cell to cell communication Flashcards
what is defined as a mediator
-a chemical, peptide or protein that conveys information from one cell to another
when is a mediator released
-in response to a stimulus
-the releases causes a particular kind of response e.g. contraction
what classes something as a mediator
-released from cells in sufficient amounts to produce a biological action upon target cells within an appropriate time frame
-application of an authentic sample of the mediator reproduces the original biological effect
-interference with the synthesis, release or action (e.g. using receptor sensitive drugs) ablates or modulates the original biological response
what are the general principles of chemical communication and cell signalling
1) chemical mediators= Extracellular signal molecules such as hormones or neurotransmitters
2)these bind to specific receptors on target cells
3)initiates intracellular signals that alter cell behaviour through effector proteins AKA cell signalling
what’s signal transduction
-process of converting extracellular signal to an intracellular signal
what are the main types of intercellular communication
-contact-dependent
-paracrine
-synaptic
-endocrine
what’s contact-dependent signalling
-cells have to be in contact with one another
-can be quick
-shortest range of all types of cellular communication
-e.g. immune response of T cell receptors interacting with receptors on the antigen present cells
what’s paracrine signalling
-diffuses from one cell to another
-either created in advance or stored in vesicle depending on its properties
-e.g. steroid hormone couldn’t be stored because it can easily pass along the cell membrane
-extracellular signal molecules act locally
-e.g. histamine: makes blood vessels expand when stung by activation sensory nerve ending,
Nitric oxide: simple gas, released by endothelial cell to muscle cells close by to relax them
eicosanoids (prostaglandins): involved in inflammation
what’s neuronal signalling
-uses specialised structures: synapses
-restricts signalling to specific target cells
-synapses can be short or long distances from neuronal body
-signalling is fast
-neurotransmitters= chemical mediators for neuronal signalling
-e.g. acetylcholine
what’s endocrine signalling
-secretion through the blood stream
-long distance: a cell signals to cells distributed widely in the body
-signalling molecules are secreted into bloodstream : hormones
-signalling is low and not specific
-hormones can be proteins, amino acid derived ( when you start with an amino acid and enzymes will modify the AA to a different substance) or a steroid
what are the two ways that chemical mediators occur
1) synthesis of small molecular mediators is regulated by specific enzymes- which mediators a cell produces will depend on which enzyme are active
2) synthesis of peptides is regulated by transcription- which mediators a cell produces will depend on which genes are active
how does storage and release of chemical mediators vary
1) mediators which are pre-formed (in vesicles, and released on demand), are stored in vesicles and released by exocytosis (pores open)
-molecules reach mM concentrations inside vesicles (really high)
-allows for ‘rapid’ communication
-can include small molecule mediators and peptides e.g. insulin
2) mediators produced on demand and released by diffusion or constitutive secretion
-takes longer (minutes-hours) e.g. nitric oxide
-exocytosis and diffusion in both is regulated by the calcium activity
termination of neurotransmitter action
-neurotransmitter action needs to be terminated to ensure neurotransmission is accurately representing the action potential frequency
-enzyme: acetylcholinesterase at cholinergic synapses
-uptake of NT back to neurone or supporting cells
