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The Human Body

Investigation 1 – PostLab









The human body is organized into systems that are made up of many parts and that these systems each perform both individual and complementary functions that occur at the same time in the body.


Biomedical research scientists study the function of normal and diseased body systems. They study the human body at the systems level, the cell level, and the molecular level. Great medical advances have come from the understanding of the human body discovered through biomedical research.




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In this PostLab session, we will go over the experiences and results from the Lab for Investigation 1 and incorporate a more detailed discussion of the senses and how the brain is involved in interpreting information that is obtained through our senses.


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Think about the pathway of a signal from the brain to your hand. The brain sends a signal (an electrical impulse) through the nervous tissue in the spinal cord to the nerves in a person’s arm. These nerves connect to others which eventually lead to the hand.


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This slide will be used by your teacher to review the four Trials that your performed in the lab.


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Do you remember what it was like to catch the ruler? What was the first signal that you listened for to get your body ready to catch the ruler?

First, your mind and your hand got ready when you heard your partner start to count. What was the second thing that happened that told your body to catch the ruler?

What did your body do so that you caught the ruler?

How did you know when you caught the ruler and no longer had to reach for it?

What parts of the body were used first in this trial?

After you heard the counting, what part of your body was used?

Next, walk through the process of how signals traveled in the body in Trial 1 using the diagram.  

  • Your brain sent a signal telling you to catch the ruler. The brain sent a signal to the arm and the hands, telling the hand to close and catch the ruler.
  • After you caught the ruler, the nerves in your hand sent a signal telling the body that the ruler had been caught. The nerves in the hand and the arm sent the signal to the spinal cord and back to the brain. 

Finally, how did the signal move from the ears to the brain to the fingers and back to the brain?  What part of the body communicates this signal? 


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This slide takes a closer look at the results of the ruler drop experiment that was conducted in the lab:

Did you catch the ruler at the same number each time?” 

With each trial, did you get better at catching the ruler?

If you did get better at catching the ruler, how might this improvement relate to the function of the nervous system?


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This slide begins a discussion of Trial 2 in which you investigated the involuntary action of blinking. 

The brain controls two different kinds of actions, voluntary and involuntary.  Voluntary actions are those that we choose to do or think about doing. Involuntary actions are those that we do without thinking about them. We do not choose to do them; our bodies automatically do them. Blinking is an involuntary action. 

Can you think of other involuntary actions?


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This slide compares the action of catching the ruler to the action of blinking. 

When you wanted to catch the ruler, you had to think about catching it. When you blinked, did you have to think about blinking?

Focus on blinking. During the ruler drop activity, the signals moved through the nerves in a process with many steps. The blinking activity, however, required fewer steps. Which parts of the body were involved when you blinked?

When you blinked, where did the signal begin? What was the path of the signal?

How did the signal move from the brain to the eyelids?  Which part of the body communicates this signal?


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This slide addresses data collected in Investigation 2 lab.

Look at your Student Data Record. Does everyone blink the same number of times in one minute?

What does this tell us about the nervous system?


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Do you think that the nervous system controls things other than the physical actions of the body?

Trial 3: Think about Trials 3 and 4 that you performed in the lab. Both trials have one main element in common. When you listened to the noise the object made as it dropped, did you do something? Did your brain tell you to move—to blink, to catch a ruler, or to perform some other activity?

Trial 4: When you tried to remember the pattern of shapes, did you do something? Did your brain tell you to move or to perform an activity?

  • Actually, during both trials, your nervous system was working. Your nervous system was allowing you to receive information and to think about it.

Which parts of your body did you use when you predicted the identity of the dropped objects?

Which parts of your body did you use when you remembered the pattern of shapes?


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This is a summary slide. The first two trials showed that the brain and the nervous system guide our physical actions. Trials 3 and 4 showed other ways that the nervous system controls the body.

You should now begin to understand that the nervous system controls the actions of the body, helps us to interpret and understand the world around us, and helps us to think about and recall information. We think, learn, and remember by using our brains.


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This activity encourages you to apply your knowledge of the nervous system as your teacher reads a short story aloud.

How often in your day do you think you use your nervous system?

  • Find the story in your Scientist Data Record and follow along as your teacher read aloud.
  • Listening to this story is a good time to use the Mind Movie Cognitive Tool.  The Mind Movie is a tool that can be used to help a person draw a picture or create a movie that shows something with a lot of detail. 


  • The story is about a man named Mr. Freeman. While you listen to the story, try to picture Mr. Freeman in your mind, creating a movie with your imagination. 
  • After the story is finished, think about and answer the questions in your Student Data Record about how Mr. Freeman used his nervous system.  By picturing Mr. Freeman and his activities in your mind, you will be better able to answer the questions. 


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Continue to read the story.


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How did Mr. Freeman use his nervous system throughout his trip from the breakfast table to his office?

You should realize that every time Mr. Freeman thought about something or made a decision, he used his nervous system. Every time Mr. Freeman made an observation he used his nervous system, and every time he moved he used his nervous system.


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This is the first of three slides in which you will use the short story to highlight times when Mr. Freeman used his nervous system to either perform actions, make observations, or think and make decisions.

How did Mr. Freeman use his nervous system to move?” Underline the phrases in youyr Scientist Data Record


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How did Mr. Freeman use his nervous system to make observations and gather information from his senses? In your Student Data Record, put a box around the times in which he uses his senses. Answers may include: feeling the sun and the cool air on his skin, seeing the red signal, hearing and watching the fire truck pass, seeing the white WALK signal, feeling the laces on his shoes, and tasting his breakfast.


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How did Mr. Freeman use his nervous system to make decisions or to think? Circle the choices or decisions he makes. Sample answers include:  choosing to walk on the nice spring day, deciding to stop at the edge of the street, and wondering where the fire truck is going.

Do you think that Mr. Freeman’s nervous system was ever not being used in this story?


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The last set of slides emphasizes the relationship between the senses and the nervous system. 

In this slide, we begin our effort to impress upon you that the five senses are part of the nervous system and feed directly to the brain for interpretation. The remaining slides will do the same, one sense at a time.

The eye does not know what it is looking at, for example. Nerve impulses from the eye to the brain are interpreted as the object our eyes are looking at. When the eyes are moved to look at other components of a scene, to understand it further, that is directed by the brain as well. Thus, our senses are each essentially tools that the brain uses to interact with and understand the world around us.


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This slide focuses on the sense of sight. The eye transmits nervous signals to the brain that contain information about color, brightness, shape, movement, and so forth. This information, when received and processed by the brain, is interpreted as the object we are looking at, in this case, a tree.



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Just like humans, animals use their sense of sight to interact with the world. In these examples, information is transmitted to the brain for interpretation.

Flies, octopi, and chameleons have variations in their eyes to help them with specific functions necessary for survival.  Flies, for example, have 3000 lenses around each eye, compared to just one lens in a human eye.  This allows flies to see all around them, making them very hard to catch!

Octopuses have rectangular pupils in their eyes.  A human eye has a circular pupil. Rectangular pupils may permit octopi to see almost all around them and see in dark areas. It may be interesting to remind students that octopuses are invertebrates, meaning they do not have a backbone like humans. However, octopuses have a nervous system that includes a brain.

Chameleons have eyes that can each move in different directions. Scientists used to think that the eyes moved independently.  However, now we know that they can either look at two different objects at the same time or coordinate the eyes so they are both focused on the same objects. Scientists have discovered that each eye knows exactly what the other eye sees.


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This slide is included to impress upon you that hearing sounds in our surroundings, in this case, a bell is only interpreted as a bell by our brain. The ear itself has no idea or capacity to associate the sound waves it is collecting as the tone of a bell.


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This slide emphasizes that animals also have a sense of hearing. In all of these examples, information is transmitted to the brain for interpretation.

Crickets have a thin membrane on their front legs. The membranes vibrate when sound waves are present, allowing crickets to “hear.”

Cats hear similar to the way humans hear. However, there is a big difference in what cats can hear. While humans hear high and low pitches or frequencies of sound, cats can hear sounds lower and much higher. Many people comment on dogs’ abilities to hear sounds higher than humans can hear. Humans hear frequencies as high as 23,000 Hz, while dogs hear sounds as high as 45,000 Hz. However, cats have them beat!  They can hear sounds as high as 64,000 Hz.

Dolphins use echolocation to locate objects around them. They send out high-frequency sound waves, then listen for the echoes that occur when the sound waves reflect off of the objects. The reflected waves are detected by bones in the dolphins’ jaws. The sound waves pass from the jaws to the middle and inner ear. From there, information is transmitted to the dolphins’ brains for interpretation.


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This slide focuses on the sense of smell.


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Animals such as moles and mosquitoes have a sense of smell similar in some respects to humans. Information from a mosquito’s or star-shaped mole’s nose is interpreted by the animal’s brain.

For many animals, the sense of smell is a more dominant sense than for humans and may be interpreted in the brain differently. For example, scientists think that a mosquito’s brain mixes smells and tastes to produce unique “flavors.”  Female mosquitoes use their sense of smell to find humans. The carbon dioxide released by humans is one of the substances that female mosquitoes try to “sniff” out. Male mosquitoes don’t bite humans. Instead, they use their sense of smell to find nectar.


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This slide focuses on the sense of taste.


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This slide emphasizes that animals can sense taste and that the sense of taste is transmitted to their brains for interpretation just as it is for humans. Interestingly, this slide shows two invertebrates, animals without a backbone. Although earthworms and octopi are invertebrates, they each have a nervous system, which includes a simple brain.

In each example, you might find it interesting that the taste receptors for each organism are not located in the mouth.


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This slide focuses on the sense of touch. 


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Just as humans have a sense of touch, so do other animals. Our sense of touch helps us to feel sensations such as temperature, pressure, and pain.  Some of these same sensations are felt by other animals.

Much like our hands, the scorpion’s pincers are very sensitive.  Hairs on its pincers allow it to sense the slightest movement of air, at speeds as small as 0.072 km/hr.  To put that into perspective, the wind speed on a calm day, when branches are still and flags hang limp, is about 2-5 km/hr.

Iguanas require the temperature of sand to be 30°C (86°F) in order to lay their eggs. Otherwise, their eggs won’t hatch. It makes sense then, that they have sensors under their skin that can tell the difference between as little as 1°C!

Located along the head and trunk of fish are receptors that can sense pressure. This helps fish to move, change direction, and locate prey in the water.


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You may find it interesting that some animals also have different senses than humans. For example, a platypus has electric sensors in its bill. These sensors can detect electricity as low as 0.05 microvolts. To give you an idea of just how low that is, it would take 30,000,000 microvolts to equal a 1 D cell battery.

Worker honey bees have iron oxide, a natural magnet, in their abdomens. Scientists think this natural magnet may give the bees the ability to detect changes in the Earth’s magnetic fields, helping them navigate.


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The next Investigation continues our exploration of body systems by introducing two new systems: the skeletal system and the muscular system.