Photo Credit: By Redbloodcells.jpg: hematologist derivative work: patient-doc (Redbloodcells.jpg), via Wikimedia Commons
To develop an understanding of cell-to-cell communication.
Research shows that high-school students hold various misconceptions about cells after traditional instruction. For example, students might think that cells are within the human body rather than understanding that the human body is itself composed of cells. An example of when these types of misconceptions can be established occurs when students learn that red and white blood cells flow within arteries and veins. While this is correct, students may not realize that the arteries and veins themselves are composed of cells specialized to form these vascular structures. It is important to clarify these misconceptions prior to this activity.
Students should also have a basic understanding of the endocrine and nervous systems. This lesson necessarily refers to various hormones, neurotransmitters, and body organs and tissues. Thus, this lesson may serve as a good summative activity after students have gained familiarity with the different structures and functions of the endocrine and nervous systems.
By the end of middle school, students should know that all living things, including themselves, are composed of cells. They should have an understanding that all body tissues and organs are made up of different kinds of cells. Each cell, as a living entity, carries out the basic functions of life, such as extracting energy from the environment and removing waste.
This lesson expands upon their basic understanding of the cell as a single unit by considering the cell as part of a larger system or community. Within this community, cells are differentiated, each performing a special function necessary for the survival of the entire community of cells. In order to perform their unique functions effectively, cells must react to situations in their surrounding environment as well as communicate with each other.
This lesson focuses on cell communication. Students will examine two types of cell communication—hormone and nerve signaling. In order to better understand the importance of effective cell-to-cell communication, students will examine various diseases in which faulty cell communication negatively impacts the entire community of cells and in effect, normal total body functioning. Instances of such diseases include diabetes, hypo- and hyperthyroidism, multiple sclerosis, and cancer.
While these diseases can be directly linked in most cases to genetic mutations, this lesson will also examine the impact of environmental factors on cellular communication. Drugs, such as marijuana, opiates, and caffeine, can mimic or block certain hormones and neurotransmitters, thereby altering body functioning. By studying the effects of both genetic and non-genetic (environmental) factors on hormone and nerve signaling, students will learn the importance of cell-to-cell communication.
Because it may help students to understand the interdependency of cells if they think of an organism as a community of cells, each of which has some common tasks and some special jobs, begin by discussing the role of communications in communities.
- Describe a community.
- Explain why all members of a community do not all perform the same function. (For example, ask students why everyone in the world cannot be a doctor or a firefighter or a teacher.)
- How is communication important within a community?
(Answers may vary. Encourage students to explain their answers.)
Relate the importance of communication to students' lives. For example, if most students in the classroom hold working jobs, ask them why communication is important in the workplace community. Ask students to explain how a breakdown in communication would impact the functioning of the business. Students in the classroom may be highly involved in sports activities. Ask them to point out the importance of communication within a team, where each player has a particular function. Have students describe what happens when player communication breaks down or when one player does not pay attention to the roles and actions of other players on the team.
Tell students that our bodies are composed of a community of cells. Ask students:
- What are some of the reasons that cells might communicate with each other?
- How do you think cells communicate with one another? (For example, how do the cells in your brain communicate with the cells in your stomach?)
- Describe what might happen if communication between certain cells failed.
(Answers may vary. Encourage students to explain their answers.)
Review with students that there are two basic types of cellular communication—hormonal and nerve signals. Ask students:
- What are hormones?
- What is the importance of hormones?
- How are hormones produced?
- How are hormones important in cellular communication?
- What are nerve signals?
- What is the importance of nerve signaling?
- How are nerve signals involved in cellular communication?
- What is the difference between hormonal and nerve signaling?
- (Hormones are chemical messengers that travel throughout the body coordinating complex processes like growth, metabolism, and fertility.)
- (They can influence the function of the immune system, and even alter behavior. They guide development of the brain and reproductive system. Hormones are the reason why your arms are the same length, why you can turn food into fuel, and why you changed from head to toe at puberty. )
- (They are produced by organs called ductless glands (endocrines). These include the two adrenal glands, the pituitary gland, the four parathyroid glands, the sex glands, and the thyroid gland.)
- (They are important because they help control certain bodily functions, like: the way the body uses food; growth; sex and reproduction; the regulation of the composition of the blood; the reaction of the body to emergencies; and the control of hormones themselves.)
- (A momentary change in electrical potential on the surface of a cell, especially of a nerve;or muscle cell.)
- (Nerve signaling is important because many functions depend on it, such as: speech, movement, coordination, and vision.)
- (The nerve signal stimulates the vesicles containing serotonin to fuse with the cell membrane and dump serotonin into the synaptic cleft.)
- (Hormonal signaling sends slow, graded messages throughout the body that are read by cells with relevant receptors.. Nerve signaling sends rapid, digitized messages over fixed anatomical connections.)
Review the following with students:
Hormones generally act slowly and are produced in small amounts, often in bursts, influenced by factors in both the environment and within the body. Each hormone has different effects on different tissues, organs, and behaviors and, in general, affects metabolic processes, including the build-up and breakdown of carbohydrates, lipids, and proteins.
Hormones can affect only those cells with receptors that recognize the hormone and alter cell function. Neural communication sends rapid, digitized messages over fixed anatomical connections while hormonal communication sends slow, graded messages throughout the body that are read by cells with relevant receptors. Neural communication is more readily under voluntary control than hormonal communication. Both neurons and endocrine glands produce their transmitters or hormones and store them for later release.
Neurons are stimulated to produce an action potential that causes the release of transmitters into the synapse; endocrine glands are stimulated to secrete hormones into the bloodstream.
To begin this part of the lesson, students should use their Cell Communication student esheet to go to and read the first three paragraphs of the Scientific American article: Cell Communication: The Inside Story, including the introductory illustration. Then, students should read "Getting a Line on Human Diseases," found on page 6 of the PDF. Ask students:
- How are the two cells in the illustration communicating with one another?
- What are the messenger molecules? (e.g. hormones or neurotransmitters)
- Why might one cell need to communicate with another cell?
- How is our normal body functioning dependent upon cellular communication?
- What can happen when cell communication breaks down?
- What types of diseases occur as a result of a breakdown of cellular communication?
- (They are communicating through the use of hormones.)
- (The messenger molecules are hormones.)
- (One cell might need to communicate with another in order to get the cell to perform a certain function.)
Tell students they will examine two diseases in which cellular communication has broken down. Diabetes is a disorder that results in a lack of correct hormonal signaling. Multiple sclerosis is a disease that results in a lack of correct nerve impulse signaling.
Provide each student with the worksheet: Diseases of Faulty Cell Communication. Students should use their esheet to go to and read the following articles and answer questions on the worksheet.
- Neuron Conversations: How Brain Cells Communicate
- About MS (National Multiple Sclerosis Society)
Have students follow the sequence: "What is MS", "What causes MS"...through "Diagnosis"
- Multiple Sclerosis Foundation
Have students go to each of the sections under MS Information.
- Normal Regulation of Blood Glucose
- What is Insulin?
- Introduction to Diabetes
- How is MS an example of a disease that results from faulty cellular communication?
- How is diabetes an example of a disease that results from faulty cellular communication?
Provide each student with the worksheet: Factors That Disrupt Cell Communication. Students should use their esheet to go to and read the following articles and answer questions on the worksheet:
- How does heroin interfere with neuronal communication?
- Why do heroin and other opiates affect the "pleasure" system in the brain?
- Why do you think heroin and other opiates become addictive?
- How can addiction be treated?
- How do endocrine disrupters interfere with hormonal signaling?
- What is DES? How has it impacted women?
- Why do you think endocrine disrupter can result in large, detrimental effects in such small concentrations?
- The same level of an endocrine disrupter may have no apparent effect on humans but cause deformities in other animals. Why might this be so?
Working in groups of 3-4, have students research the impact of a genetic disease or external drug on cellular communication. Provide each group with the worksheet: Researching Cell Communication.
The following is a list of possible research topics:
Good starting points for research include:
Each group should be provided 3-5 days to research in groups, using their worksheets as guides. Have groups present their findings to the rest of the class. They must address the questions posed in the Researching Cell Communication student sheet.
Alternatively, students can individually choose a topic, research the topic, and write a short essay. Students can also each draw colorful diagrams or cartoons depicting how hormonal or neural communications are disrupted in a particular disease or with a specific drug.
Have students review current research in cellular communication with special emphasis on disease treatment.
Have students research the different ways in which cells communicate with each other. Students can compare and contrast these situations. A class list of cellular communication can be compiled. This list can include the following types of information:
- Type of cell initiating communication
- Target cell/tissue/organ
- Method of communication
- Purpose of communication
- Other ways to characterize communication, such as are cells close together or far apart
Students can also:
- Draw an example of cell communication from one of the Web resources that have been examined.
- Label each part correctly; draw arrows that indicate the path of communication.
- Write a sentence that summarizes the importance of that communication both to the cell and to the larger organism.
Students can also research the EPA's Endocrine Disruptor Screening Program, its actions, and its initiatives.
The following sites can be used to develop further activities and/or extensions:
- Scientists Reveal Details Of Brain Cell Communication: Implications For Learning & Memory
- PBS: Probe the Brain