Week 12 - Scientific Investigation and Medical Applications
Week 12 - Scientific Investigation and Medical Applications
|Site:||AB Course Sharing Hub|
|Course:||Science 8 LearnNet|
|Book:||Week 12 - Scientific Investigation and Medical Applications|
|Printed by:||Guest user|
|Date:||Thursday, 18 July 2019, 9:50 PM|
Table of contents
1 Sensory Awareness
Science in Action 8
|Your nervous system, with the help of all the other body systems we have studied, tries to keep your body stable. For example, the ideal body temperature for humans is 37 degrees Celsius. But throughout the day you may have times of strenuous exercise and times of sitting quietly. The temperature regulating region of your brain ( the hypothalamus) coordinates the behavior of you're your skin, blood vessels and muscles to ensure your body maintains its ideal temperature. The brain tries to maintain this stability in, and between, all body systems.||
Stimulus / Response
A stimulus is anything that causes an organism to react. A response is a reaction to a stimulus. A stimulus can come from outside the body and be received by your five senses, or it can arise internally. An internal stimulus might cause a response to breath faster.
You have external sensory organs that constantly monitor your external environment. Do you remember what they are?
We all know that it is very important that we get enough oxygen and so we assume that our body monitors the amount of oxygen we receive. But interestingly, it doesn't work that way. Our body monitors the build up of carbon dioxide in our blood stream not oxygen. So we breath faster when the carbon dioxide levels rise - usually due to exercise
Never hyperventilate before you swim under water!
|Knowing that the body monitors carbon dioxide, not oxygen, is important for swimmers. I'm sure we've all seen kids playing around lakes or pools. Sometimes they compete with each other to see who can swim the farthest underwater. You might see them take many deep breaths before they dive. This is called hyperventilating and is very dangerous. The children think that they are building up reserves of oxygen for their swim, but actually they are dramatically lowering their carbon dioxide levels without really changing the oxygen levels. This means they don't feel the need to breath even though they are running short of oxygen. Every year children drown because they blacked out under water when they ran out of oxygen.|
The Nervous System
The nervous system is composed of specialized cells called neurons . Neurons receive a message at one end through structures called dendrites. The message travels through the cell body and then through very long extensions called axons. The axons relay the message on to the next neuron.
Nervous System Organization
The nervous system can be divided into two basic divisions. The central nervous system is made up of the brain and spinal chord . All the nerves that radiate from the central nervous system are considered to be part of the peripheral nervous system .
The Central Nervous System
Your brain receives all the incoming sensory information and decides how to deal with it. Once a response is decided on, it sends out instructions to the appropriate muscles and organs. The brain can be divided into three major parts: the cerebrum, the cerebellum and brain stem (medulla). The cerebrum receives sensory information and does the decision-making. You could also think of it as the thinking , feeling part of your brain. The cerebellum coordinates muscle movements. For example, do you remember when you first learned to ride a bike ? For a while you were probably all over the place. But as cerebellum learned to coordinate your muscles and balance, you got better and better. Your brain stem looks after organ system functions like breathing and digestion, so you don't have to consciously think about all the things that go on inside you - thank goodness!
The spinal cord 's job is to connect the brain to all the peripheral nerves. Think of it as a highway for all the sensory and motor nerve messages traveling throughout your body.
The Peripheral Nervous System
Peripheral nerves connect the muscles and organs throughout your body to the spinal chord. Nerves that carry sensory information to your central nervous system are called sensory neurons . Instructions from the brain back to organs and muscles are called motor neurons .
The peripheral nervous system can be further divided into automatic responses and those that you consciously decide to carry out. The autonomic nervous system deals with automatic responses which include: your blood pressure, heart rate, breath rate and rate of peristalsis in the digestive tract. Somatic nerves carry voluntary responses such as reaching for a piece of pizza or turning or head to follow a sound.
Exercise 4.1: Measuring Your Reaction Time
© 2002 Alberta Online Consortium
2 Cells, Tissues, Organs and Systems
Lesson 14No textbook readings for this lesson
Human Cells are Specialized
Cells are the basic unit of all living things. They are truly amazing. You could become a cell biologist and study your whole lifetime and still not truly understand all the functions in a single cell. Many organisms are only made as a single cell, but other organisms, like ourselves, are made of trillions of cells. A single celled organism has to do all that's necessary for life by itself, but multicellular organisms are usually made up of many kinds of specialized cells.
When cells with single special function combine together into a tissue. Tissues are groups of similar cells that have similar structure and function to carry out a specific job. There are four main groups of Tissues:
Type of Tissue
|Epithelium (Skin tissue)||This tissue forms glands, and covers surfaces, Your skin for example.|
|Connective Tissue||This tissue holds all the parts of your body in place. Boy, would you be a mess without this tissue!|
|Nerve Tissue||Nerve tissue (neurons) transmits messages throughout the body.|
|Muscle Tissue||Muscle tissue has only one job - it contracts (shortens) when told to do so.|
Tissues that combine together to perform a particular job are called organs . For example, the stomach contains epithelial (skin) tissue inside and out, nerve tissue and muscle tissue. It is held in place by connective tissue.
Combinations of organs work together to accomplish larger tasks like digesting food (digestive system), transporting materials (circulatory system) or receiving information from the environment and deciding what to do - the nervous system. We call these combinations of organs - organ systems.
When you put all of them together the final product of all this coordination and activity is YOU!
© 2002 Alberta Online Consortium
3 Responding to Internal and External Environments
We have nearly come to the end of our discussion about the human body, but we need to tie it all together. We need to see how our body responds to internal and external changes.
|In order to do this we need a subject.
We're going to study a person who is going to go mountain climbing. Let's call her Judy.
She's a provincial park ranger in Kananaskis Country in southern Alberta.
Judy is a very fit person. She trains often because she may be doing all sorts of jobs such as mountain rescue work or back country patrols on horseback. Her resting pulse is usually around 60 beats per minute, and her respiration rate is 11 breaths per minute. On this day she is going to climb a nearby mountain with her team and practice rescuing someone off the mountain. She will be carrying a 13 kg pack which has all the clothing and supplies she will need.
Short Term Changes
The journey starts with a fairly strenuous hike as she approaches the mountain. With the extra weight she is carrying and the steep hills she is climbing, her muscles need to do more work and therefore her metabolic rate increases. The carbon dioxide is building up in her blood and this triggers the internal sensor and she begins to breath faster. Her heart rate is now up to 70 beats per minute and her breath rate is 16 breaths per minute. With this increase in metabolism her cells are generating more waste heat. Her body temperature rises to 38 degrees Celsius. To remove this excess heat, her skin releases perspiration which, as it evaporates, removes this extra heat and maintains her body temperature near her normal 37 degrees Celsius. In order to stop the perspiration she removes her pile jacket and feels comfortable again. This increased metabolism has increased the work load on the heart and lungs and now both are working faster. This ensures that both oxygen and nutrients are getting to her hard working cells and cell wastes, including heat, are removed. As she continues up the slope she is constantly nibbling on a fruit and nut bar to keep her energy up and drinking to replace the fluids lost in perspiration and through respiration.
After a short break Judy and her team put on their mountaineering equipment and begin the ascent. Mountain climbing is a very strenuous activity and over the course of the afternoon Judy's metabolic rate increases dramatically. All the affects mentioned in the paragraph above are increased as well. Her vital signs are now: heart rate = 90 bpm, respiration = 18 bpm, temperature = 38 degrees Celsius. By the end of the day Judy is tired and hungry. Her vital signs have returned to normal. Because she has been doing this kind of activity for years her muscles are use to this strenuous activity, but a new member of the team will be sore for a few days as the lactic acid that built up in his muscles is slowly removed and excreted. As she drops off to sleep her metabolic rate slows even further. Her vital signs are: pulse rate = 55 bpm, respiration = 9 bpm, and her body temperature drops to 36 degrees Celsius. Good night Judy.
Long Term Changes
Judy was student from Vancouver, in British Columbia. The air at sea level contains more oxygen than the thin air of the mountains of Alberta. When she first came to Kananaskis Country she was constantly tired and out of breath. But over a period of a few weeks the number of red blood cells increased in her blood. This allowed her to collect more oxygen molecules from the thin air and she felt more active and her breath rate returned to normal.
|As a student, Judy did a lot of studying and so could not be active all the time. Because her metabolic rate was fairly low, she didn't need to eat very much to keep her going.|
Each and every day of our lives our bodies constantly adjusting to internal and external factors. The overall goal of our system is to remain stable. Your nervous system ensures that your internal systems have what they need and can get rid of wastes as soon as they can. A day in Judy's life showed us that these changes are natural and normal.
Exercise 4.3: Responding to Environments
1. In the table below record Judy's vital signs and then suggest some internal causes to these affects.
4 Viruses and Bacteria
Science in Action 8
Lesson 16: Viruses and Bacteria
|One of the things that is most important to us as humans is our health. Though we can do much to remain healthy through our diet, rest, and exercise; we encounter other threats. Two of these are bacteria and viruses. Over the years these two groups of organisms have proven to be a major problem for our health. Through experimentation and medical research, we have learned many ways to fight these threats to our health. Bacteria and viruses can be helpful or harmful. When they are the harmful kind, they can cause many well known diseases such as colds, the flu, and AIDS.|
We will examine both bacteria and viruses from three points of view:
1. the nature of the organism
2. our natural defenses
3. defenses developed from medical research
The Nature of Bacteria
Bacteria are one celled organisms found often with living organisms. Some of these bacteria are beneficial such as the ones that live in your large intestine and make Vitamin K for your body. Unfortunately, many bacteria are harmful to humans. Some examples are the bacteria that cause tuberculosis, anthrax, whooping cough, food poisoning and even Ecoli infection.
Bacteria can use the nutrients from the human body to grow and multiply and once the numbers growing in the human body become large, we get really sick. The only solution is to prevent infection or to stop the bacteria in the body from growing.
Our Natural Defense against Bacteria
|Our first defense against bacteria infection is our skin which provides a physical barrier to bacteria entering our body. The mucus membranes on the inside of the body provide an internal skin. A break in our skin, like a cut, is a chance for bacterial infection.
Our second line of defense is our immune system As soon as bacteria enter a cut, white blood cells are sent to the site where they work to kill the invading bacteria and stop the infection. If the numbers of bacteria are too large, then the infection will spread and medical attention is needed.
|Bacteria come in three general shapes:
bacillus (rod shaped)
spirillum (spiral shaped)
Some bacteria can increase virulence (strength) by secreting a slime layer on the outside of itself, which acts as protection (from things like antibiotics).
Food poisoning is caused by particular kinds of bacteria in the food consumed, either reproducing in your digestive tract, or producing a toxin (poison), that remains after cooking.
There are 4 main types of food poisoning:
-caused by salmonella bacteria
-some of the symptoms include severe headaches, vomiting, diarrhea,cramps, fever
-can last several days
-found in chicken, turkey, & egg containing foods, like egg salad and meringue
-can be prevented proper refrigeration and reheating completely
2. Perfringens Poisoning
-caused by a bacterium can survive cooking temperatures called clostridium perfringens
-some symptoms include nausea, diarrhea, cramps usually only lasts for 1 day
-found in foods with gravies
-can be prevented by proper refrigeration
-caused by a toxin producing bacterium called clostridium botulism, that can live in n sealed can
-some symptoms include double vision, difficulty swallowing where more that half affected die
-can be prevented proper sterilization methods (boiling for 10 to 20 minutes) before home-canning
4. Staphylococcal Poisoning
-most common caused by staphylococcus aureus (from an infection, cough or sneeze) contaminating the food
-some symptoms include vomiting, diarrhea, cramps can last 1 or 2
-daysfoods conducive to this type of bacterial growth are mayonnaise containing foods like sandwiches, pastries, custards, and salads can be prevented by proper refrigeration and reheating.
Bacterial Defenses Developed from Medical Research
The simplest defense against bacteria is preventing the infection. In 1857, Louis Pasteur first found that microbes(bacteria) cause disease. He began the process of heating milk to kill these microbes before it was cooled for human use ( process of pasteurization). In 1865, a surgeon, Joseph Lister, applied Pasteur's theories to his surgical practice. He found that by destroying microbes in the operating room and on his hands, using disinfectants, before the operation, many more of his patients survived.
When infections do occur, we need additional help. Until well into the twentieth century, there was very little we could do. In 1938, Alexander Fleming noticed that some bacteria growing in his lab were dying when they grew close to the mold Penicillium. This led to the development of the drug penicillin - an important antibiotic. It works by breaking down the wall of the bacteria cell, thus killing the bacteria. It does not work on a virus. Since that time there have been many other antibiotics developed which have greatly improved our ability to recover from bacterial infections.
1. The Nature of Viruses
A virus is a very small non-cellular particle that cannot reproduce on its own. The virus must take over the cell of another living thing in order to make new viruses. Some examples of virus caused diseases include mumps, measles, chicken pox, the common cold and AIDS.
Viruses were first studied in 1892, but they could not be seen until 1944 when the electron microscope was perfected (because viruses are too small to be seen without high level magnification).
2. Our Natural Defenses against Viruses
Once again the best defense against a virus is to prevent it entering our bodies. Since viruses are so very small, it is easier for them to enter the body and so techniques like thorough hand washing and avoiding coughs will help.
When a viral infection has occurred, we are dependent on our own immune system. Antibiotics will not work as they break down cell walls and a virus does not have a cell wall. There are very few options for treatment of a viral infection that are effective. If you see your doctor and you are told you have a bad cold, the treatment will likely be plenty of fluids and rest for a couple of weeks. This is to allow your own immune system to defeat the virus.
Viral Defenses Developed from Medical Research
About 200 years ago, many people died from smallpox. In 1796, a doctor Edward Jenner noticed that milkmaid that got a mild form of this disease called cowpox, seemed to be immune to the much more serious smallpox. Somehow, the milder disease was protecting people from the much more serious disease. He actually injected the cowpox pus into a healthy boy. Months later, the boy did not get smallpox when everyone else in his family did. This was the first vaccine. A vaccine is an injection of dead disease organisms. This allows our bodies to make antibodies to this disease. Then if we come into contact with the actual disease organism, the body is ready to flight it off. This is known as immunization for the disease.
HOW DOES IMMUNIZATION WORK?
The general process involved with an immunization is:
|i. the dead virus is injected into your body|
stream and begins to make special cells called antibodies.
iii. The antibodies prepare to attack and kill the foreign dead virus cells. They are now ready and available (in the bloodstream) to kill any new living viruses that may enter the body. This prevents the new, living virus from reproducing and causing damage to the body.
Antibodies are also formed naturally by contracting (catching) the disease. The antibodies made from the disease are prepared to attack anymore of the same virus cells entering the body. Antibodies can live from a few days to several years, depending on the individual and the type of antibody formed.
Viruses can mutate or change in strength (virulence) , and they require the use of immunization to prevent the outbreak or onset of the disease. This is not a cure for the disease but rather a means of controlling the disease
Comparison between Bacteria and Viruses
seen under a microscope
very, very small
antibiotics are used to kill bacteria
no drugs kill viruses
three basic shapes
only two main parts (protein coat and nucleic acid core)
Did you notice that we did not talk about treatment for a virus once you have it? That is because there are very few effective treatments. Antibiotics do nothing to a virus. Only your own immune system can defeat the virus infection.
Exercise 4.4: Health Research
1. Using an encyclopedia and Internet research resources, write a short report on three different diseases or illnesses:
2. For each disease or illness, explain: