What are the differences between the nervous and endocrine systems in maintaining homeostasis?

The nervous system and endocrine system work together to maintain a state of constancy in the body's internal environment despite changes in the external environment. The effect of both systems is achieved by a chemical substance. However, differences lie in the tissues involved and in the speed, duration and localisation of effects of both systems.

The nervous system comprises nerve cells, called neurones, that communicate by sending electrical impulses towards the target tissues. These impulses are tranmitted rapidly, in the order of milliseconds, and upon reaching a target tissue, the impulse stimulates the neurones to release neurotransmitters (the chemical substance) which trigger an effect. Therefore the effect is generally well localised. Neurotransmitters are then either taken back up by the neurones or degraded, terminating the effect, and hence the effects of the nervous system tend to be short-lived.

On the other hand, in the endocrine system, glands release hormones (the chemical substance) directly into the bloodstream which then has to travel through the circulatory system to the target organs. The effect is therefore slower than that of the nervous system, and more widespread.

Notwithstanding these differences, the nervous system and endocrine system are closely connected . For example, the sympathetic nervous system releases noradrenaline that has a localised, but otherwise identical, effect to adrenaline which is screted by the adrenal medulla.