Understanding the Endocrine System and Its Functions
Endocrine System
A system is a combination of parts and appliances that work in concert to fulfill a specific function. The Endocrine System is specialized in producing chemical compounds called hormones.
The endocrine system consists of a set of endocrine glands located throughout the body, responsible for coordinating and regulating various body functions. This regulation is achieved by compounds; hormones produced by endocrine glands are transported by the blood and act on distant organs.
All glands are interrelated: there are endocrine glands that produce hormones that act on other endocrine glands, which, in turn, produce hormones that act on the so-called target organs.
Some endocrine glands act exclusively by stimulating other endocrine glands, such as the hypothalamus and pituitary.
Other endocrine glands produce hormones that act on other organs or tissues in the body, such as the pancreas and gonads (ovaries and testes).
The action of the nervous system is fast and short-term, while the action of the endocrine system is slow and long-term; their effects are seen throughout the life of an individual. The two systems are closely related. In reality, the endocrine system is regulated from the hypothalamus, which could be considered part of both systems. Besides, the pituitary, as discussed later, has some other endocrine and nervous functions.
The Body’s Internal Control
All functions of the human being are controlled and coordinated by two large systems or apparatus: the nervous system and the endocrine system.
The nervous system can reach every corner of the body through nerve fibers and neurotransmitters. The endocrine system is shared by different regions of the body through the endocrine glands. Both systems could be considered as communication systems between organs, tissues, and cells of the body.
The action of different hormones is exerted on the organs or target cells that are programmed to respond to hormonal stimuli. The effects are varied. In general, we can say that they affect cellular metabolism, activating or deactivating specific genes or proteins.
Both excess and deficiency of a specific hormone production usually cause illness due to an overactive or underactive gland.
Glands of the Human Body
The components of the endocrine system, endocrine glands, are scattered throughout the body, forming a functional unit.
Hypothalamic-Pituitary Axis
This may be considered a functional unit that is located within the skull at the base of the brain.
The hypothalamus has nerve functions (related to sleep and sensations such as thirst and hunger) and other endocrine functions (coordinates overall neuronal function). It produces hormones that are related to the role of the pituitary. The compounds released by the hypothalamus activate or inhibit the production of pituitary hormones.
The pituitary is a small endocrine gland that hangs from the hypothalamus. It is divided into several lobes. Those related to the endocrine system are:
* The adenohypophysis or anterior pituitary.
* The neurohypophysis or posterior pituitary.
Thyroid and Parathyroid
These are located at the front of the neck, surrounding the trachea and the larynx.
The thyroid is regulated by the pituitary gland and has an action on bone growth. The parathyroid is attached to the thyroid and acts on the metabolism of calcium and phosphorus. The secretion of parathyroid hormone is regulated by calcium levels in the blood.
Excess thyroid hormone production causes a condition called hyperthyroidism. Deficiency leads to hypothyroidism.
Adrenal Glands
They are located above the kidneys and adhere to them. In these glands, there are two distinct areas:
• Marrow, which produces compounds called neurotransmitters. These compounds act on the autonomic nervous system, alerting the body to emergencies.
• The bark, which produces two hormones. The same hormonal secretion is regulated by the pituitary gland.
Pancreas
This is a gland that is part of the digestive and endocrine systems. It lies beneath the stomach and is connected to the duodenum.
The digestive pancreatic juice is involved in the digestion of food. It produces two hormones for the endocrine system: insulin and glucagon. These two hormones regulate the concentration of sugar in the blood, and their effects are antagonistic. Glucagon promotes the breakdown of glycogen stored in the tissues and releases glucose into the blood for distribution to the organs that need it; glucose is used as an energy source for cells. Insulin has the opposite effect because it facilitates the absorption of glucose from the blood by various tissues, mainly muscles. When the pancreas cannot produce enough insulin, glucose accumulates in the blood, causing a condition called diabetes.
Sex Glands or Gonads
These glands are part of the reproductive tract, with secretions discharged outside through ducts and also produce hormones that pour into the blood.
The sex glands or gonads are ovaries in females and testes in males.
Sex hormones begin to occur during puberty and cause sexual differentiation and secondary sex characteristics.
Hormone Balance
Hormones are chemical compounds that exert their action in small quantities. There is a balance between hormone secretion and clearance. Variations in the amounts of hormones in the blood can cause disruption and resulting illnesses.
The elimination of hormones occurs through urine or by destruction in the liver. The mechanism of production-action-gate is summarized in the following scheme:
To a stimulus, usually nervous or chemical, the body starts producing a hormone in small quantities. The hormone travels through the blood to the target organ and there exerts its action. The hormone levels in the blood are what interrupt their production. The mechanism that maintains hormonal balance is called feedback or feedback loop.
Hormones in Invertebrates
In invertebrates, there are not true glands. Hormones are secreted by nerve cells, so hormones are neurohormones. Such hormones are responsible for regulating animal growth and sexual maturation. They can also control color changes, which allow the animal to blend with the environment. For example, they control the change of insect molting, the color change for the squid, and so on.