mammalian cardiac cycle Flashcards
outline the movement of blood through the heart
- deoxygenated blood enters RA through vena cava
- goes to RV through tricuspid valves
- goes to pulmonary artery through semi-lunar valves to lungs
- from lungs oxygenated blood enters LA of heart through pulmonary vein
- goes to LV through bicuspid valves
- goes to aorta through aortic valve to rest of body
what is the heart made out of
cardiac muscle
function of coronary arteries
supply heart muscle with oxygen and glucose in order to keep it contracting and relaxing continuously
what are the pericardial membranes + their function
a protective, fluid-filled sac that surrounds the heart
it helps to prevent the heart from over distending / swelling with blood
which side of the heart is thicker + why
left side, because there is a thicker layer of muscle in left ventricle wall as it must pump blood around whole body and all extremities
this means it must provide sufficient force to overcome resistance of aorta and arterial systems of whole body
systole definition
the state of contracting
diastole definition
the state of relaxing
outline the cardiac cycle with pressure differences and systole/diastole
- blood flows into atria through veins, increasing atrial pressure
- atrial pressure > ventricular pressure
- this causes atrio-ventricular valves to open so blood flows into ventricles
- atrium walls contract - ATRIAL SYSTOLE
- this pushes all blood out of atria into ventricles, increasing ventricular pressure
- ventricular pressure > atrial pressure
- this causes atrio-ventricular valves to close and semi-lunar valves to open
- ventricle walls contract - VENTRICULAR SYSTOLE
- atrium walls relax - ATRIAL DIASTOLE
- blood is pumped out of ventricles into arteries, increasing arterial pressure
- pressure in blood vessels > ventricular pressure
- this causes semi-lunar valves to close
- ventricles relax - VENTRICULAR DISATOLE
- cycle starts again
myogenic definition
muscle is intrinsically able to produce its own stimulus/rhythm
outline the process by which the heart generates its own heart beat, which reference to atrial + ventricular systole
- cells in SAN depolarise/become electrically excited
- this triggers a wave of excitation to spread across atria - ATRIAL SYSTOLE
- this wave cannot pass to ventricles due to non-conducting tissues separating them
- this means the AVN detects the wave of excitation after a short delay
- AVN transmits wave of excitation down purkyne fibres - VENTRICULAR SYSTOLE
SAN definition
sinoatrial node
located in the right atrium wall
what is the purpose of the SAN
it acts as a pacemaker
also known as the pacemaker region
AVN definition
atrioventricular node
located in between atria and connected to purkyne fibres
purkyne fibres definition
conducting fibres
initially bundled together in the Bundle of His, then they branch out as the fibres run down septum to the apex of the heart, then up ventricle walls
why is the short delay imposed by AVN important
this delay ensures the atria have contracted
what does a P-wave show on an ECG
electrical activity in atrial systole
what does the QRS complex show on an ECG
electrical activity in ventricular systole
what does the Q-T interval represent in an ECG
ventricles contracting
what does the T-wave show on an ECG
the recovery of the ventricles
what does the T-P interval represent on an ECG
the heart is relaxed and filling with blood
8 examples of heart conditions
- tachycardia
- bradycardia
- heart block
- hypertrophy
- fibrillation
- flat line
- arrhythmia
- ectopic heart beat
what is tachycardia
elevated heart rate for no reason
- can sometimes be so high that little blood is pumped as filling time is too short
treatment - relaxation therapy, beta blockers
what is bradycardia
reduced heart rate for no reason
- could indicate good aerobic fitness, or drug use
- leads to increased risk of blood clots + stagnation
treatment - lifestyle changes or pacemakers
what is heart block
a delay in conduction between atria and ventricles, appears on an ECG as the separation of P-wave and QRS complex
treatment - pacemaker
what is hypertrophy
when 1 side of the heart is enlarged, causes QRS complex to be distorted
- cause of enlargement could be high blood pressure that ends up thickening left ventricle
treatment - beta blockers
what is fibrillation
cardiac muscle contraction is not coordinated, ECG will appear distorted
- little blood is pumped as a result
what is flat line
no electrical activity within heart
- only 2% of people with a flatline leave the hospital alive
what is the length of 1 cardiac cycle in humans
approx 0.8 seconds
how to work out beats per minute
no. beats x 60/time
time = time that no. of beats was counted in
function of the septum in heart
prevents the mixing of oxygenated and deoxygenated blood
what is the function of valves in the heart
prevents backflow of blood and ensure efficient movement of blood
why do ventricles contract from the apex up
blood needs to be moved upwards + ensures complete emptying of ventricles
what does an ECG show
the spread of electrical excitation through the heart as a way of recording what is happening as it contracts
x axis = time
y axis = electrical potential mV
what does ECG stand for
electrocardiogram
how can heart rate be measured using an ECG
using the time between R peaks
cardiac cycle definition
the sequence of events that occur in the heart during 1 heartbeat
what causes the sounds of a heart beat
blood hitting the heart valves
what causes the lub sound
blood hitting atrioventricular valves as ventricles contract
- occurs during ventricular systole
what causes the dub sound
backflow of blood hitting semilunar valves
- occurs during ventricular diastole
what is arrythmia
when the heart has an abnormal rhythm
treatment - pacemakers
what is an ectopic heartbeat
when there are extra heartbeats outside of the normal rhythm
treatment - beta blockers
how are ECGs measured
electrodes are stuck on skin which can measure electrical differences in the skin
this signal is fed into a machine which produces an ECG
