Why are hormones called chemical messenger?

• Hormones are called chemical messengers because they are chemical agents that travel through the body, directing specific cells to perform particular actions.
• The term "hormone" refers to a variety of signaling chemicals, which may include proteins, amino acids, or steroids.
• The body’s endocrine system is made up of several glands that secrete hormones when triggered by signals from the brain.

Hormones regulate a wide range of activities:

• Some signal the body when cells need energy.
• Others influence appetite or sex drive when sperm or eggs are being produced.
• Hormones bind only to target cells that have the appropriate receptors, instructing them to carry out specific functions.

Additional Information

• The endocrine system works closely with the nervous system, as both regulate signaling and coordination in the body.
• Nerve cells release their own chemical messengers at axonal endings, often acting in an endocrine or paracrine manner.
• When neural signaling molecules are released into a synaptic gap to activate receptors on adjacent cell membranes, they are called neurotransmitters.

Key differences between neurotransmitters and hormones:

• Neurotransmission: Fast signaling (milliseconds), highly specific, and localized to synaptic connections.
• Hormonal signaling: Slower (seconds to hours), but messages are diffused throughout body fluids, reaching a large number of target cells.