What is afterload?
Pressure of blood pushing backwards against the heart.
After load = BP
What is contractillity?
How forcefully a heart muscle fibre can contract.
What is the location of the heart?
In the thorax
- rests on the diaphragm
- near the midline of the thoracic cavity
- in the mediastinum
- between the lungs
- base is directed posteriorly & to the right
- apex points inferiorly & to the left
What is the pericardium?
Double layered sac that surrounds the heart
What are the 3 layers of the heart wall?
PERICARDIUM
covers the outer surface
MYOCARDIUM
muscular wall of the heart - cardiac muscle tissue
ENDOCARDIUM
covers the inner surface
What are the features of the myocardium?
- atrial walls are thinnest
- right ventricle thinner than left
- left ventricle walls are the thickest
- right & left ventricles pump the same volume of blood with each beat
Where are the heart valves?
ATRIOVENTRICULAR VALVES - between atria & ventricle - right side is Tricuspid valve - left side is bicuspid ( Tri before Bi)
SEMILUNAR VALVES
- beginning of arteries that leave the heart
- 3 cusps per valves
- pulmonary semilunar valve
- aortic semilunar valve
How is blood supplied to the heart muscle tissue?
Coronary circulation
Arteries from the base of the aorta & encircle heart in atrioventricular groove
What are the names & positions of the heart valves?
TRICUSPID
- between right atrium & right ventricle
PULMONARY SEMILUNAR VALVE
- start of the pulmonary artery
BICUSPID VALVE (mitral) - between left atrium & left ventricle
AORTIC SEMILUNAR VALVE
- start of the aorta
What is the order of blood flow through the heart?
Vena cave -> R atrium -> tricuspid valve -> R ventricle -> pulmonary semilunar valve -> pulmonary trunk -> pulmonary arteries -> lungs -> pulmonary veins -> L atrium -> bicuspid valve -> L ventricle -> aortic semilunar valve -> aorta -> systemic circulation
What do the heart sounds represent?
‘Lubb-Dubb’ represents turbulent blood flow caused be heart valves closing
Sound 1
Lubb= long, AV valve closing
Dubb= short, SL valve closing
What are the 2 main phases of the cardiac cycle?
SYSTOLE
contraction
DIASTOLE
relaxation
What happens during diastole?
VENTRICLES RELAXED
blood flows back towards the heart in the pulmonary trunk & aorta
SEMILUNAR VALVE CLOSES
pressure within the ventricles decreases below the pressure of the atria
AV VALVES OPEN
ventricles fill with blood
TOWARDS END OF DIASTOLE
the 2 atria contract
What is preload?
How much blood is in the ventricle & how stretched the ventricle is.
More blood in the ventricle = more stretched the ventricle
When will each heart valve open & close?
- open to allow blood to flow through
- close to prevent back flow
Ventricles relaxed
- AV opens
- SL closed
Ventricles constrict
- AV closed
- SL opens
What is end- diastolic volume (EDV)?
The amount of blood in ventricles just prior to the ventricle contraction
Approx 130ml
- shorter the time for ventricle filling= less EDV will be
- more efficient venous return = great EDV will be
What happens during systole?
- ventricles contract as atria relax
- pushes blood against AV valve, forcing then to close
- when pressure in ventricles exceeds the pressure in the arteries, the SL valves open
- blood is ejected from ventricles into pulmonary trunk & aorta
What end-systolic volume (ESV)?
The amount of blood left in the ventricles at the end of systole.
- at rest, volume of blood ejected from the ventricles is approx 70ml
- at rest, ESV is approx 60ml
- the stronger the ventricles contract, the smaller the ESV will be
What is an intercalated disc & what is its purpose in cardiac muscle?
Hold cells together as the heart muscle contracts to form a functional syncytium
What is an ECG?
Recording of the electrical changes that accompany a heart beat.
What do the waves of the ECG mean?
P Wave
- atrial depolarisation
QRS Complex
- ventricular depolarisation
T Wave
- ventricular repolarisation
What is cardiac output?
The amount of blood pumped out of the heart & in to the systemic circuit per minute
What is stroke volume?
The amount of blood pumped out with each heart beat
What is heart rate?
The number of times the heart beats per minute
