Basic Science Flashcards
alpha 1 adrenoceptor physiological effect
vasoconstriction of blood vessels
alpha 2 adrenoceptor physiological effect
presynaptic inhibition of noradrenaline in CNS
Relaxation GIT
Beta 1 adrenoceptor physiological effect
increases HR and cardiac muscle contraction
B2 adrenoceptor physiological effect
Dilation of bronchi
Increased HR and cardic muscle contraction (lesser extent than B1)
B3 adrenoceptor physiological effect
thermogenesis in skeletal muscle, lipolysis
what type of G protein is bound to alpha 1 adrenoceptors and what occurs
G alpha q subunit
activates phosphlipase C to increase IP3 and DAG causing Ca2+ release and vasoconstriction of blood vessels
what type of G protein is bound to alpha 2 adrenoceptors and what occurs
G alpha i subunit
inhibits adenylyl cyslase to decrease cAMP, increasing K+ channels (= hyperpolarisation relaxing GIT) and decreasing Ca2+ channels
what type of G protein is bound to beta 1 adrenoceptors and what occurs
G alpha s subunit
stimulates adenylyl cyclase to increase cAMP
what type of G protein is bound to beta 2 adrenoceptors and what occurs
G alpha s subunit
stimulates adenylyl cyclase to increase cAMP
what type of G protein is bound to beta 3 adrenoceptors and what occurs
G alpha s subunit
stimulates adenylyl cyclase to increase cAMP
what type of receptor is the insulin receptor
multi-functioning kinase linked receptor - as when insulin binds it triggers several pathways
autocrine vs paracine vs endocrine signalling
autocrine = released from one cell to target receptors on that same cell
paracrine = signalling molecules bind to adjacent cells
endocrine = secretions enter circulatory system to reach target cell
highest level of endocrine control
hypothalamus
3 main roles of hypothalmic control of endocrine system
- releases regulatory hormones which contrl activity of anterior pituitary cells
- synthesises and transports hormones to posterior pituitary via infundibulum
- controls secretion of adrenaline and noradrenaline by adrenal medulla
3 classes of hormones + examples
lipid derived/steroids (oestrogen)
amine-derived (adrenaline)
peptide hormones (oxytoxin, ADH, GH, insulin)
how do the different classes of hormones bind to their receptors
amino acid derived and peptide hormones = water soluble, so are insoluble in lipids so cannot cross the cell membrane and so bind to receptors on cell surface (starting cascade with G proteins)
steroid hormones = lipid souluble so can enter cells to bind, so can alter gene expression and cause more or less protein to be made
how can a hormone influence a cells
directly = changing which genes are activated
indirectly = stimulating signalling pathways within the cells to affect other processes (eg: insulin)
what does ADH do
(released by post. pit)
Causes more water to be retained by the kidneys when water levels are low
Does this by creating special channels called aquaporins, inside the kidneys so that more water can be reabsorbed before its excreted (decreases urine volume)
so is triggered when blood more concentrated and water is low to try to increase water and decrease concentraction
what does aldosterone do
causes retention of water in body by increasing levels of Na+ and K+ ions in blood (water follows)
so is triggered when blood more concentrated and water is low to try to increase water and decrease concentraction
what does renin do
released if low BP
cleaves angiotensinogen to angiotensin I
angiotensin I -> II by ACE
angiotensin II signals aldosterone and ADH release to increase water retention (also inc symp activity and vasoconstriction of arterioles)
explain how insulin is released in detail
elevated BG concentration
increased diffusion of gluocse into B-cell by GLUT2 transporter
phosphorylation of glucose by glucokinase
glycolysis of G6Pin mitochondria -> ATP
increased ATP/ADP ratio within cell closes ATP sensitive K+ channels -> depolarisation
voltage activated Ca2+ channels open and increased intracellular Ca2+ triggers insulin secretion
