Endocrine and Nervous System Control: Hormones and Body Regulation

Endocrine and Nervous System Control

Introduction. The endocrine system and the nervous system work together to control the body. The nervous system receives information and sends messages to the body, and it acts differently depending on the type of action.

Endocrine system. Messages are chemical messengers that travel through the blood to reach their target. The response may be muscle contraction, secretion of substances, or changes in muscle activity.

Nervous system. Messages are electro-chemical signals carried by neurons. They travel through neurons, and the response is a stimulus that drives another neuron to cause muscle contraction or the secretion of substances.

Types of Glands

• Exocrine glands: Their products are not released into the blood. Example: sweat glands.
• Endocrine glands: Their secretions are released directly into the blood. Examples: thyroid and pituitary glands.
• Mixed glands: Example: the pancreas, which produces hormones.

Characteristics of Hormones

Hormones are proteins, amines, and some steroids. Most organs are affected by hormones that act on different cells. Hormone concentrations act in very low amounts, and they can increase or decrease certain reactions. The speed of chemical reactions in cells varies. Over time, hormones disappear as they are degraded or eliminated once they have fulfilled their function.

Target Organs

A target organ is an organ whose operation is regulated by specific hormones. These hormones are secreted and travel through the blood to the cells where they act.

Hypothalamus

The hypothalamus is a part of the brain that establishes the connection between the nervous and endocrine systems. It is connected to the pituitary gland, and it manufactures hormones that are sent to stimulate or regulate its operation.

• Oxytocin: Affects the uterine muscles and the fibers of the mammary glands.
• Antidiuretic hormone (ADH): Acts on the kidneys.

Pituitary Gland

The pituitary gland controls the functioning of other glands and their hormone products, and it stimulates their action. It is the size of a chickpea and is located at the base of the brain.

Hormonal Mechanism of Action

A hormone exerts its action on the target cells that have specific receptors for it. Some hormone receptors are located in the cell membrane and modify the activity of the cell. For example, insulin acts on the entry of glucose from the blood into the cell. Other hormones pass through the cell membrane and bind to receptors in the cytoplasm or nucleus, where the hormone-receptor complex enters the nucleus to regulate genetic activity.

Feedback

Feedback. The gland stops producing the hormone once it detects that the hormone has already fulfilled its function.