·
Haemoglobin
- Haemoglobin is a protein which has a quaternary structure.
- Each haemoglobin molecule can carry up to 4 oxygen molecules.
- The binding of haemoglobin with oxygen is a reversible reaction showing that oxygen can easily detach which is vital for respiring cells.
- At high partial pressures of oxygen (in the lungs), haemoglobin has a high affinity for oxygen so the oxygen binds to the haemoglobin to become oxyhaemoglobin.
- At low partial pressures of oxygen (in tissues such as muscle), the haemoglobin had a low affinity for oxygen and so the oxyhaemoglobin will release the oxygen to become haemoglobin.
Veins and Arteries of Heart, Lungs and Kidneys
- Heart
Veins: Vena Cava and Pulmonary Vein
Arteries: Aorta and Pulmonary artery - Lungs
Veins: Pulmonary Vein
Arteries: Pulmonary Artery - Kidneys
Veins: Renal Vein
Arteries: Renal Artery
- Ventricular contraction causes the atrioventricular valves (AV valves) to close preventing backflow of blood into the atrium and begins the ventricular systole while semi-lunar valves (SL valves) remain close.
- Continued pressure causes a high pressure and so the semi-lunar valves open.
- As the ventricles are relaxing the semi-lunar vales shut preventing backflow of blood into the ventricles.
- The ventricular diastole and the AV valves remain shut.
- When the pressure in the ventricles becomes lower than the pressure in the atrium, the AV valves open and blood flows into the ventricles.
- The atria contracts to complete the ventricular filling.
Exchange of Substances in the Capillaries
- As the blood comes in from the arterioles into the capillaries, it comes in with high hydrostatic pressure forcing plasma out through the capillary walls into the tissues to become tissue fluid.
- The extensive network of capillaries is called a capillary bed and provides a large surface area for exchange.
- Oxygen diffuses down its concentration gradient from the capillary into the tissue fluid for the respiring cells.
- CO2 diffuses down its concentration gradient from the respiring cells in the tissue fluid to the capillary.
- Once the exchange of substances are done which includes glucose and amino acids, the proteins in the capillaries create a low water potential and so the water from the tissues fluid goes down its concentration gradient into the capillaries by osmosis.
- This flows through the venules back to the heart.
- The remaining fluid in the tissues is sent as lymph through the lymphatic system through the lymphatic vessels.
- It is directed to the blood vessels near the heart to be part of the circulation.
Heart Rate
Do you know how to calculate heart rate in AS/A-level Biology?
Cardiac output = Strove volume x Number of heart beats
To work out heart rate from a graph, it is 60 divided by the time for one cycle (i.e. from the plateau point to when it reaches this line again.)
For example,
- For one heart beat it takes 1.6 seconds (3.4 - 1.8).
- Then 60 divided by 1.6 will give you a heart rate of 37.5 beats per minute.
That's the end of the topic!
Drafted by Bonnie (Biology)