The Heart

De-oxygenated blood flows into the right atrium from the body, via the vena cava.The blood then moves into the right ventricle, where it is pumped to the lungs via the pulmanory artery.Oxygenated blood from the lungs enters the left artrium via the pulmanory vein.The blood then moves into the left ventricle, it is then pumped all around the body via the Aorta

Ventricles.The left ventricle has to pump the blood all around the body, so has thicker walls so as to be able to pump the blood under high pressure.The right ventricle is only pumping de oxygenated blood to the lungs and so has no need for thick muscle walls.

ValvesValves in the heart prevent back flow through the body.The left side of the heart has the tricuspid valve. AtriumThe right side has the bicuspid valve. AtriumBoth ventricles have a semi lunar valve.

Exercise and heart rate.When we exercise, the cells in our body need more energy, so the respire quicker.  This means there will be an increased need for O2 and an increase need to remove CO2.To do this the heart rate will increase.Exercise increases the concentration of CO2 in the blood, high levels of CO2 are detected by receptors in the aorta and carotid artery.

These receptors send signals to the brain, the brain then sends signals to the heart to make it contract more frequently and with more force.

Hormonal response.When faced with a threat by a predator, and organism will stimulate its adrenal gland, the adrenal gland will release adrenaline into the blood stream.Adrenaline will bond to specific receptors in the heart, this will cause the cardiac muscle to contract more frequently and with more force, so the heart rate will increase and therfore pumps more blood.This will increase O2 supply to the tissue, getting it ready for action  Fight or Flight

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