Cell to cell communication Flashcards
Semester 1 year 1
Who discovered that acetylcholine acts as a chemical mediator and how?
-Loewi: stimulate vagus nerve of donor heart so heart rate slows. Remove fluid sample and add to recipient heart - heart rate slowed
What is a mediator?
A chemical, peptide or protein that conveys information from one cell to another
What does a mediator do?
It’s released and produces a biological response as a result of a stimulus
What are the criteria to establish a substance as a mediator?
-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
Are chemical mediators intra or extracellular?
Extracellular signal molecules
What is cell signalling?
Chemical mediators travel through organism and bind to specific receptors on target cells, initiating an intracellular signal that alters cell behaviour through effector proteins
What is signal transduction?
Converting an extracellular signal to an intracellular signal
What are the 5 main types of intercellular communication?
-contact dependent
-paracrine
-autocrine
-synaptic
-endocrine
What is contact-dependent intercellular communication?
-Cells have to be in contact with each other
-shortest range of all cellular communication
-used in development and immune response
What is paracrine intercellular communication?
-a local mediator diffuses from one cell to another close cell
-mediators stored in vesicles (released by exocytosis) or synthesised on demand
Why do substances that move across the membrane easily need to be made on demand?
They would move out of the cell at anytime if they were made continuously
What is autocrine signalling?
Releases signals that then bind to receptors on the same cell
What is synaptic intercellular signalling?
-signal passed between neurons across a synapse
-restricts signalling to specific target cells
-fast signalling
-the mediators are neurotransmitters
What is endocrine intercellular signalling?
-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
What is the synthesis of small molecular mediators regulated by?
Specific enzymes - mediator production of the cell is dependent on which enzymes are active
What is the synthesis of peptides regulated by?
Transcription
How are pre-formed mediators stored and released?
-stored in vesicles
-They are released by exocytosis
-can pack them into high concentrations
-allows for rapid communication
-includes small molecular mediators + peptides
How are on demand mediators released?
Diffusion or constitutive secretion (occurs all the time, not in response to stimulus)
In the release of both pre-formed and on-demand mediators, what triggers the movement of vesicles?
Calcium ions
Why must neurotransmitter action be terminated?
Ensure the neurotransmission accurately represents action potential frequency
What are 2 ways that neurotransmitter action is terminated?
-enzymes
-uptake of neurotransmitter back into neurons or supporting cells
How do enzymes terminate neurotransmitter action?
acetylcholinesterase is at cholinergic synapses
How does the uptake of neurotransmitter into neurons or supporting cells terminate neurotransmitter action?
-specific transports in membrane for different neurotransmitters
-vesicle transporters load transmitters into synaptic vesicles
