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Firstly, the 'wave of excitation' is produced by the sinoatrial node (SAN) in the top of the right atrium - this is also known as the pacemaker, as this is what controls the rate of contractions. This wav...

When a neurone is stimulated an action potential is generated by a change in ion concentrations across the cell membrane. The resting membrane potential (the potential of charge across the membrane when t...

Water moves into the plant stem from the soil, and up to the leaves via the xylem. Water is taken up by the hairs on the root of the plant down the water potential gradient via osmosis, following the acti...

Beta cells have vesicles containing insulin inside them (1). (2) High glucose levels cause glucose uptake via glucose channels into the beta cell and glucose is metabolised into ATP (3) inside the cell, w...

In humans, the pancreas can sometimes be described as an endocrine gland. This means it releases some of its substances staight into the bloodstream; this is the mechanism used to secrete...