Signal transmission: definition, ways, examples | Biological Dictionary (2023)

Definition of signal switching

Signal transduction is the process of transmitting a signal through an organism, specifically through or through a cell. Signaling relies on proteins known asreceptorswaiting for a chemical, physical, or electrical signal. Chemical signals are calledLiganderand can be produced by organisms to control their bodies or obtained from the environment. Regardless of the type of signal, it must be transmitted throughout the body and across cell membranes. This process is called signal transduction. A general picture of signal switching is shown below.

Receptor proteins are specialized depending on the type of cell they bind to. Each cell type receives different signals from the body and the environment and must be specialized in order for the body to elicit a specific and coordinated response. Each of these specialized proteins has a specific method of signaling to the cell. Some proteins activate other molecules, so-calledother boats, which transports the message to the cell nucleus or other organelles. Other proteins use the energy from ATP to activate enzymes that carry out metabolic reactions. The different paths through which the signal switch transmits a signal are referred to assignal transduction pathways.

signal switching path

In signal switching, a signal can have many components. existschief messengerThis can be a chemical signal, an electrical impulse, or even physical stimulation. Then the receptor protein embedded in the cell membrane must receive the signal. Upon receiving the signal, this protein passes through aconformational change. This changes its shape and, with it, the way it interacts with the molecules around it.

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The many different receptor proteins work in different ways. Above is a simple representation of the many different signal transduction pathways in mammals. Don't let the complexity of the design overwhelm you. It is important to realize that all of these signal transduction pathways contain the same elements. A signal is received by a receptor protein, and the protein transmits the signal across the cell membrane into the cell. The types of receptors and the second messengers they produce can vary widely. This is based on the action you want the signal to stimulate. The next section provides some examples that will help illustrate the many differences and similarities between the paths.

Examples of signal switching

Touch and see

The signaling pathway for touch and vision works in the same way as many nerve signals. Instead of generating a second messenger or processing a signal internally, the stimulation of the receptor protein leads to an influx of ions into the cell. This creates the cell membraneDepolarisation. A normal cell membrane ispolarized, or is under tension. This voltage potential results from the cell drawing active ions out of the cell. Because ions are charged, their build-up in place can create a voltage. When only one protein receptor is stimulated, only a small portion of the membrane is depolarized.

However, when you receive a strong signal, such as when you press your finger on a surface or see a bright light, the entire membrane of many cells depolarizes at once. This event triggers aoptions for action, this is how the signal propagates in a nerve. This is mediated by a number of other receptor proteins that are sensitive to changes in voltage. When they sense the change in voltage, they also allow the ions to smooth out and send the signal through the cell.

When you reach the end of the first cell, the signal should cross aSynapseto another nerve cell. A different signal transduction pathway is used for this purpose. When the action potential reaches the end of the first cell, specialized receptor proteins receive the signal and trigger releaseNeurotransmitter. These small ligands travel through the space between cells, diffusing into the fluid and reaching receptor proteins in the next cell. These receptors are tooclosed ion channelsand when activated, cause another action potential in the next nerve. This is how a signal can travel from your finger or eye to your brain in microseconds.


Unlike touch and sight, hormones are signals your body creates to regulate itself. Hormones can cause the body to do many different things, and are often themselves triggered through a separate signal transduction pathway.

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Typically, a hormone is released by an endocrine gland such as the thyroid or pancreas. These hormones control everything from metabolism to growth. The signals they transmit are almost always transmitted via a ligand-receptor signal transduction pathway. The reproductive organs also release hormones that prepare the body for reproduction. They work in the same way, which will be discussed below.

By activating hormone secretion, the cells of the endocrine glands release their stored hormone that they have built up over time. They do this by causing hormone-filled vesicles to fuse with the cell membrane and release the hormone into the intracellular space.capillariesSmall blood vessels run through this space. The hormone dissolves in the bloodstream and can be transported from there throughout the body.

Some cells have specific receptors that can activate different signaling pathways when receiving a signal. For example, the hormone insulin can cause muscle cells to take up and store glucose while liver cells stop producing glucose. This helps regulate the total amount of glucose in the blood. The receptors in these different tissues both accept insulin as a ligand, but the signal transduction pathway is different. One pathway stimulates a cellular process in muscle cells that increases the number of glucose transporters in their cell membrane. The second signal transduction pathway in the liver inactivates a key enzyme required for glucose production.


1. Which of the following is NOT an example of signal switching?
IN.A molecule found in the blood binds to a protein in a shark's olfactory cells. A signal is sent to the brain.
AND.Cow's milk contains growth hormones. By absorbing these hormones, a baby cow's cells grow and divide.
AGAIN.A cell uses the energy of a glucose molecule to power other reactions.

Answer to question #1

Againthat's right. In response C there is no receptor and no signal is sent. Cells use many molecules and rearrange them in a variety of ways. Signal transduction refers to the instances where a molecule or signal elicits a response or series of responses. This is sometimes calledSignal cascade.

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2. Why is it necessary that different cell types have different receptors for the same ligand or hormone?
IN.Different cells have to react differently
AND.It is not necessary
AGAIN.Different receptors receive different types of ligands

Answer to question #2

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INthat's right. Different cells in an organism must respond differently to the same signal in order to coordinate multiple events. In order to lower blood sugar levels, the cells must take up glucose and the liver must stop producing it. Ligands like carbon dioxide cause your blood vessels to dilate and your breathing to speed up. It is this coordinated response of different tissues that produces the most efficient and adaptable organisms.

3. A particular plant species in the Australian region has evolved an interesting defense involving signal transduction pathways. When herbivores feed on it, it gives off a gas into the air. The gas reaches neighboring plants and stimulates receptors that cause the cells of those plants to produce toxins. Which mammalian protection is most similar?
IN.A mouse biting a predator to escape
AND.Prairie dogs call out to each other when a hawk is done
AGAIN.A skunk that emits a poisonous odor when attacked

Answer to question #3

andthat's right. This behavior in plants is more akin to defensive behavior when loudly calling out to mates in wildlife. The signal does not represent a direct defense for the predator, it merely prepares neighboring individuals for an attack. This is one of the best documented cases of plant communication.

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bibliographical references

  • Lodish , H. , Berk , A. , Kaiser , C. A. , Krieger , M. , Scott , M. P. , Bretscher , A. , . .... .... Matsudaira, P. (2008).Molecular Cell Biology(6th edition). New York: W.H. Freeman and Company.
  • McMahon, M.J., Kofranek, A.M., and Rubatzky, V.E. (2011).Plant Sciences: Development, growth and use of crop plants(5th edition). Boston: Prentice Hall.
  • Nelson, D. L. & Cox, M. M. (2008).principles of biochemistry.New York: W.H. Freeman und Company.


Signal transmission: definition, ways, examples | Biological Dictionary? ›

Signal transduction pathways involved in the regulation of insulin are one such example. If the hormone is needed by muscle cells (to aid in increased physical activity, for example) then the pathway will signal for an increase in glucose transporters in the cell membrane.

What is an example of signal transduction? ›

Signal transduction pathways involved in the regulation of insulin are one such example. If the hormone is needed by muscle cells (to aid in increased physical activity, for example) then the pathway will signal for an increase in glucose transporters in the cell membrane.

What is signal transduction for dummies? ›

Signal transduction is the process in which binding of an extracellular messenger to the cell surface receptor is translated into changes in biochemistry, cell biology, and gene transcription that make it possible for the cell to respond to the information that was received.

What are the different ways of Signalling? ›

Forms of signaling

There are four basic categories of chemical signaling found in multicellular organisms: paracrine signaling, autocrine signaling, endocrine signaling, and signaling by direct contact.


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