Biology Unit 1.5 Revision Notes (Heart)

I hope you find these useful!

Basically, I have divided my notes up into parts of the syllabus, so 1.1, 1.2, 1.3, 1.4 and 1.6 are separate documents, but are all on here.

The part of the syllabus relevant to these notes is on the cover page at the start of the notes.

Sorry for any spelling mistakes or anything :L.

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Heart The gross structure of the human heart and its associated blood vessels in relation to function.
Structure Pressure and volume changes and associated valve movements during the cardiac cycle.
Function Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity.
Roles of the sinoatrial node (SAN), atrioventricular node (AVN) and bundle of His.
Cardiac output as the product of heart rate and stroke volume.…read more

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The valves only open in one way ­ whether they are open or
closed depends on the relative pressure of the heart
If there is higher pressure behind a valve, it is forced open
If there is higher pressure in front of the valve, it is forced
Myogenic Stimulation
Cardiac muscle is myogenic ­ it can relax and contract without receiving signals from nerves
This pattern of contractions controls the regular heartbeat
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Cardiac Output
Cardiac output is the volume of blood pumped by the heart per minute (measured in cm3 per
It is calculated with this formula:
Heart rate
o The number of heart beats per minute
o You can measure your heart rate by measuring your pulse
Stroke volume
o The volume of blood pumped during each heartbeat, measured in cm3
Cardiac output increases during exercise
The Cardiac Cycle
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Pressure and Volume Graph of the Cardiac Cycle
Positio Explanation
Atrium is contracting ­ blood
A flows into ventricles
Ventricles start to contract ­
ventricular pressure exceeds
B atrial pressure, so
atrioventricular valve close
Pressure is higher in the
C ventricle than in aorta ­ blood is
pushed into aorta
Pressure in ventricles is less
D than in the aorta ­ so semi lunar
valves close
Ventricular pressure falls below
atrial pressure, so blood flows
E from atrium to ventricle;
ventricular volume rises rapidly…read more

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Atrium continues to fill with
blood from pulmonary vein;
F atrial pressure exceeds
ventricular pressure, so blood
flows from atrium to ventricle
Changing Heart Rate
Nervous Control:
To speed up heart rate:
o More impulses are sent down the accelerator nerve
o To the SAN
o Which send more impulses through the heart
To slow down heart rate:
o More impulses are send down vagus nerve
o To the SAN
o Which sends fewer impulses through the heart
Hormonal Control:
To speed up heart rate:…read more

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The Atheroma as the presence of fatty material within the walls of arteries.
Biological The link between atheroma and the increased risk of aneurysm and thrombosis.
Basis of
Heart Myocardial infarction and its cause in terms of an interruption to the blood flow to heart muscle.
Risk factors associated with coronary heart disease: diet, blood cholesterol, cigarette smoking
and high blood pressure.…read more

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An atheroma plaque can rupture the
endothelium of an artery, damaging the artery
wall and leaving a rough surface
Platelets and fibrin accumulate at the site of
damage and from a blood clot (a thrombus)
The clot can cause a complete blockage of the
artery or can become dislodged and block a
blood vessel elsewhere in the body
Debris from the rupture can cause another
blood clot to form further down the artery
Myocardial Infarction
The heart muscle is with blood by the
coronary…read more

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