Control of the cardiac cycle

The heart beat is generated myogenically i.e. autorhythmically however the rate of the heart beat can be altered in response to the body's needs

The rate of the heart beat is under both hormonal and nervous control.

Nervous Control of the Heart Beat

The heart is under the control of the autonomic nervous system (ANS). The ANS controls involuntary activity.

The ANS is divided into two parts both of which act on each body system in an antagonistic manner: 

• the sympathetic system (which generally stimulates organs)
• the parasympathetic system (which generally inhibits organ activity)

In the heart the sympathetic nerve is called the Sympathetic Nerve. It stimulates the heart via the release of noradrenaline at the neuromuscular junction

In the heart the parasympathetic nerve is called the Vagus Nerve. It inhibits the heart via the release of acetylcholine at the neuromuscular junction.

Artificial pacemakers

The role of leucocytes

The role of lymphocytes

The role of erythrocytes, haemoglobin and myoglobin

Skeletal muscle contraction and venous blood flowa a

Cardiac output and the effect of exercise on cardiac output

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