Detailed Notes - Topic 5 Homeostasis and Response - AQA Biology GCSE

Detailed Notes - Topic 5 Homeostasis and Response - AQA Biology GCSEHomeostasis (5.1) Homeostasis is the maintenance of a constant internal environment. Mechanisms are in place to keep optimum conditions despite internal and external changes. This is needed for enzyme action and all cell functions. In the human body, homeostasis controls: ● Blood glucose concentration ● Body temperature ● Water levels Nervous ​and ​hormonal communication​ is involved in the automatic control systems, which detect changes and respond to them. All control systems have: ● Receptors ​- cells that detect stimuli (changes in the environment) ● Coordination centres​ - process the information received from the receptors, e.g. brain, spinal cord and pancreas ● Effectors​ - bring about responses to bring the conditions in the body back to optimum levels, e.g. muscles or glands The Human Nervous System Structure and Function (5.2.1) The nervous system allows us to react to our surroundings, and coordinate actions in response to stimuli. 1. Receptor cells convert a stimulus into an electrical impulse. 2. This electrical impulse travels along cells called ​sensory neurons​ to the central nervous system (CNS). 3. Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along ​motor neurones ​to effectors. 4. The effectors carry out the ​response​ (this may be muscles contracting or glands secreting hormones). Automatic responses which take place before you have time to think are called ​reflexes​. They are important as they prevent the individual from getting hurt. This because the information travels down a pathway called a ​reflex arc​, allowing vital responses to take place quickly. This pathway is different from the usual response to stimuli because the impulse does not pass through the conscious areas of your brain. 1. A stimulus is detected by receptors. 2. Impulses are sent along a sensory neuron. 3. In the CNS the impulse passes to a ​relay neuron​. 4. Impulses are sent along a motor neuron. 5. The impulse reaches an effector resulting in the appropriate response. Examples of reflex arcs are: pupils getting smaller to avoid damage from bright lights, moving y