AP Biology 4.1 Cell Communication

We've discovered now that cells can't get too large and, instead, large organisms are composed of many small cells. But how do these cells "talk" to each other and relay information about what other cells are doing and how to keep the entire being moving? Cells communicate by generating, transmitting, receiving, and responding to chemical signals. Use logic and root words to determine which type of signaling is which and then we'll discuss what it does in more detail Self Signaling autocrine self signaling - internal signals Some cells communicate by direct contact cell-cell contact physically touching another cell Some cells communicate over short distances by using local regulators that target cells in the vicinity paracrine short local signals (like muscles to nerves or nerves to nerves) Some cells release signals that travel long distances to target cells of another cell type endocrine glands to glands, or glands to systems Direct Cell-to-cell Contact In the case of the immune system cells interact by physically touching to the markers on the cells surface.In this image you can see how a cell who has been infected demonstrates this information so that the immune system can recognize the infection. The antigen (bit of digested bacteria) is captured and displayed on the cells surface by an MHC (major histocompatibility complex protein). This cell is now considered to be an Antigen Presenting Cell (APC) and the immune system will interact directly with the MHC to launch a response.This can then lead to a complex multi-faceted attack against the invader Match the terms from the direct contact example to their correct definition or explanation. APC A cell that is showing that it has a foreign antigen MHC A "snapshot" of the cells interior that can display foreign bits Cytotoxic T Cell Also known as a natural killer cell it recognizes APCs by their MHCs and secretes perforin to perforate and kill the infected cell Helper T Cell sends out signals (cytokines) to alert the immune system to an invader activating B cells and NK cells B cells Clone cells that can disable invaders and launch rapid responses against future invasions. Sketch an image of immune system response to invader using B cells and T cells Secondary Immune Response Your body doesn't naturally carry a ton of every type of antibody it may need to have. HOWEVER, after exposure to a particular antigen the body increases the production of that particular antibody so it can be prepared for future invasion. Sketch immune system response to mRNA vaccine What are some ways that our bodies fight off invaders? How does this compare to common side effects from vaccines? Another example of direct contact On the far right you'll see an example of a gap junction in animal cells. Gap junctions allow cells that are touching to trade cellular contents such as ions and mall molecules back and forth. This is similar to the small room between myself and Ms. Eighme. We don't have to leave our rooms to trade supplies - we have our own gap junction with our cells (I mean classrooms) directly touching each others. Paracrine Signaling Paracrine signaling is local, short lived, signaling.A great example of this is with neurotransmitters in the nervous system.The neurotransmitters released from one axon's terminal to the next neurons dendrites relay information across the small synaptic gap. Draw signal transmission between two neurons and label all processes. How specific is this process and can we accidentally (or purposefully) impact it? Check it out at this link and with our discussion on mental health.Mouse Party Let's check out some other cell communication examples.Get ready to have your mind explode! Bacteriua quorum So it's not just the type of signal but also the concentration of signal. Let's take a look at morphogens Morphogens are signals that diffuse across developing fetuses with the cells closest getting the largest dose and the cells further away getting a smaller dose. This gradient allows a cell to determine where it is and what it should be doing. An example would be in hand development where the pinky finger cells get the highest dose of morphogens and the thumb getting the least. The amount of morphogen each area receives signals how much to grow. Take a look at when this doesn't go right:The type of signal and concentration of signal is essential for normal development. Endocrine Signaling The final type of signaling is Endocrine. Endocrine signaling is long distance, long lived signaling. In your body specific glands produce hormones (long range signals) to alert other organs to do a task. For example, the pituitary gland (often known as the master gland) releases several types of hormones, each with their own destination. ADH (antidiuretic hormone) is a hormone produced by the pituitary gland that travels to the kidneys to stimulate water absorption.Even this master gland which controls so many functions has a regulator. The Hypothalamus links the nervous system and endocrine systems together to maintain homeostasis. It then sends signals to the pituitary gland to respond. Fill in the blanks from the table above regarding endocrine signaling. The adrenal gland produces adrenaline with allows you to respond in a fight or flight manner and later produces cortisol to calm your body back down. The pancreas regulates blood sugar levels (let's see if you can recall from our diabetes work earlier) releasing glucagon when the glucose levels are low stimulating the liver to release glycogen and, on the other hand, releasing insulin when the glucose levels are high stimulating the liver to absorb it from the blood stream. These are endocrine signals because a regulatory organ sends the signals long distance to trigger a different cell to perform a task. Human growth hormone (GH) is another example of a pituitary endocrine hormone that is responsible for stimulating bone growth. It also helps regulate body composition, fluids, muscle growth and metabolism.When GH is expressed in tissues it may signal the cell it's being produced from (an example of autocrine signaling) or cell that is close by (an example of paracrine signaling) The thyroid is another important endocrine gland. Research some consequences with having a thyroid that is hyperactive with a thyroid that is hypoactive. Hypothyroidism Hyperthyroidism Which type of cell communication would this qualify as?Plasmodesmata between plant cells allow materials to be transported from cell to cell. Autocrine Direct Contact Paracrine Endocrine What kind of communication is shown here Autocrine Paracrine Endocrine Density dependent signaling such as that in V. fischeri is an example of autocrine paracrine endocrine