Cell to cell communication

Question 1

Who discovered that acetylcholine acts as a chemical mediator and how?

Answer 1

-Loewi: stimulate vagus nerve of donor heart so heart rate slows. Remove fluid sample and add to recipient heart - heart rate slowed

Question 2

What is a mediator?

Answer 2

A chemical, peptide or protein that conveys information from one cell to another

Question 3

What does a mediator do?

Answer 3

It’s released and produces a biological response as a result of a stimulus

Question 4

What are the criteria to establish a substance as a mediator?

Answer 4

-released from cells in sufficient amounts to produce a biological action within an appropriate time frame
-using an authentic sample of the mediator reproduces the original biological effect
-interference with the synthesis, release or action prevents the original biological response

Question 5

Are chemical mediators intra or extracellular?

Answer 5

Extracellular signal molecules

Question 6

What is cell signalling?

Answer 6

Chemical mediators travel through organism and bind to specific receptors on target cells, initiating an intracellular signal that alters cell behaviour through effector proteins

Question 7

What is signal transduction?

Answer 7

Converting an extracellular signal to an intracellular signal

Question 8

What are the 5 main types of intercellular communication?

Answer 8

-contact dependent
-paracrine
-autocrine
-synaptic
-endocrine

Question 9

What is contact-dependent intercellular communication?

Answer 9

-Cells have to be in contact with each other
-shortest range of all cellular communication
-used in development and immune response

Question 10

What is paracrine intercellular communication?

Answer 10

-a local mediator diffuses from one cell to another close cell
-mediators stored in vesicles (released by exocytosis) or synthesised on demand

Question 11

Why do substances that move across the membrane easily need to be made on demand?

Answer 11

They would move out of the cell at anytime if they were made continuously

Question 13

What is autocrine signalling?

Answer 13

Releases signals that then bind to receptors on the same cell

Question 13

What is synaptic intercellular signalling?

Answer 13

-signal passed between neurons across a synapse
-restricts signalling to specific target cells
-fast signalling
-the mediators are neurotransmitters

Question 14

What is endocrine intercellular signalling?

Answer 14

-substances released by cells and travel throughout blood
-long distance as cells signal to cells across the body, so slow signalling
-signalling isn’t specific
-the mediators are hormones
-hormones can be: protein, amino acid derived, steroid

Question 15

What is the synthesis of mall molecular mediators regulated by?

Answer 15

Specific enzymes - mediator production of the cell is dependent on which enzymes are active

Question 16

What is the synthesis of peptides regulated by?

Answer 16

Transcription

Question 17

How are pre-formed mediators stored and released?

Answer 17

-stored in vesicles
-They are released by exocytosis
-can pack them into high concentrations
-allows for rapid communication
-includes small molecular mediators + peptides

Question 18

How are on demand mediators released?

Answer 18

Diffusion or constitutive secretion (occurs all the time, not in response to stimulus)

Question 19

In the release of both pre-formed and on-demand mediators, what triggers the movement of vesicles?

Answer 19

Calcium ions

Question 20

Why must neurotransmitter action be terminated?

Answer 20

Ensure the neurotransmission accurately represents action potential frequency

Question 21

What are 2 ways that neurotransmitter action is terminated?

Answer 21

-enzymes
-uptake of neurotransmitter back into neurons or supporting cells

Question 21

How do enzymes terminate neurotransmitter action?

Answer 21

acetylcholinesterase is at cholinergic synapses

Question 22

How does the uptake of neurotransmitter into neurons or supporting cells terminate neurotransmitter action?

Answer 22

-specific transports in membrane for different neurotransmitters
-vesicle transporters load transmitters into synaptic vesicles