OCR A-Level Biology Cardiac Cycle Summary

Carotid arteries


Diastole Heart relaxes chambers of
·
Aorta
the
:


,




venava heart fill ,
low
pressure in the arteries
Pulmonary vein
sino-atrial pulmonarytery
Systole Heart Chambers contract , blood leaves
·
:


node left atrium
Right
atrium
Atrio-ventricular
in the arteries
mode semilunar
value
I
the chambers ,
high pressure
atrioventricular left ventricle
Fetal heart Blood oxygenated
-
value
is in the
· :

Bundle of his

Rightentricle Purhyne tissue


e
septum

Purkyne fibers
placenta so a hole is present in the
septum
blood and lungs
so bypasses the ventricles
The Cardiac Cycle :
The sequence of'events in one full beat of the heart

1 .


Right side
:

Blood enters by the vena cava

Left side :

Blood enters by the
pulmonary vein

The SAN produces electrical impulses causing atrial
.
2 ,
systole
3 .

High atrial
pressure forces blood past the Ar values into the ventricles

↳
Non-conducting fibers prevent ventricular systole at this time

The AU conducts impulses through the bundle of his to the ventricles .




s The ventricles contract the Ar values shut and blood leaves via the arteries semilunar values
.
, , past
Right side Blood leaves via the
pulmonary artery the lungs to
:




Left side
:

Blood leaves via the aorta to oxygenate the rest of the
body
When Atrial




~
pressure is lower than
·




- semilunar
sure ventricular pressure sAuvalve Closes
- ·
When aortic pressure is
greater than

E trial pressure


centricular
pressure semi-lunar value closese
Ar value ventricular
-
Ar value
CloseS
·
opens
pressure
vice versa
time /S


ECG Electrocardiagram- shows the basic rhythm of the heat
:




R

down the
·- of
T
P Atrial G : Electrical impulses traver bundle his
systole
:




as R-s Ventricular
systole T Ventricular
repolarisation
: :


-




Heart Problems :




Bradycardia <60kpm Tachycardia: 120bpm Atrial fibrillation Abnormal heart
rhythm
: :




Ectopic Extra heartbeats outside of
:
the normal
rhythm