Final answer:
The pituitary gland, also known as the 'master gland,' is the endocrine gland that receives messages from the nervous system to regulate various bodily functions such as sleep cycles and hormone production.
Step-by-step explanation:
The gland that receives messages from your nervous system and ensures the body's internal balance, including overseeing sleep cycles, sweat gland function, digestion, adrenaline production, and sex hormone regulation, is the pituitary gland. Often referred to as the 'master gland,' the pituitary gland produces hormones that control other endocrine glands such as the thyroid gland, parathyroid glands, pineal gland, pancreas, adrenal glands, gonads (testes and ovaries), and the thymus gland. The hypothalamus, located below the thalamus, controls the endocrine system by sending signals to the pituitary gland. Additionally, the hypothalamus is responsible for regulating the body's thermostat to maintain appropriate body temperature and managing circadian rhythms, which are sometimes referred to as sleep cycles.