Chemical messengers that reach their target cells traveling in blood are called __.
The correct answer and explanation is:
Chemical messengers that reach their target cells traveling in blood are called hormones.
Hormones are chemical substances produced by various glands in the endocrine system, such as the pituitary, thyroid, adrenal, and pancreas. They are secreted directly into the bloodstream, which transports them to organs and tissues throughout the body. These hormones help regulate a variety of physiological processes, such as growth, metabolism, mood, and reproduction. For example, insulin, produced by the pancreas, helps regulate blood sugar levels, while adrenaline, produced by the adrenal glands, prepares the body for the “fight or flight” response during stress.
Once hormones are released into the bloodstream, they travel to specific target cells that have receptors designed to bind with the hormone. The binding of the hormone to its receptor triggers a response inside the target cell, which can vary depending on the type of hormone and the cell involved. This can lead to changes in the cell’s function, gene expression, or activity.
There are different types of hormones, including:
- Peptide hormones like insulin and growth hormone, which are made of chains of amino acids.
- Steroid hormones like cortisol and estrogen, which are derived from cholesterol and are lipid-soluble.
- Amine hormones like thyroid hormones and adrenaline, which are derived from amino acids.
Hormones act as messengers because they allow communication between different parts of the body, ensuring that the body’s functions are coordinated and homeostasis is maintained. The effects of hormones can be long-lasting, and their regulation is often tightly controlled through feedback mechanisms, ensuring they are released at the right time and in the right amounts.