Cell Communications Flashcards
what are the ways of cellular communication BETWEEN cells
electrical and chemical communication
what is electrical transmission?
direct contact via gap junctions
what do gap junctions allow?
flow of current from cell-cell
what is a syncytium?
linked cells acting together as one unit
where is chemical transmission used?
cell-cell and cell-several cells and many cells-many cells
where is cell-cell chemical transmission used?
synpase
where is cell-several cells chemical transmission used?
paracrine
where is many cells-many cells chemical transmission used?
endocrine
describe the chemical synpase
cell-cell. Effect depends on transmitter and the receptor it acts on. One way transmission.
where is chemical synapse common?
nervous system
what is the first step in the chemical synapse?
impulse arrives at terminal of presynaptic cell
what is the second step in the chemical synapse?
transmitter released from storage vesicles
what is the third step in the chemical synapse?
transmitter diffuses in synaptic cleft
what is the fourth step in the chemical synapse?
transmitter binds to receptor on postsynaptic cell
what alters the postsynpatic cell?
excitatory/inhibitory
what is paracrine communication?
one cell-several cells. can be part of a cascade of reactions
what cells often use paracrine communication?
Defence cells
what is autocrine communication?
where chemical acts on cell releasing it (feedback)
what is endocrine transmission?
chemical sent to all parts of the body via the blood stream. hormone acts only on cells with the correct membrane receptor protein
describe nerve communication
actions often very specific or localised, quick impulse transmission and is suitable for rapid responses
give examples of communication by nerves
control of voluntary muscle contractions, sensory systems, salivary gland responses, control of blood pressure
where does communication by hormones (humoral) affect?
many cells in different parts of the body
describe humoral communication
coordinated, body-wide actions. slow to act but effect persists
give some examples of humoral communication
gastro-intestinal gland responses, control of metabolism and growth, regulation of menstrual cycle
what can many intracellular signalling molecules act as?
second messengers
what are first messengers?
chemical transmitter which acts on a receptor
what can some first messengers do?
pass through the target cell membrane and act on receptors inside the target cell
what are steroids?
lipids that can pass through the outer cell membrane
what do steroids do?
act on receptors inside the target cell
what does the steroid-receptor complex do?
act on the DNA in the nucleus to initiate protein synthesis
what does the protein produced from steroid transmitters do?
alters cell function
can peptide transmitters pass through the cell membrane?
no
how do peptide transmitters transmit their signal?
they bind to the plasma membrane receptors and set up a series of reactions controlled by G-proteins
what do G-proteins do?
activate second messengers
give 2 examples of second messengers
Cyclic AMP (cAMP) and calcium ions (Ca++)
what is the first step in hydrophilic signal transmission?
the transmitter binds to a membrane receptor
what is the second step in hydrophilic signal transmission?
G-protein is activated
what is the third step in hydrophilic signal transmission?
guanosine triphosphate (GTP) activates the G-protein
what is the fourth step in hydrophilic signal transmission?
ATP is converted to cyclic AMP by the enzyme adenyl cyclase
what are steps 5 and 6 of hydrophilic signal transmission?
cAMP activates an enzyme called protein kinase
what is step 7 of hydrophilic signal transmission?
protein kinase activates a specific enzyme which catalyses a chemical reaction
what is step 8 of hydrophilic signal transmission?
formation of a molecule
what is step 1 of calcium as a second messenger
transmitter binds to a membrane receptor
what is step 2 of calcium as a second messenger
G-protein activates which activates the phospholipase enzyme which causes the opening of calcium channels and calcium enters by diffusion
what is step 3 as calcium as a second messenger?
calcium binds to a protein in the cytosol
what does Ca2+-calmodulin complex act as?
a second messenger
what is step 4 of calcium as a second messenger?
Ca2+-calmodulin regulates an enzyme which regulates a chemical reaction
