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Web LinksUNIT 30AUNIT 30BUNIT 30C
UNIT 30D
Chapter 16 Nervous SystemPage 15
Chemistry Connection Page 20
Mini Investigation: Examining Neurons 3. Refer to the Nelson Web site to view different scientific models
of synapses and photomicrographs of synapses taken from scanning electron
microscopes and electron microscopes.
(a) What additional information about neuromuscular junctions is
revealed by observing these high-magnification, high-resolution photomicrographs?
(b) How do the scientific models help explain the functioning of the synapse? Photomicrograph
of the Human Brain Synapse Model
of Synapses Fruit
Fly Synapses
Page 23
Case Study: Drugs and the Synapse 9. Amphetamines are drugs that are often abused. Find out how amphetamines affect the synapse and the effects they have on the brain. Amphetamines
and the Nervous System Amphetamines
Page 24
Section 16.2 Questions The neurotransmitter serotonin is normally involved in temperature regulation, sensory perception, and mood control. A class of compounds known as selective serotonin reuptake inhibitors (SSRIs) has proven highly successful in the treatment of depression, anxiety, and obsessive-compulsive disorder (OCD). (The drug Prozac is a commonly prescribed SSRI.) How do these therapeutic drugs affect serotonin? Are there any risks involved? Search for information in newspapers, periodicals, CD-ROMs, and on the Internet. Serotonin
Reuptake Inhibitors and the Treatment of Bulimia Nervosa Selective
Serotonin Reuptake Inhibitors
Page 29
Web Activity - Canadian Achiever: Wilder G. Penfield Wilder G. Penfield (1891-1976), founder of the Montreal Neurological Institute, was the foremost pioneer in brain mapping. Using electrical probes, Penfield (Figure 6) located three speech areas within the cerebral cortex. Interestingly, the predominant speech areas reside on the left side of the brain. Penfield's finding dismissed the once-held notion that the two hemispheres were mirror images of each other. Penfield also spent a great deal of his time mapping the cerebral cortex of people with epilepsy. Penfield developed a surgical technique that involved removing a section of the skull and probing the brain with electrodes to locate the diseased area. Find out more about Dr. Penfield and how his research improved understanding and treatment of this brain disorder. In a classic experiment, Penfield applied an electrode to a particular speech area and then showed the subject a picture of a foot. Although the subject was able to recognize the foot, the word would not come. Once electrical stimulation ceased, the subject could say "foot." Penfield concluded that the thought processes associated with recognizing the foot reside within a particular location separated from the areas of the brain that control the human speech function. Penfield spent a great deal of his time mapping the cerebral cortex of people with epilepsy. Epilepsy is often associated with injuries to the cerebral cortex; electrical "storms" spread across the damaged tissue, creating anything from a tingly sensation to violent convulsions. Penfield developed a surgical technique that involved removing a section of the skull and probing the brain with electrodes to locate the diseased area. The damaged tissue can be removed, but adjacent functional tissues must not be extracted. Since the brain does not contain any sensory receptors, the surgeon can be guided by the conscious patient-only a local anesthetic is required. During the mapping process, the surgeon stimulates various areas of the brain, and the patient talks to an observer to ensure preservation of functional tissue. Penfield noted that some patients would begin to laugh as they recalled past events. One woman heard songs as clearly as if a record player were in the operating room. Incredibly, the song stopped once the electrode was removed from that area of the brain. A
Science Odyssey Wilder
G. Penfield Wilder
Penfield-Flavelle Medal Winner
Page 30
Web Activity: Neuroimaging Noninvasive imaging techniques are now available to researchers studying normal body functions and to physicians diagnosing various disorders, including cancer. These techniques are especially useful in neuroimaging - viewing the brain. Visit the Nelson Web site to learn more about positron-emission tomography (PET scans) and magnetic resonance imaging (MRI) and other techniques. How do these techniques work and what can they reveal about the brain? It was once very difficult to observe brain structure and function in living humans. Noninvasive imaging techniques are now available to researchers studying normal body functions and to physicians diagnosing various disorders, including cancer. These techniques are especially useful in neuroimaging - studying the brain. One imaging technology widely used in brain research is called positron-emission tomography (PET). PET scans can reveal various physiological and biochemical processes in the body. In preparation for a PET scan, water, glucose, or another molecule (depending on the process to be studied) is labelled with a radioactive isotope and injected into the patient's bloodstream. The radioactive compound goes to the most active areas of the brain, allowing the researcher to map the brain as it is performing particular tasks. The positrons interact with oppositely charged electrons on the body's atoms, and the resulting radiation is detected by a PET camera connected to a computer. The computer then creates a brain map that shows localized brain activity under different conditions. Physicians use the PET scanner to evaluate brain disorders, as well as heart problems and certain types of cancer. Magnetic resonance imaging (MRI) and functional MRI (fMRI) are computer-aided imaging techniques that can produce two- and three-dimensional pictures of the brain. Functional MRI differs from MRI in that it measures brain function rather than structure. MRI takes advantage of the behaviour of hydrogen atoms in water molecules. The nuclei of hydrogen atoms are usually oriented in random directions. MRI uses powerful magnets to align the nuclei, then knocks them out of alignment with a brief pulse of radio waves. Still under the magnets' influence, the hydrogen nuclei spring back into alignment, emitting faint radio signals that are detected by the MRI scanner and then translated into a computer image. Soft tissues have a relatively high water content and appear more opaque in the images than dense structures, such as bone, which contain relatively little water. For this reason, MRI is useful for detecting problems in the brain and spinal cord, which are surrounded by bone. A third imaging technique, computerized tomography (CT), produces images of thin X-ray sections through the body.As the patient is slowly moved through the CT machine, an X-ray source circles around the body, illuminating successive sections from various angles. A computer then produces high-resolution video images of the sections, which can be studied individually or combined into various three-dimensional views. CT is especially useful for detecting ruptured blood vessels in the brain. The main limiting feature of imaging technology is its cost. Imaging machines cost millions of dollars to buy, maintain, and operate; therefore, access is usually limited to major urban and teaching centres. Neuroimaging
for Kids
Page 31
Section 16.3 Questions 7. Conduct an information search on strokes, including the causes, risk factors, warning signs, and effects on the various body systems. Include statistics on the incidence of strokes in Canada and on some lifestyle strategies for reducing the risk of stroke. Prepare a poster summarizing your research results in the form of charts, graphs, and tables. Be prepared to share your findings with your class. Search for information in newspapers, periodicals, CD-ROMs, and on the Internet. Stroke
Links Stroke
Page 37
Investigation 16.2: Brain Dissection (g) Research the role of melatonin and the pineal gland in their regulation of biological rhythms in other vertebrates. Pineal Gland
Melatonin Biological
Clocks
Page 43
Chapter 16 Review 19. People with Parkinson's disease have low levels of the neurotransmitter dopamine. Researchers have been able to coax rat embryonic stem cells to develop into dopamine neurons. When these neurons were implanted into rats with a rodent version of Parkinson's, the characteristic tremor of the disease disappeared. Conduct library and Internet research to identify the latest research into treating Parkinson's disease. Parkinson Society
Canada Parkinson'
Disease Links National
Institute of Neurological Disorders and Stroke
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