Physiology 2- Force Generation by the Heart Flashcards
How are cardiac myocytes electrically coupled?
Gap junctions
Where does cardiac excitation reach?
All the myocytes
What is the contractile unit of a cardiac muscle?
Microfibril
What filaments do microfibrils contains?
Thick myosin and thin actin
What causes muscle tension?
Actin sliding on myosin
What is required for both contraction and relaxation of cardiac muscle?
ATP and calcium
What does troponin do?
Covers the myosin binding site on actin
What does calcium do to troponin?
Calcium binds to troponin which produces a conformational change to move the tropomyosin complex out of the way to allow actin and myosin to interact
When are where is calcium released in cells?
Sarcoplasmic reticulum when there is already calcium in the extracellular fluid- Ca++ induced Ca++ release
When actin and myosin can interact to allow contraction, what does this induce?
Ventricular systole
What is the refractory period?
The period following an action potential during which no ore action potentials can take place
Where does the refractory period take place?
Plateau phase in myocytes
When ventricular muscle contracts, it ejects what?
The stroke volume
What is the stroke volume defined as?
The volume of blood ejected by the each ventricle per heartbeat
How can you work out stroke volume?
End diastolic volume- end systolic volume
