1. Regulatory Mechanisms in Animals

2. Regulatory Pathways Animals need to communication systems to regulate their functions effectively. The two systems which are used are the nervous system and the endocrine (hormonal) system. The nervous system provides rapid responses to produce efficient coordinated movements. The endocrine system is generally a slower system, although some responses are still very quick. These regulatory systems allow animals to maintain a relatively stable internal environment in the face of changing conditions, which is called homeostasis.

3. Although the two systems seem quite different, they are very similar in that they both send signals from one cell to another. In the endocrine system the signal is a hormone released from glands and in the nervous system it is a chemical called a neuro-transmitter released from nerve endings. Both involve chemical communication because the response is specific to a specific receptor on the cell being affected.

4. Negative Feedback Systems Negative feedback systems involve nervous or hormonal systems or both together to maintain a stable internal environment. They are a stimulus-response mechanism where the response produced reduces the effect of the original stimulus. The response provides feedback has a negative on the stimulus

5. Negative feedback systems have key elements: Disturbance/Stimulus: which starts the loop. Receptor: detects the stimulus, is activated and sends a signal to the control centre. Control Centre: The signal is received and compares this to the set-point. Effector: the endocrine or nervous system responding. Response: the action caused by the effector.

6. Regulation is therefore the reaction to fluctuations around the set-point for optimal performance. The size of fluctuations depends on the sensitivity and location of receptors, the tolerance of the control centre to variations from the set-point and the efficiency of response mechanisms. Ie. Blood glucose levels very by a wide margin, while core body temperature stays fairly consistent.