Transport in Animals: the Heart Flashcards
what causes the opening and closing of valves
pressure changes in the cardiac cycle
4 stages of cardiac cycle
diastole, atrial systole, ventricular systole, after systole
why is heart muscle myogenic
it can initiate its own contraction
natural frequency of contraction
muscles from the atria and ventricles have their own but atrial muscle tends to contract at a higher frequency
what if the contractions of the heart chambers aren’t synchronised
it could cause inefficient pumping (fibrillation) so needs a mechanism to coordinate the contractions
sino-atrial node (SAN)
small patch of tissue that generate electrical activity by initiating a wave of excitation at regular intervals which occurs 55-80 times in humans
why is the wave of excitation delayed in the SAN
it allows time for the atria to finish contracting and blood to flow down into the ventricles before they begin to contract
electrocardiogram (ECG)
monitors electrical activity of the heart by attaching sensors to the skin and pick up excitation created by the heart- converted into a trace
wave P
shows the excitation of the atria
wave QRS
indicated the excitation of the ventricles
wave T
shows diastole
atrio-ventricular valves
valves between atria and ventricles which ensure blood flows in correct direction
semilunar valves
prevent blood re-entering the heart from the arteries
cardiac cycle
sequence of events in one full beat of the heart
bradycardia
a slow heart rhythm
