cardiac physiology Flashcards
define systole
contraction
define diastole
relaxtion
describe sequence of mechanical events in the cardiac cycle
- ventricular filling
- atrial contraction
- isovolumetric ventricular contraction
- ventricular ejection
- isovolumetric ventricular relaxation
what happens during ventricular filling?
low pressure due to ventricular diastole so blood flows in from venous systems
what happens during artial contraction?
extra small volume of blood pushed into ventricle
what happens during isovolumetric ventricular contraction?
- ventricles are electrically stimulated to contract
- pressure in ventricles increases but volume stays the same
- very brief period
what happens during ventricular ejection?
pressure in the ventricles is greater than in the arteries, so blood moves out of ventricles and into arteries
what happens during isovolumetric ventricular relaxation?
pressure drops but volume stays the same for a brief period
what causes heart sounds?
valves snapping shut
how can valves cause an altered sound?
valvular diseases
- stenosis - narrowing
- incompetence or regurgitation
what do intercalculated disks do?
dock and form direct contact with another muscle
identify where to listen to the heart sounds for different valves
describe process of atrial and ventricular contraction
- action potential from adjacent cell enters, triggering opening of calcium ion channels
- calcium ion influx triggers release of calcium ions from sarcoplasmic reticulum
- calcium ions bind to troponin to initiate contraction
describe process of atrial and ventricular relaxation
- calcium ions unbind from troponin
- calcium is pumped back into sarcoplasmic reticulum for storage
- some calcium is exchanged for sodium at the cell membrane
- sodium ion gradient is maintained by Na+/K+ ATPase
what does the SAN do?
sets heart rate and initiates cardiac cycle