Biology Topic 8:Exchange and transport in animals (Training for cardiac…
Biology Topic 8:Exchange and transport in animals
Training for cardiac output
Cardiac output = Stroke volume x heart rate
Stroke volume is the volume pumped out of the heart in one beat. It is measured in units of litres/beat.
Cardiac output is the amount of blood pumped out of the heart, measured in litres/minute
Heart rate is how fast the heart beats, and is measure in beats/minute
Carries blood through tissues and organs
Substances are exchanged between blood and cells as capillaries pass through tissues
One cell thick walls means substances in blood are very close to cells, the distance for diffusion with cells is as small as possible.
Carry blood back from the heart
Lowest blood pressure of the 3 vessels
Width of the veins allows blood to flow easily along the vessel
Contain valves which help blood flow in muscles:
When a pair of muscles contract blood is pushed through the valve towards the heart.
When a pair of muscles relax the valves close, stopping blood flowing back away from the heart.
Highest blood pressure of the 3 vessels
Thick elastic muscular walls stretch as blood arrives from the heart
Carry blood away from the heart
rate of diffusion ∝ (surface area x concentration difference) /thickness of membrane
Surface Area to Volume Ratio
Multicellular Organisms need exchange surfaces
Exchange substances with their environment
Diffusion in the lungs