systems and receptors Flashcards
what do G-protein coupled receptors do
activate adjacent enzymes like adenylyl cyclase
what happens when adrenaline binds to beta2adrenoceptor
conformational change that allows the alpha subunit to attach to receptor
-then alpha subunit is activated by exchange of GDP to GTP
what does alpha subunit do when it has a GTP
attach to adenylyl cyclase which then causes the change of ATP to cAMP
when does adenylyl cyclase switch off
when GTP attached turns back into GDP
where are alpha 2 adrenoceptors located
gut
what happens when adrenaline binds to the alpha 2 adrenoceptor
relaxation of the GI tract
what is the principle transduction of alpha 1
Galpha q - activation of phospholipase C increase IP3 and DAG
what is the physiological effect of the activation of alpha 1
vasoconstriction of blood vessels
principal transduction of alpha 2
Galpha i - inhibition of adenylyl cyclase, decreases cAMP, increase K channels, decreases Ca channels
principal transduction of beta 1
G alpha s - stimulation of adenylyl cyclase, increases cAMP
physiological effect of beta 1 activation
increased heart rate and cardiac muscle contraction
prinicpal transduction of beta 2
Galpha s - stimulation of adenylyl cyclase which increases cAMP
physiological effect of beta 2 activation
- dilation of bronchi
- increased HR and cardiac contraction (less than beta 1)
principal transduction of beta 3
stimulation of adenylyl cyclase which increases cAMP
physiological effect of activation of beta 3
thermogenesis in skeletal muscle and lipolysis
what is tyrosine activated by
ATP
does tyrosine produce more than one cellular response
yes
what is autocrine regulation
chemicals released from the cells bind to receptors on or in the cell that is releasing them
what is paracrine regulation
chemicals released from the cells bind to receptors on adjacent cells
what is endocrine regulation
chemicals released from the secretory cells are usually transported via the circulatory system
what provides the highest level of endocrine control
hypothalamus
how does the hypothalamus integrate activities of nervous and endocrine system
- secretion of regulatory hormones
- synthesises hormones and transports them to posterior pituitary via infundibulum
- direct neural control function - control secretion of adrenaline and noradrenaline
what are the diurnal control of hormone levels
- external cues evoke fluctuations in hormone secretions
- hormone levels are also influenced by the rate at which they are eliminated by the body
what does adrenaline cause the pancreatic alpha cells to do
release glucagon
how does stress affect glucose levels
increases them
what are the three groups hormones are classed into
- steroid
- amine-derived
- proteins
are steroids hydrophilic or hydrophobic
hydrophobic
-transported in blood by binding to carrier proteins
what do steroids initiate to happen?
- activated hormone-receptor complex forms within cell
- the complex binds to DNA and activates specific genes
- gene activation results in production of key proteins
what are amine proteins secreted from
thyroid and adrenal medulla
are peptide hormones hydrophilic or hydrophobic
hydrophilic
where are peptide hormones secreted
by pituitary, parathyroid, heart, stomach, liver and kidneys
what does binding of hormones to carrier proteins make happen
- facilitation of hormone transport
- increased half-life of the hormone
- a reservoir for the hormone
name some important carrier proteins
- cortisol binding globulin
- thyroxine-binding globulin
- sex steroid binding globulin
what hormones does the hypothalamus release
TRH and CRH
what hormones does pituitary release
- TSH
- ACTH
- LH
- FSH
- Growth hormone
- oxytocin
- prolactin
- MSH
- ADH
what hormones does thyroid/parathyroid release
- T4
- T3
- CT
- PTH
