Cell Communication Flashcards
what is autocrine signalling?
cells signalling to themselves or identical versions of cells
- cells produce a factor that allows cells to signal to themselves.
- growth factors (ligands) bind to receptors of same cells / group of cells
- early development, cancer
what are the names of short and long range cell signals? ?
short range signals:
- contact dependent:
- paracrine
Long range signals:
- neuronal
- endocrine
explain contact dependent intercellular signalling
where does it exist?
contact-dependent:
- the target cell contains receptor and signalling cell has membrane bound signal molecule. direct contact with each other. no signals secreted
- e.g in embryonic development
explain paracrine intercellular communication
e.g. where found?
- signals secreted and diffuse a short distance. signal is local mediator
- signals stay close to signalling cell and bind to
explain neuronal signalling
- messages carried by axons to specialised junctions - synapses
- synapses are adjacent to the target nerve cells where chemical signals binds to receptors (post synaptic receptors)
- neurotransmiting
explain endocrine signalling
signals (hormones) can be secreted into the bloodstream
- cells which produce hormone are endocrine cells
- e.g. insulin
explain basic overview of intracellular signalling pathway
- extracellular signal molcule binds to specific receptor protein, activates series of intracellular signalling proteins
- intracellular signalling proteins interact with target proteins -> change behaviour within the cell
what do cells recieve signals for?
- survival
- division
- differentation
- if no surivial signals: apoptosis
what is acetylcholine?
how does acetylcholine work in cardiac and skeletal muscle?
- acetylcholine is a neurotransmitter
- cardiac muscle: inhibitory signal to descrease in contraction / bradycardia
- skeletal muscle: acts as excitatory signal to induce contraction
SAME LIGAND, BUT DEPENDING ON WHICH TARGET CELL - VERY DIFFERENT EFFECT
explain what acetylcholine does in cardiac muscle
acetylcholine triggers membrane hyperpolarisation (moving away from potential to trigger activation)
- acetylcholine binds to acetylcholine receptor on heart muscle (called muscarinic receptor)
- muscarinic receptors are G protein coupled receptors that activate ionic channels via a second messenger cascade
- this causes hyperpolarisation and a decrease in cardiac activity
explain effect of acetylcholine on skeletal muscle?
acetylcholine triigers membrane depolarisation in skeletal muscle
- acetylcholine binds to skeletal muscle cell receptors called nicotinic acetylcholine receptors (nAChR)
- depolarisation occurs (action potential more likely to happen)
- contraction of skeletal muscle
explain acetylcholine effect on acinar cells
- same receptor (mAChR) as cardiac muscle cells
- acetylcholine binds to mAChr
- activates the secretion of digestive molecules
where do u find acincar cells?
many exocrine glands:
-
the stomach[1]
the sebaceous gland of the scalp
the salivary glands of the tongue[2]
the liver
the lacrimal glands
the mammary glands
the pancreas[3]
the bulbourethral (Cowper’s) glands
is differntial effect of cell-signalling always because of different receptor differences?
NO
- differences in internal machinery causes different effects
(e. g. mAChR in cardiac and acinar cells causes different effects despite being same receptors)
what are second messengers?
Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules
- need to be switched on / off
what is cAMP ?
what activated / deactivated by?
(cyclic adenonsine 3’5’ monophosphate) cAMP - secondary messenger
- activated / generated from ATP by the enzyme adenylyl cyclase
- cAMP degraded / inactivated by enzyme phosphdiesterase
what does cAMP stimulate?
- stumulates protein kinase A (PKA) PKA aka cAMP-dependent protein kinase
PKA
2 subunits:
- catalytic subunit: carries out phosphorylation
- regulatory subunit
how do you switch on / off PKA?
switch on: cAMP binds
switff off: cAMP leaves
whats the mechanism of calcium ions being used as an intracellular messenger?
- calcium ions are stored in the ER
- calcium enters cytoplasm via transmembrane calcium channels or via channels in the ER
- calcium ions can bind to proteins and trigger events within the cell
- after events occurred, calcium signals are deactivated by pumping ions back into ER or out of cell
