In this module you will cover:

• Plant responses: In plants, responses are coordinated by hormone-like substances called plant growth regulators, which control processes such as growth and phototropism.
• Simple responses in animals: Simple responses to stimuli in simple animals are known as taxes and kineses.
• Nervous co-ordination: A stimulus is any change in the internal or external environment that can be detected. A receptor detects the stimulus, and a coordinator (such as the brain or spinal cord) processes this information to produce an appropriate response. An effector (usually a muscle or gland) then carries out this response.
  • Each type of receptor is specific to a particular kind of stimulus, meaning it only responds to one form of environmental change (e.g., light, temperature, pressure). You will study photoreceptors in the eye and a mechanoreceptor called the Pacinian corpuscle.
  • Nerve cells (neurones) transmit information as electrical impulses along their axons. These impulses are highly specific because the neurone releases a chemical (usually a neurotransmitter) directly onto a target cell. This results in a response that is typically rapid, short-lived, and localised.
• Hormonal co-ordination: In contrast to the nervous system, hormones in mammals are transported through the bloodstream. They only affect cells that have specific receptors with a complementary tertiary structure. Hormonal responses are generally slower, but they tend to be long-lasting and widespread throughout the body. You will study how hormones regulate blood glucose concentration and the water potential of the blood (osmoregulation).