The integration of endocrine organs with the nervous system is important for many critical processes in animals. The growth and development of invertebrates, such as the caterpillar, occurs in distinct stages. An endocrine pathway that originates from the brain controls this process of growth. Neural cells in the brain produce a hormone. When this hormone reaches an endocrine organ, it induces a cascade of hormones that control the transition of a caterpillar's development from one stage to another.
Organs of the Endocrine System
- The hypothalamus is a structure in the brain that links the nervous and endocrine systems, responding to signals from other parts of the brain and hormone feedback mechanisms. The hypothalamus produces hormones that regulate the pituitary gland.
- The pituitary gland is located near the bottom of the brain and is often called the master gland because its hormones control several other endocrine glands. It consists of two lobes, each producing different hormones. One such hormone is growth hormone (GH), which aids in development and growth.
- The pineal gland is a small endocrine gland located in the brain that plays a role in the production of melatonin, a hormone that aids in the regulation of sleep patterns.
- The thyroid gland is an endocrine gland located in the front of the neck that produces thyroid hormones that help regulate metabolic processes, heat production, and the development and function of other organ systems. The thyroid hormones contain iodine.
- A parathyroid gland is one of four small endocrine glands located near or within the thyroid gland that release hormones that help maintain calcium and phosphorus levels in the body. These hormones are important for bone development.
- An adrenal gland is one of two endocrine glands located on the top of each kidney consisting of the medulla and the cortex that release hormones that help regulate critical functions in the body, such as blood pressure, the immune system, and the metabolism. The inner portion, called the adrenal medulla, releases hormones such as epinephrine that increase heart rate and increase blood flow to the muscles. The adrenal cortex, found on the outer portion of the gland, helps control blood sugar levels, responds to stressful stimuli, and helps the kidneys regulate blood pressure.
- The pancreas is found near the stomach and small intestine. It secretes digestive enzymes that help with digestion. It also releases hormones to help maintain healthy glucose levels in the body. If blood sugar levels are too high, the pancreas secretes insulin. If blood sugar is too low, the pancreas causes the release of stored glucagon to increase blood sugar.
- There are reproductive glands in both males and females. The ovary aids in production of estrogen and progesterone hormones in females. Both hormones are important to maintain sexual traits and aid in pregnancy. The testes produce testosterone that helps with male development and the maintenance of male sexual traits.
The Nervous System
The autonomic nervous system plays a role in involuntary processes such as heartbeats and digestion. It also plays a role in homeostasis through the components of the sympathetic nervous system, the system that stimulates the body for a fight-or-flight response during an environmental stimuli response. The autonomic nervous system stimulates routine functions like the regulation of digestive enzymes or saliva production through the components of the parasympathetic nervous system. The parasympathetic nervous system slows down the heart rate after the fight-or-flight response elicited from the sympathetic nervous system.