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An efficient exchange surface should have a high surface area as this increases the rate at which diffusion can occur across it. For instance, roots have many root hair cells. These root hair cells have thin...

The heart muscle is myogenic , meaning that it is able to initiate its own contraction. The wall of the right atria has a region of specialised fibres known as the sinoatrial node (SAN). This node acts as th...

A pathogen is a harmful organism that causes infectious diseases. There are many types of pathogens: bacteria, fungi, viruses, protoctists, worms and insects. They allow diseases to be transmitted from perso...

Blood from the body enters the right atrium of the heart via the vena cava. It then travels into the right ventricle by a combination of gravity and contraction of the right atrium. After the right atrium ha...

When an action potential arrives at the motor end plate it causes depolarisation to occur in the sarcolemma of the effector muscle cells.2) Depolarisation spreads via T-tubules to the sarcoplasmic reticulum ...