Circulatory System Flashcards
Circulatory systems in Mammals
Mammals have a four-chambered heart and a double circulation. This means that for every one circuit of the body, the blood passes through the heart twice
The right side of the heart receives deoxygenated blood from the body and pumps it to the lungs (the pulmonary circulation)
The left side of the heart receives oxygenated blood from the lungs and pumps it to the body (the systemic circulation)
Monitoring Activity of the Heart
Heart activity can be monitored by using an ECG, measuring pulse rate or listening to the sounds of valves closing using a stethoscope
Heart rate (and pulse rate) is measured in beats per minute (bpm)
To investigate the effects of exercise on heart rate, record the pulse rate at rest for a minute
Immediately after they do some exercise, record the pulse rate every minute until it returns to the resting rate
coronary heart disease
The blood is supplied by the coronary arteries
If a coronary artery becomes partially or completely blocked by fatty deposits called ‘plaques’ (mainly formed from cholesterol), the arteries are not as elastic as they should be and therefore cannot stretch to accommodate the blood which is being forced through them - leading to coronary heart disease
Partial blockage
coronary arteries creates a restricted blood flow to the cardiac muscle cells and results in severe chest pains called angina
Complete blockage
cells in that area of the heart will not be able to respire and can no longer contract, leading to a heart attack
Why does the ventricle have thicker walls than the atria
pumping blood out of the heart and so need to generate a higher pressure
why does the left ventricle have a thicker muscle wall than the right ventricle
pump blood at high pressure around the entire body, whereas the right ventricle is pumping blood at lower pressure to the lungs
The 2 valves
The valve on the right side of the heart is called the TRICUSPID and the valve on the left side is called the BICUSPID
When do the two valves get pushed open and when do they shut?
they are pushed open when the atria contract but when the ventricles contract they are pushed shut to prevent blood from flowing back into the atria
What happens when the ventricle contract
blood squeezes past them out of the heart, but then shut to avoid blood flowing back into the heart
Explaining the Effect of Physical Activity on Heart Rate
- sufficient blood is taken to the working muscles to provide them with enough nutrients and oxygen for increased respiration
- An increase in heart rate allows for waste products to be removed at a faster rate
- After exercise, heart beat faster for a while to ensure that all excess waste products are removed from muscle cells
It is also likely that muscle cells have been respiring anaerobically during exercise and so have built up an oxygen debt - This needs to be ‘repaid’ following exercise and so the heart continues to beat faster to ensure that extra oxygen is still being delivered to muscle cells
- The extra oxygen is used to break down the lactic acid that has been built up in cells as a result of anaerobic respiration
Arteries
- Carry blood at high pressure away from the heart
- Carry oxygenated blood (other than the pulmonary artery)
- Have thick muscular walls containing elastic fibres
- Have a narrow lumen
Speed of flow is fast
Veins
- Carry blood at low pressure towards the heart
- Carry deoxygenated blood (other than the pulmonary vein)
- Have thin walls
- Have a large lumen
- Contain valves
Capillaries
- Carry blood at low pressure within tissues
- Carry both oxygenated and deoxygenated blood
- Have walls that are one cell thick
- Have ‘leaky’ walls
- Speed of flow is slow
Arterioles
The narrow vessels that connect arteries to capillaries are called arterioles
