Force Generation by Heart Flashcards
cardiac muscle is striated (T/F)
True
What are cardiac myocytes electrically coupled by?
gap junction
Define gap junctions
protein channels which form low resistance electrical communication pathways between neighbouring myocytes
gap junctions importance
ensure each electrical excitation reaches all cardiac myocytes
desmosomes importane
- provide mechanical adhesion between adjacent cardiac cells
- tension developed by 1 cell transmitted to next
define myofibrils
contractile units of muscle
actin are _____ filaments
thin
myocin are ____ filaments
thick
actin and myocin are arranged into what?
sacromere
how is muscle tension produced?
sliding of actin filaments on myocin filaments
force generation is dependent on?
ATP-dependent interactions
What is required for contraction and relacation
ATP
What is Ca++ required for
Switching on cross bridge formation
Define diastole
Ventricular muscle relaxes
Define systole
Ventricular muscle contracts
Long refractory period importance
prevents generation of tetanic contraction
define refractory period
period following action potential in which it’s not possible to produce another action potential
Contraction of ventricular muscle ejects?
Stroke Voume
Define SV
vl of blood ejected by each ventricle per heart beat
Calculate SC
SV = End diastolic vl - end systolic volume
What is SV regulated by
Intrinsic + extrinsic mechanisms
explain intrinsic
within heart muscle itself
explain extrinsic
nervous and hormonal control
deine cardiac output
vl blood pumped by each ventricle per minute
calculate CO
SV x HR
what causes changes in stroke volume
changes in
- diastolic length
- myocardial fibres
define diastolic length
vl of blood within each ventricle at end of diastole
AKA End Diastolic Volume
what does EDV determine
Cardiac preload
What is EDV determined by
venous return to heart
Explain Frank-Starling Mechanism
- Relationship between end diastolic volume and stroke volume
- greater EDV = greater stroke volume
How is optimal length in cardiac muscle achieved
stretching muscle (Frank-Starling mechanism)
Explain starling’s law
RIght
venous return to RA increases = EDV right ventricle increases = increased Sv in pulmonary artery
Left
venous return to LA from pulmonary vein increases = EDV of LV increases = increased SV in aorta
Deine afterload
resistance into which heart = pumping
after heart contracted
What does Frank-Starling mechanism partially compensate for
Decreased Sv caused by increased AL
