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| Question | Answer |
| Cardiac muscle is myogenic. What does that mean? | It can contract/relax without nervous impulses |
| Where is the sino-atrial node (SAN) located? | In the wall of the right atrium |
| What is the bundle of His? | A group of muscle fibres |
| What does AVN stand for? | Atrioventricular node |
| Outline the electrical system of the heart | 1. The SAN causes the right and left atria to contract. It acts as a pacemaker 2. A band of non-conducting tissue (collagen) prevents waves from being passed directly from the atria to the ventricles 3. Waves are transferred from the SAN to the AVN 4. The AVN passes the waves on to the bundle of His. BUT! There is a slight delay before the AVN reacts so that the atria have time to be emptied 5. The bundle of His conducts the waves to the purkyne tissue (finer muscle fibres - purkinje fibres - in the right and left ventricle walls) 6. Purkyne tissue carries the waves of electrical activity into the muscular walls of the right and left ventricles, causing them to contract from the bottom up |
| The SAN is like a pacemaker. What does that mean? | The SAN sends regular waves of electrical activity over the atrial walls to set the rhythm |
| Complete the sentences: The heart muscle ___________ (loses electrical charge) when it contracts, and ___________ when it relaxes. An _________________ records these changes in electrical charge. | The heart muscle DEPOLARISES (loses electrical charge) when it contracts, and REPOLARISES when it relaxes. An ELECTROCARDIOGRAM records these changes in electrical charge. |
| What does a PQRST wave look like? |
Image:
Image (binary/octet-stream)
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| What does the P wave indicate? | Atrial systole (depolarisation) |
| What does the QRS complex indicate? | Ventricular systole (depolarisation) |
| What does the T wave indicate? | Diastole (repolarisation) |
| What equation do you use to calculate heart beat (bpm)? | 60 / time taken for 1 heartbeat (s) |
| What is tachycardia? | Heartbeat is too fast (around 120bpm) This is alright after exercise but at rest, it shows that the heart isn't pumping blood efficiently |
| What is bradycardia? | Heartbeat is too slow (around 50bpm) This is normal in trained athletes but in others it can indicate a problem (e.g. something preventing impulses from the SAN being passed on properly) |
| What is ectopic heartbeat? | An 'extra' heartbeat that interrupts the regular rhythm Occasional ectopic heartbeats in a healthy person don't cause a problem |
| What is fibrillation? | A really irregular heartbeat The atria or ventricles completely lose their rhythm and stop contracting properly This can result in anything from chest pain and fainting to lack of pulse and death |
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