The Nervous System: Sniffing out cancer

Transcription

1 Biology The Nervous System: Sniffing out cancer This lesson introduces you to the nervous system. In this lesson you will investigate the following: What is the nervous system? How is the nervous system used to transfer messages to and from the brain? How are our senses of smell, taste, touch, sight and sound related to the nervous system? How can our nervous system protect us from danger? How can dog s noses help to develop devices to detect diseases? So let s sniff out the information! This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to

2 Introduction: Using our Senses (P1) We use dogs to help us in all sorts of ways, from rounding up sheep to helping blind people cross the road. But new research now makes these things seem rather simple, showing that dogs can use their amazing sense of smell to help detect diseases like cancer, just by sniffing a person s breath. Some people have been using dogs like this for a while and they say they have a very good record in telling if people are sick or not, just through their sense of smell. Of course, dogs noses are much better at the job than ours. They have millions and millions more smell receptor cells specialised cells that can pick up a scent for their brains to process. Other scientists are not using dogs, but are instead making new machines that work like a dog s nose. In order to do so they must first work out what it is that cancer smells like and then build the incredible machines sensitive enough to detect it. But they are making progress and one day soon, they hope, they will be able to make the machines so small and reliable that you will be able to breathe into your smartphone and send the results to a lab to work out if you are sick. The technology could save many lives, as the earlier we can diagnose cancer, the better the chance of curing it. Read the full Cosmos Magazine article here or listen to it below. 00:00-17:48

3 Left: Jobi, a "Medical Detection Dog", gets down to work. Middle and right: Prototype machines used for detecting smells. Image credits: Medical Detection Dogs, Hossam Haick and Menassa Research. Question 1 Think: What are some other ways that animals are used to detect smells and odours?

4 Gather: Using our Senses (P1) Loading Video credit: Ted Ed / YouTube. Question 1 Recall: A dogs olfactory epithelium is approximately 20 times larger than that of humans. Question 2 Recall: The olfactory receptor cells are the most frequently replaced neurons in the body. True True False False Question 3 Describe: Cast your mind back to the last time that you had a cold. Describe how it affected your senses of smell and taste.

5 Question 4 Infer: Why do you think that your cold affected your senses of smell and taste as you described above? Hint: You can sniff out some clues to help answer this question in the second half of the clip. Question 5 Calculate: The clip stated that adult humans can distinguish about 10,000 different smells. As part of a check-up with her doctor, Josephine was told that she had mild anosmia and that she can only distinguish about two thirds of the smells that most adults can. How many different smells can Josephine distinguish? The nervous system So far we have learned about the signal pathway from our nose to our brain that allows us to smell, but how do our other senses work? To answer this question we must first understand that our body relies on its nervous system to interact with the world around us. The nervous system is made up of the central nervous system and the peripheral nervous system. The central nervous system, sometimes referred to as "the coordinator", consists of the brain and the spinal cord. It is responsible for making sense of the messages it receives from the peripheral nervous system and sending "instructional messages" back to all parts of the body. The peripheral nervous system consists of the rest of the nerves in our body and is responsible for relaying messages between the central nervous system and the rest of the body. The central and peripheral nervous systems enable us to interact with the world around us.

6 Receptors Receptors allow us to respond to specific stimuli. For example, olfactory receptor cells located in your nose respond to odour molecules. These receptors launch a chain of messages around the body via the nervous system. There are five primary types of receptors: Chemoreceptors are sensitive to chemicals, such as odour molecules in the air, and are located in your nose and tongue. Mechanoreceptors are sensitive to touch, pressure, sound and motion and are located in the skin, the inner ear and muscles. Pain receptors are sensitive to chemical changes in damaged cells and are located throughout your body, but most are located in your skin. Thermoreceptors are sensitive to temperature changes and are located in the skin. Photoreceptors are sensitive to light and are located in your eyes. Some of these receptors are neurons (described below), like the olfactory receptor cells, while others are not, such as the hair cells in your inner ear that enable you to hear. Question 6 Identify: Use the information above to complete the table below by matching the receptors and responses with each given stimuli. Include an example of your own in the bottom row. Stimulus Receptors responsible Typical response The bell rings at the end of class A very hot day down at the beach Pack up your books Body starts to sweat Your friend waves to you from across the school yard Photoreceptors in the retina of the eye You've put sour milk on your cereal and only realise when you take a mouthful Spit milk out or pull a face Mum has cooked your favourite meal and you smell it as you walk in the door Neurons Neurons are specialist cells that transmit messages, in the form of electrical signals, to and from the central nervous system. They are like the wires of an electric circuit. There are a number of different types of neurons: Interneurons transmit messages from sensory neurons to motor neurons. Motor neurons transmit messages from the central nervous system to "effectors" such as muscles and glands to initiate a response. Sensory neurons transmit messages from receptors to the central nervous system. Although they have different roles, neurons generally have the same structure. They are made up of dendrites (branches that receive messages), a cell body (where the nucleus is found), axons (that transmit a message away from the cell body) and myelin sheaths (a fatty layer that insulates the axon). There are different types of neurons in our body.

7 Question 7 Label: Use the following terms and the information above, to label a typical neuron. The terms you have to choose from are: Axon Cell body Myelin sheath Dendrites Nucleus Also, use purple arrows to show the direction in which an electrical impulse would travel through the neuron.

8 Process: Using our Senses (P1) Loading Video credit: Medical Detection Dogs / YouTube. Question 1 Debate: The Cosmos Magazine article states that after five years of training dogs can correctly sniff out bladder cancer samples 93% of the time. Is this statistic alone sufficient to be able to state that these dogs can "sniff out cancer"? What scientific evidence and tests are needed to be able to make claims such as these? Generate some points in the space provided and discuss them with a friend. When a dog sniffs, the odours in the air pass through the olfactory epithelium and trigger the olfactory epithelium cells which then send electrical impulses to the brain via the nervous system. This maps a path for that particular odour, like cutting a path through a jungle. If that path is mapped enough times, the brain starts to be able to easily recognise that odour.

9 Question 2 Think: Complete the flow chart to show what happens once a dog recognises a particular odour. Hint: Receptors, coordinators and effectors are all described in "Gather". Question 3 Research: Use the internet to find out the similarities and differences between the way a dog's nose and an electronic nose detect an odour.

10 Question 4 Discover: So far we have learned that messages, in the form of electrical impulses, are transmitted around the body via the nervous system by millions of specialised cells called neurons. But how is a signal transferred between neurons? Use the space below to write a report on synapses. Your information can presented in any number of ways, including written information, labelled sketches, flowcharts, YouTube clips and images.

11 Apply: Using our Senses (P2) Experiment: Are we smelling it or tasting it? Background We eat a variety of foods and enjoy their delicious tastes, but are we really tasting them or are we in fact smelling them? This experiment will help you find out. You will eat a variety of foods first with your nostrils blocked, then with your nostrils open. To make sure that you don't cheat, you will be wearing a blindfold! So find a partner, apply your blindfold and get tasting. Materials Blindfold Variety of food Pen Paper Method Your teacher will provide plates of food for you to test, but you are not allowed to see them so move away from the table and apply your blindfold! 1. Put your blindfold on 2. Hold your nostrils closed and open your mouth. 3. Your partner will place a piece of food from plate 1 in your mouth. 4. Write down what you initially taste (in Question 2 below). 5. Open your nostrils and remove your blindfold. 6. Write down what you taste (in Question 2 below). 7. Repeat for each of the remaining plates of food.

12 Question 1 Write: Read the method carefully and, in the space provided below, write an appropriate aim for this experiment. Question 2 Complete: Use the table below to record your results. Plate number First taste (Nostrils closed, blindfold on) Second taste (Nostrils open, blindfold off) Question 3 Discuss: Use what you have learned about the nervous system, particularly the receptors responsible for taste and smell, to explain your observations. Question 4 Evaluate: How could the experimental method be improved or extended upon?

13 Question 5 Conclude: Formulate an appropriate conclusion for this experiment. Make sure to: State your findings clearly. State what have you learned about taste and smell receptors by conducting this experiment.

14 Career: Using our Senses (P2) Claire Guest is a behavioural psychologist who specialises in human-dog relationships. She trains dogs to use their exceptional sense of smell to detect cancer and other diseases in humans. One day, a few years ago, one of Claire s dogs saved her life. The dog, a Golden Labrador with big brown eyes named Daisy, had been acting a bit differently all week anxious and overly attentive. Claire was taking her team of dogs to the park for a walk when Daisy suddenly leapt up and planted her paws on Claire s chest. Daisy s impact was very painful and led Claire to discover that she had a tumour growing there. While it s impossible to know for sure, Claire believes that the early detection was life-saving. You can say Daisy s behaviour was a mere coincidence but the fact remains that it s because of her I found my cancer, she says. It was while she was training hearing dogs for deaf people that Claire heard a talk on the radio about dogs detecting cancer. Her interest was piqued. Not long afterwards she started an organisation called Medical Detection Dogs, which trains dogs to smell the signs of certain diseases. The dogs that Claire works with are almost like office workers they live at home with families and come in to work during the week. They are chosen because they love to search for things with their noses, are responsive to training, and enjoy the company of humans. Medical Detection Dogs is a charity, so Claire spends a lot of her time promoting the organisation's work, and raising money so that they are able to train more detection dogs like Daisy, and save more lives. The founder of Medical Detection Dogs, Claire Guest, with her dog Daisy. Credit: Medical Detection Dogs Question 1 Think: What do you think are the challenges or special considerations that need to be taken into account working with animals, particularly dogs?

15 Cosmos Lessons team Education Editor: Bill Condie Art director: Robyn Adderly Profile author: Edwina Berry Lesson authors: Deborah Taylor and Daniel Pikler