Signalling

Question 1

Stages of Signalling

Answer 1

1. Generic Signalling Molecule Must be Produced
2. Molecule is sometimes packaged for later use
3. Molecule is released from the sending cell and travels for the target/receiving cell
4. Molecule is detected by target cell and response is elicited
5. The molecule itself is terminated

Question 2

Autocrine Signal

Answer 2

Form of cell signalling that acts on the same cell that secreted them (short-distance signal)

Question 3

Paracrine Signal

Answer 3

Secreted by one cell and diffuse to adjacent cells (short-distance signal)
(Feedback loop)

Question 4

Endocrine Signal

Answer 4

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

Question 5

Neuronal Signal - Neurotransmitters

Answer 5

Chemicals secreted by neurons that diffuse across a small gap to the target cell (long-distance signal)

Question 6

Neuronal Signal - Neurohormones

Answer 6

Chemicals released by neurons into the bloodstream for action at distant targets (long-distance signalling)

Question 7

Short-distance Signalling

Answer 7

Distance travelled often very limited (gap junctions, contact dependent, autocrine types)

Question 8

Long-distance Signalling

Answer 8

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

Question 9

Synaptic Signalling

Answer 9

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)

Question 10

Signal Transduction Pathway

Answer 10

Signal molecule binds to -> membrane receptor protein -> activates intracellular signal molecules -> after target proteins -> create response + termination

Question 11

Intracellular Signal Receptors

Answer 11

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

Question 12

Cell Membrane Receptors

Answer 12

Extracellular signal molecule binds to a cell membrane receptor; rapid cellular response

Question 13

Dose-response Curve

Answer 13

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

Question 14

Why are controls in experiments needed?

Answer 14

To ensure that the effect you see is due to the experimental manipulation you have carried out

Question 15

Positive control

Answer 15

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)

Question 16

Negative control

Answer 16

Use something that you are reasonably confident WILL NOT result in the effect (saline, medium, vehicle, etc)

Question 17

Structural Experimental Approach

Answer 17

Measurement or assessment of structures; describes properties, presence, location, sequence… who? what? where? how much? is it there?

Question 18

Functional Experimental Approach

Answer 18

Behaviour of the system; demonstrates activities/actions of structures, changes under different conditions, overtime, etc… when? how? what happens when?

Question 19

Mast Cells

Answer 19

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

Question 20

In Vitro - cell culturing

Answer 20

Performed with microorganisms, cells, or biological molecules outside their normal biological context; single cells or cell lines

Question 21

Pro of In Vitro

Answer 21

Exquisite control over environment and cell properties

Question 22

Con of In Vitro

Answer 22

Difficult to generalize to more complex biological conditions; responses that can be measured are not always obvious

Question 23

Ex Vivo - Ussing Chamber

Answer 23

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

Question 24

Pro of Ex Vivo

Answer 24

Multiple cell types involved (cell-to-cell interactions expected)

Question 25

Con of Ex Vivo

Answer 25

Does not allow for endocrine or neuronal control

Question 26

In Vivo

Answer 26

Involve a whole animal or a human. Whole organism studies reflect the real situation much better than the other levels of analysis

Question 27

Pro of In Vivo

Answer 27

Whole organism and all cell types can be involved; animals can be purchased with specialized properties (engineered mice)

Question 28

Con of In Vivo

Answer 28

Very complex interactions can make results difficult to interpret; often ethically and financially challenging to perform

Question 29

Different levels of analysis

Answer 29

1. In Vitro - experiments with cells usually have the most controlled experimental conditions but are less directly relevant to humans
2. Ex Vivo - work with tissues and organs retains some of the features of experimental control but allows for interactions between cell types
3. 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)

Question 30

Degranulation of Mast Cells

Answer 30

Release of the contents of the granules (histamine) in mast cells

Question 31

Signal Amplification

Answer 31

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

Question 32

Gap junction signals

Answer 32

-form of cytoplasmic connections between adjacent cells
-occurs when cells are close

Question 33

Contact dependant signals

Answer 33

-require interaction between membrane molecules on 2 cells
-molecule of 1 touches the receptor of the other