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The Human Body

Investigation 1 CAP


The Human Body: Investigation 1 – CAP


In this CAP we wish to impress upon you that animals receive different types of information through their senses, process the information in their brain, and respond to the information in different ways. We will discuss the nervous system and the five senses. However, the main point to be made is that all of the information collected by the senses is interpreted by the brain. The eye makes no decision about what it sees, for example, it simply transmits the information it collects directly to the brain for interpretation. The same is true for the other senses.


This slide simply introduces the nervous system, stating that animals sense their surroundings (environment) through their nervous systems.


This slide points out the three components of the nervous system. In general, the nerves radiate to all areas of the body. They have special receptors for pressure, temperature, and pain and are located throughout our skin. The information about the environment collected by touch throughout the body is sent, along the nerves, to the spinal cord and then to the brain for interpretation.

Note to Student: While we are focusing on the “input” of information from the nerves, we should remember that any act, for example, the movement of the hand or arm, is directed by the brain. In this case, nerve signals from the brain travel down the spinal cord and to the nerves located in the body area that the brain wishes to move. Therefore, the nervous system is a two-way street, leading to and from the brain.


This slide simply shows the five senses; touch, taste, sight, smell and hearing. Notice that the sense of touch is located throughout the entire body whereas the other senses are concentrated in the head.


This slide emphasizes that the five senses feed directly to the brain for interpretation. The remaining slides will do the same, one sense at a time.

This is a very basic concept. 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 information 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.


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.

Note to Student: While we will not discuss this issue in great detail at this time, remember that the visual information from our eyes to the brain is only the initiation of an enormously complex series of neurological events collectively called cognition. Thus, our brain is capable of knowing that we are looking at a tree but then, through cognitive processing, compares it to other kinds of trees we have seen before and may even associate memories of similar images and events surrounding them.


Like humans, many 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 in 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 is interesting that octopuses are invertebrates, meaning they do not have a backbone like humans. However, octopuses have a nervous system which 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.


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.


This slide emphasizes that animals also have a sense of hearing. In 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-pitched 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.


This slide focuses on the sense of smell.


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

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 when they exhale 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.


This slide focuses on the sense of taste.


This slide emphasizes that animals can sense taste and that the sense of taste is transmitted to their brains. 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 brain.

In each example, you might be surprised that the taste receptors for each organism are not located in the mouth.


This slide focus on the sense of touch.


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 at 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.

In each of these examples, information is relayed from the sense organ to the animal’s brain for interpretation.


Some animals have senses that are quite different from our own. 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, it would take 30,000,000 microvolts to make just one 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.