Signalling Flashcards
Stages of Signalling
- Generic Signalling Molecule Must be Produced
- Molecule is sometimes packaged for later use
- Molecule is released from the sending cell and travels for the target/receiving cell
- Molecule is detected by target cell and response is elicited
- The molecule itself is terminated
Autocrine Signal
Form of cell signalling that acts on the same cell that secreted them (short-distance signal)
Paracrine Signal
Secreted by one cell and diffuse to adjacent cells (short-distance signal)
(Feedback loop)
Endocrine Signal
Hormones are secreted by endocrine glands or cells into the blood. Only target cells with receptors for the hormones respond to the signal (long-distance signal); receiving cell must be extremely sensitive to the signal for response to occur
Neuronal Signal - Neurotransmitters
Chemicals secreted by neurons that diffuse across a small gap to the target cell (long-distance signal)
Neuronal Signal - Neurohormones
Chemicals released by neurons into the bloodstream for action at distant targets (long-distance signalling)
Short-distance Signalling
Distance travelled often very limited (gap junctions, contact dependent, autocrine types)
Long-distance Signalling
Either electrical signals passing along neurons or chemical signals that travel through the circulatory system (endocrine, nervous system signalling); generally slower, may require a way to stabilize far-travelling signalling molecules
Synaptic Signalling
Occurs at a specialized area on neurons; allow for a rapid local release of signal molecules to communicate with adjacent neurons (molecule must be stable)
Signal Transduction Pathway
Signal molecule binds to -> membrane receptor protein -> activates intracellular signal molecules -> after target proteins -> create response + termination
Intracellular Signal Receptors
Receptor proteins found on the inside of the cell (cytoplasm or nucleus). The ligands of intracellular receptors are small, hydrophobic molecules, since they must be able to cross the plasma membrane in order to reach their receptors; slower responses related to changes in gene activity .. thyroid hormones, glucocorticoids, mineralocorticoids and the sex steroid hormones
Cell Membrane Receptors
Extracellular signal molecule binds to a cell membrane receptor; rapid cellular response
Dose-response Curve
Derived from testing a biological response to a stimulus with a range of doses of that stimulus. The characteristics of the resulting curve can be used to infer how the stimuli and responses are related - multiple responses to derive curve
Why are controls in experiments needed?
To ensure that the effect you see is due to the experimental manipulation you have carried out
Positive control
Use a manipulation that you are confident WILL give you the effect you want to observe (a known drug, antagonist, protein of specific size, etc)
Negative control
Use something that you are reasonably confident WILL NOT result in the effect (saline, medium, vehicle, etc)
Structural Experimental Approach
Measurement or assessment of structures; describes properties, presence, location, sequence… who? what? where? how much? is it there?
Functional Experimental Approach
Behaviour of the system; demonstrates activities/actions of structures, changes under different conditions, overtime, etc… when? how? what happens when?
Mast Cells
Blood cells part of the immune system; live longer than normal cells. Play an important role in how the immune system responds to certain bacteria and parasites and they help control other types of immune responses. They contain chemicals such as histamine, heparin, cytokines, and growth factors
In Vitro - cell culturing
Performed with microorganisms, cells, or biological molecules outside their normal biological context; single cells or cell lines
Pro of In Vitro
Exquisite control over environment and cell properties
Con of In Vitro
Difficult to generalize to more complex biological conditions; responses that can be measured are not always obvious
Ex Vivo - Ussing Chamber
Takes samples of tissues from living systems and place them into a controlled environment in which the responses can then be monitored while conditions are changed; tissues, organs, or membranes, & organ baths, using chambers
Pro of Ex Vivo
Multiple cell types involved (cell-to-cell interactions expected)
Con of Ex Vivo
Does not allow for endocrine or neuronal control
In Vivo
Involve a whole animal or a human. Whole organism studies reflect the real situation much better than the other levels of analysis
Pro of In Vivo
Whole organism and all cell types can be involved; animals can be purchased with specialized properties (engineered mice)
Con of In Vivo
Very complex interactions can make results difficult to interpret; often ethically and financially challenging to perform
Different levels of analysis
- In Vitro - experiments with cells usually have the most controlled experimental conditions but are less directly relevant to humans
- Ex Vivo - work with tissues and organs retains some of the features of experimental control but allows for interactions between cell types
- In Vivo - work is much more representative of whole organism physiology, can either stay with a more controlled environment (animal) or move into clinical work (humans)
Degranulation of Mast Cells
Release of the contents of the granules (histamine) in mast cells
Signal Amplification
Process in which the strength of the signal is increased, this signal will be able to produce multiple responses; the activation of numerous molecules after binding one signal molecule to the receptor
Gap junction signals
-form of cytoplasmic connections between adjacent cells
-occurs when cells are close
Contact dependant signals
-require interaction between membrane molecules on 2 cells
-molecule of 1 touches the receptor of the other
