The Refractory Period Very shortly (about 1 ms) after an action potential has been generated in a section of the axon membrane, all the sodium ion voltage-gated channel proteins in this section clo...
Speed of Conduction of Impulses The speed of conduction of an impulse refers to how quickly the impulse is transmitted along a neurone It is determined by two main factors: the presence or absence ...
Transmission of Nerve Impulses Neurones transmit electrical impulses, which travel extremely quickly along the neurone cell surface membrane from one end of the neurone to the other Unlike a normal...
Sequence of Events Resulting in an Action Potential The surface of the tongue is covered in many small bumps known as papillae The surface of each papilla is covered in many taste buds Each taste b...
Sensory Receptor Cells A cell that responds to a stimulus is called a receptor cell Receptor cells are transducers – they convert energy in one form (such as light, heat or sound) into energy in an...
Neurones Neurones have a long fibre known as an axon The axon is insulated by a fatty sheath with small uninsulated sections along its length (called nodes of Ranvier) The sheath is made of myelin,...
The Nervous System The human nervous system consists of the: Central nervous system (CNS) – the brain and the spinal cord Peripheral nervous system (PNS) – all of the nerves in the body It allows u...
The Endocrine System A hormone is a chemical substance produced by an endocrine gland and carried by the blood They are chemicals which transmit information from one part of the organism to another...
Abscisic Acid & Stomatal Closure During times of water stress, the hormone abscisic acid (ABA) is produced by plants to stimulate the closing of their stomata Certain environmental conditions c...
