Heart Contraction Flashcards
4 Valves
- Tricuspid (right AV)
- Bicuspid (mitral valve)
- Aortic semilunar valve
- Pulmonary semilunar valve
What helps the direct the flow of blood?
- valves
- if the cuspids are closed then the semilunar will be open
- they work opposite of each other
What supports the tricuspid (right AV)?
- -papillary muscle
- chordae tendineae
Chordae Tendineae
-connect the papillary muscles to the tricuspid valve
Systole
- ventricular contraction
- blood ejection
- lasts about 0.3 sec
Diastole
- rest of chamber
- period of relaxation
- ventricular filling
- lasts about 0.5 sec
tricuspid valve
-directs blood from the right atrium to the right ventricle
mitral (bicuspid) valve
-directs blood flow from the left atrium to the left ventricle
aortic semilunar valve
-between the left ventricle and aortic artery
pulmonic semilunar valve
-between the right ventricle and pulmonary artery
Semilunar valves
- are thicker
- not supported by fibrous cords
Function of Valves
- open and close according to pressure gradients
- pressure stops the blood from flowing back through the vena cava’s
Blood Return to the Heart (2 ways)
- Superior vena cava
- Inferior vena cava
- both go to the right atrium
Blood Flow through Heart
- right atrium through tricuspid valve
- into right ventricle through pulmonary valve
- ejected to pulmonary arteries passes through lungs = oxygenated
- returns to left atrium through mitral valve
- left ventricle through aortic valve to aorta
Preload
- blood in atria moving to ventricles
- stretches ventricles
- related to sarcomere length
- this is the beginning stretch and only force that can stretch the sarcomeres of the heart
- affected by venous blood pressuer
Afterload
- tension or stress on ventricles to push blood out to lungs or the aorta
- aortic pressure
Cardiac Cycle
- any events related to the flow or blood pressure from the beginning of one heartbeat to the beginning of the next
- both systole and diastole
- lasts about 0.8 sec
Why is there a slight delay at the AV node?
-so the after and preload can fill up!
When HR increases
- the time in diastolic phase decreases
- fast beating heart my not remain relaxed long enough for adequate filling
- stroke volume will be decreased
Mechanically systole
-defined as the interval between the closing of the AV valves and the opening of the semilunar vales
Electrically Systole
-defined as the time between Q-T interval
Isovolumetric Contraction
-systole
atrioventricular valves: closed
semilunar vales: closed
-the sarcomeres shorten but the intraventricular pressure has not exceeded arterial pressure
Rapid Ventricular Ejection
- pulmonic
- semilunar valve is forced open, AV valve closed
- left ventricular pressure exceeds 80mmHg
- blood is rapidly ejected as sarcomeres shorten
Reduced Ventricular Ejection
- aortic pressure rises and ventricular pressure and volumes fall
- ventricules are full contracted - force blood to flow out!
- semilunar and AV valves are closed
Cardiac or Ventricular Systole
- electrical impulses spread through the myocardium across intercalated discs
- action potentials result in excitation-contraction coupling and ventricular sarcomere shortening
- ejection of blood from the ventricles occurs
Ventricular Diastole (4)
- Isovolumetric Relaxation
- Rapid Ventricular Filling
- Reduced Ventricular Filling
- Atrial systole - end of diastole
Phases of Diastole
- Passive Filling - blood enters ventricle due to pressure gradient
- Active filling phase - atrial systole, blood forced into ventricle by atrial contraction
Pressure Changes
-reflect the alternating contraction and relaxation of the heart
Which pressure is larger?
Atrial pressure slightly exceeds ventricular pressure even when both chambers are relaxed
When does myocardial excitation occur?
- during diastole
- the SA node is the pacemaker (by right atrium)
- the impulse emitted from the SA node travels to the AV node by the intranodal pathway
Lubb
- 1st sound is low pitched, soft, long
- closure of the AV valves (onset of systole)
Dub
- 2nd sound is higher pitched, shorter, and sharper
- closure of semilunar valves (onset of diastole)
Opening of AV Valve
-diastole
Closing of AV Valve
-onset of isovolumic contraction
Opening of semilunar valve
-onset of ejection
Closing of semilunar valve
-end of systole
How is ECG composed?
- einthoven triangle
- heart is the center of this triangle
- gives 3 leads
- combining these gives us a normal tracing
