Physiology: Frank Starling law Flashcards
what is Frank starling law
as end-diastolic volume increases, stroke volume(SV) increases
what are sarcomeres
the contractile unit of heart, found in myfibril
describe what happens to sarcomeres and actin-myosin if end-diastolic volume is too low
sarcomeres are squeezed together
fewer myosin heads bind to actin
what effect does low end-diastolic volume have on contractions and SV
weaker contraction
lower SV
describe what happens to sarcomeres and actin-myosin as end-diastolic volume increases
sarcomeres stretch
increased myosin-actin binding
what effect does increased end-diastolic volume have on contractions and SV
stronger contraction
greater SV
describe what happens to actin-myosin binding as end-diastolic volume is too high
myosin and actin get too far apart, binding decreases
what effect does end-diastolic volume being too high have on contractions and SV
weaker contractions
decreased SV
what does inotropic mean
affects strength of contraction
what does chronotropic mean
changes heart rate
what does dromotropic mean
affects speed of conduction in AV node
what does lusitropic mean
affects rate of myocardial relaxation
what effects does something have if its a positive inotropic effect and give an example
increases strength contraction
increases SV
e.g. sympathetic nervous system
what effect does something have if its a negative inotropic effect
decreases strength contraction
decreases SV
e.g. beta-blockers
