A group of students investigated the effect of a person's fitness level on the heart rate before, during and after exercising. They measured the resting heart rate of an unfit person leading a sedentary lifestyle and that of a trained athlete. After monitoring their resting heart rate for 10 minutes, both participants were asked to run for a period of 10 minutes. Their heart rates were monitored during this time by a heart rate monitor that was attached to their wrists. After exercising, their heart rates were monitored for a period of 40 minutes.
The results of this investigation is shown in the following graph.
Ebstein's anomaly is a birth defect where the tricuspid valve is displaced from its normal position between the right atrium and ventricle. This defect will often cause the valve to not function properly. Babies born with Ebstein's anomaly will require surgery to correct the defect.
The following diagram compares the structure of a normal heart with the heart of a person born with Ebstein's anomaly.
Explain the effect that a faulty heart valve may have on the flow of blood through the right side of the heart.
Tricuspid valve surgery is a very effective way to treat patients born with Ebstein's anomaly and restore heart function back to normal. One way to measure the effectiveness of this treatment is to investigate the increase in cardiac output before and after surgery.
Cardiac output is the amount of blood that the heart pumps per minute.
A patient born with Ebstein's anomaly has a mean heart rate of 78 beats per minute and with every heart beat, 45 cm3 of blood leaves the heart.
Calculate the cardiac output (dm3min-1) of this patient. Show your working.
Carnitine is a chemical that plays an essential role in energy metabolism by transporting long-chain fatty acids into mitochondria in cells where they are then oxidised. It is often used as a supplement by athletes to enhance their athletic performance and to aid in weight loss.
Recent studies have linked the prolonged use of carnitine supplements with increased levels of trimethylamine N-oxide (TMAO) in the bloodstream. TMAOs can trigger inflammatory and immune responses in the body, as well as elevated blood glucose levels.
Based on the information provided, explain why increased TMAO levels could increase the risk of suffering a heart attack.
Scientists investigated the effect of carnitine in the diet on the plasma concentration of TMAO in mice. Four groups, consisting of ten mice each, were fed one of four possible diets.
Diet 1 - a normal mouse diet with natural carnitine levels
Diet 2 - a normal mouse diet with added carnitine
Diet 3 - a low carnitine mouse diet
Diet 4 - a normal mouse diet with added carnitine and antibiotics
The TMAO levels in the bloodstream of the mice were measured over time and a mean for each group was calculated.
Suggest a possible hypothesis for this investigation.
