Cell Communications Flashcards
where can cellular communication occur?
between cells
-chemical
-electrical
within cells
describe how electrical transmission happens between cells?
direct contact via gap junctions
what do gap junctions allow?
flow of current to go from cell to cell
describe features of electrical transmission between cells.
-rapid transmission in both directions
-linked cells can act as 1 unit (syncytium)
eg. cardiac and some smooth muscle
describe 3 types of chemical transmission.
cell to cell = synapse
cell to many cells = paracrine
many cells to many cells = endocrine
describe 3 types of chemical transmission.
cell to cell = synapse
cell to many cells = paracrine
many cells to many cells = endocrine
describe cell to cell chemical transmission through a synapse.
-effect depends on transmitter and the receptor it acts on
-one way transmission
-common in nervous system
describe the sequence of events in cell to cell chemical transmission through a synapse.
- impulse arrives at terminal of presynaptic cell
- trfansmittwe released from storage vesicle
- transmitter diffuses in synaptic cleft
- transmitter binds to receptor on postsynaptic cell
- alters post synaptic cell
what happens in cell to cell chemical transmission when the transmitter alters the post synaptic cell?
‘excitatory’ eg. impulse generated; muscle contracts; gland secretes
‘inhibitory’ cell is switched off
describe paracrine communication.
- one cell communicates with several cells locally
- often used by defence cells (inflammation)
- can be part of ‘cascade’ of reactions
describe autocrine communication.
chemical acts on cell releasing it (feedback)
describe endocrine transmission.
chemical sent to all parts of body via blood stream
hormone acts only on cells with correct membrane receptor protein (target cells)
which is better for communication in organisms, nerves or hormones?
not have advantages and disadvantages depending on circumstances.
describe communication by nerves.
actions specific or localised.
quick impulse transmission.
suitable for rapid responses.
give examples of communication by nerves.
- control of voluntary muscle contraction
- sensory systems
- salivary gland response
- control of blood pressure
describe communication by hormones.
affect many cells in different parts of body.
coordinated, body-wide actions.
slow to act by effect persists.
give examples of communication by hormones.
- gastro-intestinal gland responses
- control of metabolism and growth
- regulation of menstrual cycle
what is the first messenger in intracellular communication?
chemical transmitter which acts on receptor protein.
how do first messengers act on receptors in intracellular communication?
passes through the target cell membrane and acts on receptors inside target cell.
can first messengers enter the cell in intracellular communication?
not all but some can
what are second messengers in intracellular communication?
various intracellular signalling molecules and pathways
what is transcription?
RNA converted to protein
what is translation?
translates DNA to mRNA to protein
what are steroid transmitters?
lipids that can pass through outer cell membrane
describe the process of steroid transmitters?
- act on receptors inside the target cell
- steroid-receptor complex acts on the DNA in nucleus to initiate protein synthesis
- protein then alters cell function
- these hormones have delayed action
can peptide transmitters pass through cell membrane?
no
out of steroid and peptide transmitters which one can pass through cell membrane?
steroid
how to peptide hormones work on receptors?
- bind to plasma membrane receptors and set up series of reactions controlled by ‘G proteins’
- these activate 2nd messenger systems
eg. cyclic AMP
calcium ions
describe the process of g-protein and cyclic AMP.
- transmitter binds to membrane receptor
- g-protein is activated by GTP
- ATP (in cytosol) is converted to cyclic AMP bye enzyme adenyl cyclase
- cAMP activates enzyme called protein kinase
- this activates specific enzymes which catalyses chemical reaction
- results in formation of molecule
describe the process of calcium as a 2nd messenger.
- transmitter binds to membrane receptor
- this activates g-protein which activates enzyme: phospholipase C
- this causes opening of Ca2+ channels and it enters by diffusion
- Ca2+ binds to protein in the cytosol, here it is calmodulin
- this regulates an enzyme which regulates a chemical reaction
name a Ca binding protein? what is it involved in?
troponin
involved in muscle contractions
