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Cell to Cell Communication

A webquest exploring the Endocrine and Nervous Systems

Background info: Your body is composed of trillions of cells all working together to perform all your necessary functions. Communication between those cells is vital. Recall that 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.

Procedure: Read the first three paragraphs of the Scientific American article: Cell Communication: The Inside Story, including the introductory illustration.

Next, read the following passage from the June 17, 2000 Scientific American (no longer available online): Getting a Line on Human Diseases

A surprising number of human disorders involve aberrant (unusual) signaling in cells. Cancer, marked by uncontrolled cell proliferation and migration, is a prime example. At its root, cancer results from genetic mutations. Certain of those mutations work their mischief by leading to the overactivity of proteins in signal-relaying pathways within cells--notably, in pathways that normally induce the cells to divide in response to external commands. The affected proteins cause cells to behave as if other cells were constantly telling them to reproduce even when no such orders were sent.

Signal blockers are already in use against breast cancer, and more are under development. For instance, recent clinical trials suggest that a drug able to halt excessive "talk" by an enzyme called Abelson tyrosine kinase might help treat particular forms of leukemia.

Overzealous signaling is similarly destructive in an inherited syndrome known as X-linked lymphoproliferative (XLP) disease. In XLP patients, the normally benign Epstein-Barr virus sparks a deadly runaway response by "killer" T cells of the immune system.

Two years ago investigators found the reason for that lethal overreaction. People with XLP turn out to be missing a small protein termed SAP, which consists of a single SH2 domain (related to the SH2 domains mentioned in the main article). When killer T cells detect that other cells have become infected by the Epstein-Barr virus, they switch on an internal signaling cascade that enables them to attack the infected ones. Usually SAP keeps the attack under control--by sheathing interactive sites on some of the signaling components and thus breaking the signaling chain. But without SAP, XLP patients lack an important inhibitor of T cell hyperactivity.

Disease can also arise when intracellular signaling systems that should be busy are too quiet, as happens in various disorders involving inadequate immune responses. Insufficient signaling occurs as well in type 2 (maturity-onset) diabetes. Muscle and fat cells of the body take up sugar from the blood only after being told to do so by insulin sent from the pancreas. If insulin receptors on those cells fail to deliver insulin's message to relay molecules inside, diabetes (abnormally high blood sugar levels) can result. Oral medications designed to increase the activity either of the insulin receptor or of later players in the signaling cascade could potentially replace therapeutic insulin injections for some diabetics. One such compound, which stimulates the insulin receptor, has been tested successfully in mice.

Bacteria and viruses are experts at exploiting the signaling systems of human cells to spread and reproduce. This capacity is especially evident in such bacteria as Yersinia pestis, which caused the "black death" plague of the 14th century, and in disease-causing strains of Escherichia coli. The microbes inject their own proteins into human cells. Some of these proteins alter signaling pathways in ways that can both promote the association of the bacteria with a host's cells and disarm the cells' antibacterial defenses.

Viruses, for their part, often gain entry into human cells by attaching to receptors that head signaling circuits; then they may modify a cell's internal communication networks to enhance their own replication and release. The human immunodeficiency virus (HIV), the cause of AIDS, is one of many viruses that act in these nefarious ways.

As the links between signaling abnormalities and disease become clearer, therapies that repair or compensate for those disruptions should become increasingly commonplace.

After reading these two articles cut and paste these questions to a new WORD document and put your responses in a COLOR so I can easily see them. Remember to save your work in your student folder so you can email it to me when you are finished!

  • 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?

The remainder of this webquest will have you examining 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. Click on each of the links below, read the information and answer the questions. Again, cut and paste this section into your word doc so you can just type in your responses. Please type your answers in color so that I can read them easily.

How Do Nerve Cells Communicate? (Medical Research Council)

  • Describe how neurotransmitters relay messages from one neuron to another.

About MS (National Multiple Sclerosis Society)
Follow the sequence: "What is MS", "What causes MS"...through "Diagnosis"

  • Describe how Multiple Sclerosis (MS) occurs.
  • How can MS affect people physically?

Multiple Sclerosis Foundation (FAQs)

  • How many people in the US are diagnosed with MS every year?
  • Why is MS known as an “autoimmune” disease? What tissues are specifically targeted in the case of MS?

Normal Regulation of Blood Glucose

  • What are the two hormones that regulate blood sugar?
  • Which endocrine gland produces the two hormones?
  • When blood sugar is high, which hormone is secreted?
  • Which cells and/or tissues does this hormone target?
  • When blood sugar is low, which hormone is secreted?
  • Which cells and/or tissues does this hormone target?

What is Insulin?

  • When insulin is released into the bloodstream, how does it signal to cells in the body to take up glucose?
  • Describe Type 1 diabetes.
  • Describe Type 2 dieabetes.
  • Explain how insulin is manufactured currently.

Introduction to Diabetes

  • How many people in the US are affected by diabetes?
  • What body tissues and/or organs can be affected in diabetes?

As you finish this series of questions, reflect on what you have learned…

  • 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?

Next, we will look at the factors that disrupt cell communication. Click on and read the following articles: Answer the questions following each article…don’t forget to cut and paste into your word doc!

Neuroscience for Kids: Heroin

  • What is the chemical name for heroin?
  • From which plant is heroin made? In what parts of the world is this plant found?
  • The receptors for heroin and other members of this class of drugs are located on neurons of parts of the brain. What aspects of human life do these parts of the brain control?
  • What are endorphins? When are they released?
  • What other drugs besides heroin are produced from the opium plant?
  • What are some long and short-term effects of heroin use?
  • Heroin and other opiates interfere mostly with what neurotransmitter in the brain?

Endocrine Disrupters

  • How have animals been affected by endocrine disruptor chemicals spilled by humans?
  • Describe the four types of endocrine disruptors with molecular structures similar to that of hormones.
  • Why are small does of endocrine disruptors so dangerous to animals?
  • Describe the three ways endocrine disruptors can interfere with normal hormonal signaling?
  • How did DDT affect hormonal signaling in eagles and peregrine falcons?

After reading these two articles, reflect on what you have learned and answer the following:

  • 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?

Implications for humans:

Visit the US Fish andWildlife Services article and watch the accompanying video. What do you think of the possibility of the endocrine disrupters affecting humans?

Lastly, visit this website dedicated to women’s health. As most endocrine disrupters are mimicking estrogen, the effects on women are THOUGHT to be more dangerous than that of men (men do have some estrogen in their bodies, but not nearly as much…)

List your final thoughts here…or list 3 questions you still have after all this research.

Adapted from