Cell Signalling and the Endocrine System Flashcards
what is the function of a ligand-gated ion channel
when activated, by binding of a ligand/hormone, they will allow movement of ions in or out of the cell
(ie depolarisation or hyperpolarisation of plasma membrane)
(occurs in milliseconds)
in what direction do ions move through a ligand-gated ion channel
down the conc. gradient, ie from area of higher charge to lower
what types of endocrine receptors are membrane-bound
ligand-gated ion channels, G-protein coupled receptors(GPCR), Kinase-linked receptors
describe the general mechanism of a G-protein coupled receptor(GPCR)
agonist(eg hormone) binds to receptor bringing conformation change of GPCR which allows activation of signalling response
give an example of a hormone and a GPCR in the endocrine system
adrenaline, binds to B2 adrenoreceptor which is a GPCR, activates signalling response of enzyme to convert ATP to cAMP, and ultimately results in bronchodilation
(occurs in seconds)
describe how the action of a GPCR ends
ends when GTP bound to the alpha-subunit hydrolyses to become GDP, so self-limits the action
what happens when the agonist/hormone dissociates from the GPCR
resets confirmation of GPCR, subunits return to original positions, ready to receive another agonist and repeat process
what is an adrenoreceptor
a receptor bound and activated by the neurotransmitters/hormones adrenaline and noradrenaline
what is the principal transduction of the a1 adrenoceptor(it is a GPCR)
Galpha-subunit q, activates phospholipase, which increase IP3 and DAG
what is the principal transduction of the a2 adrenoceptor
Galpha-subunit i, inhibits adenylyl cyclase, decreasing cAMP and Ca2+ channels, increasing K+ channels
what is the principal transduction of the B1, B2 and B3 adrenoceptors
Galpha-subunit s, stimulation of adenylyl cyclase, increasing cAMP
give an example of a hormone that is an agonist for Kinase-linked receptors
insulin
describe what happens when a hormone/agonist binds to a Kinase-linked receptors
dimerisation of receptor, with subsequent phosphorylation by ATP of tyrosine residues linked to receptor
what binds to the phosphorylated tyrosine residues in a Kinase-linked receptor action
relay proteins
describe the signalling response of a Kinase-linked receptor
diversified, different relay proteins bind to the tyrosine residues and illicit varied cellular responses
(response occurs in hours)
in order from fastest to slowest order the endocrine receptors
Ligand-gated(milliseconds), GPCR(seconds), Kinase-linked(hours)
what is autocrine regulation
when chemicals(ie signalling molecules) released from the cells bind to receptors on or in the cells they are released from
what is paracrine regulation
when chemicals(ie signalling molecules) released from the cells bind to receptors on adjacent cells
what is endocrine regulation
when chemicals(ie signalling molecules), released from the secretory cells are transported(usually by circulatory system) to target cells elsewhere in body
