduction: The Smart Conduit Before we begin, understand that the most important tool you will need while experiencing the concepts and information in this chapter is your imagination. Some of the concepts here can be difficult, simply because while we all have experience being human, few of us have really taken a close look at what goes on inside our brains. We lack a frame of reference—something we already know that we can compare new concepts to. For example, let’s say you are reading a chapter on child development. You might have younger siblings, or perhaps you have babysat. You have experience interacting with babies and children, and this provides that frame of reference. But no one babysits neurons or lobes of the brain. Thus, you don’t necessarily have visual associations or practical experience with the inner workings of the brain. Throughout this chapter, we will use the things in your life that you have experienced and relate those experiences to the content here. a O p. w of or tta ity C rs cle ve o ni on U m e at Let's start with a basketball example. How is Steph Curry of the Golden State Warriors able to shoot from th ph ith o w ©T ed ht seemingly anywhere on the basketball court? How do gifted rappers like Kendrick Lamar craft words so vividly ar rig Sh opy C to convey ideas and emotion? How have scientists figured out how to split the atom and create devices that store energy from the sun?  a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.2: What is it about Steph Curry’s nervous system that allows him to be so precise in his shooting far away from the basket? Experience is one thing that shapes and changes the nervous system. He grew up shooting at his grandfather’s house with a misshapen rim. Genetics also play a role. His father, Dell Curry, was also a three-point shooting champion as an NBA player. The answer to all the above is the human nervous system. Your nervous system is the main interpreter of both the events in your body and those in the outer world. Your brain and spinal cord are the ultimate problem solvers that send and receive information to and from all areas of your body, and your nervous system is a maze of complex cellular networks that relay and process information. Its overall purpose is to create behavior. It also helps you to make sense of the things around you and make decisions about what to do next. This integrated set of networks is composed of specialized cells called neurons (cells that transmit electrical configurations to perform dedicated tasks. You will see the term neural used throughout this chapter. This means “relating to the nerve or nervous system.” Our neural networks also help us communicate with one another through movement and sound. Think about how people from diverse cultures and with different personalities don’t speak or move exactly alike. Some people use their hands a lot. Some languages sound more musical. We can even communicate different ideas and emotions through different styles of dance. These differences stem from the fact that each person’s nervous system is made unique by their experiences. As a child, you may have taken apart toys to see how they worked. In this chapter, our multifaceted, complicated nervous system will be broken down into its parts. We will also discuss specific examples of human behavior and how the design of your nervous system creates these actions. 3.2 Cells of the Nervous System Try to remember what you learned in high school biology. Different kinds of cells are organized into specific a O p. w of or tta ity C kinds of tissues, which are then further assembled into organs. These organs are then organized in a way that rs cle ve o ni on U m makes sense to create a system dedicated to a certain set of functions. We will first talk about the cells, and e at th ph ith o w ©T then how they are organized and connected. There are two main types of cells in the nervous system. Neurons ed ht ar rig Sh opy C act as the main communicators. The second type of cell are called glia; they perform numerous support functions in the nervous system. We will explore the neuron's structure and function first. 3.2.1 Neurons The basic building block of the nervous system is the neuron. Neurons have a cell body, a nucleus, and internal machinery similar to other living cells. However, they also have specialized structures that allow them to communicate in ways that make them unlike any other cell in your body. Neurons communicate with each other through chemical messages that alter the electrical activity of other neurons (Koelle, 1968). The substructures of the neuron play an intricate role in this process and deserve their own review. The simulation below is an interactive image of a neuron. You can click on various structures for an overview of each substructure. We will discuss this process in more detail later. 3.2.1.1 Dendrites Receive Messages Let's look at each part of the neuron in more detail. Dendrites are extensions of the membrane of the cell body and they receive chemical messages from many other neurons. As we grow, learn, and experience the world around us, the dendrites spread and form connections with new neurons. Over time these webs of communication become more complex. The more dendritic branches a neuron has, the greater the number of other neurons the cell communicates with. Dendrites have proteins called receptors that are embedded in their membranes. These receptors bind with molecules called neurotransmitters ; chemicals, released by other cells, that help to communication in the nervous system. When a neurotransmitter binds to a receptor, it has the potential to influence the behavior of the cell. Generally, after receiving a chemical signal, cells will either "fire" (send their own signal) or they will reduce their firing rate and the signals sent to other neurons. a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.4: Basic structure of a neuron. The structure of a neuron is specially designed to communicate and transmit. The dendrites give neurons the ability to form connections with many other neurons. The axons provide a mechanism to transmit chemicals across a synapse, thus influencing activity in other neurons. Neurons that need to communicate over longer distances are myelinated to speed up the electrical impulse. Note that the myelin sheath is in sections. The small spaces between these sections are the nodes of Ranvier, which help the charge leap down the axon. 3.2.1.2 The Soma and Axon Work Together to Send Messages Dendrites are actually extensions of the membrane of the soma , or cell body. The soma is the location of branch out from the soma; however, there is only one axon. The axon acts much like a wire, transmitting the signal from the soma to the end of the axon, where you will find the axon terminals and terminal buttons (sometimes called synaptic knobs). The terminal buttons play an important role in neural communication. This terminal button houses vesicles , little bubbles containing the neurotransmitters. At the terminal buttons the neuron will release neurotransmitters, sending the signal to other nearby dendrites. Because this portion of the cell sends signals into the space between neurons, it is also called the presynaptic neuron. The vesicles release their contents into the synaptic cleft , which is the space between two neurons, usually the axon and the dendrite. Remember, the synapse is the connection between two neurons that allows them to communicate. Once the neurotransmitters are released from the vesicles, they float in the synaptic cleft until they bind to postsynaptic receptors on the dendrites of adjacent neurons, are recycled, or degraded. This process is illustrated in Figure 3.5 below. Click on the icons to learn more about each part. a O p. w of or tta ity C rs cle ve o ni on U m iFrame e at th ph ith o w ©T ed ht ar rig Please visit the textbook on a web or mobile Sh opy C device to view iframe content. Figure 3.5: The terminal button. Vesicles in the axon's terminal button package the neurotransmitter molecules in vesicles to be released at the right time. When the electrical impulse (action potential) reaches the end of the axon, this signals the vesicles to fuse with the membrane and release neurotransmitters into the synaptic cleft. Another way to imagine this process is to think of Iron Man (see Figure 3.6). Energy is generated in the body of the suit (the soma) and travels down the arms of his suit (the axon). When the energy reaches his gloved fingers (the axon terminals), a jolt is released from the tips of his fingers (the terminal buttons).  Figure 3.6: Imagine Iron Man’s arms as axons, and the beams of light as neurotransmitters that cause electrical impulses in, or disable, their targets. Remember that your nervous system is a network. Imagine this whole sequence occurring trillions of times a O p. w of or tta through 80–90 billion neurons that are arranged to connect with each other in different configurations. Each ity C rs cle ve o ni on communication between neurons occurs within about 5 milliseconds! Think about this happening U m e at th ph ith o w ©T simultaneously or in rapid succession trillions of times a day. ed ht ar rig Sh opy C Another feature of some axons is a protein and fatty substance called myelin (Simons & Nave, 2015). This substance acts kind of like the insulation wrapped around the wires you use every day to plug things into the wall (or your phone). It keeps the electrical impulse flowing down the axon. There are also breaks in the myelin called nodes of Ranvier. These are not flaws, rather the nodes play an important role in helping the signal to travel down the axon by allowing ions to enter and change the charge inside the cell. This allows for more efficient signal transmission. The structures in the neuron are optimized to transform and transfer energy, and send chemical messages, at specific times. Question 3.03 Show Correct Answer Show Responses Neurotransmitters are released into the synapse then join with postsynaptic receptors. Where are these receptors? A Axon B Myelin Sheath  9 The 2 divisions: Central and Peripheral Nervous Systems. Even simple movements require both. Your NS is: Distinct and unique. Receives: Receives info from environment and internal body. Analyzes: Organize analyze and integrate the information. Uses this information to: Use info in order to send out messages to muscles, glands, etc. in order to produce behaviours. Along the way: Nervous system creates consciousness and awareness (see chapter 6). The question: Why do we learn about the nervous system in psychology? Anything psychological is biological and physiological. II. Cells of the NS: A. Neurons: Basic unit : Basic unit of communication in the nervous system. In a nutshell: The communication: It is an electrochemical process. When: A neuron decides to communicate with another neuron, it fires an action potential (AP). Action potential/neural impulse/electrical impulse: they all mean the same thing Ultimately: The action potential is going to lead to the release of NTM. Neurotransmitters: Chemicals that neurons use to send out messages to other neurons. Neurons come: In a variety of shapes and sizes. Basic structure: Neurons have roughly the same structure. Cell body → soma: Contains the nucleus and the DNA. Manufactures everything the neuron needs to survive and thrive. Dendrites: Two main functions: a) Receive messages from other neurons. b) They increase the SA of the soma without taking up much space. Axon: When the neuron fires and produces an AP, it is the axon that will carry it. AP travels all the way down the axon. Axon branches/ Axon terminals:  10 Axon branches off into axon terminals. Terminal buttons: Little nubs at the ends of axon branches. They release the NTM’s. Myelin sheath: Some axons in the NS are covered in a myelin sheath. White fatty substance that traps around some axons. Provides insulation Speeds up transmission of info. Synapse: This is where neurons meet to communicate. Synaptic cleft/gap: Tiny gap between two neurons at the synapse. Presynaptic neuron is the neuron that sends out messages. Postsynaptic neuron is the neuron that receives messages. B. Glial Cells (Glia): Another type of cell found in the NS. There are billions of them. Nannies of the neurons because they help neurons: develop nutrition insulation protection clean after them remove dead neurons More than just nannies: Seem to be involved in complex functions including cognitive ones such as learning, attention, intelligence, and creativity. They seem to be also linked with brain diseases. There are different types of glia cells carrying out a variety of different functions. Below are some examples: Oligodendrocytes and Schwan cells are both involved in the production, laying down, and repair of the myelin sheath. Oligodendrocytes do so in the CNS while Schwan cells do so in the nerves outside of the brain and spinal cord. Microglia: Immune function. Play a role in learning and memory: degeneration linked with Alzheimer’s disease. Astrocytes: Immune function. Linked to neurodegenerative diseases. III. Communication: A & B:  Question 3.07 Show Correct Answer Show Responses Which part of the neuron pictured below forms connections with many other neurons? a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C 3.2.2 How Neurons Transmit Messages: More Detail on the Action Potential Neurons share information within and between parts of the nervous system, but there must be control of when and how this happens. The main way this sharing of messages happens is through a burst of electrical energy in the neuron that signals it to release a neurotransmitter. This can either be triggered or shut down.  Video Please visit the textbook on a web or mobile device to view video content. First, let’s address how the nervous system creates and uses this burst of electrical energy, called an action potential. We all have electrically charged particles in our bodies called ions. Electrical activity in the body exists because of the movement of these charged particles. You know of some ions already, like sodium (Na+) and chloride (Cl–), the particles that make up table salt. Sodium has a positive charge, and chloride has a a O p. negative charge. Positively charged Potassium (K+) is another player in this process. w of or tta ity C rs cle ve o ni on U m e at th ph ith o A large number of negatively charged ions inside the cell causes the neuron to have a negative charge, usually w ©T ed ht ar rig Sh opy around -70 millivolts (mV). This is called "polarized" because the charge is far away from 0, which is neutral. C When the cell is polarized it is at rest and will not release neurotransmitters. The more positively charged particles inside the cell, the more positive the charge inside that cell will be. This is called "depolarization" because we are moving away from the state of being polarized. The more depolarized the neuron is, the more likely it is to activate (action potential) and send a neurotransmitter to message other neurons or organs. For example, if we bring Na+ into the cell, it gets closer to the action potential. If we push K+ out of the cell, it gets closer to deactivating because losing the positive ions makes the neuron more negative (polarized). But how do ions get in and out of the cell to make it more positive or negative? We know that a neuron, like any living cell, has a membrane barrier keeping things from getting in or out. Of course, you can’t get through a barrier unless you have some sort of opening. The membrane of a neuron is kind of like that. It has several kinds of doors, or channels, that open in different ways. Some are locked and need a special key, like a neurotransmitter, and some are waiting for a stimulus or the charge (voltage) to change inside the cell (Kwong & Carr, 2015; Zhu & Gouaux, 2017). Opening each of the channels changes something different inside the cell. In the scenarios where we are changing electrical activity to activate or deactivate a neuron, the channels are designed to allow ions to leave or enter the cell (see Figure 3.7). channels at the right time. Imagine a nightclub scenario with Na+ ions as party people. There is only one door (channel) open because there are only a few party people (Na+ ions). But if enough come in (threshold, see Figure 3.6), you might say “let’s open all the doors and rooms for more party people (more Na+ ions).” This is what voltage-gated channels do. They are waiting to see how many positive ions show up, to see if there is enough excitement to open up more. When the party hits the climax, this is the action potential. a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.6: This graph of the increase and decrease in voltage inside the neuron corresponds with the movement of positive ions. Depolarization is brought about by the influx of Na+, and repolarization happens because of the e lux of K+. Since there are multiple Na+ channels lined up strategically along the axon - this process causes the electrical impulse to continue in succession along the axon (see Figure 3.7). As the gated channels in each successive section “sense” the positive shift in voltage, they pop open too, repeating the rush of Na+. This is propagation, the process by which electrical impulses get sent to the end of a neuron (Rama et al., 2018). When this electrical impulse gets to the axon terminal, it triggers the release of neurotransmitters, which are of course those chemicals we discussed earlier that neurons use to signal each other.  a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.7: The inset windows in (a), (b), and (c) depict the measured voltage inside the cell in each situation. Pay careful attention to the distribution of ions on the outside versus the inside of the membrane in each scenario. There must be some mechanism to turn neurons off as well. Can you imagine if the neurons that activated a particular muscle were always firing? In a normally functioning neuron, the opening of the K+ channels allows the neuron to return to and maintain resting potential. When its channel opens, K+ will rush out instead of in like Na+ (see part c in Figure 3.7 and "repolarization" in Figure 3.6). Potassium channels respond to depolarization as well, but after the Na+ channels do (Lesage, 2003). So in a way, Na+ coming in triggers K+ leaving. This results in quick repolarization of the neuron to negative resting potential. This also “resets” the neuron so that it can be activated again. To review the stages of action potential, click through the interactive slides linked below: the machinery in a simple way. But your brain isn't made up of a bunch of isolated neurons. It is made of integrated networks. Your neurons become active because of sensory stimulation and messages from other neurons that are arranged in networks. The interaction between chemical neurotransmitters released from axons and the receptors on dendrites is another way of controlling when neurons are active and inactive. 3.2.3 How Neurotransmitters and Receptors Work Remember that the chemicals released from axon terminals that then bind with receptors on another neuron are called neurotransmitters. Although there are over 100 different types of neurotransmitters in the body, we will only focus on a handful that play vital roles in mood (e.g., depression and anxiety), pleasure, movement, memory, and other functions. Some neurotransmitters are excitatory , meaning that they increase the probability of the neuron becoming electrically active. Other neurotransmitters are inhibitory , meaning that they decrease the probability that the neuron is activated (Schousboe, 1987). A neuron may receive inputs from both excitatory and inhibitory neurotransmitters. We were considering ion channels as doors earlier. When we have a door that we don’t want to leave open all a O p. w of or tta ity C rs cle the time, we put a lock on it. Channels have gates that are like locks (see Figure 3.8). Imagine you have a ve o ni on U m e at th ph master key that opens many doors on a particular floor in a building. Each door opens a room that has ith o w ©T ed ht different equipment in it and is set up to do something different. That is a good analogy to help us understand ar rig Sh opy C how neurotransmitters work with their protein receptors embedded in neuronal membranes. Figure 3.8: Like a key and lock, the neurotransmitter (key) is made to fit into a specially shaped binding site (lock) on the receptor (door). See the example in Figure 3.9 of two connected neurons. The axon of the first (presynaptic , or sending) neuron releases neurotransmitters from its vesicles. When these neurotransmitters enter the synaptic space, they alter cellular activity. If enough neurotransmitters activate their receptors, we can get an action potential. But this is only true for certain neurotransmitters. Click the icons in Figure 3.9 below to learn more about the parts involved in the chemical communication between neurons. iFrame Please visit the textbook on a web or mobile device to view iframe content. a O p. w of or tta ity C Figure 3.9: Chemical communication between neurons. In this representation, vesicles in the presynaptic (sending) axon terminal rs cle ve o ni on U m e at fuse with the membrane to release neurotransmitters into the synaptic cleft, where they bind with receptors on the postsynaptic th ph ith o w ©T ed ht ar rig (receiving) dendrite. Neurotransmitters are synthesized and packaged in vesicles in the presynaptic neuron. After use, they are either Sh opy C transported back into the neuron or degraded by an enzyme in the synaptic cleft. Axons in the nervous system secrete many different kinds of neurotransmitters. Each is specific for a particular class of receptor proteins. The interaction of each neurotransmitter with a receptor produces a different kind of response in the neuron. Some interactions are inhibitory (causing hyperpolarization, –) and others are excitatory (causing +). For example, GABA, an inhibitory neurotransmitter, binds with its receptor to open a chloride (Cl–) channel. This makes the cell negative, which as we know means the cell is more likely to be inactivated (inhibited). Acetylcholine (Ach) is normally an excitatory neurotransmitter. When Ach binds to its appropriate receptor, a sodium (Na+) channel is opened, making the cell more positive (more excited). Several factors influence what kinds of behaviors, feelings, or thoughts result from neurotransmitter release, including the receptors they bind with, where they are being released in the brain, the timing of the release, and the activity of other neurons in the same network. Question 3.19 Show Correct Answer Show Responses  11 A. Communication within a neuron: 80%:Water Intracellular fluid: Inside the neuron. Extracellular fluid: Outside the neuron. Dissolved chemicals, such as: Na+ Sodium I. Cl - Chloride I. K+ Potassium I. These ions: They are found inside and outside the neuron in different concentrations. Neuron at rest: Neuron is not firing, communicating, not producing an AP. More negative ions inside the neuron. (Inside = negatively charged) More positive ions outside the neuron. (Outside = positively charged) -70mV Polarized Even at rest: The neuron receives messages from other neurons. 2 types of messages: Inhibitory: Instruct the neuron Not to fire not to communicate. These messages are going to: The inside is going to become more negative than at rest. e.g., from -70 mv to -77 mv As a result, the neuron is: Less likely to fire. The membrane is said to be: Hyperpolarized. Excitatory: Instruct the neuron to Fire, communicate, produce an action potential. These messages are going to: Change the concentration of ions. less negative: Inside of neuron will be less negative than at rest. e.g., from - 70mV to - 63mV As a result, the neuron is more:  12 Likely to fire. The membrane is said to be: Depolarized. When?: When electric charge inside the neuron is about -50 mV (threshold of excitation). Now that you have a conceptual understanding of the action potential process. Let us plug in some chemicals. Please note, there is more to the process than covered here. It is beyond an INTRO PSY to cover all of it. You will learn more as you move up the years. Hello Everyone! Please make sure to have studied and mastered the communication within neurons before studying this section. Study this section one baby step at a time and slowly. And go over it few times until the information becomes more familiar. Let me introduce you to the nodes of Ranvier. Please follow the arrows. They are gaps in the myelin sheath that covers the axons. (gentle reminder: Not all axons are covered with Myelin) Why are they there? Do you have doors and windows in your walls? Clearly, the answer is yes. The nodes are the “walls and windows of the axons. Through them, ions can get in and out of the neuron. Technical term: channels. The ions do not move in and out as they please. There are “rules” that govern their movements. We are going to take a look at a couple of those “rules”. You will learn more in the second and third year. When a neuron receives inhibitory messages, Chloride (Cl-) channels open. What happens when they open? Some chloride ions move inside the neuron. (Influx) When they move in, that increases the number of negative ions inside the neuron. As a result, the inside of the neuron becomes more negative (more negatively charged) The membrane is said to be hyperpolarized and the neuron is less likely to fire. (again there is more to the process but for the purposes of this course that is all you need to know)  13 When a neuron receives excitatory messages, the sodium channels open. What happens when they open? Some sodium ions move inside the neuron. (Influx) This increases the number of positive ions found inside the neuron. As a result, the inside of the neuron becomes less negative (less negatively charged) As you know this means that the membrane is depolarized and the neuron is more likely to fire. If enough sodium ions enter the neuron for the electrical charge inside the neuron to reach -50mv (threshold of excitation> explained in the lecture) the neuron will fire. Once the neuron has fired, it needs to go back to its resting potential before it can fire again when prompted. How does the neuron return to the resting potential.? After (key word) the sodium channels have opened and sodium ions had entered the cell, potassium (K+) channels open. What happens when potassium channel open? Potassium ions start leaving the neuron (Efflux) Keep it simple. That is all you need to know for now. By potassium ions leaving the neuron, that means there are less positive ions inside the neuron. The inside of the cell becomes less positive. Ultimately, the electrical charge reaches -70mv and the neuron is polarized again. The neuron is at its resting potential. Right before the neuron reaches its resting potential, it goes through a refractory period. During this period the neuron will not fire when stimulated. The membrane is hyperpolarized (more negative than -70mv) due to the migration of a high number of potassium ions out of the cell. You might be wondering what happens to the sodium ions that entered the cell, or to the potassium ions that left the cell? Ultimately, sodium ions will be pumped out and potassium ions will be pumped back in. Again, the processes are more complex but that is sufficient for our purposes. B Communication between neurons: The presynaptic neuron fires: Action potential travels/propagates all the way down the axon until it reaches Terminal buttons (contain synaptic vesicles) Synaptic vesicles attach to membrane and bust open releasing (Little bags containing NTM)  Match the type of cell with its description: Premise Response Wrap around the axons of some neurons in 1 Oligodendrocytes  A the brain and spinal cord Wrap myelin around the nerves outside of 2 Schwann Cells  B the brain and spinal cord 3.3 Brain Anatomy: How to Build a Sophisticated Network Now that we know a bit about the building blocks of the nervous system, their properties, and their functions, we can build a nervous system. We have now learned that neurons can translate chemical messages into electrical impulses. They then use those electrical impulses as signals to trigger the release of their own a O p. neurotransmitter chemicals. But how do we get that sequence of events from point A (the brain) to point B w of or tta ity C rs cle ve o (some organ or muscle)? How do those messages get transmitted to different areas in the nervous system ni on U m e at th ph ith o itself? The answer is neural networks and nerves. w ©T ed ht ar rig Sh opy C Neural networks are complex connections between the dendrites and axons of many neurons. The 80–90 billion neurons in the brain make trillions of connections. Even a small area like the hippocampus (discussed later) has millions of neurons. A nerve is just a large bundle of axons from many neurons bundled into a tube that extends a large distance. These axons extend from cell bodies that are housed in the central nervous system (CNS), which consists of the brain and spinal cord. Some of these axons, called efferents , are carrying electrical impulses away from the CNS to trigger neurotransmitter or hormone release in an organ or muscle. Others, called afferents , are carrying impulses back to the CNS from the organs and muscles. If we are going to have a complex system that responds to a changing environment, it had better be able to change itself. Our nervous system accomplishes this through a process called neuroplasticity, which is the ability of neurons and their networks to change (see Section 3.4: Central versus Peripheral Nervous Systems; Bower, 1990). At birth, we have an excess of neurons. As we grow, we lose more neurons than we gain; however, this is not necessarily a bad thing. We need to get rid of neurons that are inefficient, damaged, or unnecessary. Our nervous system can also grow new branches on dendrites and change amounts of receptors organized. In the following video, you can see that therapists and physicians can even take advantage of neuroplasticity to accelerate healing for their patients! Video Please visit the textbook on a web or mobile device to view video content. a O p. w of or tta ity C rs cle ve o ni on However, many of the processes that occur in our brains and bodies are automatic and below the level of U m e at th ph ith o consciousness. There are other neural networks dedicated to those tasks. For example, it would be difficult if w ©T ed ht ar rig Sh opy you had to consciously remember to breathe while you were studying, or to digest your dinner, or pump blood C into and out of your heart: Headline: Student dies studying: Forgets to breathe Here is another way to think about this issue: If you had a large, busy, productive company, you would not want the CEO checking the heating and cooling systems. Now, the CEO’s attitude can certainly affect the heating and cooling systems. If he or she sends out a directive that everyone has to start working twice as hard, then we may need more cool air in the building because people will be sweating. These examples, when transferred to the brain, refer to two different parts: your neocortex (conscious thought/decision making) and medulla (basic life functions). The conscious processing of sensory input occurs in the neocortex , which is the outer layer of your brain. The neocortex is like the CEO in the corporation mentioned above. Circuits in your medulla (a structure in the brainstem) help control basic life-support functions like breathing, heart rate, and reflexes (Angeles Fernández-Gil et al., 2010). These circuits are like workers and onsite managers in the corporation mentioned above. Your heart will beat and your lungs will  Match the type of cell with its description: Premise Response Wrap around the axons of some neurons in 1 Oligodendrocytes  A the brain and spinal cord Wrap myelin around the nerves outside of 2 Schwann Cells  B the brain and spinal cord 3.3 Brain Anatomy: How to Build a Sophisticated Network Now that we know a bit about the building blocks of the nervous system, their properties, and their functions, we can build a nervous system. We have now learned that neurons can translate chemical messages into electrical impulses. They then use those electrical impulses as signals to trigger the release of their own a O p. neurotransmitter chemicals. But how do we get that sequence of events from point A (the brain) to point B w of or tta ity C rs cle ve o (some organ or muscle)? How do those messages get transmitted to different areas in the nervous system ni on U m e at th ph ith o itself? The answer is neural networks and nerves. w ©T ed ht ar rig Sh opy C Neural networks are complex connections between the dendrites and axons of many neurons. The 80–90 billion neurons in the brain make trillions of connections. Even a small area like the hippocampus (discussed later) has millions of neurons. A nerve is just a large bundle of axons from many neurons bundled into a tube that extends a large distance. These axons extend from cell bodies that are housed in the central nervous system (CNS), which consists of the brain and spinal cord. Some of these axons, called efferents , are carrying electrical impulses away from the CNS to trigger neurotransmitter or hormone release in an organ or muscle. Others, called afferents , are carrying impulses back to the CNS from the organs and muscles. If we are going to have a complex system that responds to a changing environment, it had better be able to change itself. Our nervous system accomplishes this through a process called neuroplasticity, which is the ability of neurons and their networks to change (see Section 3.4: Central versus Peripheral Nervous Systems; Bower, 1990). At birth, we have an excess of neurons. As we grow, we lose more neurons than we gain; however, this is not necessarily a bad thing. We need to get rid of neurons that are inefficient, damaged, or unnecessary. Our nervous system can also grow new branches on dendrites and change amounts of receptors organized. In the following video, you can see that therapists and physicians can even take advantage of neuroplasticity to accelerate healing for their patients! Video Please visit the textbook on a web or mobile device to view video content. a O p. w of or tta ity C rs cle ve o ni on However, many of the processes that occur in our brains and bodies are automatic and below the level of U m e at th ph ith o consciousness. There are other neural networks dedicated to those tasks. For example, it would be difficult if w ©T ed ht ar rig Sh opy you had to consciously remember to breathe while you were studying, or to digest your dinner, or pump blood C into and out of your heart: Headline: Student dies studying: Forgets to breathe Here is another way to think about this issue: If you had a large, busy, productive company, you would not want the CEO checking the heating and cooling systems. Now, the CEO’s attitude can certainly affect the heating and cooling systems. If he or she sends out a directive that everyone has to start working twice as hard, then we may need more cool air in the building because people will be sweating. These examples, when transferred to the brain, refer to two different parts: your neocortex (conscious thought/decision making) and medulla (basic life functions). The conscious processing of sensory input occurs in the neocortex , which is the outer layer of your brain. The neocortex is like the CEO in the corporation mentioned above. Circuits in your medulla (a structure in the brainstem) help control basic life-support functions like breathing, heart rate, and reflexes (Angeles Fernández-Gil et al., 2010). These circuits are like workers and onsite managers in the corporation mentioned above. Your heart will beat and your lungs will comatose state can still breathe and pump blood through the heart, despite the fact that they can’t respond to others or move. Even though the person is not conscious or active, the other networks responsible for maintaining life functions continue to operate. Question 3.28 Show Correct Answer Show Responses Match the structures to their functions. Premise Response Heartbeat‚ respiration‚ and other basic life 1 Neocortex  A support functions. Conscious thought‚ decision-making‚ outer- 2 Medulla  B most layer of the brain. However, we do have some conscious control over these functions (Jones et al., 2015). The thoughts and fears we are fully aware of can shift, or modulate, the function of the heart and lungs. We can think about things that a O p. w of or tta ity C rs cle calm us down or make us angry, and this will either slow down or speed up our heartbeat. You could be, say, a ve o ni on U m e at neuroscientist who is writing a book chapter and under pressure to meet a deadline. This knowledge could th ph ith o w ©T ed ht cause your brain to make your breathing more rapid and shallow, which speeds up blood flow to the muscles ar rig Sh opy C when we are under high alert. Stressful situations activate the same mechanisms that help us fight or flee when we are in danger. This modulation of neural networks in the lower-brain centers like the medulla and spinal cord is made possible by axons that extend from the cortex to connect with neurons in the medulla. Question 3.29 Show Correct Answer Show Responses Match the following structures with their function. Premise Response Guiding electrical impulses/messages 1 A erents  A toward the brain. Guiding electrical impulses/messages away 2 E erents  B from the brain.  An injury to the brainstem is so dangerous because: A It could lead to psychotic thought patterns B It could a ect endocrine function and cause diabetic complications. C It could a ect clusters of neurons that regulate the heart rate and breathing. D It could impact memory. a O p. Question 3.31 Show Correct Answer Show Responses w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C We can learn to do new things, even as adults, because of the concept of. 3.4 Central versus Peripheral Nervous Systems If we are comparing the nervous system to a company, consider that a typical major company has a command center and several satellite locations. When it works well, the command center should be getting information from the satellite locations and using that information to modify the commands. That is exactly why you have a central and a peripheral division to your nervous system (see Figure 3.10). Effective communication happens in all directions, not just in one direction. The central nervous system (CNS) is all the cells and supporting structures inside the skull and vertebral column. In short, the CNS is the brain and the spinal cord. The nerves outside of the skull and vertebral column, as well as the specialized sensory endings (retinal cells, touch receptors, hair cells in the ear, etc.), comprise the peripheral nervous system. system. The information in the brain is no good if it is not shared with the body. No action would occur without this connection. If the brain didn’t perceive what is happening in the environment, it would be rendered rather useless. Split into somatic (voluntary) and autonomic (automatic) divisions, the peripheral nervous system is a large part of what makes our brain a conduit and processor between the world and the self. Your vertebrae are individual joints that make up your vertebral column. This arrangement allows for two things: (a) the ability to flex (think bending over), extend (reaching high), and twist the spine; and (b) space for peripheral nerves to exit the spinal cord so that they can connect and communicate with the body. a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.11: Divisions of the peripheral nervous system. The peripheral nervous system is split into two divisions. The somatic nervous system directly controls voluntary movement, while the automatic division regulates functions we do not control consciously. The automatic division is further split into the sympathetic (common known as “fight or flight”) and the parasympathetic (“rest and restore”). 3.4.1.1 The Somatic Nervous System: Voluntary Movement The somatic nervous system contains the neurons and nerves that control the muscles for voluntary movement and bring sensory information from the body to the brain. This system includes nerves that connect to muscles and joints in the neck, arms, legs, and torso. If you throw a ball, your brain is sending commands that activate somatic neurons in the spinal cord. This injury is like a roadblock on that highway. 3.4.1.2 The Autonomic Nervous System: Automatic Movement The other subdivision of the peripheral nervous system is called the autonomic nervous system. That word sounds a little like “automatic,” doesn’t it? There is a good reason for that. Below the level of consciousness, the autonomic nervous system regulates all the automatic functions that keep you alive, functional, and healthy. The autonomic system is even further divided into sympathetic and parasympathetic connections to organs and endocrine system structures (see Figure 3.13). If you want a “quick and dirty” way of characterizing these divisions, think of them as mainly “go” and “relax.” A specific event can activate both systems, but most events activate one or the other. a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.13: The sympathetic and parasympathetic nervous divisions comprise the autonomic nervous system and exert control over functions that do not require conscious control, including digestion, heart rate, respiration, and sexual functions. These nerves are also modulated by the endocrine system. The neurons and nerves of the parasympathetic nervous system originate in the lower brain and sacral spinal cord. When activated, parasympathetic nerves transmit commands to your organs that help you recover, digest, and become sexually aroused. The sympathetic nerves mostly achieve the opposite. When we digestive activity. If you have ever been in a situation where you were nervous or frightened, your sympathetic nervous system (mainly consisting of neurons and supporting cells in the spinal cord) was activated. Think about a person in a life or death situation. Their heart would beat in overdrive to pump blood to their muscles. Their visual field would be narrowed for focus. They would produce more sweat as their body temperature rises. Blood flow would be routed toward all the systems that would help them fight or escape and away from systems involved in digestion or growth and repair. This means that while your sympathetic nervous system is activated, your parasympathetic system is deactivated. Yoga or a good meal will activate circuits in the parasympathetic nervous system (Tyagi & Cohen, 2014). Your heart rate and respiration will slow down, and more blood (think: energy) will be routed to your digestive system. The parasympathetic nervous system helps us to rest, recover, and repair. a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.14: When we do something relaxing, we begin to activate the parasympathetic (rest, digest, and repair) nervous system. Keep in mind though, if this pose is very di icult or you are nervous about your balance, you will likely activate your sympathetic nervous system! Sex actually stimulates both the sympathetic and parasympathetic divisions. The excitement of attraction will activate the sympathetic nervous system, resulting in increased heart rate and respiration. We can even feel jittery from increased neural activation of our muscles. But the parasympathetic system increases blood flow to the genitals, resulting in erection for both the male and female. conserve energy. If our systems are running at full steam all the time, we would burn out quickly. In that context, let’s consider the problem of constant (chronic) stress. Evolutionarily, we are wired to pay attention to danger—threats to our life, security, loved ones, and food. Now that we have jobs where our performance is tied to money, which provides security and food, the workplace represents a daily threat to these things (Jarczok et al., 2013). This means that the neurons in your autonomic system can shift into a state of more frequent/constant activation. Question 3.32 Show Correct Answer Show Responses Elania is watching a new horror movie, "The Clown Stalks at night". As the evil clown sneaks up on the unspespecting teenagers, Eliana feels her heart rate increase and her breathing become heavy. This is most likely due to activity in her A cranial nerves a O p. w of or tta ity C B rs cle sympathetic nervous system ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C glial cells C D parasympathetic nervous system Question 3.33 Show Correct Answer Show Responses You can change your heart rate just by thinking about it. A True B False  7 V – Peripheral Nervous System: It consists: It consists of all the nerves in the body that are outside the central nervous system (Example Nerves in arms, feet, leg, etc.). It connects: It connects the body to the external world, and it connects the body to the central nervous system. Main: Its main job is to carry information between the body to CNS and vise versa. 2: Main divisions PNS Somatic Autonomic v Somatic NS: It has two main functions; sensory and motor functions. Sensory: Our senses collect information from the world as well as from our own bodies, and they send this information to the central nervous system via sensory neurons.  8 The axons of the sensory neurons are called afferent axons because they carry information from the body/the external world to the CNS Motor: Motor functions will carry motor information from the central nervous system to skeletal muscles via motor neurons. The axons of the motor neurons are called efferent axons because they carry information from the CNS to the body v Autonomic NS: It controls: Glands, organs, visceral muscles. Visceral: Muscles we don’t voluntary control (example: muscles of the heart). 2: Autonomic nervous system carries two divisions. Autonomic Sympathetic Parasympathetic SYMATHETIC NERVOUS SYSTEM PARASYMPATHETIC NERVOUS SYSTEM The system energizes and arouses the When the threat is gone, this system kicks in. body. PNS relaxes and calms the body down. It mobilizes the resources of the body It helps the body conserve energy  9 It prepares us to fight or flight. It helps the body repair itself. Fight or flight Rest and digest The 2 systems: Have distinct functions. However, they are constantly working together to maintain the balance of the body and hemostasis.  What part of the brain was likely damaged in the case study of “H.M.?” A Amygdala B Hypothalamus C Hippocampus D Cingulate gyrus 3.5.2.2 Coordinating Movement The basal ganglia (telencephalon and diencephalon) are interconnected groups of neurons that serve to a O p. w of or tta ity C modulate movement commands in the brain before they reach the spinal cord (see Figure 3.20). You will see rs cle ve o ni on U m increased blood flow and electrical activity in this area when someone is initiating or terminating a movement e at th ph ith o w ©T (think about starting to walk, then stopping). Also, the basal ganglia are heavily involved in helping us learn to ed ht ar rig Sh opy C make complex movements more automatic. Consider the strokes of professional tennis players like Roger Federer, or the hands of an expert musician like Esperanza Spalding, as you watch the following two videos. Please click here to view the full transcript of the video below, entitled “Esperanza Spalding Overjoyed at the White House.” Video Please visit the textbook on a web or mobile device to view video content.  Video Please visit the textbook on a web or mobile device to view video content. a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy C Figure 3.20: The basal ganglia are anatomically and functionally connected nuclei (clustered groups of neurons) that help make movements more automatic. They also participate in goal-directed movement. In these videos, one can observe the masterful level of control each of these individuals has over their craft. Roger Federer's ability to control how much power and touch he puts into each shot to create just the right angle and Esperanza Spalding's ability to sing and play the upright bass simultaneously, playing with melody, rhythm, and touch, shows true mastery. This video shows the work of John Bramblitt, a visually impaired painter who uses his sense of touch and imagination instead of vision to create beautiful, intricate works of art. Please click here to view the full transcript of the video below entitled, “Blind Artist Paints With Imagination.”  Video Please visit the textbook on a web or mobile device to view video content. This all requires moment-to-moment control of the body and coordination of input from the internal and external environment, coupled with the formation of and access to both conscious and unconscious memory of all of the above. The basal ganglia and cerebellum, discussed in more detail in the following video, help us do that. Please click here to view the full transcript of the video below entitled, “Parkinson's Disease and the Basal Ganglia.” a O p. Video w of or tta ity C rs cle ve o ni on U m Please visit the textbook on a web or mobile e at th ph ith o w ©T device to view video content. ed ht ar rig Sh opy C The basal ganglia are several groups of neuronal circuits near the base of the brain that help to coordinate movement and assist in making movements more automatic. The basal ganglia consist of the dorsal striatum (caudate nucleus and putamen) as well as the ventral striatum (nucleus accumbens), the globus pallidus , the substantia nigra , and the subthalamic nucleus. The striatum is where inputs to the basal ganglia come in. Receiving many inputs from all over the cortex helps the basal ganglia coordinate multiple streams of information. This is how the basal ganglia nuclei work together to help us learn movements through practice. The ventral striatum neurons synapse with axons from the limbic system. We all know that emotion is often a motivation to learn, so it makes sense that a set of networks that function to help us learn would get a boost from emotion circuits, too. The globus pallidus and substantia nigra send inhibitory outputs to the thalamus to help integrate sensory and motor information with motor planning. Internally, the basal ganglia have two circuits that process input and behavior. This pathway facilitates the activation of motor plans that are appropriate for the present situation. The indirect pathway, when activated, has a net inhibitory effect on its targets. This helps the basal ganglia shut down motor patterns/plans that are not right for the task at hand. These basal ganglia have been the subject of much discussion because of their involvement in the development and progression of Parkinson’s disease, a progressive (gets worse over time) disease resulting in impaired movement. Parkinson’s patients exhibit a symptom called “cogwheel rigidity.” This means that the patient will have a hard time initiating and terminating movements. One part of the basal ganglia in particular is implicated in Parkinson’s—the substantia nigra (see Figure 3.20). This is a neuronal circuit that is dopaminergic, meaning that the axons of these neurons secrete dopamine. In Parkinson’s, these cells die off, and people lose part of the circuit that initiates and terminates movements. The systematic study of Parkinson’s patients, their symptoms, and brain anatomy after death is how (along with carefully controlled experiments in animals and humans) we solved part of the puzzle of this disease. The cerebellum (metencephalon) got its name because it looks like another little brain (see how it has the wrinkles and lobes like the cerebrum?). This part of your brain is basically a rhythm and timing machine. The a O p. w of or tta neuronal circuits in the layers of the cerebellum are strategically connected with other parts of the brain to ity C rs cle ve o ni on modify what they do, especially for movement but also in cognitive tasks. How does the cerebellum do all of U m e at th ph ith o w ©T this? The circuits in the cerebellum are set up to simultaneously receive and organize input from multiple ed ht ar rig Sh opy central nervous system networks. C Functionally, the cerebellum is separated into three major divisions (see Figure 3.21): spinocerebellar, vestibulocerebellar, and cerebrocerebellar. The spinocerebellar division helps to match sensory input with motor plans in order to fine-tune movement patterns. The vestibulocerebellar division processes information from the inner ear to help adjust your posture and balance. The cerebrocerebellar (lateral hemispheres and dentate nuclei) division manages connections with the pons and thalamus to adjust the timing and planning of movements.  Figure 3.21: The cerebellum coordinates movements by integrating motor commands and information from the vestibular system (inner ear and midbrain colliculi). Think about the decisions a baseball player makes while waiting for a pitch. The cerebellum, with practice, a O p. w of or helps the player decide to swing the bat at the right time along the right path and maintain balance while tta ity C rs cle ve o ni on swinging. Master musicians have been shown to have greater cerebellar volume relative to novices , which U m e at th ph ith o w ©T means they have more extensive connections in this area (Hutchinson, 2003). ed ht ar rig Sh opy C Sometimes, the circuits in the cerebellum are injured or don’t develop correctly. In these cases, the patient will present to a neurologist with symptoms such as loss of balance or an uncoordinated gait (walking). Unlike severe damage to the motor cortex or spinal cord, problems in the cerebellum do not result in paralysis. Instead, the person’s timing, planning, and balance is altered. Professor Peggy Mason discusses symptoms of cerebellar damage in more detail in the video below. Video Please visit the textbook on a web or mobile device to view video content. control of emotional responses (Schmahmann & Caplan, 2006). It does this by connecting with association areas of the neocortex and the hypothalamus. Question 3.41 Show Correct Answer Show Responses What area of this artist's brain would you expect to be more developed in comparison to the average person? Amazing Sand Art on Ukraine's Got talent - Kseniya Simono… Simono… a O p. w of or tta ity C rs cle ve o ni on U m e at th ph ith o w ©T ed ht ar rig Sh opy A The pons C B The medulla C The spinal cord D The cerebellum Question 3.42 Show Correct Answer Show Responses Multiple answers: Multiple answers are accepted for this question  3 It allows us to see the brain in action and to see the activity of neurotransmitt ers! C. Tour of The Brain: C.1 &C.2 C.1 Lower Brain Structures: C.1.1 to C.1.4 C.1.1 Brainstem: - It starts where the spinal cord ends. - It connects the brain to the spinal cord. - It is a relay station: all the info coming to the brain will have to go through it and all the information leaving the brain will have to go through it. - It is a crossover point. o The information coming from the left side of the body will cross over to the right side of the brain and vice versa. o The information coming from the right side of the body will cross over to the left side of the brain and vice versa. - It is the life center of the brain because it contains multiple structures that control and regulate vital functions that are essential for survival. These structures include the medulla, the pons and the RAS. o Medulla: Starts where the spinal cord ends; it is a structure that is essential for survival. If there is damage to the medulla, there could be serious trouble that may lead to a coma or even death. The medulla controls breathing, heartbeat, blood pressure, coughing and sneezing, swallowing, vomiting. (*study passage in book about the medulla and alcohol*) o Pons: § Explore and discover (book): In bullet form, list all the functions of the pons mentioned in your book. o RAS § Explore and discover (book): What is the RAS? Where is it located? What are its main functions? To what disorder is it linked? C.1.2 Cerebellum: The cerebellum controls: voluntary movements (ex. running), balance, muscle tone It is involved: , and it is involved in the learning of motor skills that become automatic.  4 The cerebellum is 1/10th of the volume of the brain. Yet, over ½ of the brain’s neurons are in the cerebellum. The neurons in the cerebellum have 20x more connections between them than the rest of the brain. Recent research: Cerebellum is associated to higher mental processes (ex. learning, memory, reasoning, creativity, language). A healthy cerebellum seems important to healthy cognitive development (thus, cerebellum is also associated with autism). When we drink alcohol and get drunk, our cerebellum also gets drunk (this creates dizzy/wobbly movements). - Language example: Pause VS Paws > if our cerebellum was damaged, it would be hard to differentiate between both words. C.1.3 Thalamus: A relay station: The thalamus is located right on