ABC Medical Notes.com |
|
---|---|
Free Open Access Medical Information | |
MEDICAL DISCLAIMER:The contents are under continuing development and improvements and despite all efforts may contain errors of omission or fact. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice by healthcare workers or laypeople. It is for educational purposes only. Please adhere to your local protocols. Use the BNF for drug information. If you are unwell please seek urgent healthcare advice. If you do not accept this then please do not use the website. Makindo Ltd |
Related Subjects: |Cardiac Anatomy and Physiology |Coronary Artery Anatomy
Cardiac cycle
In normal cardiac tissue stretching of the cardiac muscle improves the force and velocity of the corresponding contraction. The stretch of the cardiac muscle is due to filling and therefore equates the volume of the blood in the heart just before ventricular systole. This is the left ventricular end-diastolic volume. This enables the heart to respond to exercise and all manner of increasing cardiac demand. As a heart fails this relationship becomes altered and stretching can then result in no improvement or even a worsening of contractile function.
Pacemaker cells show a different mechanism of depolarisation than other cells. They are found in the sinoatrial node, atrioventricular node and the Purkinje fibres. The SAN pacemaker cells have the fastest rate of depolarisation.