Modes of Cell Communication: Overview

by Georgina Cornwall, PhD

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    00:00 The way that signals work depends a lot on the distance. If there is a person right next to you that you're trying to talk to in this busy room, then you can just whisper to them right here.

    00:12 However if you want to get a hold of someone all the way across the room, you might have to travel across the room first, or you may even have to yell across the room in order to signal to them.

    00:22 Cells deal with this in much the same way. So we have direct contact, paracrine signalling, endocrine signalling and synaptic signalling. And even autocrine signalling which we'll investigate here.

    00:37 Direct contact, you'll recall we looked at gap junctions in our previous lecture. Gap junctions allow passage of material directly between cells. So, gap junctions allow for direct contact.

    00:53 The signal molecule doesn't have to go very far. It can go straight from the cytoplasm of one cell to the cytoplasm of the next cell. So the next mechanism that we can look at is paracrine signalling.

    01:06 And paracrine means sort of signalling your neighbour. So if we were to use sort of an analogy here, direct contact might be like holding someone's hand and saying "Hey" you know, "I mean this.

    01:17 Come over this way". Paracrine signalling would be sort of whispering to them or you might shout a little bit louder and reach them at a little bit further distance. But still we're dealing with neighbouring cells. So in paracrine mode of signalling, one cell is releasing signal molecules in order to signal a neighbouring cell. How far that signal can reach really depends on how quickly the signal is broken down or metabolized. So here, signalling neighbour cells local or a little bit further away but not too far away. Autocrine signalling is an interesting thing. Auto means self.

    02:02 So some cells actually signal themselves and this is used in development fairly often where one cell is going to secrete a product based on what's happening developmentally to almost give itself a checking balance and tell itself where it is developmentally and whether it needs to continue on this path or we're done with that stage. We also see autocrine signalling a lot in the immune system.

    02:29 The next mechanism we can look at is endocrine signalling. Endocrine signalling is really pretty cool.

    02:35 We have hormones that are released at a origin site. For example we might release them from the pituitary gland. And the hormones are released from the pituitary gland. They'll flow through the blood until it reach a target tissue, say the adrenal gland. So the pituitary gland is dangling right of the bottom of the brain and signal travels all the way through the bloodstream and ends up eliciting a response at any cell that has a receptor for it. So in the case of the adrenal glands, it would have to have a cell that had receptors for the particular hormone that's dropped into the system. The final mode of signalling that I'll introduce is synaptic signalling. This is what neurons use to communicate with their cells.

    03:25 The cell body will be located say at the spinal cord and the axon will extend to a distant target.

    03:32 And that axon will synapse on a target cell. So the end of the axon will drop off some kind of signal molecule.

    03:42 Perhaps it's acetylcholine. We're looking at muscle contraction maybe. And then it will bind to the target cell receptors and elicit an effect in its cell. So these are cell surface receptors. When we were considering the endocrine system, sometimes those are going to be, almost often those are going to be intracellular receptors for steroid hormones. So, tying those two concepts together. So not that we've considered how signals arrive at a cell, let's start thinking about what happens after they arrive.

    04:15 How do these signal transduction pathways work to elicit some sort of cellular response? So once a signal arrives at a cell membrane and binds to the receptor, we could have a number of different options. We could have either a single response. For example if we have the glucagon receptor, glucagon is all about releasing blood sugar. Either way, whatever cell glucagon signals it should be releasing blood sugar. So a single response of releasing blood sugar. Or you could have a variety of different responses depending on the cell type. For example, in epinephrine, epinephrine causes a number of different responses. Our eyes may dilate, our heart may start to beat more strongly, we may start to sweat, So each of those cells has a different response to the same signal molecule whereas with glucagon, well its all about releasing blood sugar no matter which pathway you take to get there.

    05:20 So many of the systems that we'll look at are second messenger systems. We'll take a deeper look at those in the next lesson although we're going to introduce them briefly in this lesson.

    About the Lecture

    The lecture Modes of Cell Communication: Overview by Georgina Cornwall, PhD is from the course Cellular Structure.

    Included Quiz Questions

    1. True
    2. False
    1. Paracrine signaling is intercellular communication where the target cells lay in the vicinity of the produced cell.
    2. The spatial range of a paracrine signal is dependent on the rate of its metabolism in the cell surroundings.
    3. Neurotransmitters, growth factors, and clotting factors fall under the category of paracrine signals.
    4. All human hormones belong to the paracrine signaling system.
    5. Gap junctions allow the escape of paracrine signal molecules directly from the cytoplasm of one cell to the other.
    1. The autocrine signaling in the nervous system helps in the development of stronger connections between muscle cells and axons of the neurons.
    2. The autocrine signal system is a self-cell based developmental balance check system to regulate the cell development cycle.
    3. The cell-mediated immune response of the immune system is a perfect example of autocrine signal based communication.
    4. Auto signaling plays a crucial role in the cancer development and its self-sustainable growth.
    5. In autocrine signaling, the cell produces the autocrine molecules which bind to its own cell membrane autocrine receptors.
    1. …acetylcholine (ACh) acts as a signal molecule.
    2. …K+ and Na+ ions act as signal molecules.
    3. …ATPase protein serves as a signal molecule.
    4. …nucleotides act as signal molecules.
    5. …either acetic acid or choline act as a signal molecule.

    Author of lecture Modes of Cell Communication: Overview

     Georgina Cornwall, PhD

    Georgina Cornwall, PhD

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