The heart Flashcards
What are some special functions of the heart?
Coronary arteries supply the cardiac muscle with the oxygenated blood
= ♾️ contracting and relaxing
Surrounded by inelastic pericardial membranes
~~> prevent the heart from swelling with blood.
What happens in the right sideof the heart
?
Deoxygenated blood enters right atrium from superior vena cava
~~> low pressure.
Blood flow in = slight pressure build up until atrio-ventricular (tri-cuspid) valve open
Blood pass into right ventricle.
When both atrium + ventricle filled with blood –> atrium contract = force blood into right ventricle + stretches walls.
Valves close = prevent back flow
What happens at left side of the heart?
All happen at same time
Oxygenated blood from lungs enter left atrium from pulmonary vein.
As pressure in atrium builds –> semi-lunar valves (biscuspid) open.
left ventricle fills with blood.
When both atrium + ventricle full, atrium contracts. –> forces all blood to enter left ventricle.
Contracts + pumps oxygenated blood into aorta. ~~> transported around body.
What is a special feature of left ventricle?
Muscular wall much thicker
Produce sufficient force to pump around body + overcome resistance.
Role of septum?
Prevents mixing of oxygenated + deoxygenated blood
What is the cardiac cycle?
Describes event of single heartbeat –> lasts 0.8 seconds in human adult.
What does systole mean?
Constriction
Atria contract, then ventricles.
pressure increases –> blood forced out to lungs + body
Volume + pressure low at end of systole
Pressure in arteries = maximum
What does diastole?
Relaxation
Atria + ventricles fill with blood.
Pressure in arteries = minimum
First intersection of cardiac cycle
Ventricles contract (systole)
Pressure in ventricles increase above pressure in atrium.
Atrio-ventricular valves close = ‘lub’ sound
Prevents back flow of blood into atrium.
Second intersection pof cardiac cycle
Pressure in ventricles increase above pressure in aorta
Semi-lunar valves open
Blood flows in aorta + out of ventricles.
Third intersection of cardiac cycle
Pressure in ventricles decrease below pressure in aorta.
Semi-lunar valves close = ‘dub’ sound.
Prevent blood flowing back in ventricle.
Last intersection of cardiac cycle
Whole heart diastole
Pressure in ventricles decrease below pressure in atrium
Atrioventricular valve = open
Blood flow into ventricle
What does ‘myogenic’ mean?
Own intrinsic rhythm.
Controls own contractions by initiating own electrical impulse.
60bpm
Prevents body wasting resources.
What is the SAN?
Initiates electrical impulse to start atrial systole/contractions.
Where wave of excitation begins.
Insulating layer = prevents excitation passing directly to ventricles.
What is the AVN?
Atrioventricular node
Delays signal
Allows atria to fully contract –> complete blood flow into ventricles.
What is Bundle of His?
Transmits impulse from AVN to apex.
Wrapped around insulating layer
Ventricular walls not feel excitation so will not contract.
–>prevents ventricular contractions until apex
What are the purkinje fibres?
Spread impulse along ventricles
Ventricular systole
What is an ECG?
Records electrical activity of the heart.
Measures electrical differences in skin = result from electrical activity of heart.
Describe tachycardia?
Very rapid heart beat.
Describe bradycardia?
Slow heart rate blow 60 bpm
Describe ectopic heartbeat
Extra heartbeats out of normal rhythm
Usually normal
Atrial fibrillation?
Rapid electrical impulses generated in atria.
Atria do not contract properly = inefficient
Describe a P-wave
Activation of atria
Depolarisations (contractions) of atria
Describe QRS complex
Activation of ventricles
Depolarisations (contractions) of the ventricles
Describe T-wave
Recovery wave
Repolarisation (relaxation)of ventricles.
Bigger waves = more electrical change.
