Grade Saved


Your grade






The heart is a muscular organ.

Its function is to pump blood. [1]


The right side of the heart pumps blood through the pulmonary circuit.

The left side pumps blood through the systemic circuit.

-> The main parts of the heart, seen in cross-section from the front [2]

Effect of exercise and adrenaline

During exercise, the muscle cells need more energy than usual.

They therefore need to respire more

As a consequence, need more oxygen and glucose, and they produce more waste carbon dioxide.

To meet this demand, the heart:

- contracts more often (the heart rate increases)

- contracts more powerfully (the stroke volume increases, pumping a greater volume of blood with each beat)

The changes in heart rate are easily observed by measuring the pulse rate (for example, at the wrist or side of the neck).

Hormone adrenaline

The hormone adrenaline is secreted when we are afraid, stressed or angry.

It also causes the heart rate and stroke volume to increase, preparing us for ‘fight or flight’. [4]

Bitesize - The circulatory system



In general, blood flows into the heart from a vein -> goes into an atrium -> then a ventricle -> and out through an artery.

The heart contains valves to prevent the blood flowing backwards:

- the right side of the heart has a tricuspid valve

- the left side of the heart has a bicuspid valve

Both sides have semi-lunar valves (at the entrances to the pulmonary artery and aorta). [5]

How the blood flows

The diagram below shows how the blood flows in the heart.







You may be interested in

© 2017